Regulation of gene expression in the mouse oocyte and early preimplantation embryo : developmental changes in Sp 1 and TATA box - binding protein , TBP Diane

  • M . Worrad, Prahlad T . Ram, Richard M . Schultz
  • Published 1994

Abstract

During the growth phase, oocytes synthesize and accumulate RNA (mRNA, rRNA and tRNA), proteins and organelles (e.g., mitochondria) that constitute the maternal contribution to early development. In the mouse, this maternal contribution sustains and directs the first cell cycle, which is about 18-20 hours long (Howlett and Bolton, 1985). Oocyte maturation initiates the degradation of maternal mRNA and this destruction is essentially complete by the end of the 2-cell stage (Bachvarova and DeLeon, 1980; Bachvarova et al., 1985, 1989; Paynton et al., 1988). Zygotic gene activation (ZGA), which has definitely occurred during the 2-cell stage (Flach et al., 1982; Sawicki et al., 1982; Bensaude et al., 1983; Latham et al., 1991; Manejwala et al., 1991; Schultz, 1993), replaces maternal transcripts that are lost during this time and are common to both the oocyte and preimplantation embryo, as well as generating novel ones that are required for embryogenesis. In this regard, it should be noted that whereas cleavage to the 2-cell stage does not require transcription, subsequent cleavages do require transcription (Golbus et al., 1973; Bolton et al., 1984; Poueymirou and Schultz, 1989). Thus, ZGA in the 2-cell embryo is requisite for further development. The onset of ZGA in the mouse appears to be a function of the time following fertilization rather than on cell cycle progression, i.e., ZGA may be regulated by a zygotic clock rather than the number of cell cycles (Schultz, 1993). Although the regulation of this maternal to zygotic transition is poorly understood at the molecular level, post-translational modifications of maternally derived proteins are implicated. Numerous changes in the pattern of protein synthesis occur during the first cell cycle and these are due to the recruitment of maternal mRNAs (Cascio and Wassarman, 1982) and post-translational protein modification, mainly protein phosphorylation (van Blerkom, 1981). Inhibition of the cAMP-dependent protein kinase (PKA), but not protein kinase C or the calmodulin-modulated protein kinase, inhibits ZGA (Poueymirou and Schultz, 1987, 1989, 1990). Also consistent with a role for post-translational regulation regulating ZGA is that the increase in hsp70 mRNA that occurs between the 1-cell and 2-cell stages is not inhibited by treatment of 1-cell embryos with cycloheximide (Manejwala et al., 1991). More recent work indicates that although the 1-cell embryo has previously been referred to as transcriptionally inert, a transcriptionally permissive state develops in the late 1-cell embryo (Latham et al., 1992) and that expression of an Sp12347 Development 120, 2347-2357 (1994) Printed in Great Britain © The Company of Biologists Limited 1994

Cite this paper

@inproceedings{Worrad1994RegulationOG, title={Regulation of gene expression in the mouse oocyte and early preimplantation embryo : developmental changes in Sp 1 and TATA box - binding protein , TBP Diane}, author={M . Worrad and Prahlad T . Ram and Richard M . Schultz}, year={1994} }