ResourceHuman prefrontal cortex gene regulatory dynamics from gestation to adulthood at single-cell resolutionGraphical abstractHighlightsd Single-nucleus RNA and chromatin dynamics from gestation to adulthood in humans d Protracted and diverse timing of cell-type development to a mature state d RNA dynamics and regulators predict cellular and temporal origins of brain diseases d Atlas integration reveals few postnatal maturity neurons in long-term brain organoidsHerring et al., 2022, Cell 185, 4428–4447 November 10, 2022 ª 2022 The Authors. Published by Elsevier In https://doi.org/10.1016/j.cell.2022.09.039Authors Charles A. Herring, Rebecca K. Simmons, Saskia Freytag, Daniel Poppe, ..., Irina Voineagu, Luciano Martelotto, Ryan Lister Correspondence ryan.lister@uwa.edu.au In brief A resource charting the gene expression and chromatin accessibility landscapes of human prefrontal cortex reveals gene expression reconfiguration at the prenatal-to-postnatal transition followed by continuous reconfiguration into adulthood.c. ll OPEN ACCESS llResource Human prefrontal cortex gene regulatory dynamics from gestation to adulthood at single-cell resolution Charles A. Herring,1,2,10 Rebecca K. Simmons,1,2,10 Saskia Freytag,1,2,10 Daniel Poppe,1,2,10 Joel J.D. Moffet,1 Jahnvi Pflueger,1,2 Sam Buckberry,1,2 Dulce B. Vargas-Landin,1,2 Olivier Cle´ment,1,2 Enrique Gon˜i Echeverrı´a,1 Gavin J. Sutton,3 Alba Alvarez-Franco,4 Rui Hou,1 Christian Pflueger,1,2 Kerrie McDonald,5 Jose M. Polo,6,7 Alistair R.R. Forrest,1 Anna K. Nowak,8 Irina Voineagu,3 Luciano Martelotto,6,9 and Ryan Lister1,2,11,* 1Harry Perkins Institute of Medical Research, QEII Medical Centre and Centre for Medical Research, The University of Western Australia, Perth, WA 6009, Australia 2ARC Centre of Excellence in Plant Energy Biology, School of Molecular Sciences, The University of Western Australia, Perth, WA 6009, Australia 3School of Biotechnology and Biomolecular Sciences, Cellular Genomics Futures Institute, and the RNA Institute, University of New South Wales, Sydney, NSW 2052, Australia 4Centro Nacional de Investigaciones Cardiovasculares Carlos III (CNIC), Madrid 28029, Spain 5Lowy Cancer Research Centre, University of New South Wales, Sydney, NSW 2052, Australia 6Adelaide Centre for Epigenetics and the South Australian Immunogenomics Cancer Institute, Faculty of Health and Medical Sciences, The University of Adelaide, Adelaide, SA 5000, Australia 7Faculty of Medicine, Nursing and Health Sciences, Monash University, Melbourne, VIC 3000, Australia 8Medical School, University of Western Australia, Perth, WA 6009, Australia 9University of Melbourne Centre for Cancer Research, Victoria Comprehensive Cancer Centre, Melbourne, VIC 3000, Australia 10These authors contributed equally 11Lead contact *Correspondence: ryan.lister@uwa.edu.au https://doi.org/10.1016/j.cell.2022.09.039SUMMARYHuman brain development is underpinned by cellular andmolecular reconfigurations continuing into the third decade of life. To reveal cell dynamics orchestrating neural maturation, we profiled human prefrontal cortex gene expression and chromatin accessibility at single-cell resolution from gestation to adulthood. Integrative analyses define the dynamic trajectories of each cell type, revealingmajor gene expression reconfiguration at the prenatal-to-postnatal transition in all cell types followed by continuous reconfiguration into adulthood and identifying regulatory networks guiding cellular developmental programs, states, and functions. We un- cover links between expression dynamics and developmental milestones, characterize the diverse timing of when cells acquire adult-like states, and identify molecular convergence from distinct developmental origins. We further reveal cellular dynamics and their regulators implicated in neurological disorders. Finally, using this reference, we benchmark cell identities and maturation states in organoid models. Together, this captures the dynamic regulatory landscape of human cortical development.INTRODUCTION The human prefrontal cortex (PFC) does not fully mature until well into adulthood (Molna´r et al., 2019; Sydnor et al., 2021), in a highly protracted process unique among primates (Miller et al., 2012). Neurological executive functions rely on complex spatial, electrical, and chemical interactions of diverse neural cell types that mature through a coordinated process spanning development from in utero to adulthood (Silbereis et al., 2016). Essential processes of synaptogenesis, synaptic pruning, myeli- nation, and plasticity during postnatal development give rise to the functional complexity and capabilities of the mature brain4428 Cell 185, 4428–4447, November 10, 2022 ª 2022 The Authors. This is an open access article under the CC BY license (http://creative(Silbereis et al., 2016). However, the molecular dynamics driving the cellular identities and functional changes that emerge during brain development, in particular postnatally, remain largely unknown. Gene expression changes throughout brain development have been studied using bulk tissue samples (Hernandez et al., 2012; Kang et al., 2011), and recent studies have analyzed tran- scriptome and chromatin states at single-cell resolution at early fetal and adult stages (Morabito et al., 2021; Nowakowski et al., 2017; Figure S1A; Table S1A). However, there has been no sys- tematic characterization of gene expression and chromatin dynamics throughout the entirety of postnatal human brainPublished by Elsevier Inc. commons.org/licenses/by/4.0/). A C D E F G B (legend on next page) ll OPEN ACCESS Cell 185, 4428–4447, November 10, 2022 4429 Resource ll OPEN ACCESS Resourcedevelopment. This gap spans major milestones, such as lan- guage acquisition and development of executive functions. Consequently, we lack a detailed understanding of the timing and nature of gene expression and chromatin dynamics that un- derpin these developmental processes. Here, we characterize at single-cell resolution the gene expression and chromatin acces- sibility changes that occur through human PFC development, from gestation to adulthood. This enables characterization of active pathways and their dynamics in diverse cortical cell types throughout development, cell-type-specific maturation timing, and prediction of the controlling cis-regulatory logic and associ- ated factors, underpinning molecular dissection of neural cell developmental processes. RESULTS A single-nucleus resolution transcriptome reference of human brain development We performed single-nucleus RNA-seq (snRNA-seq) profiling of 26 postmortem PFC samples from individuals spanning fetal, neonatal, infancy, childhood, adolescence, and adult stages of development (Figure 1A; Table S1B), providing extensive sam- pling of stages poorly represented by previous single-cell studies (neonatal, infant, child, and adolescent). We generated 154,748 single nuclei transcriptome profiles after quality filtering (Figures S1C–S1F; Table S1C) and assembled an integrated developmental reference with distinct chronological ordering of all major neural lineages (Figure 1B). We identified 86 distinct clusters across all developmental stages (Figure S1G) and anno- tated them by separating nuclei into either excitatory principal neurons (PNs), inhibitory interneurons (INs, from medial gangli- onic eminence [MGE] or caudal ganglionic eminence [CGE]), or glia, followed by further separation of the major clusters using layer and subtype-specific marker genes (Figures 1C and S2A; Tables S2A–S2C). This developmental map revealed systematic expression changes through postnatal development (Figure 1B) and temporal changes in cell-type abundance (Figures 1D, S1H, and S1I), such as expansion of oligodendrocytes (ODCs) from ODC precursor cells (OPCs) beginning in infancy and progress- ing to adulthood (Figure 1D; Perlman et al., 2020; van Tilborg et al., 2018). We further identified modules representing the organized coexpression of multiple genes in various subsets of nuclei using hotspot (DeTomaso andYosef, 2021; Figure 1E; TableS2D). Each module reflects cell-type-specific transcriptional changes align-Figure 1. A single-nucleus resolution transcriptome reference of huma (A) Schematic of developmental stages, sample ages, brain region, profiling me mental stages: fetal (ga22 to 1 kb from their respective gene (Figure 5G). ClusteringCRE-gene pairs into groups by CRE accessibility similarity revealed seven groups specific to neuronal cell types at different developmental stages (Figure 5H). For example, a mature PN group (C9) is linked to pro- cesses including learning andmemory, cognition, and potassium ion transport, supporting the importance of such transporter up- regulation for mature PNs. CREs in this group are enriched for motifs of TFs involved in cell survival, such as SP1 and SP3 (Fig- ure S5L; Gao et al., 2009; Liang et al., 2013). As CREs are identified mainly by variation across cell types, we assessed whether changes in CRE accessibility reflected gene expression dynamics. For all snRNA-seq gene trends, weFigure 5. A single-nucleus resolution chromatin accessibility map of h (A) UMAP of 87,339 nuclei based on chromatin accessibility (snATAC-seq), ann donor age. (B) Percentages of cell types/states for each developmental stage. (C) snATAC-seq signal at MYRF for each trajectory and developmental stage. promoter. (D) Proportion of peaks overlapping chromHMM-predicted enhancers, heteroch (E) First principal component of accessibility in OCRs for each trajectory across (F) CRE identification strategy: pseudo-bulks of matching snRNA-seq and snA transcriptional start sites (TSSs, <250 kb) of respective gene. (G) Distribution of the distance between CREs to the nearest TSS of their linked ge (>1,000 bp). (H) Heatmap of CRE accessibility (right) and expression (left) of linked CRE-gene clustered into groups. CRE-gene pairs assigned to only one group are shown (n charts for selected groups. (I) Average of normalized snATAC-seq Tn5 insertions per kilobase per million read in each gene trend. (J) Enrichment of TF motif similarity modules in CREs linked to devDEGs in each s TF motif similarity modules enriched in <5 gene trends are displayed. Bias correc binding site (bottom). (K) Enrichment of TF motifs in CREs linked to devDEGs in the ion transporter GO similarity modules (motif family indicated on x axis). Color represents adjusted p 4438 Cell 185, 4428–4447, November 10, 2022observed that their linked CRE accessibility recapitulated their expression trend over development (Figure 5I). To predict tran- scriptional regulators of these expression dynamics, we tested for TF motif enrichment in CREs linked to particular gene trends (Figure 5J; Table S5C). Genes with slowly decreasing trends (G11–13, ‘‘down’’) are enriched in developmental TF motifs, such as POU2F1. Further trajectory-specific analysis showed that POU2F1 enrichment is restricted to neurons (Figure S6A; Table S5D), mirroring findings in early human fetal development (Domcke et al., 2020). STAT3, a TF involved in neurite outgrowth (Ihara et al., 1997), is enriched in transiently up gene trends in all major trajectories (Figure 5J). Gene trends with rapidly increasing expression through development (G4, ‘‘up’’) are en- riched for TFs in the CCAAT/CEBP family, which plays an essen- tial role in memory (re)consolidation (Arguello et al., 2013), whereas other members, such as TEF, have been associated with major depressive disorder (Hua et al., 2014). TF footprinting analyses further supported the presence of these TFs at the pu- tative CREs (Figure 5J). We used the predicted TF binding sites to construct cell type- and stage-specific regulatory networks (Figure S5M), revealing a central role for NTRK3 in PNs for ensheathment of neurons during infancy and adolescence. We leveraged our devDEG gene trends (Figure 2) to investigate trajectory-specific TF enrichment in CREs for devDEGs linked to ion transport (Figure 5K). This identified bZIP family TFs, in partic- ular FOS and JUN that dimerize to form the AP-1 complex (Shau- lian and Karin, 2002), as potential regulators of transcriptional pro- gramswith increasingexpressionoverdevelopment inall neuronal trajectories (Figure 5K). FOS and JUN function in activity-depen- dent transcriptional control of neural circuitry form and function and support higher cognitive functions (Yap and Greenberg, 2018). Although the predicted regulators of developmentally upre- gulated ion transporter expression programs showed substantial commonality inMGEandupper-layer PN trajectories, theCGE tra- jectory appears to be governed by TF regulatory networks shared with deeper layer PN trajectories (Figure 5K), supporting differ- ences observed by snRNA-seq. Collectively, this validates ouruman PFC development otated by cell type/state. Inset UMAP depicts nuclei colored by their sample Peaks in boxes exemplify stage- and trajectory-specific dynamics. Red box: romatin, and promoters across fetal and adult human tissues. developmental stages. TAC-seq nuclei used to correlate expression and accessibility in peaks near nes, and proportion classified as genic (0 bp), proximal (1–1,000 bp), and distal pairs (rows) across 400 pseudo-bulks of snRNA-seq and snATAC-seq nuclei, = 707). Enriched GO terms and cell-type and stage composition shown in pie s mapped (IPKM) across developmental stages for all CREs linked to devDEGs nRNA-seq gene trend. Color indicates summarized adjusted p value (top). Only ted ATAC-footprints for SOX10, POUF21, and TEF centered around the motif- term for general gene trends and major trajectories. TF motifs are summarized value. A B C Figure 6. Cell-type- and dynamics-resolved brain-related disease associations and their regulatory drivers (A) Enrichment of known disease genes for neurological and psychiatric disorders and three control diseases (DisGeNet) in general gene trends across cell type trajectories. Color represents the adjusted p value. (B) Enrichment of TF motifs in linked CREs for significant combinations of general gene trend and disease. TF motifs are summarized to the TF motif similarity modules. Color represents adjusted p value. TF motif family indicated on the x axis. (C) TF binding regions: average of normalized snATAC-seq Tn5 IPKM (snATAC-seq reads) in L5/6 trajectory nuclei over development in CREs with a FOS/JUND motif linked to genes from up gene trends, and that are associated with bipolar disorder. Expression: log2 CPM ofMCTP1 over development in L5/6 neurons (dot: sample; line: GAM fit). CRE region: snATAC-seq signal at a CRE with FOS/JUND motifs (indicated by vertical gray bar) and linked toMCTP1. Browser: snATAC- seq signal over developmental stages at MCTP1, with linked CRE highlighted. ll OPEN ACCESSResourceobservations from the