Antisense RNA inhibits endogenous gene expression in mouse preimplantation embryos: lack of double-stranded RNA "melting" activity.

beta-Glucuronidase activity increases 60-fold from the 4-cell to the blastocyst stage during in vitro development of mouse preimplantation embryos, secondary to a 13-fold increase in beta-glucuronidase mRNA. Injections of antisense RNA from a beta-glucuronidase cDNA clone lacking the 5'-untranslated region and the coding sequences for approximately equal to 150 N-terminal amino acids were effective in partially blocking the appearance of beta-glucuronidase activity. Injection of the same RNA, capped with guanosine(5')triphospho(5')guanosine (GpppG), into each blastomere at the 4-cell stage yielded 75% inhibition of enzyme activity at the blastocyst stage. Injections of the sense strand or of an unrelated RNA did not alter the normal increase in activity of the enzyme. These results are in accord with our inability to detect RNA-duplex "melting" activity in 1-cell mouse embryos. We suggest that it may be possible to analyze genetics of mammalian development by antisense techniques.