Embryonic Stem Cells/induced Pluripotent Stem Cells

Understanding the regulation of cell-cell interactions during the formation of compact myocardial structures is important for achieving true cardiac regeneration through enhancing the integration of stem cell-derived cardiomyocytes into the recipient myocardium. In this study, we found that cellular repressor of E1A-stimulated genes 1 (CREG1) is highly expressed in both embryonic and adult hearts. Gainand loss-of-function analyses demonstrated that CREG1 is required for differentiation of mouse embryonic stem (ES) cell into cardiomyocytes and the formation of cohesive myocardium-like structures in a cell autonomous fashion. Furthermore, CREG1 directly interacts with Sec8 of the exocyst complex, which tethers vesicles to the plasma membrane. Site-directed mutagenesis and rescue of CREG1 knockout ES cells showed that CREG1 binding to Sec8 is required for cardiomyocyte differentiation and cohesion. Mechanistically, CREG1, Sec8 and N-cadherin co-localize at intercalated discs in vivo and are enriched at cellcell junctions in cultured cardiomyocytes. CREG1 overexpression enhances the assembly of adherens and gap junctions. By contrast, its knockout inhibits the Sec8-N-cadherin interaction and induces their degradation. These results suggest that the CREG1 binding to Sec8 enhances the assembly of intercellular junctions and promotes cardiomyogenesis. STEM CELLS 2016 00:000–000 SIGNIFICANCE STATEMENT: Understanding the regulation of cell-cell interactions during the formation of compact myocardial structures is important for achieving true cardiac regeneration through enhancing the integration of stem cell-derived cardiomyocytes into the recipient myocardium. In this study, we uncovered a novel mechanism whereby CREG1 promotes cardiomyogenesis and myocyte interactions by binding to the exocyst. The findings are important to our understanding of the formation of intercalated discs that connect myocytes in the myocardium. Furthermore, CREG1 gene transfer may improve the integration of stem cell-derived cardiomyocytes into the recipient heart. CREG1 regulates cardiomyogenesis www.StemCells.com ©AlphaMed Press 2016 2