snRNA-seq and reveals cell-type-specific regulatory programs of postnatal brain development. Cell-type- and dynamics-resolved disease associations and their regulatory drivers Symptoms for many neurological and psychiatric diseases manifest or worsen at distinct ages, suggesting the involvementof dynamically regulated cellular processes in development. To test for cell type and developmental dynamics contribution to disease, we used our atlas to explore developmental dis- ease-gene associations. Assessing enrichment of brain-dis- ease-associated genes with devDEGs enabled us to identify potentially causative cell types and predict expression dynamics that may indicate when their dysregulation is relevant to disease.Cell 185, 4428–4447, November 10, 2022 4439 AB C D FE G H (legend on next page) ll OPEN ACCESS 4440 Cell 185, 4428–4447, November 10, 2022 Resource ll OPEN ACCESSResourceOf the 23 diseases analyzed, all show associations with cell- type-specific gene expression trends, except for three blood dis- orders included as negative controls (Figure 6A). The majority (80%) of associated expression trends have up or transiently up dynamics, demonstrating that developmental upregulation of these disease-gene functions is important. The dynamics of individual genes potentially indicates the developmental timing of their dysfunction relevant to diseasemanifestation (Figure 6A). Enrichment for the analyzed neurodevelopmental diseases covers all general gene expression trends and almost all cell types. For example, autism spectrum disorder (ASD) shows enrichment for most cell types and dynamics, reflecting the dis- ease complexity (Figure S6B). Multiple disorders that typically occur later in life (dementia, mild cognitive disorder, amnesia, and Huntington’s disease) are enriched predominantly for genes transiently upregulated during postnatal development in PN and IN subtypes (Figure 6A) and highly enriched for roles in synaptic signaling (Table S5G). This suggests that disruption of synaptic functions refined during postnatal brain maturation is linked to cognitive disorders of later life. TFs may play an important role in mediating the temporally defined onsets of these diseases through their regulation of disease-linked genes. For the significant disease associations, we predicted TFs regulating the developmental expression changes by motif enrichment analysis in the CREs linked to the known disease genes of the relevant gene trend (Figure 6B; Table S5F). Perturbation of regulatory activities of such TFs may cause cell-type- and developmental stage-specific dysregu- lation leading to disease. This revealed a potential role of the AP1/ 1 and CREB/AFT/1 TF motif families, which includes FOS and JUN, in many brain diseases (Figure 6B). Especially interesting is the association of FOS and JUNwith impaired cognition across multiple PNs, as these TFs have been linked to learning andmem- orymechanisms (Gass et al., 2004). Further analysis revealed that genes associated with bipolar disorder are upregulated during development in L5/6 PNs and linked to CREs enriched for the binding motif of FOS and JUND (Figures 6A and 6B), which are known to be regulated by common bipolar medications (Gao et al., 2021). For example, the bipolar-associated gene MCTP1 (Scott et al., 2009) is upregulated after birth in L5/6 PNs, has anFigure 7. A reference for cell developmental analysis in health, diseas (A) UMAP plot overlaid with sample nuclei age (left) and cell type labels (right). (B) Distributions of age prediction for query astrocyte and L2/3 PN nuclei from con 443 days). (C) Projection onto reference of nuclei from snRNA-seq of ga39, and 261- and 44 D and F). (D) Projection of glioblastoma snRNA-seq nuclei. (E) Microscopic images of human cerebral organoids cultured for 9 months, sho dendrites (MAP2+, red) on top left, and detailed views on right. RNAscope in 3- DAPI counterstain (blue, nuclei). Scale bars, 100 mm. (F) Projection onto reference of nuclei from snRNA-seq of human cerebral organ (G) Projection of all organoid snRNA-seq indicating location of PNs reaching po expressed gene (DEG) analysis between postnatally mature (purple) and immatu (bottom). See also Table S6C. (H) Projection of all organoid snRNA-seq indicating location of postnatally mature (top left). Volcano plot: DEG analysis between postnatally mature PNs in normal b brain PNs (bottom left). Ranking of TFs upregulated in brain PNs by z score of n dicates if TF is a devDEG of an indicated general gene trend. TF family specified See also Table S6E.intronic linked CRE that gains accessibility from infancy onward, and contains a FOS/JUND-binding motif (Figure 6C). This exem- plifies how our atlas of PFC development can yield insights into regulatory drivers and implicated cell types in brain disorders. A reference for cell developmental analysis in health, disease, and organoid models of maturation We also leveraged our atlas to enhance interpretation of additional snRNA-seq analyses of the PFC and its in vitro models, modifying a transfer learning strategy (Lotfollahi et al., 2022) to stably integrate additional snRNA-seq datasets into our reference. We first integrated neurotypical control samples from snRNA-seq characterization of the PFC in ASD (Velmeshev et al., 2019), correctly predicting the original cell-type assign- ment (>86% accuracy; Figures 7A, S7A, and S7B). We next investigated whether this strategy would enable prediction of developmental state, restricting predictions to astrocytes or L2/3 PNs as they represent the most well-captured develop- mental trajectories (Figure 1D; Table S3O). For the 4–22 years Velmeshev et al. (2019) samples, predicted ages and actual ages correlate well (Spearman correlation = 0.77 for astrocytes, 0.59 for L2/3 PNs; Figure 7B). We also generated and integrated three additional PFC samples (Table S1B), from donors 261 and 443 days of age and gestational age (ga, in weeks) 39. We correctly estimated their developmental stages using predicted astrocyte nuclei ages (Figure 7B), whereas using L2/3 PNs we predicted that the ga39 sample was neonatal (Figures 7B and 7C). Our strategy shows improved age prediction accuracy and technical variability robustness (Figures S7C and S7D), al- lowing confident assessment of maturity. We also explored prediction of cell type and developmental age for contextualizing disease states by integrating an adult glioblastoma snRNA-seq dataset, identifying mesenchymal, neuronal, astrocyte-like, and ODC-like populations (Figure 7D). Around 18% of nuclei align with fetal astrocytes and OPCs (Fig- ure S7E; Table S6A) and likely correspond transcriptomically to progenitor cells and functionally to pluripotent apical glioma stem cells (Couturier et al., 2020), based on higher expression of embryonic stem cell network and cell-cycle pathway genes (Figure S7G).e, and organoid models of maturation trol samples (Velmeshev et al., 2019) and our PFC samples (ga39, and 261 and 3-day samples. Density of points indicated by orange contour lines (as also in wing astrocytes (GFAP+, white), neuronal nuclei (NeuN+, green), and neuronal and 9-month-old organoids, detecting BHLHE22 (gray) and ARHGAP26 (red). oids cultured for 5, 9, or 12 months. stnatal maturity versus those that do not (top left). Volcano plot: differentially re (green) PNs. Enriched GO terms for upregulated and downregulated DEGs PNs versus matched nearest neighbors in snRNA-seq data of normal PFC cells rain (blue) and organoids (purple). Enriched GO terms for upregulated DEGs in etwork connectivity with other upregulated non-TF genes. Left side of plot in- in parentheses. Cell 185, 4428–4447, November 10, 2022 4441 ll OPEN ACCESS ResourceWe next sought to identify the distribution of cell states and their developmental ages in an in vitro model of cortical devel- opment, by generating cerebral organoids cultured for 5, 9, or 12 months (Iefremova et al., 2017) and profiling them by snRNA-seq (Figures 7E, 7F, and S7E). These organoids con- tained the expected major cell types (astrocytes, OPCs, PNs, and INs; Figure 7F). With 12-month organoids, we identified non-neuronal nuclei mapping to mature ODCs and vascula- ture-associated cells, confirming the emergence of these cells with increased culture time (Kanton et al., 2019; Ormel et al., 2018). Organoid neurons mapped to most cortical layers for PNs and both CGE- and MGE-clusters for INs (Figures 7F and 7G). Strikingly, most organoid nuclei align with early fetal populations; however, with increasing organoid age more nuclei show signatures of early postnatal neurons, in particular for PNs and astrocytes, with 2% of PNs at 5 months aligned to early postnatal stages, compared with 15% for the 9- and 12-month organoids (Figures 7F and S7E). Based on this eval- uation of molecular equivalence using a real brain development reference, most organoid PNs remain immature. Notably, the less numerous mature PNs could not be discerned using tradi- tional analysis methods in the absence of our reference map (Figure S7H). To identify genes associated with increased maturity in in vitro neuronal development, we conducted differential expression analysis between organoid PNs classified as postnatally mature versus those that are not. Consistent with the temporal changes uncovered in our developmental reference, we found several potassium ion channels (e.g., KCNB2, KCNMA1) and neuro- transmitter receptors (e.g., GABRB1, GRIA4) that are also upre- gulated during normal postnatal development (Figure 7G; Table S6B). Furthermore, upregulated DEGs show a high overlap with devDEGs in up gene trends and are enriched in pathways that are hallmarks of neuronal and brain functional development, whereas downregulated DEGs are enriched in early differentia- tion and developmental processes (e.g., neuronal precursor cell proliferation, stem cell population maintenance; Figures 7G and S7I; Table S6C). By matching the mature PNs in organoids to their nearest neighbor nuclei in our developmental reference, we identified genes and their programs that are dysregulated in the postnatal maturity organoid PNs compared with their closest brain equiv- alents (Figure 7H; Table S6D). We detected downregulation of many genes (n = 7,497) enriched in canonical pathways for syn- aptic organization, structure, activity, and regulation (Table S6E). Similar to the previous analysis, this included several potassium ion channels (e.g.,KCND2,KCNQ5) and neurotransmitter recep- tors (e.g.,GRIN2B,GRIA1). Using network approaches based on estimated CREs in PNs and TF motif-binding sites, we ranked TFs by their likelihood of regulating these differences. Many of the highly ranked TFs (n = 31) correspond to devDEGs upregu- lated in normal brain development (Figure 7H) and were identi- fied as regulators ofmaturation-induced changes in ion transport in PNs (Figure 5K). Together, this suggests that organoids lack the synaptic networks to achieve PN maturation (Figure 7H) and highlights regulators that may be manipulated in the future to overcome these in vitro deficiencies. Overall, these integration analyses exemplify the value of our developmental map as a4442 Cell 185, 4428–4447, November 10, 2022reference for gauging cellular development in normal, disease, and in vitro contexts. DISCUSSION Here, we provide a thorough characterization of gene expression and chromatin accessibility dynamics throughout human PFC development at single-cell resolution, allowing the molecular investigation of critical developmental events, some previously only described using neuroimaging and microscopy studies (Sydnor et al., 2021). Although past studies of gene expression in bulk brain tissue showedmajor expression changes at the pre- natal-to-postnatal transition, it was not possible to determine whether they reflected differences in cell-type-specific tran- scriptional regulation or changes in cellular composition. Our atlas reveals that individual brain cell types respond with sub- stantial and specific transcriptional changes to the transition from fetal to postnatal environment, unique to this early stage. Characterizing the timing of when each neural cell subtype rea- ches an adult-like transcriptional state reveals surprising diver- sity in maturation timing across cell types, which will inform future efforts to link subtype-specific functions to the emergence of brain activities during development. By linking molecular dy- namics of key genes to the known timing of functional milestones they are associated with, we demonstrate the value of these maps for exploring molecular processes of brain development. Our analyses provide detailed characterization of postnatal cortical IN development andmaturation, unveiling the complexity of the neural subtypes and their development. By charting IN emergence, dynamics, and specialization, detecting poorly described neuronal subtypes, and resolving previously unknown developmental origins, these findings significantly extend our knowledge of human cortical IN maturation and composition. This developmental map provides a powerful resource for improving our understanding of brain-related disorders, including causative cell types, developmental windows of dysregulation, and regulators for multiple disorders. Our reference and stable integration technique enable investigation of cell-type-specific acceleration of maturation. Applying this approach to cerebral or- ganoids, which are increasingly used tomodel brain development and disorders (Sidhaye and Knoblich, 2021; Tian et al., 2020), suggests that in their current state these may be unsuitable to model postnatal onset disorders. Prediction of TFs that regulate neuronal maturation processes that are dysregulated in brain or- ganoids indicates regulatory pathways that may be pivotal in advancing neuronal maturity. Collectively, this reference consti- tutes an important advance in the understanding of brain cell states and dynamics in health and disease. Limitations of the study Although our study spans gestation to adulthood, the scarcity of biobanked samples, particularly in the third trimester, makes complete temporal coverage and controlling for inter-sample variability challenging, limiting interpretation of cell-type abun- dance changes. Although sex differences play a role in PFC maturation, with males typically developing executive functions later than females, we were unable to account for this due to sample availability limitations. We acknowledge that our ll OPEN ACCESSResourceapplication of velocity-based trajectory methods is outside the implied theory, where the robustness of velocity is untested. STAR+METHODS Detailed methods are provided in the online version of this paper and include the following: d KEY RESOURCES TABLE d RESOURCE AVAILABILITYB Lead contact B Materials availability B Data and code availability d EXPERIMENTAL MODEL AND SUBJECT DETAILS B Cell lines B Human subjects d METHOD DETAILS B Data reporting B Generation of cerebral organoids B Histology and imaging B RNAscope in-situ hybridization B Sample preparation B Library preparation d QUANTIFICATION AND STATISTICAL ANALYSIS B snRNA-seq analysis B snATAC-seq analysis d ADDITIONAL RESOURCES SUPPLEMENTAL INFORMATION Supplemental information can be found online at https://doi.org/10.1016/j.cell. 2022.09.039. ACKNOWLEDGMENTS This work was supported by the following grants: R.L.