Kaempferol from Alpinia officinarum hance induces G2/M cell cycle arrest in hepatocellular carcinoma cells by regulating the ATM/CHEK2/KNL1 pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Alpinia officinarum Hance (A. officinarum), a perennial herb known for its medicinal properties, has been used to treat various ailments, such as stomach pain, abdominal pain, emesis, and digestive system cancers. A. officinarum is extensively cultivated in the Qiongzhong and Baisha regions of Hainan, and it holds substantial therapeutic value for the local Li people of Hainan. Kaempferol, a flavonoid derived from A. officinarum, has demonstrated anticancer properties in various experimental and biological studies. Nevertheless, the precise mechanisms through which it exerts its anti-hepatocellular carcinoma (HCC) effects remain to be comprehensively delineated.

AIM OF THE STUDY

This investigation aims to elucidate the anti-HCC effects of kaempferol derived from A. officinarum and to delve into its underlying mechanistic pathways.

MATERIALS AND METHODS

Using ultra-high performance liquid chromatography-mass spectrometry/mass spectrometry (UPLC-MS/MS) to identify active compounds in A. officinarum. HCCLM3 and Huh7 cells were used to study the anti-HCC effect of kaempferol from A. officinarum. The cytotoxicity and proliferation of kaempferol and A. officinarum were measured using CCK-8 and EDU staining. Wound-healing assays and three-dimensional tumor spheroid models were further used to evaluate migration and the anti-HCC activity of kaempferol. The cell cycle and apoptosis were evaluated by flow cytometry. Western blot and qRT-PCR were used to detect the expression of proteins and genes associated with the cell cycle checkpoints. Finally, bioinformatics was used to analyze the relationship between the differential expression of core targets in the ATM/CHEK2/KNL1 pathway and a poor prognosis in clinical HCC samples.

RESULTS

UPLC-MS/MS was employed to detect five active compounds in A. officinarum, such as kaempferol. The CCK-8 and EDU assays showed that kaempferol and A. officinarum significantly inhibited the proliferation of HCC cells. A wound-healing assay revealed that kaempferol remarkably inhibited the migration of HCC cells. Kaempferol significantly suppressed the growth of tumor spheroids. In addition, kaempferol markedly induced G2/M arrest and promoted apoptosis of HCC cells. Mechanically, kaempferol significantly reduced the protein and mRNA expression levels of ATM, CHEK2, CDC25C, CDK1, CCNB1, MPS1, KNL1, and Bub1. Additionally, the combination of kaempferol and the ATM inhibitor KU55933 had a more significant anti-HCC effect. The results of bioinformatics showed that ATM, CHEK2, CDC25C, CDK1, and KNL1 were highly expressed in patients with HCC and cancer tissues, indicating that these genes have certain value in the clinical diagnosis of HCC.

CONCLUSIONS

Collectively, our results revealed that kaempferol from A. officinarum inhibits the cell cycle by regulating the ATM/CHEK2/KNL1 pathway in HCC cells. In summary, our research presents an innovative supplementary strategy for HCC treatment.

MEIKIN expression and its C-terminal phosphorylation by PLK1 is closely related the metaphase-anaphase transition by affecting cyclin B1 and Securin stabilization in meiotic oocyte

Oocyte meiotic maturation failure and chromosome abnormality is one of the main causes of infertility, abortion, and diseases. The mono-orientation of sister chromatids during the first meiosis is important for ensuring accurate chromosome segregation in oocytes. MEIKIN is a germ cell-specific protein that can regulate the mono-orientation of sister chromatids and the protection of the centromeric cohesin complex during meiosis I. Here we found that MEIKIN is a maternal protein that was highly expressed in mouse oocytes before the metaphase I (MI) stage, but became degraded by the MII stage and dramatically reduced after fertilization. Strikingly, MEIKIN underwent phosphorylation modification after germinal vesicle breakdown (GVBD), indicating its possible function in subsequent cellular event regulation. We further showed that MEIKIN phosphorylation was mediated by PLK1 at its carboxyl terminal region and its C-terminus was its key functional domain. To clarify the biological significance of meikin degradation during later stages of oocyte maturation, exogenous expression of MEIKIN was employed, which showed that suppression of MEIKIN degradation resulted in chromosome misalignment, cyclin B1 and Securin degradation failure, and MI arrest through a spindle assembly checkpoint (SAC)-independent mechanism. Exogenous expression of MEIKIN also inhibited metaphase II (MII) exit and early embryo development. These results indicate that proper MEIKIN expression level and its C-terminal phosphorylation by PLK1 are critical for regulating the metaphase-anaphase transition in meiotic oocyte. The findings of this study are important for understanding the regulation of chromosome segregation and the prevention meiotic abnormality.

Bisphenol M inhibits mouse oocyte maturation in vitro by disrupting cytoskeleton architecture and cell cycle processes

Bisphenol M (BPM), an alternative to bisphenol A (BPA), is commonly utilized in various industrial applications. However, BPM does not represent a safe substitute for BPA due to its detrimental effects on living beings. This research aimed to assess the influence of BPM exposure on the in vitro maturation of mouse oocytes. The findings revealed that BPM exposure had a notable impact on the germinal vesicle breakdown (GVBD) rate and polar body extrusion (PBE) rate throughout the meiotic progression of mouse oocytes, ultimately resulting in meiotic arrest. Investigations demonstrated that oocytes exposure to BPM led to continued activation of spindle assembly checkpoint. Further studies revealed that securin and cyclin B1 could not be degraded in BPM-exposed oocytes, and meiosis could not realize the transition from the MI to the AI stage. Mechanistically, BPM exposure resulted in abnormal spindle assembly and disrupted chromosome alignment of oocytes. Additionally, abnormal positioning of microtubule organizing center-associated proteins implied that MTOC may be dysfunctional. Furthermore, an elevation in the acetylation level of α-tubulin in oocytes was observed after BPM treatment, leading to decreased microtubule stability. In addition to its impact on microtubules, BPM exposure led to a reduction in the expression of the actin, signifying the disruption of actin assembly. Further research indicated a heightened incidence of DNA damage in oocytes following BPM exposure. Besides, BPM exposure induced alterations in histone modifications. The outcomes of this experiment demonstrate that BPM exposure impairs oocyte quality and inhibits meiotic maturation of mouse oocytes.

Maternal genetic variants in kinesin motor domains prematurely increase egg aneuploidy

The female reproductive lifespan depends on egg quality, particularly euploidy. Mistakes in meiosis leading to egg aneuploidy are common, but the genetic landscape causing this is not well understood due to limited phenotypic data. We identify genetic determinants of reproductive aging via egg aneuploidy using a biobank of maternal exomes linked with maternal age and embryonic aneuploidy data. We found 404 genes with variants enriched in individuals with high egg aneuploidy rates and implicate kinesin protein family genes in aneuploidy risk. Experimental perturbations showed that motor domain variants in these genes increase aneuploidy in mouse oocytes. A knock-in mouse model validated that a specific variant in kinesin KIF18A accelerates reproductive aging and diminishes fertility. These findings suggest potential non-invasive biomarkers for egg quality, aiding personalized fertility medicine.

One sentence summary

The study identifies novel genetic determinants of reproductive aging linked to egg aneuploidy by analyzing maternal exomes and demonstrates that variants in kinesin genes, specifically KIF18A , contribute to increased aneuploidy and accelerated reproductive aging, offering potential for personalized fertility medicine.

