COMPARATIVE-ANALYSIS OF FIBRILLAR AND BASEMENT-MEMBRANE COLLAGEN EXPRESSION IN EMBRYOS OF THE SEA-URCHIN, STRONGYLOCENTROTUS-PURPURATUS

The time of appearance and location of three distinct collagen gene tr anscripts termed 1 alpha, 2 alpha, and 3 alpha, were monitored in the developing S. purpuratus embryo by in situ hybridization. The 1 alpha and 2 alpha transcripts of fibrillar collagens were detected simultane ously in the primary (PMC) and secondary (SMC) mesenchyme cells of the late gastrula stage and subsequently expressed in the spicules and gu t associated cells of the pluteus stage. The 3 alpha transcripts of th e basement membrane collagen appeared earlier than 1 alpha and 2 alpha , and were first detected in the presumptive PMC at the vegetal plate of the late blastula stage. The PMC exhibited high expression of 3 alp ha at the mesenchyme blastula stage, but during gastrulation the level of expression was reduced differentially among the PMC. In the late g astrula and pluteus stages, both PMC and SMC expressed 3 alpha mRNA, a nd thus at these stages all three collagen genes displayed an identica l expression pattern by coincidence. This study thus provides the firs t survey of onset and localization of multiple collagen transcripts in a single sea urchin species.