—National Health and Medical Research Council (NHMRC) Project Grant 1130168, NHMRC Investi- gator Grant 1178460, Silvia and Charles Viertel Senior Medical Research Fellowship, Howard Hughes Medical Institute International Research Scholar- ship, and Australian Research Council (ARC) LE170100225; S.F.—NHMRC Ideas Grant 1184421; I.V.—ARC Future Fellowship FT170100359, UNSW Sci- entia Fellowship, and NHMRC Project Grant RG170137; S.B.—NHMRC-ARC Dementia Research Development Fellowship 1111206; C.P.—Raine Founda- tion Priming Grant RPG66-21; J.M.P.—Silvia and Charles Viertel Senior Med- ical Research Fellowship, ARC Future Fellowship FT180100674. This work was supported by a Cancer Research Trust grant ‘‘Enabling advanced single cell cancer genomics inWA’’ and Cancer Council WA enabling grant. Genomic data were generated at the ACRF Centre for Advanced Cancer Genomics and Genomics WA. Human brain tissue was received from the UMB Brain and Tis- sue Bank at the University of Maryland, part of the NIH NeuroBioBank. The glioblastoma sample was procured and provided by the AGOG biobank, funded by CINSW grant SRP-08-10. L.M. was a fellow of The Lorenzo and Pa- melaGalli Medical Research Trust.We thank Ankur Sharma andGregNeely for valuable feedback. The graphical abstract and elements of Figure 1A were created with BioRender. AUTHOR CONTRIBUTIONS R.L. conceived the study. R.L., S.F., C.A.H., R.K.S., and D.P. designed exper- iments and analyses. Sample preparation and data collection, R.K.S., D.P., D.B.V.-L., L.M., C.P., O.C., and J.M.P.; sequencing, D.P. and J.P.; data anal- ysis and interpretation, C.A.H., S.F., R.K.S., D.P., S.B., O.C., C.P., A.A.-F., and R.L.; algorithm implementation, C.A.H., S.F., and J.M.P. Manuscript was writ-ten by R.K.S., S.F., C.A.H., D.P., S.B., and R.L. All authors approved of and contributed to the final manuscript. 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Cell 109, 61–73.Cell 185, 4428–4447, November 10, 2022 4447 ll OPEN ACCESS ResourceSTAR+METHODSKEY RESOURCES TABLEREAGENT or RESOURCE SOURCE IDENTIFIER Antibodies mouse anti-MAP-2 Millipore Cat# AB5622; RRID: AB_91939 rabbit anti-GFAP Dako Cat# ZO33429-2; RRID: AB_10013482 APC-linked mouse anti-NeuN Novus Biologicals Cat# NBP1-92693APC; RRID: AB_2894834 AlexaFluor 555, goat anti-mouse IgG (H&L) Abcam Cat# ab150114; RRID: AB_2687594 AlexaDluor 647, donkey anti-rabbit IgG (H&L) Abcam Cat# ab150063; RRID: AB_2687541 Chemicals, peptides, and recombinant proteins Essential 8 medium Thermo Fisher Cat# A1517001 Y-27632 2HCl Selleckchem Cat# S1049 DMEM/F12 medium Thermo Fisher Cat# 11320033 Neurobasal medium Thermo Fisher Cat# 21103049 N2 MAX Media Supplement (100x) R&D Systems Cat# AR009 MACS NeuroBrew-21 Miltenyi Biotec Cat# 130-093-566 MEM Non-Essential Amino Acids Solution (100x) Thermo Fisher Cat# 11140050 GlutaMAX Supplement Thermo Fisher Cat# 35050061 Penicillin-Streptomycin (10,000 U/ml) Thermo Fisher Cat# 15140122 Heparin Sigma Cat# H3149 LDN-193189 Cayman Chemical Cat# 19396 A83-01 Cayman Chemical Cat# 9001799 IWR-1-endo Adooq Bioscience Cat# A12737 Cultrex 3D RGF BME R&D Systems Cat# 3445-005-001 MACS NeuroBrew-21 w/o Vitamin A Miltenyi Biotec Cat# 130-097-263 Insulin solution human Sigma Cat# I9278 DAPI Cayman Chemical Cat# 14285 RNAsin Plus RNAse inhibitor Promega Cat# N2615 Critical commercial assays Chromium Single cell 30 GEM, Library & Gel Bead Kit v3 10x Genomics PN: 1000075 ATAC-seq NextGEM kit 10x Genomics PN: 1000175 Experimental models: Cell lines Human: Passage 40 H9 ES cells (WA09 cell line) WiCell RRID: CVCL_9773 Deposited data snRNA-seq, snATAC-seq This study GEO: GSE168408 Bulk RNA-seq Li et al., 2018 http://development.psychencode.org scRNA-seq data Velmeshev et al., 2019 https://autism.cells.ucsc.edu Software and algorithms Original code used for data analysis This paper https://doi.org/10.5281/zenodo.7113422 ImageJ (Fiji) Schindelin et al., 2012 https://imagej.net/software/fiji Genome assembly Genome Reference Consortium https://www.ncbi.nlm.nih.gov/grc/human (hg19/GrChr37.p13) Gene annotation Harrow et al., 2012 https://www.gencodegenes.org/ human/release_19.html (Continued on next page) e1 Cell 185, 4428–4447.e1–e14, November 10, 2022 Continued REAGENT or RESOURCE SOURCE IDENTIFIER Cell Ranger 10x Genomics https://support.10xgenomics.com/ single-cell-gene-expression/software/ downloads/3.1 Cell Ranger-ATAC 10x Genomics https://support.10xgenomics.com/single- cell-atac/software/downloads/1.2 scanpy Wolf et al., 2018 https://pypi.org/project/scanpy/1.6.0 anndata Wolf et al., 2018 https://pypi.org/project/anndata/0.7.4 scrublet Wolock et al., 2019 https://pypi.org/project/scrublet/0.2.2 Harmony Korsunsky et al., 2019 https://pypi.org/project/harmonyTS/0.1.4 BBKNN Polanski et al., 2020 https://pypi.org/project/bbknn/1.5.1 Hotspot DeTomaso and Yosef, 2021 https://github.com/yoseflab/Hotspot/ tree/0.9.1_release loompy Linnarsson Lab https://pypi.org/project/loompy/3.0.6 scVelo Bergen et al., 2020 https://pypi.org/project/scvelo/0.2.2 CytoTRACE via CellRank Gulati et al., 2020 https://pypi.org/project/cellrank/1.5.1 edgeR Bioconductor; Robinson et al., 2010 https://bioconductor.org/packages/ 3.12/bioc/html/edgeR.html (v3.31.4) Glimma Bioconductor; Su et al., 2017 https://bioconductor.org/packages/ 3.13/bioc/html/Glimma.html (v2.2.0) pyGAM Serve´n et al., 2018 https://pypi.org/project/pygam/0.8.0 scipy Virtanen et al., 2020 https://pypi.org/project/scipy/1.7.1 connectomeDB2020 Human Connectome Project https://www.humanconnectome.org/ software/connectomedb gProfiler Raudvere et al., 2019 https://biit.cs.ut.ee/gprofiler_archive3/ e102_eg49_p15/gost TransportDB Ren et al., 2007 http://www.membranetransport.org/ transportDB2/index.html fgsea Bioconductor; Korotkevich et al., 2016 https://bioconductor.org/packages/ 3.13/bioc/html/fgsea.html (v1.17.1) SpatialLIBD Maynard et al., 2021 https://bioconductor.org/packages/ release/data/experiment/html/ spatialLIBD.html (v1.0) Symphony Kang et al., 2021) https://CRAN.R-project.org/ package=symphony (v1.0) DisGeNET Pin˜ero et al., 2020 https://www.disgenet.org/ (v7) disgenet2r Pin˜ero et al., 2020 https://bitbucket.org/ibi_group/ disgenet2r/src/master/r (v0.99.2) scvi-tools Lopez et al., 2018 https://pypi.org/project/scvi-tools/0.11.0 reticulate RStudio, Tomasz Kalinowski https://github.com/rstudio/reticulate/ tree/release/1.20 UMAP via uwot McInnes et al., 2018 https://cran.r-project.org/src/contrib/ Archive/uwot (v0.1.10) Seurat Hao et al., 2021 https://github.com/satijalab/seurat/ releases/tag/v4.0.3 FNN CRAN https://CRAN.R-project.org/ package=FNN (v1.1.3) scran Bioconductor; Lun et al., 2016 https://bioconductor.org/packages/ 3.12/bioc/html/scran.html (v1.18.5) ArchR Granja et al., 2021 https://github.com/GreenleafLab/ ArchR/tree/release_1.0.1 (Continued on next page) ll OPEN ACCESS Cell 185, 4428–4447.e1–e14, November 10, 2022 e2 Resource Continued REAGENT or RESOURCE SOURCE IDENTIFIER MACS2 Zhang et al., 2008 https://pypi.org/project/MACS2/2.2.7.1 IDR Li et al., 2011 https://anaconda.org/bioconda/idr (v2.0.4) sklearn Buitinck et al., 2013 https://pypi.org/project/scikit-learn/0.24.0 JASPAR TF motifs Khan et al., 2018 https://jaspar2018.genereg.net/ TF motif cluster Vierstra et al., 2020 https://www.vierstra.org/resources/ motif_clustering (v1.0) igraph CRAN https://CRAN.R-project.org/ package=igraph (v1.2.6) CellRank Lange et al., 2020 https://pypi.org/project/cellrank/1.5.1 RRHO2 Bioconductor; Cahill et al., 2018 https://www.bioconductor.org/packages/ 2.13/bioc/html/RRHO.html ll OPEN ACCESS ResourceRESOURCE AVAILABILITY Lead contact Further information and requests for resources and reagents should be directed to andwill be fulfilled by the lead contact, Ryan Lister (ryan.lister@uwa.edu.au). Materials availability This study did not generate new unique reagents. Data and code availability d Single-nuclei RNA-seq and single-nuclei ATAC-seq data have been deposited at GEO under accession number GEO: GSE168408 and are publicly available as of the date of publication. Accompanying interactive browsers for this study are avail- able at http://brain.listerlab.org. All data for the Velmeshev et al. study is publicly available through the Sequence Read Archive, accession number PRJNA434002, and all data for Li et al. (2018) is publicly available through http://development. psychencode.org. d All original code has been deposited at Zenodo and is publicly available as of the date of publication. DOIs are listed in the key resources table. d Any additional information required to reanalyze the data reported in this work paper is available from the lead contact (RL) upon request.EXPERIMENTAL MODEL AND SUBJECT DETAILS Cell lines Commercial human embryonic stem cell line H9 was purchased from WiCell and authenticated by the provider. H9 cells were culti- vated in E8 media (Gibco) and passaged using EDTA (Sigma). Human subjects De-identified human prefrontal cortex (PFC) samples from neurotypical individuals of various ages from mid-gestation through to adulthood and one individual with ASD were obtained through collaboration with NIH NeuroBioBank in the United States and analyzed under a protocol approved by the University of Western Australia Human Research Ethics Committee (RA/4/20/6394). Samples were standardized as best as possible through brain region and age. Brain regions include Brodmann area 8 (BA8), Brod- mann area 9 (BA9), Brodmann area 10 (BA10), and Brodmann area 46 (BA46), corresponding regions of the dorsolateral and medial PFC in the left and right hemispheres (see Table S1B). Age, developmental stage, and sex of each sample is detailed in Table S1B. Note, it was not possible to source samples between gestational ages (ga) ga24 and ga34, largely corresponding to the 3rd trimester where samples could not be obtained due to major ethical, practical, and regulatory challenges. Nonetheless, we were able to infer broad trends across development, which includes this period. The primary glioblastoma sample was resected from an adult female and was obtained through the Australian Genomics and Clinical Outcomes of High Grade Glioma (AGOG) biobank under protocols approved by the Northern Sydney Local Health District Human Research Ethics Committee (0809-198M) and Sir Charles Gairdner and Osborne Park Health Care Group Human Research Ethics Committee (2008-094), and analyses approved by the University of Western Australia Human Research Ethics Committee (RA/4/20/5615). Organoid experiments and derivatione3 Cell 185, 4428–4447.e1–e14, November 10, 2022 ll OPEN ACCESSResourcefrom established embryonic stem cell lines were approved by the University ofWestern Australia Human Research Ethics Committee (2021/ET000182). METHOD DETAILS Data reporting This study complies with the MINSEQE guidelines for reporting high throughput sequencing experiments. No statistical methods were used to predetermine sample size. The experiments were not randomized and investigators were not blinded to allocation dur- ing experiments and outcome assessment. No replication study was performed, but key results were validated using complementary techniques. Subjects were excluded when records indicated that the individual suffered from brain disorders or diseases. Generation of cerebral organoids Cerebral organoids were generated from H9 embryonic stem (ES) cells following an established protocol (Iefremova et al., 2017). In brief, ES cells were dissociated into single cells and plated in U-shaped ultra low attachment 96-well plates (Corning) at a density of 9,000 cells per well in E8 media (Gibco) with 50 mM Y-27632 (Selleckchem). Media was changed to only E8 2 days later and to a neural induction media another 2 days later when embryoid bodies were transferred to ultra low attach- ment 24 well plates (Corning). Neural induction media contained DMEM/F12 and Neurobasal (both Gibco) at a 50:50 ratio with 1:200 N2 supplement (R&D Systems), 1:100 Neurobrew supplement (Miltenyi), 1:200 non essential amino acids (Gibco), 1:100 Glutamax (Gibco), 1:100 Pen/Strep (Gibco), 10 mg/ml Heparin (Sigma), 200 nM LDN-193189 (Cayman Chemical), 500 nM A83- 01 (Cayman Chemical), and 2 mM IWR-1 (Adooq Bioscience). After 4 days, LDN-193189, A83-01 and IWR-1 were removed from the media, and organoids were embedded in a 20 ml volume of Cultrex 3D RGF BME (R&D Systems) on day 12. Media was switched to Maintenance media contained of DMEM/F12 and Neurobasal 50:50 ratio with 1:200 N2 supplement, 1:100 Neuro- brew supplement without vitamin A (Miltenyi), 1:100 Glutamax, 1:100 Pen/Strep, 1:2,500 human Insulin solution (Sigma), and 1:350,000 beta-Mercaptoethanol (Sigma). After 6 days, Neurobrew in the media was switched to the vitamin A containing variant and organoids were moved to an orbital shaker (Instrument Choice) for constant agitation at 75 rpm with media changes every 3 days until analysis. Histology and imaging Organoids were fixed in 4% PFA in PBS for 1 h at room temperature (RT) and incubated in 30% sucrose (Sigma) in PBS at 4C over- night before being frozen at -80C and embedded in OCT compound (VWR) for cryosectioning at 20 mm. Sections were recovered on Superfrost glass slides (Menzel) and stored at -80C until processed for immunostaining. Sections were blocked in PBS with 2% FCS (Gibco), 1%BSA, 0.1% Triton X-100, and 0.05% Tween-20 (all Sigma) for 2 h at RT and incubated with primary antibodies over- night at 4C. After two washes with PBS, secondary antibodies were incubated for 2 h at RT before being counterstained with DAPI (1 mg/ml, Cayman Chemical) after 3 additional washes. Sections were mounted with fluorescence mounting medium (Agilent) and imaged on a Nikon C2+ confocal microscope. Primary antibodies: GFAP (Dako ZO33429-2) used 1:750, MAP-2 (Millipore AB5622) used 1:400. Conjugated antibody: NeuN (Novus Biologicals NBP1-92693APC) used 1:500. Secondary antibodies: anti- mouse (Abcam 150114) used 1:1,000, anti-rabbit (Abcam ab150063) used 1:1,000. RNAscope in-situ hybridization Flash-frozen brain tissue or organoids were sectioned at 20 mm using a Leica CM3050S cryostat and frozen overnight on SuperFrost Plus glass slides (Thermo Scientific). Sections were fixated with 4%PFA for 15 minutes and further