Insights into the Clinical, Biological and Therapeutic Impact of Copy Number Alteration in Cancer

Copy number alterations (CNAs), resulting from the gain or loss of genetic material from as little as 50 base pairs or as big as entire chromosome(s), have been associated with many congenital diseases, de novo syndromes and cancer. It is established that CNAs disturb the dosage of genomic regions including enhancers/promoters, long non-coding RNA and gene(s) among others, ultimately leading to an altered balance of key cellular functions. In cancer, CNAs have been associated with almost all steps of the disease: predisposition, initiation, development, maintenance, response to treatment, resistance, and relapse. Therefore, understanding how specific CNAs contribute to tumourigenesis may provide prognostic insight and ultimately lead to the development of new therapeutic approaches to improve patient outcomes. In this review, we provide a snapshot of what is currently known about CNAs and cancer, incorporating topics regarding their detection, clinical impact, origin, and nature, and discuss the integration of innovative genetic engineering strategies, to highlight the potential for targeting CNAs using novel, dosage-sensitive and less toxic therapies for CNA-driven cancer.

High Comorbidity of Pediatric Cancers in Patients with Birth Defects: Insights from Whole Genome Sequencing Analysis of Copy Number Variations

BACKGROUND

Patients with birth defects (BD) exhibit an elevated risk of cancer. We aimed to investigate the potential link between pediatric cancers and BDs, exploring the hypothesis of shared genetic defects contributing to the coexistence of these conditions.

METHODS

This study included 1454 probands with BDs (704 females and 750 males), including 619 (42.3%) with and 845 (57.7%) without co-occurrence of pediatric onset cancers. Whole genome sequencing (WGS) was done at 30X coverage through the Kids First/Gabriella Miller X01 Program.

RESULTS

8211 CNV loci were called from the 1454 unrelated individuals. 191 CNV loci classified as pathogenic/likely pathogenic (P/LP) were identified in 309 (21.3%) patients, with 124 (40.1%) of these patients having pediatric onset cancers. The most common group of CNVs are pathogenic deletions covering the region ChrX:52,863,011-55,652,521, seen in 162 patients including 17 males. Large recurrent P/LP duplications >5MB were detected in 33 patients.

CONCLUSIONS

This study revealed that P/LP CNVs were common in a large cohort of BD patients with high rate of pediatric cancers. We present a comprehensive spectrum of P/LP CNVs in patients with BDs and various cancers. Notably, deletions involving E2F target genes and genes implicated in mitotic spindle assembly and G2/M checkpoint were identified, potentially disrupting cell-cycle progression and providing mechanistic insights into the concurrent occurrence of BDs and cancers.

Loss of UBE2S causes meiosis I arrest with normal spindle assembly checkpoint dynamics in mouse oocytes

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.

C-Type Natriuretic Peptide Pre-Treatment Improves Maturation Rate of Goat Oocytes by Maintaining Transzonal Projections, Spindle Morphology, and Mitochondrial Function

C-type natriuretic peptide (CNP) is a peptide molecule naturally found in follicles and can be used to extend meiotic resumption and enhance the potential for oocytes to develop. However, the mechanism by which CNP improves goat oocyte quality remains unclear. In this study, cumulus-oocyte complexes (COCs) from goats were pre-treated with CNP prior to IVM, and the results showed that pre-treatment with CNP enhanced goat oocyte maturation. First, we discovered that CNP maintained communication between cumulus cells and oocytes by regulating the transzonal projections (TZPs). We then found that CNP treatment reduced abnormal spindle formation and increased the expression of genes associated with spindle assembly and the spindle assembly checkpoint. Moreover, further analysis showed that oocytes exhibited better antioxidant ability in the CNP treatment group, which mainly manifested in higher glutathione (GSH) and lower reactive oxygen species (ROS) concentrations. Enhanced mitochondrial activity was signified via the augmented expression of mitochondrial oxidative metabolism and fusion and fission-related genes, thus diminishing the apoptosis of the oocytes. Overall, these results provide novel insights into the potential mechanism by which CNP treatment before IVM can improve oocyte quality.

MAD2 activates IGF1R/PI3K/AKT pathway and promotes cholangiocarcinoma progression by interfering USP44/LIMA1 complex

Spindle assembly checkpoint (SAC) plays an essential part in facilitating normal cell division. However, the clinicopathological and biological significance of mitotic arrest deficient 2 like 1 (MAD2/MAD2L1), a highly conserved member of SAC in cholangiocarcinoma (CCA) remain unclear. We aim to determine the role and mechanism of MAD2 in CCA progression. In the study, we found up-regulated MAD2 facilitated CCA progression and induced lymphatic metastasis dependent on USP44/LIMA1/PI3K/AKT pathway. MAD2 interfered the binding of USP44 to LIMA1 by sequestrating more USP44 in nuclei, causing impaired formation of USP44/LIMA1 complex and enhanced LIMA1 K48 (Lys48)-linked ubiquitination. In therapeutic perspective, the data combined eleven cases of CCA PDTX model showed that high-MAD2 inhibits tumor necrosis and diminishes the inhibition of cell viability after treated with gemcitabine-based regimens. Immunohistochemistry (IHC) analysis of tissue microarray (TMA) for CCA patients revealed that high-MAD2, low-USP44 or low-LIMA1 level are correlated with worse survival for patients. Together, MAD2 activates PI3K/AKT pathway, promotes cancer progression and induces gemcitabine chemo-resistance in CCA. These findings suggest that MAD2 might be an excellent indicator in prognosis analysis and chemotherapy guidance for CCA patients.

Ectopic expression of human TUBB8 leads to increased aneuploidy in mouse oocytes

Aneuploidy seriously compromises female fertility and increases incidence of birth defects. Rates of aneuploidy in human eggs from even young women are significantly higher than those in other mammals. However, intrinsic genetic factors underlying this high incidence of aneuploidy in human eggs remain largely unknown. Here, we found that ectopic expression of human TUBB8 in mouse oocytes increases rates of aneuploidy by causing kinetochore-microtubule (K-MT) attachment defects. Stretched bivalents in mouse oocytes expressing TUBB8 are under less tension, resulting in continuous phosphorylation status of HEC1 by AURKB/C at late metaphase I that impairs the established correct K-MT attachments. This reduced tension in stretched bivalents likely correlates with decreased recruitment of KIF11 on meiotic spindles. We also found that ectopic expression of TUBB8 without its C-terminal tail decreases aneuploidy rates by reducing erroneous K-MT attachments. Importantly, variants in the C-terminal tail of TUBB8 were identified in patients with recurrent miscarriages. Ectopic expression of an identified TUBB8 variant in mouse oocytes also compromises K-MT attachments and increases aneuploidy rates. In conclusion, our study provides novel understanding for physiological mechanisms of aneuploidy in human eggs as well as for pathophysiological mechanisms involved in recurrent miscarriages.

Multitargeted inhibitory effect of Mitoxantrone 2HCl on cervical cancer cell cycle regulatory proteins: a multitargeted docking-based MM\GBSA and MD simulation study

Cervical cancer remains a significant global health concern that starts in the cervix, the lower part of the uterus that connects to the vagina and is caused by the human papillomavirus (HPV), necessitating the development of effective multitargeted effective and resistance-proof therapies. In early-stage cervical cancer may not show any symptoms, however, as the cancer progresses, some people may experience- abnormal vaginal bleeding, watery or bloody vaginal discharge, pain in the pelvis or lower back, pain during sex, and frequent and painful urination. In this study, we screened the complete FDA-approved drug library using a multitargeted inhibitory approach against four cervical cancer proteins, namely mitotic arrest deficient -2, DNA polymerase epsilon B-subunit, benzimidazole-related -1, and threonine-protein kinase-1 which crucially plays its role for the in its development process. We employed the HTVS, SP and XP algorithms for efficient filtering and screening that helped to identify Mitoxantrone 2HCl against all of them with docking and MM\GBSA scores ranging from - 11.63 to - 7.802 kcal/mol and - 74.38 to - 47.73 kcal/mol, respectively. We also evaluated the interaction patterns of each complex and the pharmacokinetics properties that helped gain insight into interactions. Subsequently, we performed multiscale MD simulations for 100 ns to understand the dynamic behaviour and stability of the Mitoxantrone 2HCl -protein complexes that revealed the formation of stable drug-protein complexes and provided insights into the molecular interactions that contribute to Mitoxantrone's inhibitory effects on these proteins and can be a better drug for cervical cancer. However, experimental studies of these findings could pave the way for therapies to combat cervical cancer effectively.

