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Dysregulation of methylation and expression of imprinted genes in oocytes and reproductive tissues in mice of advanced maternal age.

ABSTRACT: To evaluate reproductive outcomes in aged compared to young female mice, and determine associated methylation and expression of imprinted genes in reproductive tissues.Fetal, placental, and ovarian tissue were collected on d16.5 of pregnancy from young (4-5 weeks) and aged (15 months) mice. Uterine tissue and in vivo matured oocytes were collected from non-pregnant females. Methylation of imprinted genes was determined by restriction enzyme based assays, and transcript abundance of imprinted and nutrient supply genes were analyzed by quantitative PCR (qPCR).Maternal age was associated with fetal growth restriction and placental overgrowth. In maternally aged mice, methylation was minimally dysregulated in fetal tissue, while placental tissue showed aberrant methylation and transcript abundance of imprinted genes. Ovarian methylation and gene expression was severely dysregulated, although oocyte gene expression was only minimally altered. Abundance of Kcnq1 transcripts was significantly (P < 0.05) increased in oocytes obtained from aged females compared to young females. Gene expression was also severely dysregulated in the uterus, including nutrient transport genes.Fetal and placental growth abnormalities correspond to aberrant methylation and gene expression in reproductive tissues from maternally aged mice. Significant alterations in gene expression and methylation in the aged ovary suggests that the follicular environment may be compromised. Aberrant methylation and expression of imprinted genes in the aged uterus may contribute to reduced implantation. Maternal age negatively affects imprinted gene methylation and expression in both germ cells and somatic cells of the reproductive tract, contributing to the reduced fertility observed with advanced maternal age.

SUBMITTER: Paczkowski M

PROVIDER: S-EPMC4429446 | biostudies-literature | 2015 May

REPOSITORIES: biostudies-literature

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Dysregulation of methylation and expression of imprinted genes in oocytes and reproductive tissues in mice of advanced maternal age.

Paczkowski M M Schoolcraft W B WB Krisher R L RL

Journal of assisted reproduction and genetics 20150324 5

<h4>Purpose</h4>To evaluate reproductive outcomes in aged compared to young female mice, and determine associated methylation and expression of imprinted genes in reproductive tissues.<h4>Methods</h4>Fetal, placental, and ovarian tissue were collected on d16.5 of pregnancy from young (4-5 weeks) and aged (15 months) mice. Uterine tissue and in vivo matured oocytes were collected from non-pregnant females. Methylation of imprinted genes was determined by restriction enzyme based assays, and trans ...[more]

PMID: 25800995

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Project description:BACKGROUND:Over the last several decades, the average age of first-time mothers has risen steadily. With increasing maternal age comes a decrease in fertility, which in turn has led to an increase in the use of assisted reproductive technologies by these women. Assisted reproductive technologies (ARTs), including superovulation and embryo culture, have been shown separately to alter imprinted DNA methylation maintenance in blastocysts. However, there has been little investigation on the effects of advanced maternal age, with or without ARTs, on genomic imprinting. We hypothesized that ARTs and advanced maternal age, separately and together, alter imprinted methylation in mouse preimplantation embryos. For this study, we examined imprinted methylation at three genes, Snrpn, Kcnq1ot1, and H19, which in humans are linked to ART-associated methylation errors that lead to imprinting disorders. RESULTS:Our data showed that imprinted methylation acquisition in oocytes was unaffected by increasing maternal age. Furthermore, imprinted methylation was normally acquired when advanced maternal age was combined with superovulation. Analysis of blastocyst-stage embryos revealed that imprinted methylation maintenance was also not affected by increasing maternal age. In a comparison of ARTs, we observed that the frequency of blastocysts with imprinted methylation loss was similar between the superovulation only and the embryo culture only groups, while the combination of superovulation and embryo culture resulted in a higher frequency of mouse blastocysts with maternal imprinted methylation perturbations than superovulation alone. Finally, the combination of increasing maternal age with ARTs had no additional effect on the frequency of imprinted methylation errors. CONCLUSION:Collectively, increasing maternal age with or without superovulation had no effect of imprinted methylation acquisition at Snrpn, Kcnq1ot1, and H19 in oocytes. Furthermore, during preimplantation development, while ARTs generated perturbations in imprinted methylation maintenance in blastocysts, advanced maternal age did not increase the burden of imprinted methylation errors at Snrpn, Kcnq1ot1, and H19 when combined with ARTs. These results provide cautious optimism that advanced maternal age is not a contributing factor to imprinted methylation errors in embryos produced in the clinic. Furthermore, our data on the effects of ARTs strengthen the need to advance clinical methods to reduce imprinted methylation errors in in vitro-produced embryos.

