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 amount of this RNA rises similar to 100-fold during preimplantation development to a level approximately equal to that of p-actin mRNA in blastocysts, although the level of these transcripts per cell remains fairly constant during these stages at similar to 2,000-4,000 copies. An antisense RNA that is complementary to approximately the last one-third of the message and contains an open reading frame of 455 nt was found in blastocysts at a 2-3-fold higher level than the mRNA. In situ hybridization with sense and antisense riboprobes showed that both strands are distributed throughout the embryo. The abundance of the SGP-1 mRNA indicates that the encoded protein may play an important role in the development of embryos, and the excess of antisense RNA raises the possibility of an unusual mechanism of regulating its expression. (C) 1995 Wiley-Liss, Inc.