EXPRESSION OF OSTEOPONTIN IN THE HEAD PROCESS LATE IN GASTRULATION INTHE RAT

Osteopontin (OPN) is a secreted, glycosylated phosphoprotein. Previous studies have implicated OPN in calcification/decalcification and infl ammation. We became interested in developmental expression of OPN beca use of our previous findings that suggest OPN may play a role informat ion of new vascular layers after injury, and because of our observatio n of developmental regulation in vascular smooth muscle cells. While O PN was expressed at low levels in vessels, only late in development, e xamination of very early expression patterns revealed a surprising fin ding. OPN was expressed exclusively in the head process, on day 9.0, l ate in gastrulation in the rat. In vitro studies of vascular smooth mu scle cells have previously demonstrated that OPN promotes cell adhesio n and migration. It is suggested that OPN may promote migration of cel ls, during gastrulation, via integrins which may be present in the hea d process or overlying ectoderm. (C) 1995 Wiley-Liss, Inc.