Deciphering the role of cytoskeletal-nuclear interactions in peripheral chromatin organization - Project Abstract The mammalian genome is organized into various regions at different scales as one mechanism to regulate gene expression and mediate cellular identity. One type of well-characterized region is the lamina-associated domain (LAD), which contains areas of chromatin that directly interact with the nuclear lamina (NL) at the nuclear periphery. Found across all chromosomes, LADs dynamically interact with the NL to release or attach genes and regulatory elements in accordance with cell-type and differentiation state-specific gene expression programs. Patients with mutations in LMNA, encoding the A and C type lamins in the NL, develop a heterogenous group of diseases, known as laminopathies. Laminopathies preferentially affect striated muscle, and patients often develop dilated cardiomyopathy (DCM), which can be fatal. Evidence from mouse models and human genetic studies of laminopathies have suggested a potential role for the Linker of Nucleoskeleton and Cytoskeleton (LINC) complex in mediating the disease phenotype. Abrogation of the LINC complex in a laminopathy mouse model resulted in a phenotypic rescue. Additionally, characterization of LMNA mutations in various cell types demonstrated a disruption to chromatin-lamina interactions in a cardiomyocyte-specific manner. This suggests a mechanism where the nuclear lamina and LINC complex are each playing a role in the pathogenesis of laminopathy phenotypes, and potentially affecting genome organization. However, while a LINC-LMNA-gene positioning axis has been previously suggested, the mechanism of how this may occur remains elusive. Using a combination of population-based genomics analyses, single-cell microscopy, and cellular functional assays, I will test the hypothesis that cytoskeletal-nuclear interactions in lamin variant cardiomyocytes destabilize LADs and contribute to abnormal cellular function. I aim to define the role of the LINC complex in mediating chromatin organization in LMNA mutant cardiomyocytes and will determine if disruption of LINC complex components can preserve the changes to genome organization observed. In addition, I aim to determine how cardiomyocyte function is affected by disruption of the LINC complex in the presence and absence of LMNA mutations. These studies will provide mechanistic insights into how the nuclear lamina and LINC complex are contributing to both LAD organization and cardiomyocyte function, which will begin to provide novel understanding of the molecular basis of laminopathy phenotypes.
