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This Article Full Text Full Text (PDF) All Versions of this Article: 76/3/476    most recent biolreprod.106.057422v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by LaRosa, C. Articles by Downs, S. M. Search for Related Content PubMed PubMed Citation Articles by LaRosa, C. Articles by Downs, S. M. Agricola Articles by LaRosa, C. Articles by Downs, S. M.

Meiotic Induction by Heat Stress in Mouse Oocytes: Involvement of AMP-Activated Protein Kinase and MAPK Family Members

Biology Department, Marquette University, Milwaukee, Wisconsin 53233

ABSTRACT

In this study, we examined the effect of heat pulsing on oocyte maturation and assessed the possible role of stress-activated enzymes during heat stress-induced meiotic maturation. Denuded oocytes from immature eCG-primed mice were pulsed for 30 min at increasing temperatures from 40°C to 43°C in dibutyryl cAMP-containing medium and were subsequently cultured at 37°C for a total incubation time of 17–18 h. Oocytes exposed to 42°C showed the greatest stimulation of maturation, with no effect at 43°C. A heat pulse did not compromise progression to metaphase II as observed by polar body (PB) formation. The AMP-activated protein kinase (PRKA) inhibitors compound C and Ara-A each blocked the meiosis-stimulating effects of heat. Western blots showed that acetyl-CoA carboxylase, an important substrate of PRKA, was phosphorylated in heat-treated germinal vesicle-stage oocytes, indicating activation of PRKA before maturation. The mitogen-activated protein 2 kinase (MAP2K1) inhibitor PD98059 also prevented heat-induced maturation, but this effect was unrelated to MAPK1/3 activation, which was not observed until after germinal vesicle breakdown (GVB). Phosphorylated MAPK14 was not detected in the oocyte under any experimental condition, and only high concentrations of the MAPK14 inhibitor SB203580 blocked heat-stimulated maturation, suggesting that MAPK14 is not involved in meiotic induction. MAPK8/9 was activated by heat, and the MAPK8/9 inhibitor SP600125, but not JUN N-terminal kinase I, blocked heat-induced maturation. Heat treatment transiently suppressed GVB and PB formation in spontaneously maturing oocytes by a mechanism that is apparently different from its meiosis-inducing action. Collectively, these data show that an acute heat pulse stimulates GVB in meiotically arrested oocytes and suggest that this effect is mediated through the activation of PRKA.

gamete biology, meiosis, oocyte development, stress