ANTISENSE INHIBITION OF NUCLEAR-ENCODED CYTOCHROME-C-OXIDASE SUBUNITS IV AND VIIC ACTIVITY IN THE PREIMPLANTATION EMBRYO

It had not previously been known whether synthesis of nuclear-encoded mitochondrial subunits occurs in pre-implantation embryos. We have used cytoplasmic injections of antisense RNA transcribed in vitro to study this question. Capped, in vitro transcribed RNA antisense to either cytochrome c oxidase subunit IV or VIIc injected into each cell at the two-cell stage markedly inhibited synthesis of adenine nucleotides by the 8- to 16-cell stage, whereas injection of the cognate sense RNAs gave levels similar to those previously published for normal embryos. These results strongly suggest that translation of nuclear-encoded mRNAs for mitochondrial subunits is required during pre-implantation development. It was of additional interest that, not only was ATP decreased, but ADP and AMP as well, with the effect that the charge ratio remained constant. The results also suggest, therefore, that the mechanism by which cells normally regulate their charge ratio, thought to be with adenylate deaminase, is already in place. (C) 1993 Wiley-Liss, Inc.