Oxygen-Regulated Gene Expression in Bovine Blastocysts1

A.J. Harvey, K.L. Kind, M. Pantaleon, D.T. Armstrong, J.G. Thompson
2004 Biology of Reproduction  
Oxygen concentrations used during in vitro embryo culture can influence embryo development, cell numbers, and gene expression. Here we propose that the preimplantation bovine embryo possesses a molecular mechanism for the detection of, and response to, oxygen, mediated by a family of basic helix-loophelix transcription factors, the hypoxia-inducible factors (HIFs). Day 5 compacting bovine embryos were cultured under different oxygen tensions (2%, 7%, 20%) and the effect on the expression of
more » ... e expression of oxygen-regulated genes, development, and cell number allocation and HIF␣ protein localization were examined. Bovine in vitro-produced embryos responded to variations in oxygen concentration by altering gene expression. GLUT1 expression was higher following 2% oxygen culture compared with 7% and 20% cultured blastocysts. HIF mRNA expression (HIF1␣, HIF2␣) was unaltered by oxygen concentration. HIF2␣ protein was predominantly localized to the nucleus of blastocysts. In contrast, HIF1␣ protein was undetectable at any oxygen concentration or in the presence of the HIF protein stabilizer desferrioxamine (DFO), despite being detectable in cumulus cells following normal maturation conditions, acute anoxic culture, or in the presence of DFO. Oxygen concentration also significantly altered inner cell mass cell proportions at the blastocyst stage. These results suggest that oxygen can influence gene expression in the bovine embryo during postcompaction development and that these effects may be mediated by HIF2␣. developmental biology, early development, embryo, environment, gene regulation 1
doi:10.1095/biolreprod.104.028639 pmid:15163614 fatcat:u2umypbxvna4pecpnb7tomuv3a