Reproductive Outcomes from Maternal Loss of Nlrp2 Are Not Improved by IVF or Embryo Transfer Consistent with Oocyte-Specific Defect

From chromosomal aberrations to mutations in individual genes - the significance of genetic studies of chorions after miscarriage in the search for causes of miscarriages

OBJECTIVE

To determine the frequency of chromosomal aberrations in chorions after a miscarriage. The second was to examine selected euploid chorions using a next-generation sequencing (NGS) panel designed to assess 43 genes associated with pregnancy loss.

MATERIALS AND METHODS

The 1244 chorions were tested by targeted quantitative fluorescent PCR (QF-PCR, 827 chorions) and microarray-based comparative genomic hybridization (aCGH, 417 chorions). Then, 9 euploid chorions were examined using a designed NGS panel.

RESULTS

Trisomies were the most common chromosomal aberration identified in the spontaneous miscarriage samples. The second chromosomal abnormality in the aCGH group and the third most common in the QF-PCR group was monosomy X. Structural aberrations were the third most common aberration in the samples screened by aCGH (7.7% of chorions). In 19% of 647 couples who submitted chorions for analysis after pregnancy loss, the chromosomal abnormality in the chorion originated from a woman with a balanced chromosomal rearrangement. This discovery was statistically significant compared to patients with normal chorions. Using the designed NGS panel, we identified a potentially pathogenic de novo variant in the F5 gene in two euploid chorions. Additionally, among the patients who experienced miscarriages and were screened using the NGS panel, we identified variants in the MDM, ACE, and NLRP2 genes that could be associated with a predisposition to pregnancy loss.

CONCLUSION

Numerical aberrations are the most common cause of miscarriages, but structural chromosomal aberrations also account for a significant proportion of abnormal results. Our findings indicate that couples with structural chromosomal abnormalities in material post-miscarriage are at increased risk of carrying balanced chromosomal abnormalities. Moreover, NGS-based analyses can uncover previously unidentified causes of miscarriages in the chorionic villi.

Maternal loss-of-function of Nlrp2 results in failure of epigenetic reprogramming in mouse oocytes

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.

NLRP2 in health and disease

NLR family pyrin domain containing 2 (NLRP2) is a novel member of the Nod-like receptor (NLR) family. However, our understanding of NLRP2 has long been ambiguous. NLRP2 may have a role in the innate immune response, but its 'specific' functions remain controversial. Although NLRP2 can initiate inflammasome and promote inflammation, it can also downregulate inflammatory signals. Additionally, NLRP2 has been reported to function in the reproductive system and shows high expression in the placenta. However, the exact role of NLRP2 in the reproductive system is unclear. Here, we highlight the most current progress on NLRP2 in inflammasome activation, effector function and regulation of nuclear factor-κB. And we discuss functions of NLRP2 in inflammatory diseases, reproductive disorders and the potential implication of NLRP2 in human diseases.

Genetic variants underlying developmental arrests in human preimplantation embryos

Developmental arrest in preimplantation embryos is one of the major causes of assisted reproduction failure. It is briefly defined as a delay or a failure of embryonic development in producing viable embryos during ART cycles. Permanent or partial developmental arrest can be observed in the human embryos from one-cell to blastocyst stages. These arrests mainly arise from different molecular biological defects, including epigenetic disturbances, ART processes, and genetic variants. Embryonic arrests were found to be associated with a number of variants in the genes playing key roles in embryonic genome activation, mitotic divisions, subcortical maternal complex formation, maternal mRNA clearance, repairing DNA damage, transcriptional, and translational controls. In this review, the biological impacts of these variants are comprehensively evaluated in the light of existing studies. The creation of diagnostic gene panels and potential ways of preventing developmental arrests to obtain competent embryos are also discussed.

Pyroptosis and Sarcopenia: Frontier Perspective of Disease Mechanism

With global ageing, sarcopenia, as an age-related disease, has brought a heavy burden to individuals and society. Increasing attention has been given to further exploring the morbidity mechanism and intervention measures for sarcopenia. Pyroptosis, also known as cellular inflammatory necrosis, is a kind of regulated cell death that plays a role in the ageing progress at the cellular level. It is closely related to age-related diseases such as cardiovascular diseases, Alzheimer’s disease, osteoarthritis, and sarcopenia. In the process of ageing, aggravated oxidative stress and poor skeletal muscle perfusion in ageing muscle tissues can activate the nod-like receptor (NLRP) family to trigger pyroptosis. Chronic inflammation is a representative characteristic of ageing. The levels of inflammatory factors such as TNF-α may activate the signaling pathways of pyroptosis by the NF-κB-GSDMD axis, which remains to be further studied. Autophagy is a protective mechanism in maintaining the integrity of intracellular organelles and the survival of cells in adverse conditions. The autophagy of skeletal muscle cells can inhibit the activation of the pyroptosis pathway to some extent. A profound understanding of the mechanism of pyroptosis in sarcopenia may help to identify new therapeutic targets in the future. This review article focuses on the role of pyroptosis in the development and progression of sarcopenia.