GSE125300
TOP2B disturbed the quality of human oocytes with advanced maternal age
STUDY QUESTION: Does maternal age affect the maturated oocyte quality and the fol-lowing development after fertilization in human?   SUMMARY ANSWER: Maternal age affects the quality of maturated oocytes by altering the stored mRNA levels in human, such as TOP2B.   WHAT IS KNOWN ALREADY: Intracellular mRNAs in maturated oocytes are tran-scripted from the maternal genome during oogenesis and important for the zygotic genome activation (ZGA) after fertilization. Microarray data showed that maternal age affected polyadenylated transcript abundance in human oocytes. These genes are involved in in signaling pathway related to cell cycle regulation, chromosome alignment. However, which genes are the key genes affected by maternal age and important for the development after fertilization had not been reported. Therefore, single-cell RNA sequencing (scRNA-Seq) technology is employed in this study to screen the key genes affected by maternal age in human maturated oocytes.  STUDY DESIGN, SIZE, DURATION: We isolated mRNA from maturated (MII) oo-cytes donated by IVF or ICSI patients (three oocytes from young (= 30 years) and three oocytes from advanced maternal age (= 40 years) patients) undergoing controlled ovarian stimulation. Thus, a total of six maturated oocytes were individually processed for scRNA-seq analysis. The key genes screened from scRNA-seq analysis are confirmed using mouse model.   PARTICIPANTS/MATERIALS, SETTING, METHODS:  Patients undergoing infertility treatment at the Yuhuangding Hospital of Yantai underwent ovarian stimulation with FSH and received hCG for final follicular maturation prior to ul-trasound guided oocyte retrieval. We isolated RNA, generated single cell RNA-seq librar-ies (Smart-Seq2) and sequenced by Illumina Hiseq X-ten platform with 150 bp paired-end. Bioinformatics analysis of the sequencing data was done to find the biological processes and key genes that led to the decline in the quality of oocytes with advanced maternal age. To validate the findings, we used mouse model and validated candidate genes by RT-PCR and knockdown experiments.  MAIN RESULTS AND THE ROLE OF CHANCE:  We identified 1439 genes differentially expressed between older and younger women's maturated oocytes (|foldchange|>2, P < 0.05). These genes are significantly enriched with annotations related to transporter activity, cytoskeleton, oxidative stress, catalytic activity, immune function, cellular senescence and biosynthesis. The key candidate gene TOP2B was found by protein interaction network analysis, and knockdown verification on young mouse maturated oocytes showed that TOP2B was a key gene affecting the oocyte quality and disturbing early embryo development.  LARGE SCALE DATA  Raw data from this study can be accessed through GSE.  LIMITATIONS, REASONS FOR CAUTION:   The human maturated oocytes used in this study were from patients with different causes of infertility and may affect oocyte gene expression. In addition, the study was based on a lim-ited number of patients, and there are possible natural biological variance existed in human samples.  WIDER IMPLICATIONS OF THE FINDINGS:  For the first time, we used scRNA-seq to detect global gene transcriptome of maturated oocytes in young and older women. These results are useful to indicate the molecular mechanisms of female ovary aging and establishing a criterion to evaluate the quality of oocytes in women with advanced maternal age.  STUDY FUNDING/COMPETING INTERESTS:  This research was supported by the National Key Research and Development Program of China (2018YFC1004304, 2016YFA0100203), Medical and Health Science Technology Development Plan Project of Shandong Province (Grant#. 2017WS566). There are no competing interests. Overall design: We isolated mRNA from maturated (MII) oocytes donated by IVF or ICSI patients (three oocytes from young (= 30 years) and three oocytes from advanced maternal age (= 40 years) patients) undergoing controlled ovarian stimulation. Thus, a total of six maturated oocytes were individually processed for scRNA-seq analysis. The key genes screened from scRNA-seq analysis are confirmed using mouse model.