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Transcriptional and post-transcriptional regulation of oocyte and embryo messenger RNA in mouse models of diet-induced obesity
Maternal obesity increases the risk of early embryonic loss and imposes long-term effects on the metabolic and neurologic phenotype of viable offspring. Previous studies have shown an association between female obesity and increases in abundance of candidate oocyte mRNAs; however, the mechanisms associated with this increase and the contribution of increased mRNAs on successful embryo development is unclear. Three studies were conducted to determine how female obesity, which promotes a low grade inflammatory and oxidative stress environment in the ovary, alters transcriptional and post-transcriptional regulation of candidate mRNAs in oocytes and determine if these increases are functionally important in the pre-implantation embryo. In study 1 we showed that diet induced obesity caused increased pro-inflammatory signaling in the ovary including in growing oocytes. This pro-inflammatory signaling resulted in increased association of STAT3 with the Pouf51 promoter suggesting that this interaction increased the transcription of Pou5f1. In addition, we made the novel discovery that changes in cecum microbial content was positively correlated to increased ovarian expression of Tnfa, Pou5f1, Dppa3, and Bnc1. In Study 2, we modified the single molecule RNA fluorescent in situ hybridization (FiSH) technique for use with oocytes and pre-implantation embryos. This FiSH method allowed us to accurately and reproducibly monitor changes in candidate mRNA localization and absolute quantity in growing and mature oocytes as well as pre-implantation embryos. In Study 3, we used the FiSH technique to investigate the impact of oxidative stress on post-transcriptional regulation of mRNA translation and degradation during oocyte maturation and embryonic development. These experiments demonstrated that oxidative stress impaired degradation of Pou5f1 and Dppa3 in maturing oocytes resulting in increased translation of POU5F1 and DPPA3 in 1-cell and 2-cell embryos, respectively. In summary these collective studies identified both transcriptional and post-transcriptional changes in oocyte mRNA abundance which may be attributed to alterations in the gut microbiome, ovarian inflammation and oxidative stress. These findings suggest that obesity-dependent alterations during oocyte maturation may have the potential to contribute to early adaptive programming in the embryo and that may result in lasting effects on fetal development and/or postnatal phenotype expression.
Xie, Fang, "Transcriptional and post-transcriptional regulation of oocyte and embryo messenger RNA in mouse models of diet-induced obesity" (2016). ETD collection for University of Nebraska-Lincoln. AAI10117875.