Implantation Failure of Blastocysts Derived from Oocyte-directed Connexin 43 depleted Mice is Associated with Impaired Ribosomal and Translational Machinery Gene Expression. Mus musculus

Oocyte quality is a well- established determinant of embryonic fate. However, the molecular participants and biological markers that affect and predict adequate embryonic development are largely elusive. We have previously reported that oocyte- directed Connexin 43 (Cx43) depletion leads to embryo implantation defects, although both the morphology of the oocyte and processes presiding embryo implantation appear to undergo normally. In the context of previous data determining Cx43 indispensability to oocyte and embryonic development, we show here that the timing of Cx43 depletion from the oocyte and the ovarian follicle is crucial in determining the severity of subsequent embryonic defects. Specifically, we show that the implantation defects of blastocysts resulting from oocyte- directed Cx43- depleted follicles (depletion occurs at day 3 postnatal), is not due to maternal luteal insufficiency but rather depends solely on the defective blastocysts. Gene expression microarray analysis revealed global defects in the expression of ribosomal proteins, translation initiation factors and other genes associated with cellular biosynthetic and metabolic processes in these defective oocytes and specifically blastocysts. We therefore propose that timely expression of Cx43 in the oocyte and ovarian follicles is a major determinant of oocyte developmental competence, by determining the ability of the resulting blastocyst to facilitate biomass expansion and undergo adequate embryo implantation Overall design: To study the effect of CX43 on the transcriptom of the pre implantation stages, we compared CX43 KO oocytes to the WT oocytes in three different stages of the very early development. First comparison MII oocytes, second comparison blastocysts, third comparison implantation site.

卵母细胞质量是决定胚胎发育命运的公认关键因素。然而，能够影响并预测正常胚胎发育的分子调控因子与生物学标志物，在很大程度上仍未明确。我们此前曾报道，卵母细胞特异性的间隙连接蛋白43（Connexin 43, Cx43）缺失会导致胚胎着床缺陷，尽管卵母细胞形态以及调控胚胎着床的相关过程均表现正常。结合此前证实Cx43对卵母细胞与胚胎发育不可或缺的研究数据，本研究证实，从卵母细胞及卵巢卵泡中缺失Cx43的时机，是决定后续胚胎缺陷严重程度的关键因素。具体而言，我们发现，源自卵母细胞特异性Cx43缺失卵泡（缺失发生于出生后第3天）的囊胚所出现的着床缺陷，并非由母体黄体功能不全所致，而是完全源于存在缺陷的囊胚本身。基因表达微阵列分析（Gene expression microarray analysis）结果显示，在这些存在缺陷的卵母细胞及囊胚中，核糖体蛋白、翻译起始因子以及其他与细胞生物合成、代谢过程相关的基因表达均存在全局性异常。据此我们提出，卵母细胞与卵巢卵泡中Cx43的适时表达，是决定卵母细胞发育潜能的核心因素——其通过调控囊胚的生物量扩增能力与正常胚胎着床过程来实现这一作用。
实验设计：为研究CX43对着床前发育阶段转录组的影响，我们在胚胎早期发育的三个不同阶段，将CX43敲除（Knockout, KO）卵母细胞与野生型（Wild Type, WT）卵母细胞进行对比。第一组对比为MII期卵母细胞（MII oocytes），第二组为囊胚，第三组为着床位点。