RESUMEN
Background: NLRP2 belongs to the subcortical maternal complex (SCMC) of mammalian oocytes and preimplantation embryos. This multiprotein complex, encoded by maternal-effect genes, plays a pivotal role in the zygote-to-embryo transition, early embryogenesis, and epigenetic (re)programming. The maternal inactivation of genes encoding SCMC proteins has been linked to infertility and subfertility in mice and humans. However, the underlying molecular mechanisms for the diverse functions of the SCMC, particularly how this cytoplasmic structure influences DNA methylation, which is a nuclear process, are not fully understood. Results: We undertook joint transcriptome and DNA methylome profiling of pre-ovulatory germinal-vesicle oocytes from Nlrp2-null, heterozygous (Het), and wild-type (WT) female mice. We identified numerous differentially expressed genes (DEGs) in Het and Nlrp2-null when compared to WT oocytes. The genes for several crucial factors involved in oocyte transcriptome modulation and epigenetic reprogramming, such as DNMT1, UHRF1, KDM1B and ZFP57 were overexpressed in Het and Nlrp2-null oocytes. Absence or reduction of Nlrp2, did not alter the distinctive global DNA methylation landscape of oocytes, including the bimodal pattern of the oocyte methylome. Additionally, although the methylation profile of germline differentially methylated regions (gDMRs) of imprinted genes was preserved in oocytes of Het and Nlrp2-null mice, we found altered methylation in oocytes of both genotypes at a small percentage of the oocyte-characteristic hyper- and hypomethylated domains. Through a tiling approach, we identified specific DNA methylation differences between the genotypes, with approximately 1.3% of examined tiles exhibiting differential methylation in Het and Nlrp2-null compared to WT oocytes. Conclusions: Surprisingly, considering the well-known correlation between transcription and DNA methylation in developing oocytes, we observed no correlation between gene expression differences and gene-body DNA methylation differences in Nlrp2-null versus WT oocytes or Het versus WT oocytes. We therefore conclude that post-transcriptional changes in the stability of transcripts rather than altered transcription is primarily responsible for transcriptome differences in Nlrp2-null and Het oocytes.
RESUMEN
OBJECTIVE: To investigate the impact of endometrial receptivity array (ERA) before frozen embryo transfer in patients undergoing in vitro fertilization (IVF). There is a lack of consensus regarding the use of ERA for increasing the success rate of IVF cycles, mainly in terms of the live birth rate. DESIGN: PubMed, Web of Science and Embase were searched from inception up to February 15, 2022. SETTING: Not applicable. PATIENT(S): Patients undergoing ERA vs no ERA before frozen embryo transfer. INTERVENTION(S): Only comparative studies evaluating pregnancy rates of patients undergoing frozen embryo transfer cycles with or without prior ERA were included. Inter-study heterogeneity was also assessed using Cochrane's Q test and the I2 statistic. The random-effects model was used to pool the odds ratio (OR) with the corresponding 95% confidence intervals (CIs). Subgroup analyses were performed to investigate the impact of ERA on pregnancy rates according to the number of previous embryo transfer (ET) failures (≤ 2 previous failed ETs vs. > 2 failed ETs, defined as recurrent implantation failure). Separate analyses were performed according to the study design and adjustment for confounders. MAIN OUTCOME MEASURES(S): The primary outcomes of the study were live birth rate and/or ongoing pregnancy rate. Implantation rate, biochemical pregnancy rate, clinical pregnancy rate, and miscarriage rate were considered secondary outcomes. RESULT(S): Eight studies (representing data on n = 2,784 patients; n = 831 had undergone ERA and n = 1,953 without ERA) were found to be eligible for this meta-analysis. The live birth or ongoing pregnancy rate for the ERA group was not significantly different compared with the non-ERA group (OR, 1.38; 95% CI, 0.79-2.41; I2 83.0%), nor was a difference seen in subgroup analyses based on the number of previous failed ETs. The rates of implantation, biochemical pregnancy, clinical pregnancy, and miscarriage were also comparable between the ERA and the non-ERA groups. After separate analyses according to the study design and adjustment for confounding factors, overall pooled estimates remained statistically nonsignificant. CONCLUSION(S): The findings of the current meta-analysis did not reveal a significant change in the rate of pregnancy after IVF cycles using ERA, and it is not clear whether ERA can increase the pregnancy rate or not. SYSTEMATIC REVIEW REGISTRATION: Prospectively registered in PROSPERO (CRD42022310862).