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Sirt2-BubR1 acetylation pathway mediates the effects of advanced maternal age on oocyte quality.

ABSTRACT: The level of Sirt2 protein is reduced in oocytes from aged mice, while exogenous expression of Sirt2 could ameliorate the maternal age-associated meiotic defects. To date, the underlying mechanism remains unclear. Here, we confirmed that specific depletion of Sirt2 disrupts maturational progression and spindle/chromosome organization in mouse oocytes, with compromised kinetochore-microtubule attachments. Candidate screening revealed that acetylation state of lysine 243 on BubR1 (BubR1-K243, an integral part of the spindle assembly checkpoint complex) functions during oocyte meiosis, and acetylation-mimetic mutant BubR1-K243Q results in the very similar phenotypes as Sirt2-knockdown oocytes. Furthermore, we found that nonacetylatable-mimetic mutant BubR1-K243R partly prevents the meiotic deficits in oocytes depleted of Sirt2. Importantly, BubR1-K243R overexpression in oocytes derived from aged mice markedly suppresses spindle/chromosome anomalies and thereupon lowers the incidence of aneuploid eggs. In sum, our data suggest that Sirt2-dependent BubR1 deacetylation involves in the regulation of meiotic apparatus in normal oocytes and mediates the effects of advanced maternal age on oocyte quality.

SUBMITTER: Qiu D

PROVIDER: S-EPMC5770883 | biostudies-literature | 2018 Feb

REPOSITORIES: biostudies-literature

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Sirt2-BubR1 acetylation pathway mediates the effects of advanced maternal age on oocyte quality.

Qiu Danhong D Hou Xiaojing X Han Longsen L Li Xiaoyan X Ge Juan J Wang Qiang Q

Aging cell 20171025 1

The level of Sirt2 protein is reduced in oocytes from aged mice, while exogenous expression of Sirt2 could ameliorate the maternal age-associated meiotic defects. To date, the underlying mechanism remains unclear. Here, we confirmed that specific depletion of Sirt2 disrupts maturational progression and spindle/chromosome organization in mouse oocytes, with compromised kinetochore-microtubule attachments. Candidate screening revealed that acetylation state of lysine 243 on BubR1 (BubR1-K243, an i ...[more]

PMID: 29067790

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Project description: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.

Project description:It has been widely acknowledged that anti-Müllerian hormone (AMH) is a golden marker of ovarian reserve. Declined ovarian reserve (DOR), based on experience from reproductive-aged women, refers to both the quantitative and qualitative reduction in oocytes. This view is challenged by a recent study clearly showing that the quality of oocytes is similar in young women undergoing IVF cycles irrespective of the level of AMH. However, it remains elusive whether AMH indicates oocyte quality in women with advanced age (WAA). The aim of this study was to investigate this issue. In the present study, we retrospectively analysed the data generated from a total of 492 IVF/ICSI cycles (from January 2017 to July 2020), and these IVF/ICSI cycles contributed 292 embryo transfer (ET) cycles (from June 2017 to September 2019, data of day 3 ET were included for analysis) in our reproductive centre. Based on the level of AMH, all patients (= > 37 years old) were divided into 2 groups: the AMH high (H) group and the AMH low (L) group. The parameters of in vitro embryo development and clinical outcomes were compared between the two groups. The results showed that women in the L group experienced severe DOR, as demonstrated by a higher rate of primary diagnosis of DOR, lower antral follicle count (AFC), higher level of basal follicle stimulating hormone (FSH) and cancelation cycles, lower level of E2 production on the day of surge, and fewer oocytes and MII oocytes retrieved. Compared with women in the H group, women in the L group showed slightly reduced top embryo formation rate but a similar normal fertilization rate and blastocyst formation rate. More importantly, we found that the rates of implantation, spontaneous miscarriage and livebirth were similar between the two groups, while the pregnancy rate was significantly reduced in the L group compared with the H group. Further analysis indicated that the higher pregnancy rate of women in the H group may be due to more top embryos transferred per cycle. Due to an extremely low implantation potential for transfer of non-top embryos from WAA (= > 37 years old) in our reproductive centre, we assumed that all the embryos that implanted may result from the transfer of top embryos. Based on this observation, we found that the ratio of embryos that successfully implanted or eventually led to a livebirth to top embryos transferred was similar between the H and the L groups. Furthermore, women with clinical pregnancy or livebirth in the H or L group did not show a higher level of serum AMH but were younger than women with non-pregnancy or non-livebirth. Taken together, this study showed that AMH had a limited role in predicting in vitro embryo developmental potential and had no role in predicting the in vivo embryo developmental potential, suggesting that in WAA, AMH should not be used as a marker of oocyte quality. This study supports the view that the accumulation of top embryos via multiple oocyte retrieval times is a good strategy for the treatment of WAA.

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Sirt2-BubR1 acetylation pathway mediates the effects of advanced maternal age on oocyte quality.

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Sirt2-BubR1 acetylation pathway mediates the effects of advanced maternal age on oocyte quality.

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