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

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 To study the effect of CX43 on the transcriptome 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（oocyte）质量是公认的胚胎发育命运决定因素。然而，能够影响并预测胚胎正常发育的调控分子与生物标志物，在很大程度上仍未明确。我们此前曾报道，靶向卵母细胞的连接蛋白43（Connexin 43, Cx43）敲除会导致胚胎着床缺陷，尽管卵母细胞形态与主导胚胎着床的进程均看似正常。结合此前关于Cx43对卵母细胞与胚胎发育不可或缺性的研究数据，本研究证实，从卵母细胞及卵巢卵泡中清除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，靶向卵母细胞的Cx43敲除卵泡（敲除于出生后第3天进行）所产生的囊胚着床缺陷，并非源于母体黄体功能不全，而是完全由存在缺陷的囊胚本身所导致。基因表达微阵列（gene expression microarray）分析显示，在这些存在缺陷的卵母细胞及对应囊胚中，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存在全局性异常。因此我们提出，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——其通过调控子代囊胚的生物量扩增能力与正常胚胎着床进程来实现这一作用。为研究Cx43对着床前阶段转录组的影响，我们在胚胎早期发育的三个不同阶段，将Cx43敲除（CX43 KO）卵母细胞与野生型（WT）卵母细胞进行了对比：分别为MII期卵母细胞、囊胚以及着床位点。