1Universitätsklinikum Heidelberg Klinik für Innere Med. III, Kardiologie, Angiologie u. Pneumologie Heidelberg, Deutschland
We have identified the transcription factor Zeb1 as one major target of an RNA-binding protein during cardiac remodeling. Zeb1 expression is post-transcriptionally regulated both in vitro and in vivo but its function in cardiac muscle is largely unknown.
To understand the role of Zeb1 in heart we used conditional cardiomyocyte specific Zeb1 KO line. Echocardiography results of 12 weeks old mice revealed a decrease in cardiac function at an early age, which gets worse in aged animals. Since cardiac dysfunction was more pronounced in the older mice, we did histological analysis of 25 weeks and older mice. Masson’s Trichrome Staining, HE and WGA staining revealed structural damage in the sarcomeres of Zeb1 KO as compared to WT heart sections. To understand the structural damage more closely we did electron microscopy of the outer wall of left heart ventricle tissue. The results indicate towards structural damage of the cardiomyocyte sarcomere and an increased mitochondrial death in Zeb1 KO hearts. We did bulk RNA sequencing of left ventricle tissue from young and old mice to find the differentially expressed genes in Zeb1 KO mice with respect to WT. The results confirmed our findings of mitochondrial defects and an increase in extracellular matrix and epithelial markers suggesting that absence of Zeb1 is leading to epithelialization of cardiomyocytes. To confirm our findings and prove our hypothesis we performed ChIP-seq from purified adult mouse cardiomyocytes to identify directs Zeb1 targets We also found a cardiac development defect which might be connected to cell proliferation and maturation perturbations in cardiomyocytes in the absence of Zeb1. To understand it better we are going to test the cardiomyocytes’ function and structure in an inducible knockout model where the Zeb1 KO will be induced at 6 weeks, after the maturation of cardiomyocytes.
Our result indicate that Zeb1 is a major regulator of cardiomyocyte structure, and its absence drastically damages the sarcomere arrangement hence hindering the contractility of cardiac muscles.