Making a good egg: human oocyte health, aging, and in vitro development

Mammalian eggs (oocytes) are formed during fetal life and establish associations with somatic cells to form primordial follicles that create a store of germ cells (the primordial pool). The size of this pool is influenced by key events during the formation of germ cells and by factors that influence the subsequent activation of follicle growth. These regulatory pathways must ensure that the reserve of oocytes within primordial follicles in humans lasts for up to 50 years, yet only approximately 0.1% will ever be ovulated with the rest undergoing degeneration. This review outlines the mechanisms and regulatory pathways that govern the processes of oocyte and follicle formation and later growth, within the ovarian stroma, through to ovulation with particular reference to human oocytes/follicles. In addition, the effects of aging on female reproductive capacity through changes in oocyte number and quality are emphasized, with both the cellular mechanisms and clinical implications discussed. Finally, the details of current developments in culture systems that support all stages of follicle growth to generate mature oocytes in vitro and emerging prospects for making new oocytes from stem cells are outlined.

Exploring Plant Meiosis: Insights from the Kinetochore Perspective

The central player for chromosome segregation in both mitosis and meiosis is the macromolecular kinetochore structure, which is assembled by >100 structural and regulatory proteins on centromere DNA. Kinetochores play a crucial role in cell division by connecting chromosomal DNA and microtubule polymers. This connection helps in the proper segregation and alignment of chromosomes. Additionally, kinetochores can act as a signaling hub, regulating the start of anaphase through the spindle assembly checkpoint, and controlling the movement of chromosomes during anaphase. However, the role of various kinetochore proteins in plant meiosis has only been recently elucidated, and these proteins differ in their functionality from those found in animals. In this review, our current knowledge of the functioning of plant kinetochore proteins in meiosis will be summarized. In addition, the functional similarities and differences of core kinetochore proteins in meiosis between plants and other species are discussed, and the potential applications of manipulating certain kinetochore genes in meiosis for breeding purposes are explored.

Single-cell transcriptomics implicates the FEZ1-DKK1 axis in the regulation of corneal epithelial cell proliferation and senescence

Limbal stem/progenitor cells (LSC) represent the source of corneal epithelium renewal. LSC proliferation and differentiation are essential for corneal homeostasis, however, the regulatory mechanism remains largely unexplored. Here, we performed single-cell RNA sequencing and discovered proliferation heterogeneity as well as spontaneously differentiated and senescent cell subgroups in multiply passaged primary LSC. Fasciculation and elongation protein zeta 1 (FEZ1) and Dickkopf-1 (DKK1) were identified as two significant regulators of LSC proliferation and senescence. These two factors were mainly expressed in undifferentiated corneal epithelial cells (CECs). Knocking down the expression of either FEZ1 or DKK1 reduced cell division and caused cell cycle arrest. We observed that DKK1 acted as a downstream target of FEZ1 in LSC and that exogenous DKK1 protein partially prevented growth arrest and senescence upon FEZ1 suppression in vitro. In a mouse model of corneal injury, DKK1 also rescued the corneal epithelium after recovery was inhibited by FEZ1 suppression. Hence, the FEZ1-DKK1 axis was required for CEC proliferation and the juvenile state and can potentially be targeted as a therapeutic strategy for promoting recovery after corneal injury.

Combination of CNP, MT and FLI during IVM Significantly Improved the Quality and Development Abilities of Bovine Oocytes and IVF-Derived Embryos

Oocyte maturation is a critical step in the completion of female gametogenesis in the ovary; thus, for subsequent fertilization and embryogenesis. Vitrification of embryo also has been shown to be closely associated with oocyte maturation. To improve the quality and developmental potential of bovine oocytes derived from in vitro maturation (IVM), Pre-IVM with C-type natriuretic peptide (CNP), melatonin (MT) and in combination, IGF1, FGF2, LIF (FLI) were supplemented in the IVM medium. In this current study, we cultured bovine oocytes in Pre-IVM with CNP for 6 h before transferring them to the IVM medium supplemented with MT and FLI. The developmental potential of bovine oocytes was then investigated by measuring the reactive oxygen species (ROS), the intracellular glutathione (GSH) and ATP levels, the transzonal projections (TZP), the mitochondrial membrane potential (ΔΨm), cacline-AM, and the expression of related genes (cumulus cells (CCs), oocytes, blastocysts). The results revealed that oocytes treated with a combination of CNP, MT, and FLI had dramatically improved the percentage of oocytes developed to blastocyst, ATP content, GSH levels, TZP intensity, the ΔΨm, cacline-AM fluorescence intensity, and considerably reduced ROS levels of oocytes. Furthermore, the survival rate and the hatched rate after vitrification of the CNP+MT+FLI group were significantly higher than those other groups. Thus, we speculated that CNP+MT+FLI increases the IVM of bovine oocytes. In conclusion, our findings deepen our understanding and provide new perspectives on targeting the combination of CNP, MT and FLI to enhance the quality and developmental potential of bovine oocytes.

Exposure to diisononyl phthalate deteriorates the quality of porcine oocytes by inducing the apoptosis

Diisononyl phthalate (DINP), a mixture of chemical compounds composed of diverse isononyl esters of phthalic acid, is commonly applied as a plasticizer to substitute for di (2-ethylhexyl) phthalate (DEHP). It has been demonstrated that DINP exposure impairs the functions of kidney and liver in animals. However, the effects and potential mechanisms of DINP exposure on the female reproduction, especially the oocyte quality are still poorly understood. Here, we discovered that DINP exposure weakened the porcine oocyte meiotic competency (78.9% vs 53.6%, P < 0.001) and fertilization ability (78.5% vs 34.1%, P < 0.0001) during in vitro maturation. Specifically, DINP exposure induced the persistent spindle assembly checkpoint (SAC) activation caused by the disorganized spindle/chromosome apparatus (spindle: 20.0% vs 83.3%, P < 0.001; chromosome: 20.0% vs 80.0%, P < 0.01) to arrest meiotic progression of oocytes at metaphase I stage. In addition, DINP exposure disturbed the dynamics of sperm binding (146.7 vs 58.6, P < 0.0001) and fusion proteins (19.5 vs 11.6, P < 0.0001) in oocytes to compromise their fertilization ability. In particular, transcriptome data uncovered that the action mechanism of DINP on the oocyte maturation was associated with oxidative phosphorylation, apoptosis and autophagy pathways. Lastly, we validated that DINP exposure resulted in the mitochondrial dysfunction (27.2 vs 19.8, P < 0.0001) and elevated levels of reactive oxygen species (ROS; 8.9 vs 19.9, P < 0.0001) to trigger the occurrence of apoptosis (7.2 vs 13.1, P < 0.0001) and protective autophagy (68.6 vs 139.3, P < 0.01). Altogether, our findings not only testify that DINP has a potentially adverse impact on the mammalian oocyte quality, but also provide a scientific reference regarding how environment pollutants act on the female germ cell development.

Maternal genetic polymorphisms in the major mitotic checkpoint genes MAD1L1 and MAD2L1 associated with the risk of survival in abnormal chromosomal fetuses

Background: The genetic etiology of fetal chromosome abnormalities remains unknown, which brings about an enormous burden for patients, families, and society. The spindle assembly checkpoint (SAC) controls the normal procedure of chromosome disjunction and may take part in the process.

Objective: The aim of this study was to explore the association between polymorphisms of MAD1L1 rs1801368 and MAD2L1 rs1283639804, involved in SAC and fetal chromosome abnormalities.

Methods: The case–control study collected 563 cases and 813 health controls to test the genotypes of MAD1L1 rs1801368 and MAD2L1 rs1283639804 polymorphisms by polymerase chain reaction–restrictive fragment length polymorphism methods (PCR-RFLP).

