RNA G-quadruplexes (rG4s), formed through guanine self-recognition into stacked tetrads, serve as critical regulators of gene expression, yet their comprehensive mapping and dynamic regulation in physiological contexts remain technically challenging. Here, we develop Ultra-low-input rG4-seq (ULI-rG4-seq), enabling precise rG4 detection enabling precise rG4 detection with ∼140 bp resolution in samples as small as 100 oocytes, and reveal notable enrichment of rG4s near crucial regulatory regions, particularly transcription start sites and end sites. This technological advance, combined with Trim-away or oocyte-specific knockout of DHX36 (also known as G4R1 or RHAU), an rG4-specific helicase, reveals acute and chronic loss of DHX36 leads to opposing effects on rG4 levels. This observation extends beyond the traditional view of helicases as unwinding enzymes and suggests sophisticated cellular mechanisms maintaining RNA structural homeostasis. Through integrated analysis of rG4 landscapes and DHX36-binding profiles, we demonstrate coordination between cytoplasmic rG4 regulation and nuclear gene expression, revealing how RNA structure dynamics orchestrate RNA stability and translation, thereby influencing transcriptional elongation, genome stability, and alternative splicing. Finally, we show that deletion of DHX36 resulted in decreased oocyte quality, premature ovarian failure and complete female infertility due to transcriptional defects and genome instability related to R-loop accumulation. These technological and conceptual advances not only deepen our understanding of RNA-based regulation but also open new therapeutic possibilities for diseases involving RNA structure.

BACKGROUND:The high mortality rate associated with epithelial ovarian cancer (EOC) is primarily due to recurrence and chemoresistance, underscoring the urgent need for innovative therapeutic approaches that leverage newly identified vulnerabilities in cancer cells. While conventional chemotherapies induce apoptosis by targeting DNA or mitotic machinery, ferroptosis represents a new distinct form of programmed cell death characterised by the accumulation of lipid peroxides. METHODS:The sensitivity of different EOC cell lines to ferroptosis inducers was evaluated using cell viability assays and lipid peroxidation measurements. Live-cell imaging with the pH-sensitive CD63-pHuji reporter was performed to track the extracellular export of acyl-CoA synthetase long-chain family member 4 (ACSL4) via exosomes. The upstream regulator of ACSL4 were identified through immunoprecipitation-mass spectrometry (IP-MS) and validated using protein binding assays. Finally, cell-derived xenograft (CDX) and patient-derived xenograft (PDX) models were utilised to evaluate the therapeutic potential overcoming ferroptosis resistance. FINDINGS:In this study, we found that interferon (IFN)-γ combined with arachidonic acid (AA), which are endogenous ferroptosis inducers, could initiate ferroptosis in most EOC cells. However, some EOC cells displayed significant resistance. Contrary to the typical increase in ACSL4 protein observed in ferroptosis-sensitive cells, resistant EOC cells exhibited surprisingly low levels of this pro-ferroptotic lipid metabolic protein. Intriguingly, this reduction is attributed to the exosomal expulsion of ACSL4 protein, revealing a distinct cellular mechanism to evade ferroptosis. We further identified VIPAS39 as a pivotal regulator in sorting ACSL4 into late endosomes, thereby facilitating their subsequent release as exosomes. Notably, targeting VIPAS39 not only overcomes the resistance to ferroptotic cell death but also markedly suppresses tumour growth. INTERPRETATION:Our findings uncover the crucial role of VIPAS39 in ferroptosis evasion by facilitating the exporting of ACSL4 protein via exosomes, highlighting VIPAS39 as a promising target for ferroptosis-based anti-cancer therapy. FUNDING:Funded by Beijing Municipal Natural Science Foundation (Key program Z220011), National Natural Science Foundation of China (NSFC) (T2225006, T2488301, 82272948), Peking University Medicine Youth Science and Technology Innovation 'Sail Plan' Project Type B Medical Interdisciplinary Seed Fund (71006Y3171), GuangDong Basic and Applied Basic Research Foundation (2021A1515110820), and the special fund of the National Clinical Key Speciality Construction Program, P. R. China (2023).

Granulosa cells (GCs) are the most dynamically responsive cell lineage to encourage continuous folliculogenesis; however, developmental dynamics and interplay with downstream transcription circuitry remain unclear. Here, we unravel the redistribution of genome-wide chromatin areas that drive broad developmental-related transcriptomic alterations during follicular maturation in murine and porcine GCs. Distinct GC-activated accessibility regions (GAAs) at the ovulatory phase are responsible for augmenting flanking GC-involved developmental gene (GDG) expression, which are essential for transcriptional responses to developmental cues. Mechanistically, the transcription factor Fosl2 is strongly recruited to GAAs, facilitating chromatin accessibility state transition. Elevated GAA signals driven by Fosl2 loading induce a significant upregulation of adjacent GDG expression. Additionally, GC-specific Fosl2 deletion in mice perturbs GC cellularity, leading to subfertility related to reproductive aging. Together, we highlight a dynamic chromatin accessibility landscape during follicular maturation, revealing the indispensable Fosl2 function not only controls transcriptional activation via a reconfigured chromatin state, but also orchestrates intricate signaling pathways that are fundamental for ovulation and reproduction.