processed following the standard protocol for RNAscope Multiplex Fluorescent Reagent Kit v2 Assay (Advanced Cell Diagnostics), using Opal Polaris 480, Opal 570, and Opal 650 dyes (Akoya Biosciences) with the following RNAscope 2.5 probes (all Advanced Cell Diagnostics): Hs-ADARB2-C3, Hs-ARHGAP26, Hs-BHLHE22-C3, Hs-CEMIP-C2, Hs-FGF13, Hs-KCNH1-C2, Hs-LAMP5-C2, Hs-LHX6, Hs-NDNF-C3, Hs-NOS1- C2, Hs-NPY-O1, Hs-SST-C3, Hs-TACR1-C3, Hs-TAFA4-C1. Sections were counterstained with DAPI, mounted with ProLong Gold Antifade (Thermo Scientific) and imaged on a Nikon C2+ confocal microscope. Sample preparation Nuclei isolation for single nucleus RNA-seq (snRNA-seq) using fluorescence-activated nuclei sorting (FANS) A single nuclei suspension was obtained following an established protocol for nuclei isolation from small amounts of tissue (Deni- senko et al., 2020). Briefly, tissue samples were lysed in a 2.5 ml lysis buffer (10 mM Tris-HCl, 1% Nonident P40, 3 mM MgCl2, and 10mMNaCl) with 0.2 U/ml RNasin Plus RNase Inhibitor (Promega) for 17min on ice. After lysis, 2.5 ml of ice-cold PBSwas added to the lysis buffer and sample for a final volume of 5 ml. Tissue was homogenized using a Pasteur pipette until no large pieces were visible. The homogenate was then filtered through a 30 mm filter (Miltenyi) and centrifuged at 2,000 x g for 5 minutes at 4C. Supernatant was removed and the pellet was resuspended in 400 ml wash buffer (1x PBS with 1% BSA) containing DAPI at a 1:10,000 dilution and with 0.2 U/ml RNasin Plus RNase Inhibitor (Promega). DAPI-positive nuclei were isolated by sorting using a BD Influx to obtain a final concentration of 500 - 800 nuclei/ml in wash buffer with 0.2 U/ml RNasin Plus RNase Inhibitor (Promega) (Figure S1B).Cell 185, 4428–4447.e1–e14, November 10, 2022 e4 ll OPEN ACCESS ResourceNuclei isolation for snRNA-seq using sucrose gradient isolation Nuclei from two samples, ga39 and the 14 year old ASD sample, were isolated with a sucrose gradient method. Briefly, tissue sam- ples were lysed in 400 ml of lysis buffer (10 mM Tris-HCl, 1%Nonident P40, 3 mMMgCl2, and 10mMNaCl) with 0.2 U/ml RNasin Plus RNase Inhibitor (Promega) in 1.5 ml tubes and broken down with a pellet pestle. Tissue was dissociated by passing through a polished silanized Pasteur pipette 3-4 times then incubated on ice for 10 min. Dissociation with a Pasteur pipette was repeated at 5 min and 10 min. After incubation, the dissociated tissue was added to 2.5 ml of wash buffer (1x PBS with 1%BSA) in a 15 ml falcon tube. The sample was then passed through a 30 mmcell strainer (Miltenyi) into a 50ml falcon tube and centrifuged for 5minutes at 500 x g at 4C in a swinging bucket centrifuge. Following centrifugation, the supernatant was removed and the tissue was resuspended in 100 ml of wash buffer for every 30 mg of tissue used. Using only 100 ml of the resuspended sample, 180 ml of 1.8 M sucrose solution (Nuclei PURE kit, Sigma) was added to the sample and homogenized using a P1000 micropipette. 1 ml of 1.3 M sucrose solution (Nuclei PURE kit, Sigma) was placed at the bottom of a 2ml Eppendorf tube and the 280 ml of the nuclei suspension mixed with 1.8M sucrose was slowly layered on top of the 1.3 M sucrose solution. The sucrose gradient was centrifuged for 10 minutes at 3000 x g at 4C in a swinging bucket centrifuge. After centrifugation, the debris from the top of the sucrose gradient was removed with a Kimwipe wrapped around a spatula. The remaining supernatant was removed with a P1000 micropipette. Nuclei were resus- pended in 50 ml of wash buffer. 10 ml of the suspension was stained with DAPI (1:10,000) and used to count the nuclei concentration. Nuclei isolation for single nucleus assay for Transposase-Accessible chromatin using sequencing (snATAC-seq) Nuclei were isolated following the sucrose gradient isolation described above for snRNA-seq, with the addition of 0.01% digitonin added to the lysis buffer and incubated for 3 minutes after the final dissociation step. Library preparation snRNA-seq Single nuclei suspensions were loaded on 10X Genomics Chromium Chip B (10x Genomics) to generate single-cell GEMs. Single- nuclei RNA-Seq libraries were prepared using the Chromium Single Cell 3’ Reagents kit as per the manufacturer’s instructions. The protocol was followed as outlined in the user guide, with the exception of performing 18 cycles for cDNA amplification and a capture target of 10,000 nuclei per sample. Library size distribution and abundance was assessed with aD1000 ScreenTape (Agi- lent) and their concentration quantitated on a C1000/CFX96 qPCR system (Bio-Rad) using Luna Universal qPCR mix (NEB) and Tru- seq PCR primers (Illumina). Libraries were sequenced on either a NextSeq 550 or a NovaSeq 6000 (Illumina) in paired-end mode (read1: 28 cycles, read 2: 91 cycles, index1: 8 cycles) to generate approximately 200 M reads per sample. snATAC-seq Single nuclei suspensions were loaded on 10X Genomics Chromium Chip E (10x Genomics) to generate single-cell GEMS. Single- nuclei ATAC-seq libraries were prepared using the Chromium Single Cell ATAC v1 Reagents kit as per the manufacturer’s instruc- tions, with a capture target of 10,000 nuclei per sample. Library size distribution and abundance was assessed with a D5000 ScreenTape (Agilent) and their concentration quantitated on a C1000/CFX96 qPCR system (Bio-Rad) using Luna Universal qPCR mix (NEB) and Truseq PCR primers (Illumina). Libraries were sequenced on a NovaSeq 6000 (Illumina) in paired-end mode (read1: 50 cycles, read2: 49 cycles, index1: 8 cycles, index2: 16 cycles) to generate approximately 250 M reads per sample. QUANTIFICATION AND STATISTICAL ANALYSIS All statistical analyses were performed in R v4.0.5 or Python v3.8. snRNA-seq analysis Sequence Alignment and UMI counting Cellranger (v3.1.0) analysis pipeline, with default parameters, was used to process raw reads. Briefly, Cellranger mkfastq was used to convert raw base call (BCL) files of the snRNA-seq libraries into FASTQ files. A pre-mRNA transcriptomewas built using the cellranger mkref command starting with the refdata-cellranger-hg19-3.0.0 transcriptome as per the instructions provided by 10x Genomics. The Cellranger count command was used for alignment, filtering, barcode counting, and unique molecular identifier counting (Tables S1C and S1D). Nuclei and gene quality control Filtered count matrices from each sample were combined into a scanpy (v1.6.0) anndata (v0.7.4) object for processing and filtering, and unless noted otherwise, default parameters were used (Wolf et al., 2018). Genes not observed inR5 nuclei across all batches were removed and potential nuclei doublets were removed using scrublet (v0.2.2) with 10 principal components for each batch individually (Wolock et al., 2019). On a per sample basis, nuclei with gene counts <3 median absolute deviations (MADs) and <300 gene counts were removed. Nuclei with ribosomal or mitochondrial gene count percentages >20 percent or >3 per sample MADs were removed (Table S1C). Highly expressed MALAT1 gene and ribosomal and mitochondrial genes were removed. Finally, we investigated the relationship between sample quality and PMI and found them to be uncorrelated (Figure S1F). Data integration for dimension reduction and clustering A developmental reference was integrated by downsampling to 1,000 Unique Molecular Identifier counts (UMIs) per nucleus to re- move sampling bias from differing sequencing depths between batches. Downsampling was carried out by randomly sampling,e5 Cell 185, 4428–4447.e1–e14, November 10, 2022 ll OPEN ACCESSResourcewithout replacement, 1,000 UMIs from the total UMIs for a given nucleus, and nuclei with less than 1,000 total UMIs were removed. The 1,000 UMIs cutoff was selected to limit the number of nuclei removed and to include enough counts per nuclei to be informative, which was previously shown to be at 1,000 UMIs when the accuracy of cell type classification plateaus (Heimberg et al., 2016). Analysis was also performed with nuclei with less than 1,000 UMIs included. When included, these nuclei cluster together, exhibit no apparent age-related progression, and resemble a spectrum of cell states from a mixture of cell types (Figure S1E), making them difficult to categorize for further analysis and warranting removal. Downsampled data was used for dimension reduction and clustering, while the full count matrix was used for all other analyses unless noted otherwise. Post downsampling, the count matrix was scaled to Counts Per Million (CPM), natural log plus one transformed, andmatrices from all batches were combined. Five thousand Highly Variable Genes (HVGs) were selected, and data dimensions were reduced via prin- cipal component analysis (PCA) to components explaining 50% of the variance. A neighborhood graph was constructed using scanpy preprocessing neighbors function with 25 neighbors on the reduced components, and a 2-dimensional Uniform Manifold Approximation and Projection (UMAP) embedding was generated (McInnes et al., 2018). Subclusters were generated via scanpy Lei- den clustering at a resolution of 7.0 with the neighborhood graph serving as the basis (Traag et al., 2019). At the whole-tissue level, 63 Leiden clusters were identified. Inhibitory interneuron (IN) subclustering was performed using the same workflow but with 4,000 HVGs and a Leiden clustering resolution of 5.0. There were 36 IN Leiden clusters identified, replacing 13 IN whole-tissue clusters and bringing the total Leiden cluster count to 86. Alternative batch correction methods Harmony (v0.1.0) (Korsunsky et al., 2019) and BBKNN (v1.5.1) (Polanski et al., 2020) were also investigated as possible batch cor- rections.While thesemethods resulted in integrated batches, the integrations lacked a clear progression of age-related development (Figure S6C). These corrections also fully integrated the poor quality nuclei that our downsampling approach readily differentiated. Harmony and BBKNN were run using default parameters within the scanpy external application programming interface. Except for the downsampling of UMIs and removal of nuclei under 1,000 UMIs, the data was processed using the same pipeline outlined in nuclei and gene quality control and data integration for dimension reduction and clustering. Cluster annotation PNwere classified based on the expression of marker genesCUX2, RORB, THEMIS, and TLE4, while IN were classified based on the expression of marker genes PVALB, SST, VIP, and ID2. Using this approach, we identified 18 major clusters, including 5 PN major clusters (immature principal neurons [PN-dev], layer 2 and 3 [L2/3-CUX2], layer 4 [L4-RORB], and layer 5 and 6 [L5/6-THEMIS, L5/6- TLE4]), 6 IN major clusters (early developing MGE [MGE-dev], early developing CGE [CGE-dev], inhibitor of DNA binding 2-expressing [ID2], vasoactive intestinal polypeptide-expressing [VIP], somatostatin-expressing [SST], and parvalbumin-expressing [PV]), astrocytes [Astro], MBP+ oligodendrocyte precursor cells and mature oligodendrocytes [Oligo], oligodendrocyte precursor cells [OPCs], microglia [Micro], and vasculature [Vas] (which encompasses endothelial, pericytes, fibroblast-like, and pericytes/ smooth muscle cells) (Figure 1B). In cases where several subclusters within a major cluster could be grouped based on additional common markers, these were given a common subcluster name. For example, using this strategy, L5/6-THEMIS PNs could be further subclustered into L5/6-THEMIS-NTNG2 and L5/6-THEMIS-CNR1 (Figure S2A). Membership of Leiden subclusters in each major cluster is listed in Tables S2A–S2C. Principal neuron annotation Immature principal neurons (PNs). PN-developing (PN dev) (subcluster 13). Marker Genes - MEIS2 (Bayatti et al., 2008; Hoerder- Suabedissen and Molna´r, 2015), UNC5D (Cooper, 2014; Miyoshi and Fishell, 2012), FOXG1 (Cooper, 2014; Miyoshi and Fishell, 2012), LINC01158 (Fan et al., 2018), EIF1B (Bayatti et al., 2008; Hoerder-Suabedissen and Molna´r, 2015), MEF2C (Cooper, 2014), DCX (Herrero-Navarro et al., 2021). Principal neurons L2-3. Immature. L2/3_CUX2_dev-1 (subcluster 11), L2/3_CUX2_dev-2 (subcluster 15), L2/3_CUX2_dev-3 (subcluster 22), L2/3_CUX2_dev-4 (subcluster 32), L2-3_CUX2_dev-5 (subcluster 36), L2/3_CUX2_dev-6 (subcluster 43), L2/ 3_CUX2_dev-fetal (subcluster 46). Marker Genes - SATB2 (Alcamo et al., 2008; Britanova et al., 2008), FAM19A2 (Fan et al., 2018), CUX2 (Fan et al., 2018), FGF13 (Puranam et al., 2015; Wu et al., 2012), MEF2C (Leifer et al., 1997), STMN2 (Colantuoni et al., 2011; Tomita et al., 2012). Mature. L2_CUX2_LAMP5 (subcluster 8), L2_CUX2_LAMP5_dev (subcluster 34), L3_CUX2_PRSS12 (subcluster 31). Marker Genes - CUX2 (Cubelos et al., 2015), CAMK2A (Tochigi et al., 2008). Principal neurons L4. Immature. L4_RORB_dev-1 (subcluster 57), L4_RORB_dev-2 (subcluster 10), L4_RORB-fetal (subcluster 18). Marker Genes – RORB (Oishi et al., 2016), SATB2 (Britanova et al., 2008), FOXP2 (Ferland et al., 2003), FOXP1 (Ferland et al., 2003). Mature. L4_RORB_LRRK1 (subcluster 17), L4_RORB_MET (subcluster 28), L4_RORB_MME (subcluster 44). Marker Genes - FOXP2 (Baker et al., 2018; Brunjes and Osterberg, 2015), RORB (Lake et al., 2018). Principal neurons L5/6 THEMIS. Immature. L5/6_THEMIS_dev-1 (subcluster 21), L5/6_THEMIS_dev-2 (subcluster 25). Marker Genes – THEMIS (Hodge et al., 2019), SATB2 (Britanova et al., 2008), FOXP1 (Ferland et al., 2003). Mature. L5/6_THEMIS_CNR1 (subcluster 40), L5/6_THEMIS_NTNG2 (subcluster 55). Marker Genes - THEMIS (Hodge et al., 2019). Principal neurons L5/6 TLE4. Immature. L5/6_TLE4_dev (subcluster 24). Marker Genes - SOX5 (Galazo et al., 2016), TLE4 (Galazo et al., 2016), FOXP2 (Ferland et al., 2003), NFIB (Galazo et al., 2016), BCL11B (Britanova et al., 2008), HS3ST4 (Hodge et al., 2019), TUBA1A (Aiken et al., 2017). Mature. L5/6_TLE4_SCUBE1 (subcluster 26), L5/6_TLE4_SORCS1 (subcluster 27), L5/6_TLE4_HTR2C (subcluster 45).Cell 185, 4428–4447.e1–e14, November 10, 2022 e6 ll OPEN ACCESS ResourceMarker Genes - TLE4 (Galazo et al., 2016), FOXP2 (Galazo et al., 2016), NFIB (Galazo et al., 2016), BCL11B (Aiken et al., 2017), HS3ST4 (Lake et al., 2018). Inhibitory interneuron annotation IN prefix to Leiden cluster identifiers indicates cluster was identified with GABAergic interneuron clustering described in data integration for dimension reduction and clustering. Immature GABA interneurons. MGE_dev-1 (subcluster IN6), MGE_dev-2 (subcluster IN23), CGE_dev (subclusters IN8). Marker Genes - LHX6 (Fan et al., 2018; Hu et al., 2017), SOX6 (Hu et al., 2017), DLX1 (Fan et al., 2018; Hu et al., 2017), DLX2 (Fan et al., 2018; Hu et al., 2017), DCX (Herrero-Navarro et al., 2021), GAD1 (Lake et al., 2018). GABA PVALB. PV_WFDC2 (subcluster IN0), PV_dev (subcluster IN7), PV_SULF1 (subcluster IN18), PV_SULF1_dev (subcluster IN29). Marker Genes - LHX6 (Hu et al., 2017), SOX6 (Hu et al., 2017), PVALB (Ferguson and Gao, 2018), SLIT2 (Andrews et al., 2008). GABA PVALB SCUBE3. PV_SCUBE3 (subcluster IN21), PV_SCUBE_dev (subcluster IN30). Marker Genes - SCUBE3 (Hodge et al., 2019). GABA SST. SST_TH (subcluster IN31), SST_B3GAT2 (subcluster IN10), SST_STK32A (subcluster IN12), SST_BRINP3 (subcluster IN28), SST_NPY (subcluster IN35), SST_ADGRG6 (subcluster IN5), SST_ADGRG6_dev (subcluster IN15), SST_CALB1 (subcluster IN14), SST_CALB1_dev (subcluster IN12), PV_SST (subcluster IN27). Marker Genes - SST (Tasic et al., 2018), LHX6, SOX6 (Hu et al., 2017), ERBB4 (Vullhorst et al., 2009), RELN (Lake et al., 2018). GABA ID2. LAMP5_CCK (subcluster IN4), LAMP5_NDNF (subcluster IN11), CCK_SORCS1 (subcluster IN17), ID2_CSMD1 (subcluster IN22), CCK_RELN (subcluster IN26), CCK_SYT6 (subcluster IN32), ID2_dev (subcluster IN25). Marker Genes - RELN (Overstreet-Wadiche and McBain, 2015), SV2C (Boldog et al., 2018), KIT (Mickelsen et al., 2019), CXCL14 (Boldog et al., 2018), LAMP5 (Mickelsen et al., 2019), CCK (Lake et al., 2018). LAMP5_NOS1. LAMP5_NOS1 (subcluster IN13). Marker Genes - NOS1 (Tricoire et al., 2010), CA1 (Hodge et al., 2019). GABA VIP. VIP_HS3ST3A1 (subcluster IN2), VIP_CHRM2 (subcluster IN3), VIP_KIRREL3 (subcluster IN19), VIP_CRH (subcluster IN9), VIP_ADAMTSL1 (subcluster IN20), VIP_ABI3BP (subcluster IN16), VIP_DPP6 (subcluster IN24), VIP_PCDH20 (subcluster 34), VIP_dev (subcluster IN33). Marker Genes - GAD1 (Lake et al., 2018), VIP (Tremblay et al., 2016), CALB2 (Darmanis et al., 2015). Glial cell annotation Astrocytes. Immature. Astro_dev-1 (subcluster 2), Astro_SLC1A2_dev (subcluster 14), Astro_dev-2 (subcluster 19), Astro_dev-3 (subcluster 54), Astro_dev-4 (subcluster 56), Astro_dev-5 (subcluster 60). Marker Genes - MEIS2 (Fan et al., 2018), LINC01158 (Fan et al., 2018), EIF1B (Fan et al., 2018), SLC1A3 (Batiuk et al., 2020), SLC1A2 (Jolly et al., 2019). Mature. Astro_SLC1A2 (subcluster 1), Astro_GFAP (subcluster 16). Marker Genes - AQP4 (Batiuk et al., 2020), SLC1A2 (Jolly et al., 2019), SLC1A3 (Batiuk et al., 2020). Oligodendrocyte precursor cells (OPCs). OPC (subcluster 0), OPC_dev (subcluster 38). Marker Genes - PDGFRA (Rivers et al., 2008), OLIG1 (Zhou and Anderson, 2002), OLIG2 (Zhou and Anderson, 2002). Oligodendrocytes (ODCs). OPC_MBP (cluster 49), Oligo_mat (subcluster 3), Oligo-1 (subcluster 4), Oligo-2 (subcluster 6), Oligo-3 (subcluster 9), Oligo-4 (subcluster 35), Oligo-5 (subcluster 50), Oligo-6 (subcluster 61), Oligo-7 (subcluster 62). Marker Genes -MAG (Vale´rio-Gomes et al., 2018), MOG (Vale´rio-Gomes et al., 2018), PLP1 (Turnescu et al., 2018). Microglia. Micro (subcluster 5), Micro_out (subcluster 53). Marker Genes - C1QA (Fonseca et al., 2017). Vasculature. Vas_TBX18 (cluster 51), Vas_PDGFRB (subcluster 58), Vas_CLDN5 (subcluster 59). Marker Genes – Pericytes and smooth muscle cells: PDGFRB (Vanlandewijck et al., 2018), Endothelial cells: CLDN5 (Vanlandewijck et al., 2018), Fibroblast-like cells: TBX18 (Vanlandewijck et al., 2018). Identification of poor quality cells (subcluster 42) As has been previously noted, we identified a subcluster with high expression of NRNG and THY1 (Velmeshev et al., 2019; Figure S6F). We additionally observed high mitochondrial percentages per nuclei within this subcluster, potentially indicating the cluster contained nuclei of poor quality (Figure S4J). In order to assess the quality of the nuclei in this cluster versus potential contam- ination from background reads, pseudo-cells were generated by sub-sampling from a pseudo-bulked count matrix. More specif- ically, each batch’s unfiltered count matrix (containing both called and uncalled cells) from 10x Genomics Cell Ranger (v3.1.0) was summed along the gene axis. Pseudo-bulked genes were removed to match genes post preprocessing (see nuclei and gene quality control), and pseudo-bulked counts were randomly sub-sampled, without replacement, to 1,000 UMIs. Quantity and batch origin were selected to replicate cells in the labeled poor-quality subcluster. Pseudo-cells were then incorporated into the pipeline used for whole tissue clustering (see data integration for dimension reduction and clustering), and resulting clusters were checked for overlapping memberships of previously called cell types (Figures S6D and S6E). Using this method, we observed that the previously identified subcluster high in NRGN and THY1 now contained most of the pseudo-cells, indicating the quality of these nuclei is similar to background or ambient RNA. Previous studies have reported this population of nuclei as a new PN population relevant to autism (Velmeshev et al., 2019) and schizophrenia (Ruzicka et al., 2020). However, these studies also reported high expression of mitochon- drial genes and similar gene expression profiles as our study, suggesting these nuclei may also represent mostly ambient RNA. Hotspot analysis of gene coexpression Hotspot (v0.9.1) is a tool for identifying highly correlated gene modules in a single-cell dataset (DeTomaso and Yosef, 2021). Hotspot computes gene modules by finding informative genes with high local autocorrelation, evaluating the pairwise correlation between genes, and clustering the results in a gene-gene affinity matrix. The Hotspot depth-adjusted negative binomial model was run usinge7 Cell 185, 4428–4447.e1–e14, November 10, 2022 ll OPEN ACCESSResourcethe full countmatrix with the 5,000 downsampledHVGs and downsampled principal components explaining 50%of the variation (see data integration for dimension reduction and clustering). The Hotspot computed a weighted K-nearest-neighbors (KNN) graph with 25 neighbors, and 187 genes with an autocorrelation false discovery rate (FDR) greater than 0.05 were removed. Genemodules were created by agglomerative clustering with the minimum number of genes per module set to 65. 14 modules were identified, and 922 genes were not assigned to a module (Table S2D). Hotspot eigengene module scores were calculated by first centering the UMIs using the depth-adjusted negative binomial model. The centered values were then smoothed using the weighted average of their 25 nearest neighbors. These smoothed valueswere thenmodeledwith PCA using the first principal component, and the cell-loadings reported as the model scores. Trajectories Subclusters containing cells from a majority of adult samples were classified as mature, and major and sub-trajectories inferred to give rise to thesemature subclusters over development weremanually assembled based on age progression of adjacent subclusters and shared expression of markers. For example, distinct layers 2/3 and layer 4 PN sub-trajectories (L2/3-CUX2, L4-RORB) were defined that share cells of early developmental stages but subsequently differentiate into distinct terminal cell types (Figures S2A and S2C; Table S2B). 45 sub-trajectories were collapsed into 15 major trajectories for further analysis based on major clusters. scVelo velocity analysis Spliced and unspliced read counts were generated from FASTQ files (see sequence alignment and UMI counting) using loompy (v3.0.6) mapped to hg19-3.0.0 (La Manno et al., 2018). As above (see data integration for dimension reduction and clustering), a neighborhood graph [n_neighbors=50] was constructed from the normalized downsampled count matrix on the reduced compo- nents. Spliced and unspliced reads were filtered and normalized using scVelo (v0.2.2) (Bergen et al., 2020) filter_and_normalize func- tion [min_shared_counts=5, n_top_genes=1500 (500 for INs)]. Velocity scores were calculated using the scVelo stochastic model of transcriptional dynamics. Single nucleus velocities were then projected into UMAP and UMAT embeddings (see UMAP of maturation and data integration for dimension reduction and clustering). Nucleus-to-nucleus transition probabilities were calculated using a CellRank velocity kernel. CytoTRACE Cellular Trajectory Reconstruction Analysis using gene Counts and Expression (CytoTRACE, v0.3.3) is a computation framework based on the observation that the number of genes expressed in a cell decreases during differentiation (Gulati et al., 2020). More specifically, the geometric mean of the 200 most correlated genes with gene counts has been shown to predict a nucleus’ differen- tiation state accurately. To calculate the CytoTRACE values, we first KNN imputed our log normalized downsampled data (see data integration for dimension reduction and clustering) with 25 neighbors. We then utilized the CellRank (Lange et al., 2020) implemen- tation of CytoTRACE to calculate the value for each nucleus, where a low CytoTRACE value corresponds to an earlier developmental state and a higher value to a later state. Finally, within a CellRank kernel, CytoTRACE scores and the KNN graph were used to compute directed nucleus-to-nucleus transition probabilities. Mass flow analysis A transition matrix representing nucleus-to-nucleus transition probabilities was generated from each CellRank kernel (Lange et al., 2020) (see scVelo velocity analysis andCytoTRACE). A transition matrix was used to calculate the probability of mass flows from one cluster to the others at each developmental stage. These mass flows were summarized in vein plots using a CellRank re-implemen- tation of Mittnenzweig et al. (2021), where total flows between clusters at subsequent developmental stages is one. The total frequency of each cluster per stage is represented by veins with changing width proportional to the frequency of that cluster. Outflows between nuclei types are visualized by edges connecting clusters whose width is proportional to flow magnitude. Flows between clusters were simplified by eliminating low-magnitude flows with a threshold of 0.05. Pseudo-bulked trajectory data Batcheswith at least ten nuclei in eachmajor trajectory were pseudo-bulked by summing theUMI counts of all genes. Pseudo-bulked counts were then normalized by the trimmed mean of M-values (TMM) (Robinson and Oshlack, 2010) and scaled to log2 CPM, and lowly expressed genes were removed with edgeR (v3.31.4) (Robinson et al., 2010) filterByExpr function. Differential expression analysis of genes over development Differential expression analysis was carried out with the limma-voompipeline (Law et al., 2014) from the edgeR (Robinson et al., 2010) package following a published workflow (Law et al., 2016). Briefly, using pseudo-bulked trajectory data, potential confounding fac- tors were screened using multi-dimensional scaling (MDS) scatter plots (Figure S4A), where samples that cluster by a given factor suggests the factor contributes to expression differences and is worth including in the analysis and factors that show little or no effect may be left out of the downstream analysis. Of those screened, donor sex, 10x chemistry, and library prep lot number were deemed worth including (Figure S4A). These factors were used along with developmental stages to establish a design matrix, and contrasts were set up for pairwise comparisons between stages. Linear modeling was carried out using limma lmFit and contrasts.fit functions, and empirical Bayes moderation was carried out to obtain more precise estimates of gene-wise variability. Assumptions for this model were checked using exploratory visualizations, such as biological coefficient of variation plots. Differentially expressed genes (DEGs) were defined as those with an FDR <5% (Table S3). Interactive mean-difference plots (http://brain.listerlab.org) were produced via Glimma (v2.2.0) (Su et al., 2017) glMDPlot function. Note that results pertaining to major clusters are presented here to maximize statistical power and facilitate interpretability, but results on all sub-trajectories are also available at http://brain. listerlab.org.Cell 185, 4428–4447.e1–e14, November 10, 2022 e8 ll OPEN ACCESS ResourceRank-rank hypergeometric overlap analysis We conducted a leave-one-out analysis for differential gene expression analysis between different developmental stages for the L2/3-CUX2 major trajectory. We implemented our devDEG strategy, including pseudo-bulking and correction for confounding factors, but removed each sample once. Rank-rank hypergeometric overlap (RRHO2) (Cahill et al., 2018) was used to compare ranked DEGs lists between the two independent gene profiling experiments. Each pairwise comparison resulted in a RRHO2 plot showing the strength and pattern of the correlation between the DEGs found when a sample was left out and the DEGs found by the original analysis. Fitting and clustering gene trends Trend curves were fit to all development-associated differentially expressed genes (devDEGs, see differential expression analysis of genes over development), allowing for analysis of continuous expression changes across development, even where age gaps may exist. Rather than the raw data, clustering trend curves produce more coherent clusters and sharper kinetic trends, allowing analysis of a more assorted set of patterns (Trapnell et al., 2014). To fit the trends, we fit a Generalized Additive Model (GAM) to the pseudo- bulked trajectory data using the pyGAM python package (v0.8.0) (Serve´n et al., 2018). More specifically, GAM was fit with pyGAM’s LinearGAM function, which uses an identity link function, a Normal error distribution, and a cubic smoothing function. Once a GAM was fit to a gene, a response curve, or trend fit, was produced using 100 evenly spaced grid points. Gene trends on a stage scale were fit to pseudo-bulked trajectory gene expression binned by developmental stages and set at six even intervals, while trends on an age scale were fit to pseudo-bulked trajectory gene expression scaled to regularize the spacing between ages while maintaining a grounding in time. Age scaling was performed by first dividing ages in years by a cofactor of 0.55 and then arcsinh transformed. The cofactor was chosen to optimally linearize the spacing between samples in our dataset. Gene trends set on the stage scale were scaled zero to one and hierarchical clustered using scipy (v1.7.1) python package (Virta- nen et al., 2020) with a Ward linkage and Euclidean distance metric. The hierarchical tree was cut at a height of 90 using the scipy cut_tree function, resulting in 14 clusters or gene trends. The height of the tree cut was selected to maximum distinctiveness and to limit the redundancy of the gene trends. snRNA-seq pseudo-bulked trend comparison to Li et al. bulk study We analyzed an independent bulk RNA-seq dataset consisting of 40 samples from the dorsolateral prefrontal cortex (DFC) spanning 8 PCW to 40 yr, published by Li et al. (2018), restricting the analysis to 28 samples matching our age range, 19 PCW (21 ga) to 40 yr. We limited the gene comparisons to those with either