Results:MAD1L1 rs1801368 polymorphism was associated with fetal chromosome abnormalities alone or combined to lower homocysteine (HCY) levels (alone: dominant: OR: 1.75, 95%CI: 1.19–2.57, and p = 0.005; CT vs. CC: OR = 0.73, 95%CI: 0.57–0.94, and p = 0.016; lower HCY: C vs. T: OR = 0.74, 95%CI: 0.57–0.95, and p = 0.02; dominant: OR = 1.75, 95%CI: 0.79–1.92, and p = 0.005). No significant differences were found in other genetic models or subgroups (p &gt; 0.05, respectively). MAD2L1 rs1283639804 polymorphism revealed a sole genotype in the studied population. HCY is significantly associated with fetal chromosome abnormalities in younger groups (OR: 1.78, 95%CI: 1.28–2.47, and p = 0.001).

Conclusion: The results implied that the polymorphism of MAD1L1 rs1801368 may become the susceptibility factor to fetal chromosome abnormalities alone or combined to lower HCY levels but not to MAD2L1 rs1283639804 polymorphism. In addition, HCY significantly affects fetal chromosomal abnormalities in younger women.

Microenvironmentally Responsive Chemotherapeutic Prodrugs and CHEK2 Inhibitors Self-Assembled Micelles: Protecting Fertility and Enhancing Chemotherapy

Chemotherapy is a widely used and effective adjuvant treatment for cancer, and it has unavoidable damage to female fertility, with statistics showing 38% of women who have received chemotherapy are infertile. How to reduce fertility toxicity while enhancing the oncologic chemotherapy is a clinical challenge. Herein, co-delivery micelles (BML@PMP) are developed, which are composed of a reduction-sensitive paclitaxel prodrug (PMP) for chemotherapy and a CHEK2 inhibitor (BML277) for both fertility protection and chemotherapy enhancement. BML@PMP achieves fertility protection through three actions: (1) Due to the enhanced permeability and retention (EPR) effect, BML@PMP is more enriched in the tumor, while very little in the ovary (about 1/10th of the tumor). (2) Glutathione (GSH) triggers the release of PTX, and with low levels of GSH in the ovary, the amount of PTX released in the ovary is correspondingly reduced. (3) BML277 inhibits oocyte apoptosis by inhibiting the CHEK2-TAp63α pathway. Because of the different downstream targets of CHEK2 in tumor cells and oocytes, BML277 also enhances chemotherapeutic efficacy by reducing DNA damage repair which is activated through the CHEK2 pathway. This bidirectional effect of CHEK2 inhibitor-based co-delivery system represents a promising strategy for improving oncology treatment indices and preventing chemotherapy-associated fertility damage.

KIF2C Facilitates Tumor Growth and Metastasis in Pancreatic Ductal Adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is a highly lethal cancer with a poor prognosis. For PDAC, an increase in the survival time of patients and a reduction mortality have not yet successfully been achieved. In many research works, Kinesin family member 2C (KIF2C) is highly expressed in several tumors. Nevertheless, the role of KIF2C in pancreatic cancer is unknown. In this study, we found that KIF2C expression is significantly upregulated in human PDAC tissues and cell lines such as ASPC-1 and MIA-PaCa2. Moreover, KIF2C upregulation is associated with a poor prognosis when combining the expression of KIF2C with clinical information. Through cell functional assays and the construction of animal models, we showed that KIF2C promotes PDAC cell proliferation, migration, invasion, and metastasis, both in vitro and in vivo. Finally, the results of sequencing showed that the overexpression of KIF2C causes a decrease in some proinflammatory factors and chemokines. The cell cycle detection indicated that the pancreatic cancer cells in the overexpressed group had abnormal proliferation in the G2 and S phases. These results revealed the potential of KIF2C as a therapeutic target for the treatment of PDAC.

CENP-F-dependent DRP1 function regulates APC/C activity during oocyte meiosis I

Chromosome segregation is initiated by cohesin degradation, which is driven by anaphase-promoting complex/cyclosome (APC/C). Chromosome cohesin is removed by activated separase, with the degradation of securin and cyclinB1. Dynamin-related protein 1 (DRP1), a component of the mitochondrial fission machinery, is related to cyclin dynamics in mitosis progression. Here, we show that DRP1 is recruited to the kinetochore by centromeric Centromere protein F (CENP-F) after nuclear envelope breakdown in mouse oocytes. Loss of DRP1 during prometaphase leads to premature cohesin degradation and chromosome segregation. Importantly, acute DRP1 depletion activates separase by initiating cyclinB1 and securin degradation during the metaphase-to-anaphase transition. Finally, we demonstrate that DRP1 is bound to APC2 to restrain the E3 ligase activity of APC/C. In conclusion, DRP1 is a CENP-F-dependent atypical spindle assembly checkpoint (SAC) protein that modulates metaphase-to-anaphase transition by controlling APC/C activity during meiosis I in oocytes.

OXIDATIVE STRESS AND REPRODUCTIVE FUNCTION: Oxidative stress and in vitro ageing of the post-ovulatory oocyte: an update on recent advances in the field

In brief

Post-ovulatory ageing of oocytes leads to poor oocyte and embryo quality as well as abnormalities in offspring. This review provides an update on the contributions of oxidative stress to this process and discusses the current literature surrounding the use of antioxidant media to delay post-ovulatory oocyte ageing.

Abstract

Following ovulation, the metaphase II stage oocyte has a limited functional lifespan before succumbing to a process known as post-ovulatory oocyte ageing. This progressive demise occurs both in vivo and in vitro and is accompanied by a deterioration in oocyte quality, leading to a well-defined sequelae of reduced fertilisation rates, poor embryo quality, post-implantation errors, and abnormalities in the offspring. Although the physiological consequences of post-ovulatory oocyte ageing have largely been characterised, less is known regarding the molecular mechanisms that drive this process. This review presents an update on the established relationships between the biochemical changes exhibited by the ageing oocyte and the myriad of symptoms associated with the ageing phenotype. In doing so, we consider the molecular events that are potentially involved in orchestrating post-ovulatory ageing with a particular focus on the role of oxidative stress. We highlight the mounting evidence that oxidative stress acts as an initiator for a cascade of events that create the aged oocyte phenotype. Specifically, oxidative stress has the capacity to disrupt mitochondrial function and directly damage multiple intracellular components of the oocyte such as lipids, proteins, and DNA. Finally, this review addresses emerging strategies for delaying post-ovulatory oocyte ageing with emphasis placed on the promise afforded by the use of selected antioxidants to guide the development of media tailored for the preservation of oocyte integrity during in vitro fertilisation procedures.

Insights on the Role of PGRMC1 in Mitotic and Meiotic Cell Division

During mitosis, chromosome missegregation and cytokinesis defects have been recognized as hallmarks of cancer cells. Cytoskeletal elements composing the spindle and the contractile ring and their associated proteins play crucial roles in the faithful progression of mitotic cell division. The hypothesis that PGRMC1, most likely as a part of a yet-to-be-defined complex, is involved in the regulation of spindle function and, more broadly, the cytoskeletal machinery driving cell division is particularly appealing. Nevertheless, more than ten years after the preliminary observation that PGRMC1 changes its localization dynamically during meiotic and mitotic cell division, this field of research has remained a niche and needs to be fully explored. To encourage research in this fascinating field, in this review, we will recap the current knowledge on PGRMC1 function during mitotic and meiotic cell division, critically highlighting the strengths and limitations of the experimental approaches used so far. We will focus on known interacting partners as well as new putative associated proteins that have recently arisen in the literature and that might support current as well as new hypotheses of a role for PGRMC1 in specific spindle subcompartments, such as the centrosome, kinetochores, and the midzone/midbody.

