Molecular Insights into the Role of Desmin Intermediate Filament Network  in Chromatin Landscape, Early Cardiogenic Commitment and  Cardiomyocyte Differentiation and Maturation  (HiC)
The cardiac cytoskeleton is essential for the proper intracellular and intercellular integration of structure and function, failure of which leads to heart disease. However, its role during development and cardiac differentiation is often overlooked. ­­­­­Here, we sought to understand the role of the desmin intermediate filament cytoskeletal network in cardiac cell differentiation and homeostasis during embryonic development, post birth, adulthood and upon different stimuli. We show that desmin is highly expressed in cardiac progenitor cell populations during embryogenesis. In addition, using direct cellular reprogramming of fibroblasts to induced cardiomyocytes, we demonstrated that ectopic desmin expression directly influences cardiomyogenesis through a timely transcriptional regulation of the Notch1 signaling pathway. On the contrary, the absence of desmin in induced cardiomyocytes leads to substantial perturbations in cardiac maturation by diminishing the expression and proper localization of cardiac specific proteins, impairing calcium homeostasis and delaying myofibril formation. RNA and ChIP sequencing, along with chromosome conformation capture (HiC) in desmin-depleted cardiomyocytes revealed that the observed gene expression changes reflect the identified corresponding changes in chromatin architecture that cause loss of genome organization and thus contributing to pathophysiological phenotype. Overall design: 8 samples: induced cardiomycytes from WT (Des+/+) and Null (Des-/-) fibrobllasts (2samples), Neonatal Cardiomycytes (NCM) from WT (Des+/+) and Null (Des-/-) mouse hearts (2 samples),  adult Cardiomycytes (ACM) from WT (Des+/+) and Null (Des-/-) mouse hearts (2 samples), adult cardiomyocytes (ACM) from WT (Des+/+) and Null (Des-/-) hearts (2 samples) of mice that have undergone swimming stress exercise. HiC was performed per protocol in Diaz et al  (Diaz, N., K. Kruse, T. Erdmann, A.M. Staiger, G. Ott, G. Lenz, and J.M. Vaquerizas, Chromatin conformation analysis of primary patient tissue using a low input Hi-C method. Nat Commun, 2018. 9(1): p. 4938.). Analyzed by FAN-C