Generation and characterization of a new conditional mouse model of Hutchinson-Gilford Progeria Syndrome to assess disease progression upon progerin suppression and lamin A restoration

Abstract

Hutchinson-Gilford progeria syndrome (HGPS) is a rare fatal genetic disorder characterized by accelerated aging and premature death at an average age of 14.6 years. “Classical” HGPS is caused by a heterozygous de novo c.1824 C>T dominant synonymous point mutation in the LMNA gene, which encodes for lamin A and C. This mutation promotes the expression of a mutant protein called progerin, an aberrant form of prelamin A that cannot undergo complete maturation. Progerin remains permanently farnesylated and firmly anchored to the inner nuclear membrane, affecting many cellular processes in a dominant-negative manner. HGPS patients appear normal at birth but develop symptoms of the disease typically during the first and second year of life. Taking into account that there is still no definitive cure for HGPS and that patients are diagnosed when symptoms are already present, it is critically important to ascertain whether the damage caused by progerin expression is reversible or if disease progression can be slowed down or halted upon progerin suppression. It is also necessary to investigate the relative contribution of systemic and tissue-specific factors to the development of HGPS to assess the effectiveness of potential future therapies designed to suppress progerin expression in specific tissues, which, if proven effective, would likely be less challenging than whole-body progerin suppression. In order to address these questions, in this Doctoral Thesis we use the CRISPR-Cas9 system to generate LmnaHGPSrev mice, the first “reversible” mouse model of progeria which expresses progerin ubiquitously and allows a controlled spatio-temporal suppression of progerin expression with concomitant restoration of lamin A expression upon activation of the Cre recombinase. We demonstrate that LmnaHGPSrev/HGPSrev mice recapitulate the main features of human HGPS, including failure to thrive, cardiovascular alterations and premature death. Moreover, we show that Cre activation upon tamoxifen treatment starting at an advanced stage of the disease in LmnaHGPSrev/HGPSrev Ubc-CreERTtg/+ progeroid mice prolongs their life span. Finally, we show that gene therapy with adeno-associated virus overexpressing Cre ameliorates postnatal growth of adult LmnaHGPSrev/HGPSrev of the therapy. These studies with the LmnaHGPSrev scope of the present Doctoral Thesis, will shed significant light on the cellular and molecular mechanisms of HGPS and pave the way to developing more efficient therapies.