ROS-independent cytotoxicity of 9,10-phenanthrenequinone inhibits cell cycle progression and spindle assembly during meiotic maturation in mouse oocytes

Diesel exhaust particles (DEPs) are major components of ambient particulate matter and are associated with various adverse health effects. Typically, DEPs contain a vast number of organic compounds, among which 9,10-phenanthrenequinone (9,10-PQ), the quinone derivative of the polycyclic aromatic hydrocarbon phenanthrene, is one of the most abundant and toxic. 9,10-PQ can produce excessive reactive oxygen species (ROS) via redox cycling and exhibit cytotoxicity in various cells. However, the underlying mechanisms involved in cytotoxicity of 9,10-PQ remain elusive. In this study, we investigated the effects of exposure to 9,10-PQ using mouse oocytes as a model system. We found that 9,10-PQ compromised meiotic maturation by impairing acentriolar microtubule organizing center (MTOC) assembly and subsequent spindle formation during meiotic maturation. Moreover, 9,10-PQ exposure prevented cell cycle progression by inhibiting Cdk1 activation via disturbance of cyclin B1 accumulation. Importantly, meiotic defects induced by 9,10-PQ exposure were not rescued by decreasing ROS levels, revealing that 9,10-PQ has ROS-independent activity that regulates cell cycle progression and spindle assembly. Therefore, our findings reveal that 9,10-PQ has novel activity that regulates cell-cycle progression and spindle formation in an ROS-independent manner during meiotic maturation in mouse oocytes.

Kinesin KIF15 regulates tubulin acetylation and spindle assembly checkpoint in mouse oocyte meiosis

Microtubule dynamics ensure multiple cellular events during oocyte meiosis, which is critical for the fertilization and early embryo development. KIF15 (also termed Hklp2) is a member of kinesin-12 family motor proteins, which participates in Eg5-related bipolar spindle formation in mitosis. In present study, we explored the roles of KIF15 in mouse oocyte meiosis. KIF15 expressed during oocyte maturation and localized with microtubules. Depletion or inhibition of KIF15 disturbed meiotic cell cycle progression, and the oocytes which extruded the first polar body showed a high aneuploidy rate. Further analysis showed that disruption of KIF15 did not affect spindle morphology but resulted in chromosome misalignment. This might be due to the reduced stability of the K-fibers, which further induced the loss of kinetochore-microtubule attachment and activated spindle assembly checkpoint, showing with the failed release of Bub3 and BubR1. Based on mass spectroscopy analysis and coimmunoprecipitation data we showed that KIF15 was responsible for recruiting HDAC6, NAT10 and SIRT2 to maintain the acetylated tubulin level, which further affected tubulin acetylation for microtubule stability. Taken together, these results suggested that KIF15 was essential for the microtubule acetylation and cell cycle control during mouse oocyte meiosis.

Nivalenol affects Cyclin B1 level and activates SAC for cell cycle progression in mouse oocyte meiosis

OBJECTIVES

Nivalenol (NIV) is a secondary metabolite of type B trichothecene mycotoxin produced by Fusarium genera, which is widely found in contaminated food and crops such as corn, wheat and peanuts. NIV is reported to have hepatotoxicity, immunotoxicity, genotoxicity, and reproductive toxicity. Previous studies indicate that NIV disturbs mammalian oocyte maturation. Here, we reported that delayed cell cycle progression might be the reason for oocyte maturation defect caused by NIV exposure.

METHODS AND RESULTS

We set up a NIV exposure model and showed that NIV did not affect G2/M transition for meiosis resumption, but disrupted the polar body extrusion of oocytes. Further analysis revealed that oocytes were arrested at metaphase I, which might be due to the lower expression of Cyclin B1 after NIV exposure. After cold treatment, the microtubules were disassembled in the NIV-exposed oocytes, indicating that NIV disrupted microtubule stability. Moreover, NIV affected the attachment between kinetochore and microtubules, which further induced the activation of MAD2/BUBR1 at the kinetochores, suggesting that spindle assemble checkpoint (SAC) was continuously activated during oocyte meiotic maturation.

CONCLUSIONS

Taken together, our study demonstrated that exposure to NIV affected Cyclin B1 expression and activated microtubule stability-dependent SAC to ultimately disturb cell cycle progression in mouse oocyte meiosis.

A role for the mitotic proteins Bub3 and BuGZ in transcriptional regulation of catalase-3 expression

The spindle assembly checkpoint factors Bub3 and BuGZ play critical roles in mitotic process, but little is known about their roles in other cellular processes in eukaryotes. In aerobic organisms, transcriptional regulation of catalase genes in response to developmental or environmental stimuli is necessary for redox homeostasis. Here, we demonstrate that Bub3 and BuGZ negatively regulate cat-3 transcription in the model filamentous fungus Neurospora crassa. The absence of Bub3 caused a significant decrease in BuGZ protein levels. Our data indicate that BuGZ and Bub3 interact directly via the GLEBS domain of BuGZ. Despite loss of the interaction, the amount of BuGZ mutant protein negatively correlated with the cat-3 expression level, indicating that BuGZ amount rather than Bub3-BuGZ interaction determines cat-3 transcription level. Further experiments demonstrated that BuGZ binds directly to the cat-3 gene and responses to cat-3 overexpression induced by oxidative stresses. However, the zinc finger domains of BuGZ have no effects on DNA binding, although mutations of these highly conserved domains lead to loss of cat-3 repression. The deposition of BuGZ along cat-3 chromatin hindered the recruitment of transcription activators GCN4/CPC1 and NC2 complex, thereby preventing the assembly of the transcriptional machinery. Taken together, our results establish a mechanism for how mitotic proteins Bub3 and BuGZ functions in transcriptional regulation in a eukaryotic organism.

Chromosome Segregation in the Oocyte: What Goes Wrong during Aging

Human female fertility and reproductive lifespan decrease significantly with age, resulting in an extended post-reproductive period. The central dogma in human female reproduction contains two important aspects. One is the pool of oocytes in the human ovary (the ovarian reserve; approximately 10⁶ at birth), which diminishes throughout life until menopause around the age of 50 (approximately 10³ oocytes) in women. The second is the quality of oocytes, including the correctness of meiotic divisions, among other factors. Notably, the increased rate of sub- and infertility, aneuploidy, miscarriages, and birth defects are associated with advanced maternal age, especially in women above 35 years of age. This postponement is also relevant for human evolution; decades ago, the female aging-related fertility drop was not as important as it is today because women were having their children at a younger age. Spindle assembly is crucial for chromosome segregation during each cell division and oocyte maturation, making it an important event for euploidy. Consequently, aberrations in this segregation process, especially during the first meiotic division in human eggs, can lead to implantation failure or spontaneous abortion. Today, human reproductive medicine is also facing a high prevalence of aneuploidy, even in young females. However, the shift in the reproductive phase of humans and the strong increase in errors make the problem much more dramatic at later stages of the female reproductive phase. Aneuploidy in human eggs could be the result of the non-disjunction of entire chromosomes or sister chromatids during oocyte meiosis, but partial or segmental aneuploidies are also relevant. In this review, we intend to describe the relevance of the spindle apparatus during oocyte maturation for proper chromosome segregation in the context of maternal aging and the female reproductive lifespan.

SETDB1 Regulates Porcine Spermatogonial Adhesion and Proliferation through Modulating MMP3/10 Transcription

The transition from gonocytes into spermatogonia takes place during the homing process. A subpopulation of undifferentiated spermatogonia in niche then shifts to spermatogonial stem cells (SSCs), accompanied by the self-renewal ability to maintain life-long fertility in males. Enormous changes in cell morphology, gene expression, and epigenetic features have been reported during spermatogenesis. However, little is known about the difference of these features in SSCs during aging. Here, we examined the dynamics of SET domain bifurcated 1 (SETDB1) expression in porcine testes. SETDB1 was expressed in postnatal undifferentiated spermatogonia, while gradually disappeared after being packed within the basal compartment of seminiferous tubules. In addition, the cell-adhesion ability, proliferative activity, and trimethylation of the histone H3 lysine 9 (H3K9me3) level were significantly altered in SETDB1-deficient porcine SSCs. Moreover, the matrix metalloproteinases 3/10 (MMP3/10) was upregulated at both mRNA and protein levels. These results illustrate the significance of SETDB1 in modulating early male germ cell development.

