Expression of bone morphogenetic protein-5 gene during chick heart development: Possible roles in valvuloseptal endocardial cushion formation

The bone morphogenetic protein (BMP) family, comprising multifunctional pep tide growth factors, regulates many developmental processes in a variety of tissues. We examined the spatiotemporal expression of BMP5 by in situ hybr idization in chick embryonic hearts from stages 5 to 33. The BMP5 gene was first expressed in the endoderm underlying the precardiac mesoderm at stage s 5 to 8. Thereafter, BMP5 expression was restricted to the myocardium. of the atrioventricular (AV) canal and outflow tract (OT) regions, where the v alvuloseptal endocardial cushion tissue is induced. These results suggest t hat BMP5 may play important roles not only in myocardial differentiation, b ut also in the formation and maintenance of endocardial cushion tissue. Ana t Rec 264:313-316, 2001. (C) 2001 Wiley-Liss, Inc.