Prominent Beta-5 Gene Expression in the Cardiovascular System and in the Cartilaginous Primordiae of the Skeleton During Mouse Development

The alpha v beta (αvβ5) heterodimer has been implicated in many biological functions, including angiogenesis. We report the β5 gene expression pattern in embryonic and foetal mouse tissues as determined by Northern blotting and in situ hybridization. During the earliest stages, β5 mRNA is widespread in the mesoderm. During later developmental stages, it remains mostly confined to tissues of mesodermal origin, although probable inductive effects trigger shifts of β5 gene expression from some mesenchymatous to epithelial structures. This was observed in the teeth, skin, kidneys, and gut. Of physiological importance is the β5 labeling in the developing cardiovascular and respiratory systems and cartilages. Furthermore, early β5 gene expression was observed within the intra- and extraembryonic sites of hematopoiesis. This suggests a major role for β5 in the hematopoietic and angiogenic stem cells and thus in the development of the vascular system. Later, the β5 gene was expressed in endothelial cells of the vessels developing both by angiogenesis and vasculogenesis in the lung, heart, and kidneys. Moreover, the β5 hybridization signal was detected in developing cartilages but not in ossified or ossifying bones. β5-Integrin is a key integrin involved in angiogenesis, vasculogenesis, hematopoiesis, and bone formation.