Effects of post‐ovulatory aging on centromeric cohesin protection in murine MII oocytes

Purpose

Methods

Results

Conclusions

Identification and Characterization of lncRNA and mRNA in Testes of Landrace and Hezuo Boars

Simple Summary

Precocious puberty is an excellent reproductive trait in domestic animals, which can generate higher breeding benefits in livestock production. However, regulators associated with this sexual maturation process remain largely unknown. Chinese Hezuo (HZ) boars are known for their early sexual maturity. In this work, the characteristics of precocious puberty in HZ pigs were confirmed by histological analysis, and some important long noncoding RNA (lncRNA) and mRNA were identified in the testes of immature (30-day-old) and mature (120-day-old) HZ boars, which could play a key role in precocious puberty. These results will provide a theoretical basis for further research on the regulatory mechanism of precocious puberty, which is important for accelerating the breeding process of highly fertile animals.

Abstract

Chinese HZ boars are typical plateau miniature boars characterized by precocious puberty, which is closely related to testicular development and spermatogenesis. Accumulating evidence indicates that lncRNA is involved in the testicular development and regulation of spermatogenesis. However, little is known about the lncRNA precocious regulation in testicular development and spermatogenesis on early sexual maturity of HZ boars. Thus, we investigated the expression and characterization of lncRNA and mRNA in 30-day-old and 120-day-old HZ boar testes using transcriptome to explore precocious puberty. Landrace (LC) boar was treated as the control. Histological analyses indicated that HZ boar underwent puberty development at an earlier stage than LC boar and had achieved sexual maturity at 120 days old. RNA-Seq yielded a total of 187 lncRNAs and 984 mRNAs; these molecules were identified as possible candidates for precocious puberty. GO terms and KEGG pathways enrichment analyses revealed that the differentially expressed lncRNA and their targeted genes were involved in metabolic pathways regulating testis development and spermatogenesis, such as the PI3K-Akt, TGF-beta and Wnt pathways. Further screening, some lncRNA (such as LOC102166140, LOC110259451, and MSTRG.15011.2), and mRNA (such as PDCL2, HSD17B4, SHCBP1L, CYP21A2, and SPATA3) were found to be possibly associated with precocious puberty, which would add to our understanding of the molecular regulatory mechanisms of precocious puberty. This study provided valuable information for further study of the role of lncRNA and mRNA in the process of precocious puberty.

Decabromodiphenyl ethane exposure damaged the asymmetric division of mouse oocytes by inhibiting the inactivation of cyclin-dependent kinase 1

Decabromodiphenyl ethane (DBDPE) is a new brominated flame retardant and is widely added to flammable materials to prevent fire. Because it has been continuously detected in a variety of organisms and humans, it is important to reveal the biological toxicity of DBDPE. However, the influence of DBDPE for female reproduction is unclear. In this study, we investigated whether and how DBDPE exposure affects oocyte development. Female mice as a model were orally exposed to DBDPE by 0, 0.05, 0.5, 5, 50 μg/kg bw/day for 30 days (0.05 μg/kg bw/day is close to the environmental exposure concentration). We found that exposure of mice to DBDPE did not affect the first polar body extrusion (PBE) of oocytes. Strikingly, however, asymmetric division of oocytes was markedly impaired in 5 and 50 μg/kg bw/day DBDPE exposed group, which resulted in oocytes with larger polar bodies (PBs). Then, we further explored and found that DBDPE exposure inhibited the spindle migration and membrane protrusion in oocytes during anaphase of meiosis I (anaphase I), thereby impairing asymmetric division. Additionally, we found that DBDPE exposure suppressed the inactivation of cyclin-dependent kinase 1 (Cdk1), resulting in the decrease of cytoplasmic formin2 (FMN2)-mediated F-actin polymerization in oocytes at the onset of anaphase I. Simultaneously, DBDPE exposure damaged the structural integrity of the spindle and the perpendicular relationship between spindle and cortex. These together led to the failure of spindle migration and membrane protrusion required for oocytes asymmetric division. Finally, DBDPE exposure injured the development of blastocysts, leading to blastocyst apoptosis.

Paternal USP26 mutations raise Klinefelter syndrome risk in the offspring of mice and humans

Current understanding holds that Klinefelter syndrome (KS) is not inherited, but arises randomly during meiosis. Whether there is any genetic basis for the origin of KS is unknown. Here, guided by our identification of some USP26 variations apparently associated with KS, we found that knockout of Usp26 in male mice resulted in the production of 41, XXY offspring. USP26 protein is localized at the XY body, and the disruption of Usp26 causes incomplete sex chromosome pairing by destabilizing TEX11. The unpaired sex chromosomes then result in XY aneuploid spermatozoa. Consistent with our mouse results, a clinical study shows that some USP26 variations increase the proportion of XY aneuploid spermatozoa in fertile men, and we identified two families with KS offspring wherein the father of the KS patient harbored a USP26-mutated haplotype, further supporting that paternal USP26 mutation can cause KS offspring production. Thus, some KS should originate from XY spermatozoa, and paternal USP26 mutations increase the risk of producing KS offspring.

Inhibition of CDK4/6 kinases causes production of aneuploid oocytes by inactivating the spindle assembly checkpoint and accelerating first meiotic progression

Cyclin D-CDK4/6 complex mediates the transition from the G1 to S phase in mammalian somatic cells. Meiotic oocytes pass through the G2/M transition and complete the first meiosis to reach maturation at the metaphase of meiosis II without intervening S phase, while Cyclin D-CDK4/6 complex is found to express during meiotic progression. Whether Cyclin D-CDK4/6 complex regulates meiotic cell cycle progression is not known. Here, we found its different role in oocyte meiosis: Cyclin D-CDK4/6 complex served as a regulator of spindle assembly checkpoint (SAC) to prevent aneuploidy in meiosis I. Inhibition of CDK4/6 kinases disrupted spindle assembly, chromosome alignment and kinetochore-microtubule attachments, but unexpectedly accelerated meiotic progression by inactivating SAC, consequently resulting in production of aneuploid oocytes. Further studies showed that the MPF activity decrease before first polar body extrusion was accelerated probably by inactivation of the SAC to promote ubiquitin-mediated cyclin B1 degradation. Taken together, these data reveal a novel role of Cyclin D-CDK4/6 complex in mediating control of the SAC in female meiosis I.

Weighted Correlation Gene Network Analysis Reveals New Potential Mechanisms and Biomarkers in Non-obstructive Azoospermia

Non-obstructive azoospermia (NOA) denotes a severe form of male infertility, whose etiology is still poorly understood. This is mainly due to limited knowledge on the molecular mechanisms that lead to spermatogenesis failure. In this study, we acquired microarray data from GEO DataSets and identified differentially expressed genes using the limma package in R. We identified 1,261 differentially expressed genes between non-obstructive and obstructive azoospermia. Analysis of their possible biological functions and related signaling pathways using the cluster profiler package revealed an enrichment of genes involved in germ cell development, cilium organization, and oocyte meiosis. Immune infiltration analysis indicated that macrophages were the most significant immune component of NOA, cooperating with mast cells and natural killer cells. The weighted gene coexpression network analysis algorithm generated three related functional modules, which correlated closely with clinical parameters derived from histopathological subtypes of NOA. The resulting data enabled the construction of a protein–protein interaction network of these three modules, with CDK1, CDC20, CCNB1, CCNB2, and MAD2L1 identified as hub genes. This study provides the basis for further investigation of the molecular mechanism underlying NOA, as well as indications about potential biomarkers and therapeutic targets of NOA. Finally, using tissues containing different tissue types for differential expression analysis can reflect the expression differences in different tissues to a certain extent. But this difference in expression is only related and not causal. The specific causality needs to be verified later.

