Abstract 12498: AAV-Mediated LINC Complex Uncoupling Ameliorates Pathology in a Mouse Model of LMNA Dilated Cardiomyopathy

Abstract

Mutations in the LMNA gene, encoding lamin A/C, are one of the most frequent genetic causes of dilated cardiomyopathy. While gene therapy using adeno-associated virus (AAV) vectors show promise for the treatment of monogenic diseases, LMNA DCM mutations tend to be autosomal dominant and gain-of-function, precluding typical gene replacement approaches. Lamin A/C forms a filamentous network, the nuclear lamina, underlying the nuclear envelope that is thought to function in maintaining structural integrity of the nucleus by resisting cytoskeletal forces transmitted to the nucleus during cardiac contraction. Our hypothesis is that disruption to the lamin A/C network leads to nuclear envelope rupture as the weakened nuclear lamina cannot resist excess cytoskeletal force. Uncoupling the linkage between the cytoskeleton and nucleus might therefore reduce LMNA -associated pathology. This linkage is known to be mediated by the nuclear envelope-localized linker of nucleoskeleton and cytoskeleton (LINC) complex. Using AAV-mediated expression of a LINC complex uncoupling transgene, GSLA01, we were indeed able to prevent the progression of ventricular dilation, cardiac fibrosis, and decline in ejection fraction observed in a LMNA dilated cardiomyopathy mouse model. We decided to explore structure-function relationships in GSLA01 in our lead optimization studies. We generated a series of truncations of full-length GSLA01 comprising different lengths of its coiled coil domain. In vitro assays indicated that most truncations examined were able to uncouple the LINC complex. Selected truncations were delivered using AAV to LMNA DCM mice after inducing cardiac-specific deletion of Lmna with tamoxifen. Full-length GSLA01 extended the lifespan of LMNA DCM mice from 39 to ~170 days. The truncations mostly performed on par or better than full-length GSLA01 in extending the lifespan of LMNA DCM mice, to more than 250 days for certain constructs. Reducing cytoskeletal force transmission to the nucleus by uncoupling the LINC complex appears to be a viable strategy for treating LMNA -linked pathology, and multiple GSLA01 truncation variants can be used to achieve this effect.