Landscape Of MRNA In Oocytes And Preimplantation Embryos Of Mice With Polycystic Ovary Syndrome And Functions Of Related Aberrant Expression Genes

Background:Polycystic ovary syndrome(PCOS)is a multifactorial endocrinopathy affecting 6%-20%women of reproductive age.It is characterized by excessive androgen production,ovarian dysfunction,and polycystic ovarian morphology with insulin resistance and associated metabolic abnormalities.The familial aggregation of PCOS suggests a heritable feature for this disorder.Moreover,PCOS is associated with adverse obstetric and neonatal outcomes;however,the etiology of this syndrome is largely unknown.Objective:To profile the gene expression of oocytes and embryos during preimplantation development in a PCOS mouse model and explore the mechanisms that compromise the oocyte quality of PCOS mice,impairing embryo development and offspring health.Methods:Oocytes from mice with dehydroepiandrosterone(DHEA)-induced PCOS were isolated for in vitro fertilization.Single-cell RNA sequencing was used to map the gene expression of GV oocytes;M? oocytes;2-cell,4-cell,and 8-cell embryos;morula;and blastocyst stage embryos.Bioinformatics analysis was performed and related aberrant expression gene was selected for future functional analysis with microinjection.GV oocytes from women with PCOS and healthy controls were also sampled.Results:A DHEA-induced mouse model successfully exhibited endocrine and metabolic characteristics of PCOS.Although the average number and gross morphology of embryos at the 2-cell and 4-cell stages were similar between the DHEA-treated and control mice,DHEA-treated embryos after the 4-cell stage showed developmental delay or cytoplasmic fragmentation.Gene expression analysis showed that a large number of differentially expressed genes(DEGs)were detected in M? oocytes and 2-cell embryos.GO analysis showed that DEGs in M? oocytes were enriched in oxidation-reduction and protein-folding processes,whereas DEGs in 2-cell embryos were enriched in cell cycle and RNA processing.In DHEA-treated mice,there was significant enhancement in gene transcription at the 2-cell embryo stage and a large number of genes were overexpressed or even pre-activated,including several key genes important for early embryo development.Among them,the expression of Oct4 in DHEA-treated 2-cell embryos was>200-fold higher than that in the control 2-cell embryos.After depletion of Oct4,GO analysis showed that the transcriptional variations were enriched in the processes of activation of protein kinase B,oxidation-reduction,steroid and sterol biosynthesis,and lipid metabolism,which also contributed to the steroid and lipid metabolic abnormality in offspring of PCOS mice,independent of the maternal uterine environment.Several of DEGs in 2-cell embryos were also altered in GV oocytes from women with PCOS compared to those in healthy controls.Conclusions:A DHEA-induced mouse model was constructed successfully.Alteration of oocytes in a DHEA-induced PCOS mouse model could lead to an aberrated gene expression of the 2-cell embryo,which is associated with delayed embryo development.The transcription factor Oct4 contributes to steroid and lipid metabolic abnormality,which may result in metabolic dysfunction in PCOS.