FKBP25 Regulates Meiotic Apparatus During Mouse Oocyte Maturation

FK506 binding proteins 25 (FKBP25) has been shown to function in ribosome biogenesis, chromatin organization, and microtubule stability in mitosis. However, the role of FKBP25 in oocyte maturation has not been investigated. Here, we report that oocytes with FKBP25 depletion display abnormal spindle assembly and chromosomes alignment, with defective kinetochore-microtubule attachment. Consistent with this finding, aneuploidy incidence is also elevated in oocytes depleted of FKBP25. Importantly, FKBP25 protein level in old oocytes is significantly reduced, and ectopic expression of FKBP25 could partly rescue the aging-associated meiotic defects. In addition, by employing site-specific mutagenesis, we identify that serine 163 is a major, if not unique, phosphorylation site modulating the action of FKBP25 on meiotic maturation. In summary, our data indicate that FKBP25 is a pivotal factor for determining oocyte quality, and may mediate the effects of maternal aging on female reproduction.

Imperatorin Ameliorates the Aging-Associated Porcine Oocyte Meiotic Spindle Defects by Reducing Oxidative Stress and Protecting Mitochondrial Function

Imperatorin (IMP) exhibits a variety of pharmacological properties, including antioxidant, anti-inflammatory, antibacterial, anti-cancer, and anti-hypertension activities. However, its effects on animal reproduction systems, especially oocyte development, maturation, and aging are not yet clear. In this study, the effects of IMP on oocyte development and aging as well as the underlying molecular mechanisms were explored. Oocytes were cultured for an additional 24 h for aging. Results revealed that the blastocyst formation and hatching rates of embryos, which were parthenogenetically activated aged oocytes, were significantly increased with IMP treatment (40 μM). Simultaneously, well-distributed cortical granules but no significant difference in zona pellucida hardness were observed after IMP treatment. During this stage, intracellular reactive oxygen species, apoptosis, and autophagy levels were decreased, while mitochondrial membrane potential, glutathione level, and activity of superoxide dismutase and catalase were increased. IMP-treated aged oocytes also showed significantly higher expression of MOS, CCNB1, BMP15, and GDF9 than non-IMP-treated aged oocytes although their levels were still lower than those in the fresh oocytes. These results suggest that IMP can effectively ameliorate the quality of aged porcine oocytes by reducing oxidative stress and protecting mitochondrial function.

Constant light exposure causes oocyte meiotic defects and quality deterioration in mice

Artificial light at night (ALAN) exposes us to prolonged illumination, that adversely affects female reproduction. However, it remains to be clarified how prolonged light exposure affects oocyte meiotic maturation and quality. To this end, we exposed female mice to a constant light (CL) of 250 lux for different durations. Our findings showed that CL exposure for 7 weeks reduced the oocyte maturation rate. Meanwhile, CL exposure caused greater abnormalities in spindle assembly and chromosome alignment and a higher rate of oocyte aneuploidy than the regular light dark cycle. CL exposure also induced oxidative stress and caused mitochondrial dysfunction, which resulted in oocyte apoptosis and autophagy. Notably, our results showed that CL exposure reduced the levels of α-tubulin acetylation, DNA methylation at 5 mC, RNA methylation at m⁶A and histone methylation at H3K4me2 but increased the levels of histone methylation at H3K27me2 in oocytes. In summary, our findings demonstrate that constant bright light exposure causes oocyte meiotic defects and reduces cytoplasmic quality. These results extend the current understanding of ALAN-mediated defects in female reproduction.

Mps1 controls spindle assembly, SAC, and DNA repair in the first cleavage of mouse early embryos

Monopolar spindle-1 (Mps1) is a critical interphase regulator that also involves into the spindle assembly checkpoint for the cell cycle control in both mitosis and meiosis. However, the functions of Mps1 during mouse early embryo development is still unclear. In this study, we reported the important roles of Mps1 in the first cleavage of mouse embryos. Our data indicated that the loss of Mps1 activity caused precocious cleavage of zygotes to 2-cell embryos; however, prolonged culture disturbed the early embryo development to the blastocyst. We found that the spindle organization was disrupted after Mps1 inhibition, and the chromosomes were misaligned in the first cleavage. Moreover, the kinetochore-microtubule attachment was lost and Aurora B failed to accumulate to the kinetochores, indicating that the spindle assembly checkpoint (SAC) was activated. Furthermore, the inhibition of Mps1 activity resulted in an increase of DNA damage, which further induced oxidative stress, showing with positive γ-H2A.X signal and increased reactive oxygen species level. Ultimately, irreparable DNA damage and oxidative stress-activated apoptosis and autophagy, which was confirmed by the positive Annexin-V signal and increased autophagosomes. Taken together, our data indicated that Mps1 played important roles in the control of SAC and DNA repair during mouse early embryo development.

MIWI prevents aneuploidy during meiosis by cleaving excess satellite RNA

MIWI, a murine member of PIWI proteins mostly expressed during male meiosis, is crucial for piRNA biogenesis, post-transcriptional regulation, and spermiogenesis. However, its meiotic function remains unknown. Here, we report that MIWI deficiency alters meiotic kinetochore assembly, significantly increases chromosome misalignment at the meiosis metaphase I plate, and causes chromosome mis-segregation. Consequently, Miwi-deficient mice show elevated aneuploidy in metaphase II and spermatid death. Furthermore, in Miwi-null and Miwi slicer-deficient mutants, major and minor satellite RNAs from centromeric and pericentromeric satellite repeats accumulate in excess. Over-expression of satellite repeats in wild-type spermatocytes also causes elevated chromosome misalignment, whereas reduction of both strands of major or minor satellite RNAs results in lower frequencies of chromosome misalignment. We show that MIWI, guided by piRNA, cleaves major satellite RNAs, generating RNA fragments that may form substrates for subsequent Dicer cleavage. Furthermore, Dicer cleaves all satellite RNAs in conjunction with MIWI. These findings reveal a novel mechanism in which MIWI- and Dicer-mediated cleavage of the satellite RNAs prevents the over-expression of satellite RNAs, thus ensuring proper kinetochore assembly and faithful chromosome segregation during meiosis.

Nampt-mediated spindle sizing secures a post-anaphase increase in spindle speed required for extreme asymmetry

Meiotic divisions in oocytes are extremely asymmetric and require pre- and post-anaphase-onset phases of spindle migration. The latter induces membrane protrusion that is moulded around the spindle thereby reducing cytoplasmic loss. Here, we find that depleting the NAD biosynthetic enzyme, nicotinamide phosphoribosyl-transferase (Nampt), in mouse oocytes results in markedly longer spindles and compromises asymmetry. By analysing spindle speed in live oocytes, we identify a striking and transient acceleration after anaphase-onset that is severely blunted following Nampt-depletion. Slow-moving midzones of elongated spindles induce cortical furrowing deep within the oocyte before protrusions can form, altogether resulting in larger oocyte fragments being cleaved off. Additionally, we find that Nampt-depletion lowers NAD and ATP levels and that reducing NAD using small molecule Nampt inhibitors also compromises asymmetry. These data show that rapid midzone displacement is critical for extreme asymmetry by delaying furrowing to enable protrusions to form and link metabolic status to asymmetric division.

Meiotic cell division in oocytes is asymmetric and requires microtubule spindle migration after anaphase-onset. Here, the authors show that Nampt, an enzyme of the Nicotinamide adenine dinucleotide (NAD) biosynthetic pathway, contributes to post-anaphase spindle migration and oocyte division asymmetry by controlling spindle length.

