Cardiac Functional and Structural Implications of Lamin A/C Mutations

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 DESCRIPTION (provided by applicant): Cardiomyopathies and arrhythmia are conditions with high morbidity and limited therapies. Although a vast number of genes have been discovered to contribute to the etiology of these diseases, translational research- the practical application of genetic knowledge to improve screening, diagnosis, and treatment for affected individuals and their families-has been limited. One major obstacle is the lack of functional studies to understand the relationship between genotype and emergent phenotype at multiple physiological scales (cells to tissues) and to identify factors that cause clinical variability between and within families. The proposed study focuses on three affected families each with different mutation in the Lamin A/C (LMNA) gene. LMNA encodes the main protein of the nuclear lamina, the structural matrix of the nuclear envelope that interacts with both the cell nucleus and cytoskeleton. In this proposal, we will test the hypothesis that LMNA mutations are associated with defects in the structure, organization, and function at multiple length-scales. Between families, the severity of the defects is associated with the type of LMNA mutation; and within families, severity is modified by additional genetic factors. Our long term goals are to develop in vitro disease models directly from patients to understand how proper cell structure, tissue organization, and contractile function are affected by the mutation and genetic modifiers. In Specific Aim 1, we will use exome sequencing and in vitro tissue engineering techniques to evaluate genomic variation and defects in cell and nuclear morphology, intracellular architecture, motility, and tissue self-assembly and architecture in fibroblasts from LMNA patients and controls. In Specific Aim 2, we will derive induced pluripotent stem cells (iPS) from fibroblasts and analyze cell structure and tissue organization of iPS-derived cardiomyocytes from LMNA patients and controls. In Specific Aim 3, we will use RNA sequencing to test for altered gene expression and the "Heart-on-a-Chip" to characterize contractility function (frequency, systolic, diastolic, and twitch stresses) of iPS-derived cardiomyocytes from LMNA patients and controls. These results combined with information of genetic and phenotypic variances will imply pathways and functionalities we will further study. Understanding of the complex relationship between genotype and emergent phenotype and identifying modifying factors will provide insight into the mechanism of heart disease and may assist in the development of new preventative, diagnostic, and therapeutic strategies.