Abstract 14808: Protein Kinase D2 Controls Cardiac Valve Formation In Zebrafish By Regulating HDAC5 Activity
The molecular mechanisms that guide valvulogenesis are not well understood but of immense clinical importance, since defects in cardiac valve morphogenesis affiliate to the most common congenital heart defects and often lead to early embryonic death or severe cardiac dysfunction later on. The elucidation of the genetic basis of congenital heart disease is one of the prerequisites for the development of tissue-engineered heart valves. We isolated here a mutation in zebrafish, bungee (bng), which selectively perturbs valve formation and the differentiation of the outflow tract in the embryonic heart. We find by positional cloning that the bng phenotype is caused by a missense mutation (Y849N) in zebrafish protein kinase D2 (pkd2). pkd2 is expressed in the endocardial cell population of the atrioventricular canal (AVC) of the embryonic heart. The bungee mutation leads to the misexpression of important AV canal genes, such as notch1b, versican and spp1. The bng mutation selectively impairs PKD2 kinase activity and hence HDAC5 phosphorylation, nuclear export, and inactivation. As a result, expression of HDAC5 target genes Krüppel-like factor 2a and 4a, transcription factors known to be pivotal for heart valve formation and to act upstream of NOTCH signaling, is severely down-regulated in bungee mutant embryos. Accordingly, expression of NOTCH target genes such as Hey1, Hey2 and HeyL is severely decreased in bng mutant embryos. Remarkably, downregulation of HDAC5 activity in homozygous bng mutant embryos can rescue the mutant phenotype and reconstitutes notch1b expression in AV endocardial cells. In summary, we demonstrate here for the first time that PKD2-HDAC5-KLF signaling is important for proper formation of cardiac valves.
- © 2011 by American Heart Association, Inc.