Poster abstracts
Poster number 29 submitted by Tyler Stevens
Novel ACM Mouse Model Derived From a Human DSP Variant Displays a Cardiac Phenotype Upon Cardiac Stress
Tyler L. Stevens (MCDB), Heather Manring (Comprehensive Cancer Center, The Ohio State University College of Medicine and Wexner Medical Center, Columbus, OH 43215, USA.), Trevor Dew, Michael J. Wallace, Aaron Argall, Sara Koenig, Mona El Refaey (2Department of Physiology and Cellular Biology, The Ohio State University College of Medicine and Wexner Medical Center, Columbus, OH, 43215, USA), Xianyao Xu, Thomas J. Hund (Department of Biomedical Engineering, Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH 43215, USA.), Maegen Ackermann (Department of Natural Sciences, Mansfield University of Pennsylvania, Mansfield, PA 17101, USA.), Peter J. Mohler (Physiology and Cellular Biology, The Ohio State University)
Abstract:
Arrhythmogenic Cardiomyopathy (ACM) is a disease that affects 1 in 2000 Americans yearly and segregates with sudden cardiac death (SCD). Approximately 60% of all ACM cases are associated with variants in desmosomal genes, however the molecular mechanisms associated with ACM remain unclear. Up to 20% of ACM-causing variants are within the desmosomal protein desmoplakin (DSP), a structural protein responsible for linking intermediate filaments to the intercalated disc (ID) to maintain structural integrity between cardiomyocytes. A mutational hotspot of ACM-linked variants exists within the N-terminus DSP, consisting of multiple spectrin repeats surrounding an SH3 domain. One studied DSP variant was identified in a large family that segregated strongly ACM, with multiple cases of SCD being identified. Tissue analysis from genotype-positive revealed fibro-fatty infiltration within the ventricular myocardium. Immunofluorescence identified disorganization of key ID proteins when compared to control tissue. Stem cells were isolated from the family to generate engineered heart tissue to identify changes in contractility and calcium signaling. Evaluation of the biomolecular properties of pathogenic hotspot-variants identified increased susceptibility to calpain-dependent degradation in select variants. Using molecular dynamics, we assessed essential intramolecular interactions and surface area exposure of a calpain target site within DSP to predict pathogenicity. To evaluate the effects of DSP variants on cardiac function and disease development, a mouse model containing a novel pathogenic DSP variant was established. Embryonic lethality was identified in mice carrying two copies of the novel variant. Mice expressing this novel variant heterozygously display reduced DSP protein levels from the ID. In addition, this novel mouse model displays an increased propensity for inducible ventricular arrhythmias upon adrenergic stimulation. Pressure overload resulted in reduction of cardiac functional output and chamber dilation. Future studies focus on establishing a mechanism of protection for calpain sensitive variants, along with further evaluation of the novel mouse model.
Keywords: Desmoplakin, Calpain, Arrhythmogenic Cardiomyopathy