similar or dissimilar expression profiles across the major cell trajectories of our study. We defined genes with similar expression profiles as those occupying the same trend class (i.e. up or down) in enough major trajectories to account for 75% of all nuclei in the same trend class, thereby selecting a set of genes that show similar developmental expression dynamics in a large fraction of all analyzed cell types. Genes with dissimilar profiles were defined as those with >35% of nuclei in both up and down trend classes, thereby selecting a set of genes that have opposite developmental dynamics between groups of cell types. Selected genes were GAM fit to both our pseudo-bulked data and the selected published DFC data (see manu- script methods fitting and clustering gene trends). Both trend sets were normalized zero to one, and the difference measured using euclidean distance. Genes with similar expression dynamics in our major trajectories have similar expression changes over development when comparing our pseudo-bulked snRNA-seq data to the bulk RNA-seq data (Figure S3F). Genes that demonstrate very different dy- namic trends between major trajectories in our snRNA-seq data tend to disagree with the bulk data, as would be expected when comparing pseudo-bulked data to bulk data for genes that show divergent dynamics in different cell types of the analyzed tissue. Rates of change analysis The rate of change analysis was performed on a per major trajectory basis by taking themean of the absolute rate of change devDEG trend fits. Whilst the rate of change analyses on a day scale suggest only small scale changes beyond infancy, disparate time scales (days for early development versus years for older ages) could mask rate changes occurring over larger time intervals. Therefore, we calculated the difference between time points on two scales to highlight changes occurring at different time intervals. In both cases, the grid points from the GAM fit to the arcsinh transformed ages were used. The GAM grid points were left evenly distributed on the arcsinh transformed ages to highlight protracted differences between ages (Figure S3G), and the rate of change was calculated by taking the difference between gene trend values at subsequent grid points. The rate of change on a year scale was calculated by first transforming the arcsinh scaled grid points back to a year scale by transforming with the sinh function and multiplying by the 0.55 cofactor. The rate of change was then calculated by taking the difference between trend expression values at subsequent grid points and dividing by the difference of grid points on the year scale. Similarly, acceleration of expression was calculated by taking the dif- ference in the rate of change values at subsequent grid points and dividing by the difference of grid points on the year scale. Nearest neighbor acquisition of adult-like identities KNN graphs were constructed for all nuclei and separately for INs using the scanpy preprocessing neighbors function with 25 neigh- bors as described in data integration for dimension reduction and clustering. For each sub-trajectory age, the sum of the number of nuclei whose nearest neighbor is an adult nucleus and the number of adult nuclei whose nearest neighbor is within the query age is calculated. The sum of adult neighbors is normalized by sample size, the product of the number of nuclei in the query age and the number of adult nuclei within a sub-trajectory. The cumulative sum of the adult neighbor proportions is taken across the ages of development and scaled from zero to one. PN sub-trajectories in Figure 1F were hierarchically clustered using a Ward linkage. The 40yr sample was omitted from this analysis to avoid any potential detection of aging effects, and sub-trajectories with <30 adulte9 Cell 185, 4428–4447.e1–e14, November 10, 2022 ll OPEN ACCESSResourcenuclei were not included. This analysis was robust to the number of nearest neighbors, showing little change in maturity patterns with as few as 15 and as many as 100 nearest neighbors. Eigentrends To inspect the expression dynamics of a set of genes linked to brain development and function processes, we calculated the eigen- trend of devDEGs enriched in Gene Ontologies (GO) for eachmajor trajectory (see Enrichment). In order to calculate the eigentrends, we first quantile normalized the devDEG stage fit trends (see Fitting and clustering gene trends) from all major trajectories as a com- bined group. Next, the intersection of devDEGs for each major trajectory and the enriched GO term gene set was taken. For each major trajectory, PCA, without zero-centering, was performed on the quantile normalized trends of the intersected geneswith respect to the stage-scaled GAM grid points, and the eigentrend was taken as the first principal component scaled from zero to one. Statistical testing of comparisons between eigentrend values was performed with a one-sided Wilcoxon signed-rank test. Cell-to-cell communication of ensheathment genes Starting with the connectomeDB2020 database of 2293 manually curated ligand-receptor pairs with literature support (Hou et al., 2020), we filtered ligand-receptor pairs to those contained in the gene ontology term "neuron ensheathment" (Raudvere et al., 2019). For each major trajectory, only pairs where both the ligand and receptor are DEGs over development were considered. From pseudo-bulked trajectory data, the mean gene expression of batches within a developmental stage was used to calculate the product of expression for each ligand-receptor pair. Umap of MATuration (UMAT) To visualize developmental sub-trajectories we overlaid the UMAP with velocity vector fields derived from nucleus-to-nucleus transition probabilities (Bergen et al., 2020). While vector fields largely agree with age progression, some disjunct developmental pat- terns are visible (Figure S4B), potentially indicating a paucity of some intermediate cell states. To more explicitly compare transition probabilities and development, we introduce Umap of MATuration (UMAT), which limits UMAP neighbor selection to cells from adja- cent developmental stages (Figures 4F and S4C). Scanpy neighbors function was used to iteratively populate the connectivity and distancematrices so that the nearest neighbors of a nucleus were limited to nuclei within the same developmental stage or adjacent stages. For example, nuclei in the neonatal stage could only select neighbors from the fetal or infancy stages. Once fully populated, the connectivity and distance matrices were used as the basis for UMAP embedding. The same preprocessing procedures and parameters described in Data integration for dimension reduction and clustering were used within the Umap of MATuration (UMAT) workflow. Enrichment analyses Gene set enrichment analysis of GO terms was performed with gProfiler (Raudvere et al., 2019) with default parameters (adjusted p-values <0.05), and results were limited to enrichment in GO molecular function and GO biological processes. Enrichment for Hot- spot gene modules (Table S2D) and devDEGs (Table S3) for each major trajectory was done with a background consisting of genes with a least one UMI in the downsampled count matrix, while, for each major trajectory, enrichment of devDEGs within a gene trend was run with a background consisting of all genes expressed within the major trajectory. For the enrichment analysis across different types of ion transporters, the TransportDB database (Ren et al., 2007) was subsetted to transporters relevant in the brain. Next, for eachmajor gene trend andmajor trajectory using the function fora in the fgsea package (v1.17.1) we determinedwhether therewas enrichment for a particular ion transporter type (Korotkevich et al., 2016). The background was set to be all devDEGs in the respective trajectory. P-values were then adjusted for multiple testing using FDR and enrichment was deemed present when adjusted p-value <0.05. Disease enrichment analysis To investigate enrichment of known neurological and psychiatric disease genes in major trajectory-specific gene trends, gene-dis- ease associations defined in the DisGeNET database (Pin˜ero et al., 2020) were used (v7, accessed via R package disgenet2r v0.99.2). We focused on the DisGeNet database, as it represents one of the largest publicly available andmost regularly updated collections of genes associated with human diseases (Pin˜ero et al., 2020). The function fora in the fgsea package was used to calculate a p-value regarding the statistical significance of enrichment over a background set of genes (Korotkevich et al., 2016). The background set of genes was set to include all genes that were expressed inR5% of the cells of the relevant cell type. p-values were then adjusted for multiple testing using FDR. Diseases were deemed enriched where the adjusted p-value was smaller than 0.05. Stable integration into the reference atlas Integrating query datasets and organoid samples onto the reference dataset was performed using the scArches approach from scVI (scvi-tools v0.11.0) (Lopez et al., 2018), via the R package reticulate (v1.20). Raw count data from the reference was downsampled to a maximum of 1,000 UMIs per cell, as well as for query datasets. Features were then reduced to the highly variable genes in the reference that are also present in the query dataset to be integrated. A model is trained using a variational autoencoder to produce a latent space, distributing cells among 30 latent variables. This trained model informs the distribution of cells in the query dataset into the same low-dimensional space as the reference. Parameters were initialized in accordance with the scArches optimization (use_layer_norm = ‘both’, use_batch_norm = ‘none’, encodec_covariates = TRUE, dropout_rate = 0.2, n_layers =2). Once both reference and query are represented in the same latent space, we first verify the validity of their integration in a screening check called a partial initialisation. The partial initialisation employs the uwot package (v0.1.10) to create a UMAP visualization of the query dataset aligned to the reference, but allows the reference structure to change in shape (McInnes et al., 2018). The latent rep- resentations of the query and reference are combined together, and a nearest neighbor graph using 25 neighbors is constructed.Cell 185, 4428–4447.e1–e14, November 10, 2022 e10 ll OPEN ACCESS ResourceThen, point (nuclei) locations are initialized as follows: reference nuclei are initialized to the UMAP coordinates of the original refer- ence embedding, and query nuclei are randomly distributed over this coordinate range (only the reference nuclei receive a specific initialisation, hence the name ‘partial initialisation’). The UMAP is then optimized over 50 epochs to produce a final visualization of the partial initialisation of the query and reference. The partial initialisation is applied to determine whether query datasets are aligning to the reference, or largely forming their own isolated clusters. Because the later stable integration forces query nuclei onto the reference clusters and can thus result in misclas- sification of cell types, this preliminary testing is important to confirm that integrations are valid and sensible. A qualitative approach can be taken, where query datasets observed to form their own clusters in the partial initialisation are not considered for stable inte- gration, as their expression is too different to align to any reference cluster. However, understanding the context of the query samples is also important, as disease and cerebral organoid models may not completely recapitulate neurotypical brain nuclei expression and thus not align well, but will elicit meaningful results from a subsequent stable integration. Furthermore, the Partition-based graphical abstraction algorithm (PAGA) from the scanpy package can be used to calculate the strength of connections between partitions of a dataset, comparing observed interedges between expected number of interedges assuming random connections (Wolf et al., 2019). Leiden clusters are created to form partitions of the partial initialisation. Few strong connections (weight >0.15) between query-domi- nated and reference-dominated clusters suggest poor integration that may be inappropriately forced onto the reference, whereas abundant and diverse connections suggest a well-aligned integration. This method demonstrated that our organoid samples have abundant connections to astrocyte and neuronal clusters in the reference, regions they integrate onto heavily in the reference. In contrast, very few connections were inferred between non-neuroectoderm snRNA-seq datasets and our reference map, and corre- sponded to poor-quality nuclei, microglia, and vasculature, in line with expectations of minimal similarity between these datasets (Figure S7F). The glioblastoma sample shows a connectivity level between non-neuroectoderm samples and organoids, with few connections to vasculature and astrocyte populations (data not shown). As glioblastoma represents a non-neurotypical landscape, its lack of alignment during the partial initialisation step is understandable; and further, it reinforces our assignment of nuclei to be astrocyte-like, rather than astrocytic cells. Oncewe have confirmed the validity of the partial initialisation, the uwot package can be utilized to regain the UMAP visualization of our reference (McInnes et al., 2018). A nearest neighbor graph using 25 neighbors is constructed from the latent variable represen- tation of the reference. Point (cell) locations are initialized to the UMAP coordinates of the original reference embedding, with zero epochs to prevent changes to the structure. The query data points are then fitted to the reference using the umap_transform function. Nearest neighbors of the latent representations of query cells are located in the reference, which informs initial positioning of the query points onto the UMAP axes. Points are then fitted to the reference embedding through 50 epochs to approach their final location on the visualization. We also applied two similar methods. This included a method by Hao et al. (2021) utilizing canonical correlation analysis (CCA) as available in Seurat (v4.0.3), and Symphony (v1.0) by Kang et al. (2021), which incorporates soft cluster assignment. These algorithms receive the initial PCA of the reference dataset to inform their integration, and thus create dimensional embeddings equal to the number of principal components leveraged (365). For direct comparison, the Velmeshev dataset was inte- grated with the scArches parameterisation, but with 365 latent variables instead of 30. Comparison to both methods in terms of cell type prediction accuracy showed comparable performance (Figures S7B and S7C), but substantial improvement in age prediction, primarily using astrocytes (average Spearman correlation improvement = 0.52 for Velmeshev et al. samples). Note that one of the additional samples used to test the integration method (ga39) used a sucrose nuclei isolation method. Age and cell type prediction Predicting the cell type from integrated datasets involves KNN cluster prediction with 10 nearest neighbors within the integrated UMAP space. The KNN function of the FNN package (v1.1.3) facilitated this. Query cells were assigned the cell type most common among their 10 nearest neighbors in the reference dataset. For samples that supplied original cell annotations, these were used to measure the accuracy of the cluster prediction, indicating the accuracy of the integration. Accuracy was given as the percentage of cells in the dataset that had their cell type correctly predicted, relative to their original annotation. For age prediction, a KNN regression was performed using FNN’s knn.reg function, with 10 nearest neighbors. Cell ages were estimated from the arcsinh trans- formation of the reference ages, taking the mean of its neighbors. An estimation of sample age was calculated by taking the largest mode of the density of age distributions for that sample. If the density had two similarly large modes, both were considered. Alter- native predictions using k=50, 70, and 200 had little effect on age and cell type predictions. Finally, we also tested whether organoids were exhibiting higher levels of metabolic stress than postmortem brain samples that could interfere with our ability to predict cell types. Inspection of expression levels of genes involved in metabolic stress response and glycolysis (data not shown) demonstrated this was not the case, and is in line with recently reported results (Uzquiano et al., 2022). Differential expression comparing immature and mature PNs in organoids Using the R package scran (v1.18.5) (Lun et al., 2016), we identified DEGs between PNs predicted to be of fetal age (immature PNs) and PNs predicted to be non-fetal (mature PNs) using a t-test with a blocking effect indicating the nucleus organoid of origin. P-values were corrected for multiple testing using FDR. Additionally, a permutation analysis was performed to confirm that the results could not be produced when randomly shuffling the mature and immature labeling.e11 Cell 185, 4428–4447.e1–e14, November 10, 2022 ll OPEN ACCESSResourcesnATAC-seq analysis Sequence alignment and UMI counting Reads were demultiplexed by sample index using the cellranger-atac (v1.2.0) mkfastq command. Fastq files were aligned to the human (hg19) genome, cell barcodes were demultiplexed, and UMIs corresponding to genes were counted using the cellranger- atac count command and default parameters. Some samples were excluded based on indicators of low quality, such as high doublet score or low fraction of fragments overlapping called peaks (Table S1F). ArchR preprocessing ArchR (v1.0.1) is an R package for processing and analyzing snATAC-seq data (Granja et al., 2021). Using the function createArrow- Files the fragments files produced by cellranger-atac were loaded into R, excluding sex chromosomes and restricting the output to contain only barcodes for valid cells as defined by cellranger-atac. ArchR then was used for doublet removal, resulting in the removal of 6.69% of nuclei on average (Table S1E). Next, we excluded any nuclei that did not have sufficient TSS enrichment in a sample adaptive fashion by excluding any nuclei with TSS enrichment lower than median TSS enrichment in the sample minus 1 standard deviation. This resulted in the removal of 6,011 nuclei across all samples (Table S1E). Dimension reduction and clustering In order to cluster the data, features were transformed using term frequency that has been depth normalized to a constant (10,000) followed by normalization with the inverse document frequency and then log transformation (log(TF-IDF)). Next, iterative latent semantic indexing available in ArchR using the 50,000 most variable features and 20 dimensions was applied. Four iterations were performed, each time sampling 10,000 cells with 10 random starts at a resolution of 4. To combat batch effects Harmony was applied to the dataset. Using the Harmony-corrected dimension reduction, the data were clustered into 73 subclusters (Korsunsky et al., 2019). This constitutes overclustering, which was addressed during the annotation step. Cluster annotation The annotation of subclusters was driven by the snRNA-seq data. To this end, canonical correlation analysis (CCA) was used to match each nuclei in the snATAC-seq data to its closest neighbor in the snRNA-seq data (Butler et al., 2018). Note that for this anal- ysis the union of the 2,000 most variable genes in each modality. Subcluster labels were transferred from the snRNA-seq nuclei to their matched snATAC-seq nuclei. Subclusters were then annotated according to their most prevalent major cluster label as well as by manual inspection of known marker genes (as previously described in Cluster Annotation for snRNA-seq). At this stage, several clusters were removed due to high doublet score (Figure S5A). Further clusters that could not be confidently assigned to one cell type and probably constitute doublets or poor quality nuclei were identified. All these subclusters were labeled ‘‘Poor Quality’’ (constituting 4,281 nuclei) and removed from further analysis. Using the reduced dataset, dimension reduction, clustering and annotation were repeated. This resulted in 67 subclusters, which were labeled as 12 major cell types: Astrocytes, Oligodendrocytes, Oligodendrocyte Precursor Cells, Microglia, Vasculature (which encompass endothelial, fibroblast-like, and pericytes/smooth muscle cells), L2/3, L4, L5/6, PN developing (PN dev), IN developing (IN dev), MGE derived (MGE der, includes SST and PV populations), CGE derived (CGE der, includes VIP and ID2 populations). Peak calling Major cell types were first combined into the following trajectories, which match major trajectories used in the snRNA-seq analysis: Oligodendrocytes (Oligodendrocyte Precursor Cells, Oligodendrocytes), Astrocytes, Microglia, Vasculature, L2/3 (PN dev, L2/3), L4 (PN dev, L4), L5/6 (PN dev L5/6), MGE der (IN dev, MGE der), CGE der (IN dev, CGE der). Peaks were called using a modified ENCODE ATAC-seq pipeline with default parameters (Trevino et al., 2021). Fragments were first combined from nuclei according to their sample of origin and trajectory assignment. Additionally, fragments from nuclei were combined according to their trajectory assignment, ignoring their sample of origin. For each of these newly created fragment files, two pseudo replicate fragment files were created, one containing fragments from randomly sampled half the nuclei and the second containing fragments from the other half. Note that fragment files with <40 nuclei were removed from this analysis. Furthermore, sex chromosomes, the mitochondrial chro- mosome, and blacklisted regions were removed.MACS2 (v2.2.7.1) was then used to call peaks in both the pseudo replicate fragment files as well as the complete fragment files (Zhang et al., 2008). Peaks were filtered out that did not meet the significance threshold of 0.05 as well as an Irreproducible Discovery Rate (IDR, v2.0.4) of 0.05, which was calculated with the help of the pseudo replicate fragment files (Li et al., 2011). This was done in order to select for a more consistent and confident peak set. Next, the function nonOverlappingGR in ArchR was used to obtain peak sets that were non-overlapping and prevent daisy-chaining. Next, to obtain even more reliable peak sets that ensure decent replication across samples, the following procedure was applied. For each sample and cell type peak set, all peaks were removed that did not show a 50%overlap with peaks in the peak set called for the corresponding trajectory. Additionally, peaks that were smaller than 300 bp or larger than 30 kb were filtered out. All peaks had to show in at least two samples Insertions Per Kilobase perMillion readsmapped (IPKM) values above 2. This resulted in finding 152,329 peaks for L2/3, 181,948 peaks for L4, 128,135 peaks for L5/6, 74,202 forMGE-der, 80,411 for CGE-der, 72,263 for Oligodendrocytes, 45,453 for Microglia, 75,411 for Astrocytes, and 16,385 peaks for Vasculature. For each trajectory, the mean of IPKM values in each peak in a stage was also used to find the first PC. This analysis is robust with regards to the different number of nuclei across trajectories due to pseudo-bulking.Cell 185, 4428–4447.e1–e14, November 10, 2022 e12 ll OPEN ACCESS ResourceChromHMM overlap and peak annotation Identified peaks were intersected with Encode chromHMM annotations specific for humans (ENCODE Project Consortium et al., 2020) using a variety of different tissues and developmental stages (Sarropoulos et al., 2021). The fraction of identified peaks that overlapped Encode-annotated enhancers (‘‘E’’), promoters (‘‘P’’), and heterochromatin (‘‘H’’) elements by at least one base pair was determined. Identification of Cis Regulatory Elements (CREs) Using a correlation-based approach, peak-to-gene links were identified by applying pseudo-bulking of counts from nuclei of matched scATAC-seq and snRNA-seq (Di Bella et al., 2021; Trevino et al., 2020). This approach has recently been validated using single multiome technology that measures ATAC and RNA from the same cell (Trevino et al., 2021). To this end, 400 nuclei from the entire scATAC-seq dataset were randomly sampled using geosketch to preserve rarer cell types. Using the R package FNN, these 400 seed nuclei were combined with their respective 50 nearest neighbor nuclei (PCA space), such that each pseudo-bulk sample comprised 51 cells in total. Pseudobulk ATAC insertion counts for peaks were obtained by summing peak insertion counts across the respective single-nuclei members. Matching RNA nuclei were obtained by selecting the 50 nearest neighbors of scRNA nuclei matched to seed nuclei as determined by Seurat’s FindIntegrationAnchors and IntegrateData (Butler et al., 2018). Similar to the ATAC nuclei groups, the counts for each group of 51 scRNA nuclei were summed. Each matched pseudo-bulk sample was anno- tated with the majority cluster and age assignments of its contingent ATAC nuclei respectively. Candidate peak-gene pairs were obtained by associating peaks with a genomic distance between 1 and 250 kb to the TSS of the respective gene. For each candidate peak-gene pair the Pearson correlation coefficient of CPM-normalized counts of accessibility and gene expression data as well as adjusted p-values for these coefficients based on their t-statistic were computed. To further ensure selection of real CREs, we additionally determined a cut-off for the Pearson correlation coefficient value. For this, a previously described method (Sarropoulos et al., 2021) based on computing interchromosomal correlations to obtain an empirical null distribu- tion and identify a biologically meaningful correlation cut-off was adapted. For each gene, 10 randomly chosen regions located on chromosomes different to the gene were considered. We then proceeded as described above to find the Pearson correlation coef- ficient. Using this data, we then identified the 5% threshold (two-tailed) as the cut-off (Figure S5J). Regions that passed both FDR and Pearson correlation coefficient cut-off were considered CRE. This resulted in the identification of 304,741 trajectory-specific CREs (Table S5A). Clustering CREs NonnegativeMatrix Factorization (NMF) implemented via Python package sklearn (v0.24) was used to groupCREs into groups based on their CPM value across pseudo-bulk samples (Li et al., 2020). Integral to a successful decomposition of a matrix into a basis and coefficient matrix is the choice of the rank. The rank was optimized with the help of twomeasurements, sparseness and entropy, with the idea that an optimal solution would show sparsity in both resulting matrices and low entropy in the basis matrix. Average values were calculated from 10 times for NMF runs at each given rank with random seed, which will ensure the measurements are stable. Rank 31 produced the best combination of sparseness and low entropy. Next, the normalized coefficient matrix was used to associate groups with distinct pseudo-bulk samples. Since the values in the normalized matrix indicate weight of pseudo-bulk samples in a group, we assigned each pseudo-bulk sample to its respective maxi- mally weighted group. In addition, each group was associated with CREs using the basis matrix. For each CRE and each group, the basis coefficient score and feature score via the ‘‘Kim method’’ (Kim and Park, 2007), which give an indication of distinctness of as- sociation between a specific CRE and cluster, were derived. CREs that had a feature score smaller than themedian feature score plus 3 standard deviations or a basis coefficient score smaller than its median over the whole matrix were filtered. This resulted in 1,968 CREs that were distinctly associated with a small number of groups. For plotting, the CPM value of CREs associated with the same gene were combined. Both CRE accessibility and associated gene expression were normalized by their row mean. Plotting CREs trends To identify CRE accessibility trends over development, gene trends identified from the snRNA-seq datawere linked to theCRE via the devDEG. The mean IPKM of the number of Tn5 insertions across all samples for each stage was then determined. To visualize whether CREs show similar gene trends, the IPKM value across stages of each CRE was normalized to a scale from 0 to 1 and then averaged over all CREs belonging to the same gene trend. Motif enrichment Motif enrichment was performed using the JASPAR2018 catalog (Khan et al., 2018). Promoter regions were removed from this anal- ysis in order to focus on enhancer regulation. Utilizing the ArchR addMotifAnnotations function, peaks were annotated with known motifs. Appropriate GCmatched background peaks for each peakwere next determined using getBgdPeak. Using the internal ArchR computeEnrichment function then allowed determination of enriched motifs in chosen sets of regions over their respective back- ground peaks. TFs not expressed as determined via the snRNA-seq data were removed. If multiple sets of regions were tested, FDR corrections to account for multiple testing were used. Finally, motifs for the gene trend analysis were grouped into larger motif families based on their sequence similarity as described in Vierstra et al. (2020). P-values were combined using the Fisher method. Footprinting analysis To obtain Tn5 bias-corrected footprints, the ArchR function getFootprints is used. Pseudo-bulk footprints are created for the CREs regions with enriched TF motifs associated with particular gene trends across major trajectories.e13 Cell 185, 4428–4447.e1–e14, November 10, 2022 ll OPEN ACCESSResourceConstruction of networks To construct networks we adapted an approach from Kamimoto et al. (2020). The approach has the following steps: 1) For every trajectory, motif binding sites located in the CREs were identified and used to establish potential connections between TFs and the genes associated with the CREs. These connections between target genes and TFs serve as the base networks, which are the input for the machine learning process conducted with the snRNA-seq data in the next step. 2) A relatively simple machine learning model was fitted that predicts a target gene expression based on the gene expression of the potential regulatory TFs as determined by the base network. Note that only cells of a particular cell type of interest are used in order to ensure that the described process represents indeed a linear relationship and is in fact cell type-specific. The linear models were fitted with a Bayesian Ridge model using a non-informative prior via sklearn. 