Mechanisms of oocyte aneuploidy associated with advanced maternal age

It is well established that maternal age is associated with a rapid decline in the production of healthy and high-quality oocytes resulting in reduced fertility in women older than 35 years of age. In particular, chromosome segregation errors during meiotic divisions are increasingly common and lead to the production of oocytes with an incorrect number of chromosomes, a condition known as aneuploidy. When an aneuploid oocyte is fertilized by a sperm it gives rise to an aneuploid embryo that, except in rare situations, will result in a spontaneous abortion. As females advance in age, they are at higher risk of infertility, miscarriage, or having a pregnancy affected by congenital birth defects such as Down syndrome (trisomy 21), Edwards syndrome (trisomy 18), and Turner syndrome (monosomy X). Here, we review the potential molecular mechanisms associated with increased chromosome segregation errors during meiosis as a function of maternal age. Our review shows that multiple exogenous and endogenous factors contribute to the age-related increase in oocyte aneuploidy. Specifically, the weight of evidence indicates that recombination failure, cohesin deterioration, spindle assembly checkpoint (SAC) disregulation, abnormalities in post-translational modification of histones and tubulin, and mitochondrial dysfunction are the leading causes of oocyte aneuploidy associated with maternal aging. There is also growing evidence that dietary and other bioactive interventions may mitigate the effect of maternal aging on oocyte quality and oocyte aneuploidy, thereby improving fertility outcomes. Maternal age is a major concern for aneuploidy and genetic disorders in the offspring in the context of an increasing proportion of mothers having children at increasingly older ages. A better understanding of the mechanisms associated with maternal aging leading to aneuploidy and of intervention strategies that may mitigate these detrimental effects and reduce its occurrence are essential for preventing abnormal reproductive outcomes in the human population.

CHK2 is essential for spindle assembly and DNA repair during the first cleavage of mouse embryos

The quality of the early embryo is critical for embryonic development and implantation. Errors during cleavage lead to aneuploidy in embryos. As a cell cycle checkpoint protein, CHK2 participates in DNA replication, cell cycle arrest and spindle assembly. However, the functions of CHK2 in early development of the mouse embryo remain largely unknown. In this study, we show that CHK2 is localized on the spindle in metaphase and mainly accumulates at spindle poles in anaphase/telophase during the first cleavage of the mouse embryo. CHK2 inhibition led to cleavage failure in early embryonic development, accompanied by abnormal spindle assembly and misaligned chromosomes. Moreover, the loss of CHK2 activity increased the level of cellular DNA damage, which resulted in oxidative stress. Then, apoptosis and autophagy were found to be active in these embryos. In summary, our results suggest that CHK2 is an essential regulator of spindle assembly and DNA repair during early embryonic development in mice.

Cell division cycle 23 is required for mouse oocyte meiotic maturation

Precise regulation of chromosome segregation during oocyte meiosis is of vital importance to mammalian reproduction. Anaphase promoting complex/cyclosome (APC/C) is reported to play an important role in metaphase-to-anaphase transition. Here we report that cell division cycle 23 (Cdc23, also known as APC8) plays a critical role in regulating the oocyte chromosome separation. Cdc23 localized on the meiotic spindle, and microinjection of Cdc23 siRNA caused decreased ratios of metaphase-to-anaphase transition. Loss of Cdc23 resulted in abnormal spindles, misaligned chromosomes, errors of homologous chromosome segregation, and production of aneuploid oocytes. Further study showed that inactivation of spindle assembly checkpoint and degradation of Cyclin B1 and securin were disturbed after Cdc23 knockdown. Furthermore, we found that inhibiting spindle assembly checkpoint protein Msp1 partly rescued the decreased polar body extrusion and reduced the accumulation of securin in Cdc23 knockdown oocytes. Taken together, our data demonstrate that Cdc23 is required for the chromosome segregation through regulating the spindle assembly checkpoint activity, and cyclin B1 and securin degradation in meiotic mouse oocytes.

Luteinizing Hormone Action in Human Oocyte Maturation and Quality: Signaling Pathways, Regulation, and Clinical Impact

The ovarian follicle luteinizing hormone (LH) signaling molecules that regulate oocyte meiotic maturation have recently been identified. The LH signal reduces preovulatory follicle cyclic nucleotide levels which releases oocytes from the first meiotic arrest. In the ovarian follicle, the LH signal reduces cyclic nucleotide levels via the CNP/NPR2 system, the EGF/EGF receptor network, and follicle/oocyte gap junctions. In the oocyte, reduced cyclic nucleotide levels activate the maturation promoting factor (MPF). The activated MPF induces chromosome segregation and completion of the first and second meiotic divisions. The purpose of this paper is to present an overview of the current understanding of human LH signaling regulation of oocyte meiotic maturation by identifying and integrating the human studies on this topic. We found 89 human studies in the literature that identified 24 LH follicle/oocyte signaling proteins. These studies show that human oocyte meiotic maturation is regulated by the same proteins that regulate animal oocyte meiotic maturation. We also found that these LH signaling pathway molecules regulate human oocyte quality and subsequent embryo quality. Remarkably, in vitro maturation (IVM) prematuration culture (PMC) protocols that manipulate the LH signaling pathway improve human oocyte quality of cultured human oocytes. This knowledge has improved clinical human IVM efficiency which may become a routine alternative ART for some infertile patients.

Meiotic arrest occurs most frequently at metaphase and is often incomplete in azoospermic men

OBJECTIVE

To establish which meiotic checkpoints are activated in males with severe spermatogenic impairment to improve phenotypic characterization of meiotic defects.

DESIGN

Retrospective observational study.

SETTING

University medical center research laboratory and andrology clinic.

PATIENT(S)

Forty-eight patients with confirmed spermatogenic impairment (Johnsen scores 3-6) and 15 controls (Johnsen score 10).

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Quantitative assessment of immunofluorescent analyses of specific markers to determine meiotic entry, chromosome pairing, progression of DNA double-strand break repair, crossover formation, formation of meiotic metaphases, metaphase arrest, and spermatid formation, resulting in a novel classification of human meiotic arrest types.

RESULT(S)

Complete metaphase arrest was observed most frequently (27%), and the patients with the highest frequency of apoptotic metaphases also displayed a reduction in crossover number. Incomplete metaphase arrest was observed in 17% of the patients. Only four patients (8%) displayed a failure to complete meiotic chromosome pairing leading to pachytene arrest. Two new types of meiotic arrest were defined: premetaphase and postmetaphase arrest (15% and 13%, respectively).

CONCLUSION(S)

Meiotic arrest in men occurs most frequently at meiotic metaphase. This arrest can be incomplete, resulting in low numbers of spermatids, and often occurs in association with reduced crossover frequency. The phenotyping approach described here provides mechanistic insights to help identify candidate infertility genes and to assess genotype-phenotype correlations in individual cases.

Melatonin Improves In Vitro Development of Vitrified-Warmed Mouse Germinal Vesicle Oocytes Potentially via Modulation of Spindle Assembly Checkpoint-Related Genes

The present study aimed to investigate the effect of melatonin (MT) supplementation on in vitro maturation of vitrified mouse germinal vesicle (GV) oocytes. The fresh oocytes were randomly divided into three groups: untreated (control), or vitrified by open-pulled straw method without (vitrification group) or with MT supplementation (vitrification + MT group). After warming, oocytes were cultured in vitro, then the reactive oxygen species (ROS) and glutathione (GSH) levels, mitochondrial membrane potential, ATP levels, spindle morphology, mRNA expression of spindle assembly checkpoint (SAC)-related genes (Mps1, BubR1, Mad1, Mad2), and their subsequent developmental potential in vitro were evaluated. The results showed that vitrification/warming procedures significantly decreased the percentage of GV oocytes developed to metaphase II (MII) stage, the mitochondrial membrane potential, ATP content, and GSH levels, remarkably increased the ROS levels, and significantly impaired the spindle morphology. The expressions of SAC-related genes were also altered in vitrified oocytes. However, when 10-7 mol/L MT was administered during the whole length of the experiment, the percentage of GV oocytes matured to MII stage was significantly increased, and the other indicators were also significantly improved and almost recovered to the normal levels relative to the control. Thus, we speculate that MT might regulate the mitochondrial membrane potential, ATP content, ROS, GSH, and expression of SAC-related genes, potentially increasing the in vitro maturation of vitrified-warmed mouse GV oocytes.