Crispr-Mediated In Vivo Confirmation Of Rare Variants In Vinculin And Tropomysin1 Act Combinatorially To Dilated Cardiomyopathy

Background: The genetic basis of dilated cardiomyopathy (DCM) is poorly understood. We identified a family in which multiple members have DCM and novel variants encoding the costameric protein VINCULIN ( VCL c.659dupA (p.Asn220fs (p.N220fs), termed VFS ) and the sarcomeric regulatory protein TROPOMYOSIN 1 ( TPM1 c.97Gu003eA (p.Glu33Lys (p.E33K), termed TEK ). Sequencing of 31 family members showed the combination of VFS and TEK cosegregated significantly with all members diagnosed with DCM across 3 generations (Beta Hypothesis: Novel variants in VCL and TPM1 act combinatorially to predispose individuals to develop DCM. Methods: CRISPR-mediated editing was used to introduce patient-specific nucleotide variants into the mouse genome. Single and double-allelic variant mice were investigated under basal and hemodynamic stress (produced by Transverse Aortic Constriction (TAC)), with echocardiography, morphometry and histology. Results: Left ventricular (LV) contractility of VFS /+ and TEK /+ mice were normal at 15 and 34 weeks (w). At 58w doubly-heterozygous mice ( TV-Dhet ) but not VFS /+ or TEK /+ exhibited significantly decreased LV contractility (%fractional shortening (FS)) (Fig.1A) vs. WT mice. However, TV-Dhet did not display LV dilation, or alterations in morphometric values (e.g. Heart Weight /Tibia Length). Since family members with TV-Dhet variants exhibit variable DCM penetrance and expressivity, we investigated whether environmental stress induced by TAC, would mediate disease susceptibility in the complex genetic background. TV-Dhet mice provoked by TAC showed stigmata of DCM including a significant reduction in %FS (Fig.1B), increased LV dimensions and normalized mass. Conclusion: Novel variants in VCL and TPM1 combinatorially predispose to the development of DCM in a 3-generation family, as replicated in gene-edited mouse models. These results further our understanding of the complexity of multi-allelic DCM.