Abstract 14573: Dissecting Genetic Determinants Underlying Cardioskeletal Phenotypes Induced by Myopalladin Mutation in Murine Genetic Reference Population of Hybrid BXD Strains

Abstract

Introduction: Mutations in myopalladin ( MYPN) gene are associated with cardiomyopathies (CM) and skeletal myopathies (SM). This study is aimed to identify Mypn -induced cardioskeletal phenotypes in a murine genetic reference population (GRP) and uncover common genetic mechanisms underlying the development of CM and SM. Hypothesis: Mypn induces common molecular signaling in cardiac and skeletal muscles. Methods: Pearson correlation between cardiac function and expression of Mypn in gastrocnemius muscles was performed in 40 mouse BXD recombinant inbred strains derived from C57BL/6J and DBA/2J parental mice. A causal Mypn-Q526X mutation was introduced to BXDs by crossing with MypnWT/Q526X knock-in mice and this generated F1 hybrid mutant (BXDQ526X) and wild type (BXDWT) strains. Cardiac (morphology, function by echo) and skeletal muscle (muscle mass, strength) phenotypes and transcriptomics (RNA-seq) were assessed in 3- and 6-month-old hybrid mice (N=5). Results: Skeletal muscle expression of Mypn was significantly associated with heart rate (HR) and heart mass (HM) in BXDs, while it was negatively associated with interventricular septum (IVS) thickness, indicating BXD strains with higher skeletal muscle Mypn expression had faster HR, higher HM but thinner IVS. Varied phenotypes in ejection fraction (EF%), ventricular volume and hypertrophy were found among BXD Q526X mice; BXD51 Q526X , BXD48 Q526X and BXD69 Q526X strains had significantly higher EF%, while some mutant mice showed EF% decrease compared to their respective BXD WT littermates. Many mutant lines displayed significantly reduced skeletal muscle strength or mass. Overt SM-related signs (rear limb deformity, restricted movement, waddling) were seen in BXD78 Q526X , while we found overlapping CM/SM traits in BXD51 Q526X mice. Conclusions: In this study, common Mypn -induced molecular signaling in cardiac and skeletal muscles is identified. Introduction of the Mypn -Q526X mutation into the diverse genetic background of BXD GRP exposed CM- and SM-related phenotypes in hybrid lines. The most susceptible lines with overt and overlapping CM/SM phenotypes will be useful to identify common genes, networks and pathways involved in CM and SM using systems genetics methods.