PgmNr Z556: PDGF signaling directs cardiomyocyte movement toward the midline during heart tube assembly.

Authors:
D. Yelon; J. Bloomekatz; A. C. Dunn; M. Vaughan


Institutes
University of California, San Diego, La Jolla, CA.


Abstract:

Communication between neighboring tissues plays a central role in directing cell movement during organ morphogenesis.  Heart tube assembly, for example, begins with the movement of bilateral populations of cardiomyocytes toward the midline, where they merge together in a process called cardiac fusion.  Prior studies have established that cardiac fusion is regulated by interactions between the lateral plate mesoderm and the adjacent endoderm, but the molecular underpinnings of the relationship between these tissues remain unclear.  Here, we reveal a new role for platelet-derived growth factor (PDGF) signaling in mediating tissue communication during heart tube assembly.  We find that mutation of the zebrafish pdgfra gene, encoding PDGF receptor alpha, causes cardia bifida, a failure of cardiac fusion.  Cell tracking experiments demonstrate that this defect is the consequence of misdirected cell movements, indicating a specific role of PDGF signaling in guiding cardiomyocytes toward the midline.  Intriguingly, the PDGF ligand gene pdgfaa is expressed within a portion of the endoderm that is positioned just medial to the pdgfra-expressing lateral plate mesoderm.  Overexpression of pdgfaa throughout the embryo interferes with cardiac fusion, revealing an instructive role for PDGF signaling during this process.  Together, our data suggest a novel mechanism through which endodermal-myocardial communication directs the stereotyped patterns of cell movement that initiate cardiac morphogenesis.



ZFIN Genetics Index
1. pdgfra
2. pdgfaa