EXPRESSION OF SGP-1 MESSENGER-RNA IN PREIMPLANTATION MOUSE EMBRYOS

In a search for genes expressed in preimplantation mouse embryos that are important for the earliest steps in differentiation, we identified an abundant mRNA that codes for a sulfated glycoprotein, SGP-1. The a mount of this RNA rises similar to 100-fold during preimplantation dev elopment to a level approximately equal to that of p-actin mRNA in bla stocysts, although the level of these transcripts per cell remains fai rly constant during these stages at similar to 2,000-4,000 copies. An antisense RNA that is complementary to approximately the last one-thir d of the message and contains an open reading frame of 455 nt was foun d in blastocysts at a 2-3-fold higher level than the mRNA. In situ hyb ridization with sense and antisense riboprobes showed that both strand s are distributed throughout the embryo. The abundance of the SGP-1 mR NA indicates that the encoded protein may play an important role in th e development of embryos, and the excess of antisense RNA raises the p ossibility of an unusual mechanism of regulating its expression. (C) 1 995 Wiley-Liss, Inc.