| The transcription of mammalian oocyte is silenced at the germinal vesicle (GV) stage before meiosis resumption. From the meiosis resumption through the maternal genome reactivation during the early embryo cleavage stage, there is no global gene transcription. During the meiosis Ⅰ, meiosis Ⅱ, fertilization, and early embryo development, the main metabolisms and biological processes are dependent on the materials accumulated in oocytes at the GV stage. The maternal materials include mRNAs, proteins, energy materials and other small molecules.During the maturation of oocyte, the granulosa cells regulate the oocyte biological processes such as oocyte energy metabolism. However, when we remove the granulosa cells from oocytes, the oocytes can also resume the meiosis, mature in vitro, and complete fertilization. These results show that the important materials and information have been accumulated at the GV stage oocytes.The transcriptome analysis has been used to detect the whole mRNAs in cells qualitatively and quantitatively. It not only can give the sequence information of mRNAs but also the relative expression values of genes. So detecting the transcriptome of GV stage oocytes could help us get the information which mRNAs were accumulated in oocytes, and which genes may play essential roles in the fertilization and consequent embryo development.There are two types of GV oocytes in adult female mouse ovary:NSN oocytes, the Hoechst positive rim non-surrounded nucleolus oocytes; and SN oocyte, the Hoechst positive rim surrounded nucleolus oocytes. The NSN oocytes, compared to the SN oocytes, showed lower meiosis resumption rates, and when fertilized, the embryos could not overcome the2-cells arrest. So the transcriptome analysis of NSN and SN oocytes could help us understand the molecular mechanisms for meiosis and early embryo development.As the alteration of human dietary habits and the environmental conditions, the incidence of type I diabetes gradually increases. The diabetes severely affects the mammalian reproduction system, but there is no global knowledge about how diabetes affects the female oocytes. The absorption of energy materials of oocytes mainly depends on the granulosa cells. For example, the granulosa cells absorbe the glucose through glucose transfer proteins, and the glucose absorbed by granulosa cells is transferred into oocytes by the gap junctions between oocytes and granulosa cells. In addition, oocytes can also get pyruvate and fructose from granulosa cells. When the oocytes are ovulated from the ovary into oviduct, the granulosa cells (cumulus cells) detached from the oocytes, and the dependence of oocytes on cumulus cells is decreased. In our study, we compared the transcriptomes of NSN and SN oocytes, and also compared the transcriptomes of diabetic and normal MⅡ stage oocytes. We obtained the results as below:(1) The differentially expressed genes between NSN and SN oocytes.From the transcriptome data of NSN and SN oocytes, we selected627up regulated and332down regulated genes in SN oocytes. Firstly we found the metabolic manners of the NSN and SN oocytes were different. The production of PI3P production was promoted in NSN oocytes, whereas the DAG production was promoted in SN oocytes. We also found the oocyte meiosis and early embryo development associated genes were differentially expressed in SN oocytes compared to NSN oocytes.(2) The differentially expressed genes between type Ⅰ diabetic mouse MⅡ oocytes and normal MⅡ oocytes.We firstly constructed two diabetic mice models:the chemical drug STZ induced diabetic mouse and the genetically non-obese diabetic NOD mouse. By the transcriptome sequencing, we found that535genes were up regulated in both diabetic model mice oocytes and83genes were down regulated. We found that, not only the ovulation and oocyte development associated genes were differentially expressed in the diabetic mice oocytes, but also the epigenetic key genes such as Dnmt1, Mbd3were altered. |
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