Search

Abstract Background Members of the nucleotide-binding oligomerization domain, leucine rich repeat and pyrin domain containing (NLRP) family regulate various physiological and pathological processes. However, none have been shown to regulate actin cap formation or spindle translocation during the asymmetric division of oocyte meiosis I. NLRP4E has been reported as a candidate protein in female fertility, but its function is unknown. Methods Immunofluorescence, reverse transcription polymerase chain reaction (RT-PCR), and western blotting were employed to examine the localization and expression levels of NLRP4E and related proteins in mouse oocytes. small interfering RNA (siRNA) and antibody transfection were used to knock down NLRP4E and other proteins. Immunoprecipitation (IP)-mass spectrometry was used to identify the potential proteins interacting with NLRP4E. Coimmunoprecipitation (Co-IP) was used to verify the protein interactions. Wild type (WT) or mutant NLRP4E messenger RNA (mRNA) was injected into oocytes for rescue experiments. In vitro phosphorylation was employed to examine the activation of steroid receptor coactivator (SRC) by NLRP4E. Results NLRP4E was more predominant within oocytes compared with other NLRP4 members. NLRP4E knockdown significantly inhibited actin cap formation and spindle translocation toward the cap region, resulting in the failure of polar body extrusion at the end of meiosis I. Mechanistically, GRIN1, and GANO1 activated NLRP4E by phosphorylation at Ser429 and Thr430; p-NLRP4E is translocated and is accumulated in the actin cap region during spindle translocation. Next, we found that p-NLRP4E directly phosphorylated SRC at Tyr418, while p-SRC negatively regulated p-CDC42-S71, an inactive form of CDC42 that promotes actin cap formation and spindle translocation in the GTP-bound form. Conclusions NLRP4E activated by GRIN1 and GANO1 regulates actin cap formation and spindle translocation toward the cap region through upregulation of p-SRC-Tyr418 and downregulation of p-CDC42-S71 during meiosis I.

Immunoglobulins are key humoral immune molecules produced and secreted by B lymphocytes at various stages of differentiation. No research has reported whether immunoglobulins are present in the non-proliferative female germ cells—oocytes—and whether they are functionally important for oocyte quality, self-protection, and survival. Herein, we found that IgG was present in the oocytes of immunodeficient mice; the IgG-VDJ regions were highly variable between different oocytes, and H3K27Ac bound and regulated the IgG promoter region. Next, IgG mRNA and protein levels increased in response to LPS, and this increment was mediated by CR2 on the oocyte membrane. Finally, we revealed three aspects of the functional relevance of oocyte IgG: first, oocytes could upregulate IgG to counteract the increased ROS level induced by CSF1; second, oocytes could upregulate IgG in response to injected virus ssRNA to maintain mitochondrial integrity; third, upon bacterial infection, oocytes could secrete IgG, subsequently encompassing the bacteria, thus increasing survival compared to somatic cells. This study reveals for the first time that the female germ cells, oocytes, can independently adjust intrinsic IgG production to survive in adverse environments.

Objective: To investigate the effects of exogenous α-linolenic acid (ALA) on in vitro maturation (IVM) and developmental competence of human oocytes. Methods: Experiment 1 examined the effects of ALA at different concentrations (0 [control], 10, 50, 100, and 200 μmol/L) in the IVM medium on oocyte maturation. Treatment with 50 μmol/L ALA significantly accelerated oocyte maturation (P < 0.05) and resulted in significantly higher mitochondrial DNA (mtDNA) copy number compared to the control. Hence, 50 μmol/L ALA was selected for combination with follicular fluid (FF) to investigate oocyte developmental potential. mtDNA of the matured oocyte was analyzed by real-time polymerase chain reaction. Experiment 2 investigated the effects of FF with optimal ALA concentration (Group A: ALA + FF + IVM medium) or without ALA (Group B: FF + IVM medium) on oocyte maturation, fertilization, 2 pronuclear cleavage, and embryo and blastocyst development. Malondialdehyde (MDA) content and superoxide dismutase (SOD) activity were measured for maturation medium from Group A, Group B, and Group C (control group, IVM medium only). Results: Treatment with 50 μmol/L ALA obviously accelerated oocyte maturation (P < 0.05) and resulted in significantly higher mtDNA copy number (P < 0.05) in the matured oocytes compared to the control (0 μmol/L ALA). Supplementation of 50 μmol/L ALA and FF (Group A) obviously increased the total maturation rate than FF-treated group (Group B) which has higher (P < 0.05) total maturation rate than that of Group C. However, no significant differences were observed in fertilization, embryo availability, and blastocyst production among Group A, B, and C. Treatment with 50 μmol/L ALA decreased the level of MDA (P < 0.05), but had no effect on the activity of SOD in the IVM medium. Conclusions: Our results suggested that the treatment with 50 μmol/L ALA during IVM improves maturation in human oocytes. It is also likely to improve embryo availability and blastocyst formation. This might be associated with the alteration of mtDNA replication (increased mtDNA copy number) and the reduction of oxidative stress (reduced MDA level).

The timely degradation of proteins that regulate the cell cycle is essential for oocyte maturation. Oocytes are equipped to degrade proteins via the ubiquitin-proteasome system. In meiosis, anaphase promoting complex/cyclosome (APC/C), an E3 ubiquitin-ligase, is responsible for the degradation of proteins. Ubiquitin-conjugating enzyme E2 S (UBE2S), an E2 ubiquitin-conjugating enzyme, delivers ubiquitin to APC/C. APC/C has been extensively studied, but the functions of UBE2S in oocyte maturation and mouse fertility are not clear. In this study, we used Ube2s knockout mice to explore the role of UBE2S in mouse oocytes. Ube2s-deleted oocytes were characterized by meiosis I arrest with normal spindle assembly and spindle assembly checkpoint dynamics. However, the absence of UBE2S affected the activity of APC/C. Cyclin B1 and securin are two substrates of APC/C, and their levels were consistently high, resulting in the failure of homologous chromosome separation. Unexpectedly, the oocytes arrested in meiosis I could be fertilized and the embryos could become implanted normally, but died before embryonic day 10.5. In conclusion, our findings reveal an indispensable regulatory role of UBE2S in mouse oocyte meiosis and female fertility. [ABSTRACT FROM AUTHOR]