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:BackgroundAn estimated 1 in 350 women carry germline BRCA1/2 mutations, which confer an increased risk of developing breast and ovarian cancer, and may also contribute to subfertility. All mature, sex steroid-producing ovarian follicles are drawn from the pool of non-renewable primordial follicles, termed the 'ovarian reserve'. The clinical implications of early ovarian reserve exhaustion extend beyond infertility, to include the long-term adverse health consequences of loss of endocrine function and premature menopause. We aimed to determine whether conditional loss of Brca1 in oocytes impacts ovarian follicle numbers, oocyte quality and fertility in mice with advancing maternal age. We also aimed to determine the utility of AMH as a marker of ovarian function, by assessing circulating AMH levels in mice and women with BRCA1/2 mutations, and correlating this with ovarian follicle counts.MethodsIn this study, we addressed a longstanding question in the field regarding the functional consequences of BRCA1 inactivation in oocytes. To recapitulate loss of BRCA1 protein function in oocytes, we generated mice with conditional gene deletion of Brca1 in oocytes using Gdf9-Cre recombinase (WT: Brca1fl/flGdf9+/+; cKO: Brca1fl/flGdf9cre/+).FindingsWhile the length of the fertile lifespan was not altered between groups after a comprehensive breeding trial, conditional loss of Brca1 in oocytes led to reduced litter size in female mice. Brca1 cKO animals had a reduced ovarian reserve and oocyte maturation was impaired with advanced maternal age at postnatal day (PN)300, compared to WT animals. Serum anti-Müllerian hormone (AMH) concentrations (the gold-standard indirect marker of the ovarian reserve used in clinical practice) were not predictive of reduced primordial follicle number in Brca1 cKO mice versus WT. Furthermore, we found no correlation between follicle number or density and serum AMH concentrations in matched samples from a small cohort of premenopausal women with BRCA1/2 mutations.InterpretationTogether, our data demonstrate that BRCA1 is a key regulator of oocyte number and quality in females and suggest that caution should be used in relying on AMH as a reliable marker of the ovarian reserve in this context.FundingThis work was made possible through Victorian State Government Operational Infrastructure Support and Australian Government NHMRC IRIISS. This work was supported by funding from the Australian Research Council (ALW - DE21010037 and KJH - FT190100265), as well as the National Breast Cancer Foundation (IIRS-22-092) awarded to ALW and KJH. LRA, YML, LT, EOKS and MG were supported by Australian Government Research Training Program Scholarships. LRA, YML and LT were also supported by a Monash Graduate Excellence Scholarship. YC, SG and XC were supported by Monash Biomedicine Discovery Institute PhD Scholarships. LRA was also supported by a Monash University ECPF24-6809920940 Fellowship. JMS was supported by NHMRC funding (2011299). MH was supported by an NHMRC Investigator Grant (1193838).

Project description:DNA methylation reprogramming occurs during mammalian gametogenesis and embryogenesis. Sex-specific DNA methylation patterns at specific CpG islands controlling imprinted genes are acquired during this window of development. Characterization of the DNA methylation dynamics of imprinted genes acquired by oocytes during folliculogenesis is essential for understanding the physiological and genetic aspects of female gametogenesis and to determine the parameters for oocyte competence. This knowledge can be used to improve in vitro embryo production (IVP), specifically because oocyte competence is one of the most important aspects determining the success of IVP. Imprinted genes, such as IGF2, play important roles in embryo development, placentation and fetal growth. The aim of this study was to characterize the DNA methylation profile of the CpG island located in IGF2 exon 10 in oocytes during bovine folliculogenesis. The methylation percentages in oocytes from primordial follicles, final secondary follicles, small antral follicles, large antral follicles, MII oocytes and spermatozoa were 73.74 ± 2.88%, 58.70 ± 7.46%, 56.00 ± 5.58%, 65.77 ± 5.10%, 56.35 ± 7.45% and 96.04 ± 0.78%, respectively. Oocytes from primordial follicles showed fewer hypomethylated alleles (15.5%) than MII oocytes (34.6%) (p = 0.039); spermatozoa showed only hypermethylated alleles. Moreover, MII oocytes were less methylated than spermatozoa (p<0.001). Our results showed that the methylation pattern of this region behaves differently between mature oocytes and spermatozoa. However, while this region has a classical imprinted pattern in spermatozoa that is fully methylated, it was variable in mature oocytes, showing hypermethylated and hypomethylated alleles. Furthermore, our results suggest that this CpG island may have received precocious reprogramming, considering that the hypermethylated pattern was already found in growing oocytes from primordial follicles. These results may contribute to our understanding of the reprogramming of imprinted genes during bovine oogenesis.

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Dysregulation of methylation and expression of imprinted genes in oocytes and reproductive tissues in mice of advanced maternal age.

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Dysregulation of methylation and expression of imprinted genes in oocytes and reproductive tissues in mice of advanced maternal age.

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