Ontogeny of temperature-regulated heat shock protein 70 synthesis in preimplantation bovine embryos

J. Lannett Edwards, Alan D. Ealy, Victor Hugo Monterroso, Peter J. Hansen

Research output: Contribution to journalArticle

65 Scopus citations

Abstract

Development of the preimplantation embryo is very susceptible to disruption by heat shock. As embryos proceed through development, they acquire resistance to heat shock, perhaps because they become transcriptionally active and can respond to environmental changes by undergoing transcriptionally-regulated cellular adaptation. Objectives were to determine the ontogeny of heat shock protein 70 (HSP70) synthesis in preimplantation bovine embryos and to ascertain whether heat-induced increases in HSP70 in embryos are caused by environmental alterations in gene expression. Exposure of bovine embryos to heat shock induced synthesis of a 68 kDa form of HSP70 called HSP68 as early as the two-cell stage of development. Induction of HSP68 was α-amanitin independent at the two-cell stage but was blocked by α-amanitin as early as the early four-cell stage. Therefore, heat-induced synthesis of HSP68 is regulated at the level of transcription at a time before the major round of embryonic genome activation is considered to occur. Two other constitutive HSP70 molecules were identified called heat shock cognates (HSC) 71 and 70; both proteins were synthesized during all stages of development from the two-cell to hatched blastocyst stages. However, heat-induced synthesis of HSC71 and HSC70 was not evident until the expanded blastocyst stage. In conclusion, environmental signals can activate gene expression before the major round of embryonic genome activation occurs in bovine embryos. Moreover, differences in thermal sensitivity of early embryos to heat shock is not caused by an inability to synthesize HSP70, suggesting that other mechanisms are involved in developmental acquisition of thermotolerance.

Original languageEnglish (US)
Pages (from-to)25-33
Number of pages9
JournalMolecular Reproduction and Development
Volume48
Issue number1
DOIs
StatePublished - Sep 1 1997

Keywords

  • Embryos
  • HSP70
  • Heat shock

ASJC Scopus subject areas

  • Genetics
  • Developmental Biology
  • Cell Biology

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