Abstract 16457: Characterization of LTBP2 Mutation in Causing Mitral Valve Prolapse

Introduction: Mitral Valve Prolapse (MVP) is a cardiac valvular disorder often associated with significant morbidity and mortality with a prevalence of 2.4% in the general population. Familial studies of MVP suggest an autosomal dominant model of inheritance with incomplete penetrance.

Hypothesis: The aim of the current study was to identify a genetic etiology for MVP through trait segregation in a progeny with MVP.

Methods: We used exome sequencing and segregation analysis to identify mutations linked to MVP in a progeny which includes members. We then generated two strains of mice using Crisper-Cas9 technology, a complete knockout and a knock-in mouse of the top candidate mutation. At 6 months of age echocardiography was done, the mice were sacrificed and the valves were examined pathologically as well as histologically by Movat pentachrome staining. The readers of both the echo and histology were blinded to the genotype.

Results: Of 11 genes with rare deleterious mutations only LTBP2 Val1506Met variant (minor allele frequency of 0.0001) segregated with the trait with a LOD score of 1.5[-DR1] . Knockout mice were more likely to demonstrate myxomatous changes by histology (7 of 9 vs 2 of 6 animals, p=0.03) and echocardiography (14 of 22 vs 1 of 8, p=0.01). Knock-in mice demonstrated significantly higher phenotype rate by histology (8 of 8 vs 0 of 7, p<0.0005) and higher nominal phenotype by echo (4 of10 vs 1 of 9, p=0.2).

Conclusions: LTBP2 Val1506Met variant segregated with MVP in a large pedigree. Animal models that recapitulate the phenotype suggest that the mutation is indeed pathogenic and leads to myxomatous valvular change.