多能性转录因子OCT4和SOX2在体外发育的小鼠2-细胞胚胎的表达与定位

为探讨多能性转录因子OCT4和SOX2在昆明小鼠(Mus musculus)2-细胞胚胎发育过程中与2-细胞胚胎阻滞发生的相关性,本研究应用实时荧光定量PCR技术检测了小鼠卵母细胞及在M16培养液中培养的不同发育阶段体外受精胚Oct4和Sox2基因的表达,并利用实时荧光定量PCR和免疫荧光技术比较了2-细胞胚、2-细胞阻滞胚和4-细胞胚的OCT4和SOX2的表达与定位。采用ANOVA对实验所得的数据进行分析,P0.05被认为是具有显著性差异。研究结果显示,2-细胞胚只有24.8%发育成4-细胞胚,75.2%的2-细胞胚发生了阻滞。Sox2和Oct4的m RNA在MⅡ期卵母细胞、原核胚、2-细胞胚、4-细胞胚、桑椹胚和囊胚中都有表达。Oct4 m RNA的表达水平在4-细胞胚显著高于2-细胞胚和2-细胞阻滞胚(P0.05),Sox2 m RNA的表达水平在2-细胞胚显著高于2-细胞阻滞胚和4-细胞胚(P0.05),而后两者之间没有差异(P0.05)。OCT4蛋白在2-细胞胚和4-细胞胚中与核共定位,但在2-细胞阻滞胚中弥散存在于胞质中。SOX2蛋白在以上3类胚胎中始终定位于细胞核。上述结果提示,转录因子OCT4和SOX2的表达和定位与小鼠2-细胞胚胎发育阻滞相关,母源性SOX2表达的维持对胚胎合子基因组激活(ZGA)的发生具有重要作用,母源性OCT4的异常定位可能影响了合子基因组激活相关基因的激活,而合子中Oct4的表达影响合子基因组激活后胚胎的发育。     

Expression and regulation of genes associated with cell death during murine preimplantation embryo development

The newly fertilized preimplantation embryo depends entirely on maternal mRNAs and proteins deposited and stored in the oocyte prior to its ovulation. If the oocyte is not sufficiently equipped with maternally stored products, or if zygotic gene expression does not commence at the correct time, the embryo will die. One of the major abnormalities observed during early development is cellular fragmentation. We showed previously that cellular fragmentation in human embryos can be attributed to programmed cell death (PCD). Here, we demonstrate that the PCD that occurs during the 1-cell stage of mouse embryogenesis is likely to be regulated by many cell death genes either maternally inherited or transcribed from the embryonic genome. We have demonstrated for the first time the temporal expression patterns of nine cell death regulatory genes, and our preliminary experiments show that the expression of these genes is altered in embryos undergoing fragmentation. The expression of genes involved in cell death (MA-3, p53, Bad, and Bcl-xS) seems to be elevated, whereas the expression of genes involved in cell survival (Bcl-2) is reduced. We propose that PCD may occur by default in embryos that fail to execute essential developmental events during the first cell cycle. Mol. Reprod. Dev. 51:243–253, 1998. © 1998 Wiley-Liss, Inc.