Myocardial filopodia during early heart development.

We have compared the surface architecture of embryonic chick heart myocardial cells in two different grooves to see if any regional differences in surface features could be related to the developing anatomy of the myocardium. There was a qualitative difference in filopodia distribution. The developing interventricular sulcus completely lacked them whereas the ventral groove had numerous filopodia. The ventral groove is an anatomical landmark that remains after the precardiac anlage have fused. Thus, it is a post-fusion structure. This indentation "pops out" in later development and disappears. This region is therefore more compliant than the interventricular sulcus which doesn't pop out. Filopodia are therefore not associated with fusion or infolding per se but may be related to compliance.