Ethanol elevates c-Myc levels in cultured mouse preimplantation embryos

A brief exposure to ethanol accelerates the rate of early mouse embryonic d evelopment in vitro, increasing blastocyst formation, trophoblast outgrowth , and implantation rates after embryo transfer. The physiological effects o f ethanol during preimplantation development are associated with rapid chan ges in gene expression and apparently arise from the ability of ethanol to elevate cytoplasmic free Ca2+ and alter cellular signaling pathways. The pu rpose of this study was to examine whether the abundance of c-Myc, a transc ription factor that promotes cell proliferation and is required for blastoc yst development, is upregulated in mouse blastocysts challenged with ethano l. After exposure of mouse blastocysts to 0.1% (17.5 mM) ethanol, we determ ined the levels of: 1) c-Myc mRNA, using reverse transcription and the poly merase chain reaction; and 2) c-Myc protein levels, using specific monoclon al antibodies, Within 10 min of exposure to ethanol, the relative abundance of c-Myc mRNA increased G-fold, then rapidly returned to baseline levels w ithin 1 hr. As expected, elevation of c-Myc mRNA by ethanol was attenuated in embryos that were first treated with the intracellular Ca2+ chelator, BA PTA-AM. Western blot analysis of solubilized embryos revealed that c-Myc mR NA was translated into a single 62-kD protein that increased in intensity 3 0 min after treatment with ethanol. Immunocytochemical staining demonstrate d that c-Myc was localized exclusively in nuclei and that staining intensit y increased significantly after 10 min. Peak levels of c-Myc protein were f ound 30 min after ethanol exposure and persisted for at least 2 hr. The c-m yc proto-oncogene seems to be an immediate early response gene for ethanol that may regulate the transcription of other genes that influence early emb ryogenesis and growth.