热激损伤对牛孤雌激活胚胎后续发育的影响

The Effects of Heat Shock on the Development of Bovine Parthenogenetic Embryos in vitro

为了研究早期胚胎核与胞质对热激的应激反应,以及产生应激后二者之间的相互作用对胚胎体外发育、合子期激活基因的表达及胚胎细胞凋亡的影响。本研究将孤雌激活胚随机分为2组分别于38.5或41℃培养7h;随后将二者核进行置换,使用正常培养的胚胎与热激胚胎进行核置换,分别构建热激核-正常胞质重构胚以及热激胞质-正常核重构胚,检测了核质置换胚胎的体外发育率、合子激活基因的表达和胚胎凋亡情况。结果,当正常核移入41℃热激的卵胞质,重构胚的发育率显著下降;热激后的核质置换胚胎中存在合子基因激活不完全的现象,这种情况主要存在于热激胞质-正常核重构胚中;热激能诱导胚胎发生细胞凋亡,早期胚胎的胞质对热激更敏感,并在后期的诱导凋亡中起到主导作用。这些结果表明,虽然热激对核和胞质都有损伤,但胞质对热激损伤更为敏感。早期胚胎受到热激后导致发育能力降低的易感性主要是由胞质所引起的;早期胚胎受到热激可能会损伤到卵胞质中的母源因子,即使与正常核构成重构胚也依然会导致合子基因表达异常;并且胞质受到热激损伤会在热激诱导的凋亡机制中起到比核更大的作用。

The present study was conducted to investigate the stress response of nuclear or cytoplasmic components to heat shock,and the detrimental effects of heat shock on expression of zygotic genes stage,cell apoptosis and in vitro development of bovine embryos.The parthenogenetic embryos were incubated at 38.5 or 41 ℃ for 7 h,respectively;then the nuclei of embryos cultured at 41 ℃ were transferred into cytoplasts enucleated at 38.5 ℃ to construct heat shock nuclei-normal cytoplasm embryos（HN embryos） and 38.5 ℃ nuclei were transferred into 41 ℃ cytoplasts to construct heat shock cytoplasm-normal nuclei embryos（HC embryos）.The development rate of nuclei-cytoplasm exchange embryos,expression of zygotic activated genes and apoptosis of embryo cells were detected.In vitro culture showed that blastocyst formation rate for HC embryos decreased significantly compared to parthenogenetic embryos in control and HN embryos.Incomplete activation of zygotic genes was observed in nuclear exchange embryos,especially in HC embryos.It suggested that heat shock might disrupt some cytoplasmic factors required for zygotic gene activation.Apoptosis induced by heat shock was observed in both HN and HC blastocysts and the incidence of apoptosis in HC blastocysts was significantly higher than that in HN embryos.These results suggested that：although heat shock injuries exist in both nuclear and cytoplasmic components,cytoplasmic component is more susceptible to heat shock than nuclear component.