3) Utilizing the ability to easily calculate p-values for the coefficients associated with the TFs with the help of the posterior, we were able to establish connections between TFs and their targets by removing non-signif- icant connections. 4) The resulting network could then be interrogated for the relative importance of each member via the hub score and betweenness measure (igraph v1.2.6). Ranking of TFs To rank TFs that were upregulated in a differential expression analysis between mature PNs in organoids and their closest matched nuclei in the reference brain atlas, we employed a strategy based on the inferred base network described inConstruction of networks. For each TF, we counted the number of potential connections with other upregulated non-TF genes. We then transformed this num- ber into a z-score to rank the TFs according to their likelihood of regulating genes that are differentially expressed. ADDITIONAL RESOURCES An accompanying website for this study provides all code as well as interactive browser tools for interrogation of multiple datasets, available at http://brain.listerlab.org.Cell 185, 4428–4447.e1–e14, November 10, 2022 e14 Supplemental figures A B C D F E G H I (legend on next page) ll OPEN ACCESSResource Figure S1. Construction of a snRNA-seq map of the human PFC during development, related to Figure 1 (A) Number of human PFC sc/snRNA-seq and sc/snATAC-seq samples generated in previous studies and the sample ages. Brain samples not from the PFCwere included for fetal stages. ga, gestational age, in weeks. (B) Nuclei were stainedwith DAPI and gated to discriminate intact single nuclei using area plots of forward scatter (FSC Par) versus side scatter (SSC). Nuclei were sorted for DAPI+ events. (C) UMAP of snRNA-seq data overlaid with donor origin for each nucleus (left). Bar plot of number of single nuclei transcriptome profiles for each sample after stringent quality filtering (right). (D) Distribution of number of genes detected per nucleus (log10 transformed, top) and number of UMI counts per nucleus (log10 transformed, bottom), for each sample prior to stringent quality filtering. Dotted line on plot of UMI counts per nucleus indicates threshold of the minimum number of UMIs for a nucleus to be included in subsequent analyses. (E) UMAPs, Leiden clustering (left) and UMI counts (right), of downsampled snRNA-seq prior to removal of nuclei with <1,000 UMIs (STAR Methods). (F) PMI and common quality measures (nuclei counts, UMI counts, and collection year) for all snRNA-seq samples, colored by stage. (G) UMAP of snRNA-seq data with each of the 86 clusters represented by a distinct color. (H) Number of nuclei per stage. (I) Proportion of each major cell type/state in each sample. ll OPEN ACCESS Resource AB C (legend on next page) ll OPEN ACCESSResource Figure S2. Identification of developmental trajectories in the snRNA-seq human PFC map, related to Figures 1 and 2 (A) Hierarchical cluster naming strategy for all nuclei. Bold outlines indicate major trajectories. (B) UMAP representation of 40 of the 45 identified sub-trajectories, with nuclei that are members of each trajectory indicated in orange. The 5 remaining major trajectories are indicated by a red outline in (B). (C) UMAP representation of 15 major trajectories, including vasculature-associated cells, with nuclei that are members of each trajectory indicated in orange. ll OPEN ACCESS Resource A B C D F E G H I J Figure S3. Robustness of trajectories and analyses, related to Figures 1, 2, and 3 (A) UMAP overlaid with CytoTRACE scores (left) and vector fields derived from scVelo stochastic model (right). (B) Number of nuclei versus number of devDEGs in each trajectory. (legend continued on next page) ll OPEN ACCESSResource (C) RRHO2 plots comparing L2/3-CUX2 trajectory devDEGs for every stage contrast from the original analysis with the one where the indicated sample in the empty square was removed. Each such pairwise comparison results in a plot showing the strength and pattern of the correlation between the DEGs found when a sample was left out and the DEGs found by the original analysis. Negative log10 p values represent the correlation strength, and low p values in the upper right and lower left quadrants represent concordant up and down gene regulation, respectively. (D) RNAscope in PFC tissue for six further representative ages (for additional ages see Figure 2D), detecting: postnatally mature cells marked by KCNH1 (green) and ARHGAP26 (red), and immature cells marked by BHLHE22 (gray). DAPI counterstain (blue, nuclei). (E) Bar plot of proportion of PNs with non-zero expression with a line plot of average PN log2 CPM expression (left) and UMAP overlaid with log2 CPM expression (right) of new (BHLHE22, ARHGAP26, KCNH1) and conventional (SOX2, RBFOX3/NeuN) markers. (F) Euclidean distances between scaled gene expression trends of pseudo-bulked snRNA-seq data from this study and dorsolateral PFC (DFC) bulk RNA-seq from Li et al. (2018), for devDEGS identified in this study that exhibit either similar or dissimilar expression profiles across different PFC cell types (see STAR Methods). (G) Absolute mean rates of change of devDEGs calculated on arcsinh age scale. (H) Selected ligand-receptor pair expression (product of mean ligand expression 3 mean receptor expression) between PNs and ODCs across developmental stages. (I) Expression (log2 CPM; dot: individual sample; line: GAM fit) of receptor PTPRD and corresponding ligand NTRK3 across development. Points represent expression levels in individuals withR10 nuclei in the trajectory. (J) Enrichment, indicated by p value and number of intersecting genes, of investigated ion transporter types (calcium [Ca], potassium [K], sodium [Na], neurotransmitter [NT]) in general gene trends in cell types where significant enrichments were detected. See also Tables S2 and S4. ll OPEN ACCESS Resource AB C D FE G H I J (legend on next page) ll OPEN ACCESSResource Figure S4. Emergence and maturation of LAMP5+ subtypes, related to Figures 1, 3, and 4 (A) Multi-dimensional scaling log2 CPM scatterplots investigating correlation with potential confounders, including brain region, cause of death, 10x chemistry version, collection year, donor sex, ethnicity, library prep lot number, and post-mortem interval (PMI), in the pseudo-bulked snRNA-seq dataset. (B) UMAP overlaid by the arcsinh age of each nucleus and vector fields derived from scVelo stochastic model. (C) UMAP of maturation (UMAT) overlaid by the arcsinh age of each nucleus. (D) UMAT overlaid by select subcluster colorations (CGE-dev and MGE-dev), and vector fields derived from scVelo projected onto a UMAT embedding with colorations of select subclusters (LAMP5-NOS1 and LAMP5-CKK). (E) Probability mass flow plots from a CellRank CytoTRACE kernel for outflows to LAMP5-NOS1 or LAMP5-CCK clusters across developmental stages from combined CGE-dev and ID2-dev clusters (top) and MGE-dev cluster (bottom). The width of horizontal veins is proportional to nuclei type frequency at each developmental stage and the width of edges between nuclei types is proportional to flow probability. (F) Eigentrend values of devDEGs in the ion transport GO-term across development for different LAMP5 subtypes. (G) RNAscope in PFC tissue sections from 8-year-old (left) and 2-year-old (right) individuals, showing the location of LAMP5-NDNF nuclei positive for NOS1 (red) and NDNF (gray), but negative for NPY (green) at the edge of the cortical sections. Sections counterstained with DAPI (blue). (H and I) (H) Log2 CPM expression in nuclei of LAMP5+ populations from this study, and (I) mean scaled log2 CPM expression (scaled per gene) in all IN sub- clusters from this study, for previously identified marker genes for layer 1 canopy cells from Schuman et al. (2019) (NDNF+ NPY) and the layer 1 LAMP5-NDNF population from Hodge et al. (2019) (LAMP5+ SST+ NMBR+ ). (J) Percentage of mitochondrial reads per cell state. ll OPEN ACCESS Resource A B C D FE G H I J K L M (legend on next page) ll OPEN ACCESSResource Figure S5. Construction of a chromatin accessibility reference of the human PFC over development, related to Figure 5 (A) UMAP of unfiltered snATAC-seq dataset colored by annotation of different cell types/states and poor quality nuclei (left). UMAPs colored by TSS enrichment and doublet score for each nucleus (right). (B) UMAP of snATAC-seq nuclei colored by donor origin (left). Number of high quality nuclei per sample (right). (C) UMAP overlaid with all 65 identified subclusters. (D) Number of fragments, reads in peaks, fraction of reads in peaks (FRIPs), TSS enrichment, reads in promoters, and fraction of reads in promoters per sample. (E) Proportion of cell types/states in each sample (left), using the (A) cell type color key. UMAPs overlaid with matched cell type/state labels for each nucleus, derived from matched snRNA-seq data (right). (F) Number of nuclei in each stage. (G) Expression (log2 CPM; dot: individual sample; line: GAM fit) of MYRF across development in ODCs. (H) Proportion of peaks in different cell types from this study overlapping chromHMM predicted enhancers, heterochromatin, and promoters identified across a series of human tissues and developmental stages (Ernst and Kellis, 2017). (I) Proportion of peaks of particular types of genomic regions, and the observed versus expected frequency. (J) Density plot of Pearson correlation coefficients between CRE accessibility and gene activity in ±250 kb windows considered for the real target assignment (teal) and in different chromosomes used as background (red). (K) Number of CREs associated with each gene. (L) Enrichment of TFmotifs in various CREmodules; color represents enrichment. Only significant enrichments found in <3 CREmodules are displayed. TFmotifs are summarized to TF motif similarity modules. (M) Scatterplots of hub score versus betweenness of networks of interactions between genes in ensheathment of neurons GO term and TFs in L4 PNs in infancy and adolescence. Networks were constructed using motif binding sites in CRE elements, as estimated from the snATAC-seq, and co-expression of genes and TFs, as estimated from snRNA-seq (STAR Methods). Scatterplots for other PNs showed similar results. ll OPEN ACCESS Resource AB C D F E (legend on next page) ll OPEN ACCESSResource Figure S6. Enrichment of TFmotifs in CREs linked to devDEGs for different general gene trends andmajor trajectories and devDEG stability assessment, related to Figures 1 and 5 (A) CREs linked to devDEGs in general gene trends across different major trajectories were tested for enrichment of TF binding motifs. TF motifs are summarized to TF motif similarity modules. Color represents adjusted p value for enrichment. (B) Heatmap of expression (snRNA-seq) of syndromic ASD genes (Simons Foundation Autism Research Initiative) across development in 10 major trajectories. (C) UMAP of Harmony (left) and BBKNN (right) corrected snRNA-seq data, with nuclei colored by the donor age. (D) UMAP of Leiden clustering when synthetic low-quality nuclei are included in snRNA-seq data. (E) UMAP of snRNA-seq data including synthetic low-quality nuclei; also marked is the population of poor quality nuclei identified in the dataset. (F) UMAPs overlaid with normalized expression of NRGN (left) and THY1 (right). ll OPEN ACCESS Resource A B C D F E G H I (legend on next page) ll OPEN ACCESSResource Figure S7. Establishing stable integration and age prediction, related to Figure 7 (A) Projection of stably integrated nuclei from snRNA-seq data of PFC from 14 control individuals from Velmeshev et al. (2019), ranging from 4 to 22 years of age. Density of points is indicated by orange contour lines. (B) Cluster prediction accuracy for each cell type for Seurat (Hao et al., 2021), Symphony (Kang et al., 2021), and modified scArches. (C) Distributions of age prediction for nuclei from snRNA-seq data from neurotypical control PFC samples (Velmeshev et al., 2019), and our ga39, and 261- and 443-day PFC samples, using only astrocytes of L2-3 PNs for Seurat (left) and Symphony (right). (D) Distributions of age prediction for nuclei from our snRNA-seq of the ASDPFC sample prepared by two different nuclei isolationmethods (FANS versus sucrose gradient nuclei purification). (E) Distributions of age prediction for nuclei from snRNA-seq profiling of the glioblastoma and cerebral organoid samples. (F) Cell type identities of clusters connected to query-dominated clusters. For all partition-based graphical abstraction algorithm (PAGA) connections between query-dominated and reference-dominated Leiden clusters, the weight or strength of these connections (y axis) is plotted for each sample, colored by any cell type with over 100 nuclei present in the reference-dominated cluster. Where multiple cell types are prevalent within a single cluster, multiple points are plotted at the same weight. The red dashed line represents the filtering weight of 0.15. (G) snRNA-seq UMAP outline overlaid with projection of nuclei from the glioblastoma snRNA-seq in hexbin format colored by average G2MPhase Score (top) and Stem Cell Core Network Score (Ang et al., 2011) (bottom). (H) UMAP of snRNA-seq of each cerebral organoid sample, annotated by their cell type labels (top row) and stage prediction (bottom row) as determined by developmental snRNA-seq reference integration. Note that the points are transparent to allow overlaid points to be visible. (I) Proportion overlap between gene trends and the DEGs from the analysis of immature organoid PNs versus mature organoid PNs of brain organoids. ll OPEN ACCESS Resource