Understanding the impact of ovarian stimulation on oocyte and embryo quality by tandem RNA and protein expression analysis of oocytes and preimplantation embryonic stages

• Applicants: Privatdozent Dr. Michele Boiani; Professor Dr. Georg Fuellen; Dr. Leila Taher
• Subject Area: Reproductive Medicine, Urology
• Term: from 2016 to 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 279728933

Ovarian stimulation with gonadotropins is a key component of assisted reproductive technologies (ARTs), aimed at increasing the number of oocytes and embryos, and, thereby, the chance of establishing a pregnancy. However, independent studies suggest that ovarian stimulation has detrimental effects on oocyte and embryo quality. Indeed, ovarian stimulation has been shown to lead to a significantly lower proportion of normal embryos, as well as decreased implantation and post-implantation development rates. Here, we aim to combine high-throughput transcriptomics and proteomics with statistical and computational modeling in a holistic approach, to analyze preimplantation development and understand the effects of ovarian stimulation on oocyte and embryo quality in the mouse model of human reproduction. The mouse has contributed more than any other model to the advancement of ARTs. Experimentally, we will quantitatively measure RNA, mRNA poly(A) tail lengths, and protein using RNA-seq, PAL-seq, and SILAC LC-MS/MS, respectively, across the mouse oocyte and derived embryos at seven different developmental stages (1-cell, 2-cell (early and late), 4-cell, 8-cell, morula and blastocyst), with and without a background of ovarian stimulation. Computationally, we will develop and apply novel statistical methods and network-based approaches to analyze these comprehensive data and describe the gene expression cascade in early embryonic development, with and without a background of ovarian stimulation. In particular, we will propose several regression methods to (1) describe protein expression levels as a function of concomitant and precedent mRNA levels, as well as other sequence and functional properties of the protein/mRNA considered; (2) identify the transcription factors with crucial roles throughout embryonic development; (3) predict the targets of noncoding RNA and evaluate their contribution to the gene expression cascade; and (4) assess allele-specific expression, to get an insight into the time course of embryonic genome activation (EGA). Additionally, we will test the hypothesis that control mechanisms involving the poly(A) tail of mRNA are a main contributor to the discrepancies between transcriptomic and proteomic expression patterns during early development. Finally, we will use network biology approaches to identify gene/protein interactions that may underlie developmental progression, and exploit comparative genomics to establish the relevance of our results for human ARTs. With more and more women postponing childbearing to later stages in their lives and turning to ARTs, our study makes a fundamental contribution to understand the basic molecular and cellular aspects of early embryonic development, and to evaluate the impact of common ART treatments on oocyte and embryo quality.

• DFG Programme: Research Grants
• International Connection: Japan
• Cooperation Partner: Professor Yutaka Suzuki