In this thesis we investigated a novel Z-disc protein, cytoskeletal heart-enriched actin-associated protein (CHAP). Two isoforms of CHAP exist, encoded by one gene. The longer isoform CHAPa is... Show moreIn this thesis we investigated a novel Z-disc protein, cytoskeletal heart-enriched actin-associated protein (CHAP). Two isoforms of CHAP exist, encoded by one gene. The longer isoform CHAPa is predominately expressed in adult tissues, whereas CHAPb is expressed during cardiac and skeletal development. First, we investigated CHAP expression in adult mouse tissues in more detail and show that both CHAP isoforms are highest expressed in slow skeletal muscle fibers and vascular smooth muscle cells. In addition, we sequenced and investigated the expression of the chick CHAP isoform and show that CHAP expression in chick is similar to the expression observed in mouse embryo__s. To investigate the role of CHAP in vivo, we generated CHAP knockout embryonic stem cells, which can be used to generate CHAP knockout mice and we investigated the effect of morpolino mediated knockdown of CHAP in chick embryo__s. In addition, we generated heart specific CHAP transgenic (Tg) mice. Whereas in CHAPa Tg mice no phenotype was observed, CHAPb Tg mice developed cardiomyopathy with diastolic dysfunction. In addition, in the hearts of CHAPb Tg mice stress fibers were observed and the actin signaling pathway was activated. To study the effects of CHAP overexpression in vitro, we generated CHAP adenoviruses. We showed that although CHAPb also induced stress fibers in vitro, the actin signaling pathway was not activated, suggesting that this was not a direct effect in Tg mice. In addition, we showed that CHAPa is important for Z-disc integrity in vitro. Finally, we also showed that CHAP is expressed in the small intestine and kidney, and this expression is correlated with F-actin expression. These data show that CHAP is important for muscle development, Z-disc integrity and stability and actin signaling. Show less
