During heart valve development, epithelial-mesenchymal transformation (EMT) is a 
key process for valve formation. EMT leads to the generation of mesenchymal 
cells that will eventually become the interstitial cells (fibroblasts) of the 
mature valve. During EMT, cell architecture and motility change markedly; 
significant changes are also observed in various signaling pathways. Here we 
systematically examined the expression, localization, and function of zyxin, a 
focal adhesion protein, in EMT during atrioventricular (AV) valve morphogenesis. 
Expression and localization studies showed that zyxin was expressed in the AV 
canal region during crucial stages of valve development. An in vitro 3D collagen 
gel culture system was used to determine zyxin function either after siRNA gene 
knockdown or after overexpression. Our studies revealed that zyxin 
overexpression inhibited endocardial cell migration and cell differentiation and 
also led to a decrease in the number of migrating mesenchymal cells. Moreover, 
correlative cytoskeletal changes were apparent in response to both 
overexpression and knockdown treatments. Thus, zyxin appears to play a role as a 
regulator of cell migration and differentiation during EMT in chicken AV valve 
formation.