Abbey Bullard
Pronouns: She/Her/Her’s
Research Mentor(s): Adam Helms
Research Mentor School/College/Department: Internal Medicine / Cardiovascular Medicine / Medicine
Program: UROPF
Session: Session 1 (9:00am – 9:50am)
Authors: Abbey Bullard , Joshua Meisner , Adam Helms
Abstract
Hypertrophic Cardiomyopathy (HCM) is a cardiac disease with a high mortality and morbidity rate, impacting every 1/500 adults. HCM is predominantly an autosomal dominant heritable disease of the sarcomere. The most common affected gene is MYBPC3, which encodes cardiac myosin binding protein C (MyBP-c). Complete loss of functional MyBP-c in homozygous truncating and missense MYBPC3 variants result in dilated cardiomyopathy. Heterozygous pathogenic variants are disease causing in humans with ~50% reduction of MyBP-c but result in only mildly reduced MyBP-c levels in mice and no hypertrophy through altered protein degradation. We hypothesize that a mouse model with a spectrum of partial alternative splice variants can yield a spectrum of reduction in MyBP-c protein and produce a hypertrophic cardiomyopathy phenotype. Using a patient derived partial alternative splice variant as a template, we generated an initial and then 4 additional modified MYBPC3 knock-in strains through CRISPR mediated homology directed repair with five expected differential precentages in alternative splicing. Knockout strains were also generated through non-homology end joining during CRISPR editing. Heart size and function, MyBP-c protein, and RNA expression were quantified in knock-in and knockout strains along with littermate control wild-type mice. The initial knock-in strain demonstrated a 95% reduction in MyBP-c protein and alternative splicing through RNA sequencing analysis. This marked reduction in protein expression resulted in a dilated cardiomyopathy similar to homozygous knock out mice. Preliminary results of the additional 4 knock-in strains through cDNA amplicon sequencing demonstrate a range of percentage of alternative splicing with further analysis of disease phenotype pending. These preliminary data suggest our model of partial alternative splicing could produce a mouse model that appropriately displays a range in reduction of MyBP-c protein levels analogous to the MyBP-c level seen in human disease to yield a HCM mouse phenotype with a range of disease onset. This model would fulfill a critical need for preclinical testing and in vivo mechanistic studies of MYBPC3 related HCM.
