Expression of the growth factor-inducible immediate early gene cyr61 correlates with chondrogenesis during mouse embryonic development.

cyr61 is a growth factor-inducible immediate early gene initially identified in serum-stimulated mouse fibroblasts. It encodes a member of an emerging family of cysteine-rich secreted proteins that includes a connective tissue growth factor. We show here that cyr61 is expressed in the developing mouse embryo and extraembryonic tissues. In the placenta, cyr61 is expressed in regions of trophoblastic origin, including the ectoplacental cone and the trophoblastic giant cells. In the midgestation embryo, cyr61 is expressed in the smooth muscle vessel walls of the arterial circulatory system. Most notably, expression is found in developing cartilaginous elements, including the limbs, ribs, and prevertebrae. In addition, regions of the chondrocranium and craniofacial elements, such as Meckel's cartilage, also express cyr61. Thus, cyr61 transcript is found in mesenchymal cells of both mesodermal and ectodermal origin during their differentiation into chondrocytes. The temporal and spatial regulation of cyr61 expression and the biochemical features of its encoded protein suggest that cyr61 may be important for the normal growth, differentiation, or morphogenesis of the cartilaginous skeleton of the embryo.