Embryo

Early Transcriptional Activation of the Hsp70.1 Gene by Osmotic Stress in One-Cell Embryos of the Mouse

Abstract
In mouse fertilized eggs, de novo transcription of embryonic genes is first observed during the S phase of the one-cell stage. This transcription, however, is almost limited to the male pronucleus and possibly uncoupled from translation, making the functional meaning obscure. We found that one-cell mouse embryos respond to the osmotic shock of the in vitro isolation by migration of HSF1, the canonical stress activator of mammalian heat shock genes, to pronuclei and by transient transcription of the hsp70.1, but not hsp70.3 and hsp90, heat shock gene. Isolated growing dictyate oocytes also display a nuclear HSF1 localization, but, in contrast to embryos, they transcribe both hsp70.1 and hsp70.3 genes only after heat shock. Intranuclear injection of double-stranded oligodeoxyribonucleotides containing HSE, GAGA box or GC box consensus sequences and antibodies raised to transcription factors HSF1, HSF2, D. melanogaster GAGA factor or Sp1 demonstrated that hsp70.1 transcription depends on HSF1 in both oocytes and embryos and that Sp1 is dispensable in oocytes and inhibitory in the embryos. Hsp70.1 thus represents the first endogenous gene so far identified to be physiologically activated and tightly regulated after fertilization in mammals.

Key words: Embryo • Developmental biology • Early development • Gene regulation • Oocyte development

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				D. C. Wilkerson, L. A. Murphy, and K. D. Sarge Interaction of HSF1 and HSF2 with the Hspa1b Promoter in Mouse Epididymal Spermatozoa Biol Reprod, August 1, 2008; 79(2): 283 - 288. [Abstract] [Full Text] [PDF]