P-222 Differential regulation of active translation in mouse oocytes and zygotes upon maturation in vitro and in vivo
Authors: Dvoran M , Masek T , Susor A , Pospisek P , Kubelka M 
Published: June 2022

Abstract

Study question
What are the differences in the translation of specific transcripts between in vitro matured versus in vivo oocytes and IVF made versus in vivo zygotes

Summary answer
Our RNA-seq data show a selection of actively translated trancripts up and down regulated respective to total transcript among in vitro and in vivo conditions

What is known already
Our project wants to address whether there is room for an improvement towards the more physiological aspects of in vitro maturation technology. As the oocyte is transcriptionally silent during meiotic maturation, we want to approach this goal by addressing changes on global translational level. There is not much known about the employment of transcripts during meiotic maturation. Some get degraded, some silent and some recruited to be translated. To the current knowledge, nobody has so far focused on describing changes in active translation on the polysomal level between in vitro and in vivo culture conditions in mouse oocytes.

Study design, size, duration
Study performed on a mouse model. The following samples in quadruplicates have been analyzed and compared: in vitro meiotically matured denuded MII oocytes, in vitro meiotically matured cumulus-oocyte complexes supplemented with rFSH Gonal and hCG, in vivo meiotically matured MII oocytes, in vitro meiotically matured and IVF fertilized pronuclear zygotes, in vivo matured and fertilized pronuclear zygotes. Culture conditions were optimized according to the conventional clinical IVM technology.

Participants/materials, setting, methods
Mouse oocytes and zygotes were input material. Collected samples were subjected to a scarce sample profiling (polysomal fractionation on a sucrose gradient, total RNA isolation and qPCR). From respective quadruplicate fractionated samples, cDNA library was prepared and NGS deep RNA-sequencing performed. Raw data were analysed by Illumina DRAGEN software and differential gene expression was performed on Qiagen CLC Genomics. Candidate validation process is undergoing at the moment.

Main results and the role of chance
Results show a list of differentially regulated actively translated trancripts with implications for in vitro matured oocyte's ability to become fertilized. Similar pattern regarding developmental competence can be seen between in vitro and in vivo matured zygotes. Some candidate genes are in accordance with the latest publications regarding in vitro maturation. However due to ongoing validation and unpublished work we prefer not to disclose further and more concrete results.

Limitations, reasons for caution
First of all, it is a mouse model which is a kind of approximation regarding human oocyte and embryo development. RNA-seq results have to be cautiously interpreted, especially regarding the interpretation and translation of findings for further validation in clinical settings.

Wider implications of the findings
Place findings in context with the importance of correct translational regulation during oocyte meiotic maturation and present preliminary data for further validation in clinical assisted reproduction practice. Moreover we want to show key regulatory areas affected by in vitro maturation technology and suggest improvements for particular clinical applications.

Trial registration number
GA19-13491S