Ovarian cancer (OC) is diagnosed at advanced stages, resulting in limited treatment options for patients. While early detection of OC has been investigated, the invasiveness of approaches, high sample requirements, or false-positive rates undermined its benefits. Here, we present a “one-step” high-throughput microfluidic platform for epithelial ovarian cancer (EOC) detection that integrates small extracellular vesicle (sEV) capture, in situ lysis, and protein biomarker detection. We identified 1,818 differentially expressed proteins (DEPs) through proteomic analysis of sEVs from patients’ serum, combined with cell lines. Through multi-step screening of DEPs, we identified EOC biomarkers to customize the microfluidic platform. We used the microfluidic platform to test the expression of EOC biomarkers with 2 µL of serum from 209 participants in a prospective cohort. Based on the test results, an EOC detection model (P9) was constructed, which achieved a sensitivity of 92.3

Meiotic spindle is an intricate structure and required for chromosome segregation and the proper meiotic progression during oocyte maturation, and its function is regulated by a complex network of proteins located at spindle and its peripheral region. However, proteome of meiotic spindle remains poorly characterized. Here, we acquired the proteomic profile of spindles isolated from metaphase I (MI) and metaphase II (MII) mouse oocytes. In particular, we identified Ccdc69 as a novel regulator of spindle assembly in mouse oocytes. Although deletion of Ccdc69 did not affect female fertility, the MI spindles were elongated in Ccdc69 knockout oocytes. Overexpression of Ccdc69 induced spindle defects by reducing microtubule formation and disturbing acentriolar microtubule organization centers (aMTOCs) distribution. Furthermore, Ccdc69 overexpression impaired kinetochore-microtubule (K-MT) attachment and delayed meiotic progression by abnormal activation of spindle assembly checkpoint (SAC). Taken together, our study depicts the proteome of spindles during mouse oocyte maturation and demonstrates that Ccdc69 regulates spindle assembly and meiotic progression the way similar to "The Tightening Spell of Sun Wukong's Golden Headband" in the famous Chinese Classic Journey to the West.

Proteomics is transforming medical sciences, but bridging isolated samples with intact in vivo microenvironments remains a major hurdle. We present an in vivo proteomic labeling (IVPL) platform built on a new substrate, Btn-Ph-3F, and engineered ascorbate peroxidase (APEX2)-EGFPf/f mice. Btn-Ph-3F shows high stability in organs possessing complex microenvironments, while APEX2-EGFPf/f mice readily cross with commercial Cre lines, enabling specific proteomic labeling for customized cell groups in distant organs. IVPL robustly profiles in situ proteomes of intestinal epithelium, mammary gland, and tumor-infiltrating Treg cells, and, critically, labels trace exogenous proteomes from patient-derived exosomes in live mice. We identify lactate dehydrogenase A-like 6A (LDHAL6A) as a persisting exosomal effector that promotes malignant programs in recipient cells. Inhibition of LDHAL6A combined with paclitaxel treatment markedly suppresses triple-negative breast cancer growth and metastasis. Collectively, our work not only establishes an advanced model for IVPL but also profiles ultimately exosomal actors in recipient organs for targeted therapy.

In situ drug synthesis using the copper-catalyzed azide-alkyne cycloaddition (CuAAC) reaction has attracted considerable attention in tumor therapy because of its satisfactory effectiveness and reduced side-effects. However, the exogenous addition of copper catalysts can cause cytotoxicity and has hampered biomedical applications in vivo. Here, we design and synthesize a metal-organic framework (MOF) to mimic copper chaperone, which can selectively modulate copper trafficking for bioorthogonal synthesis with no need of exogenous addition of copper catalysts. Like copper chaperones, the prepared ZIF-8 copper chaperone mimics specifically bind copper ions through the formation of coordination bonds. Moreover, the copper is unloaded under the acidic environment due to the dissipation of the coordination interactions between metal ions and ligands. In this way, the cancer cell-targeted copper chaperone mimics can selectively transport copper ions into cells. Regulation of intracellular copper trafficking may inspire constructing bioorthogonal catalysis system with reduced metal cytotoxicity in live cells.

BackgroundPoly(ADP-ribose) polymerase (PARP) inhibitors have emerged as promising chemotherapeutic drugs primarily against BRCA1/2-associated tumours, known as synthetic lethality. However, recent clinical trials reported patients’ survival benefits from PARP inhibitor treatments, irrelevant to homologous recombination deficiency. Therefore, revealing the therapeutic mechanism of PARP inhibitors beyond DNA damage repair is urgently needed, which can facilitate precision medicine.MethodsA CRISPR-based knock-in technology was used to establish stable BRCA1 mutant cancer cells. The effects of PARP inhibitors on BRCA1 mutant cancer cells were evaluated by biochemical and cell biological experiments. Finally, we validated its in vivo effects in xenograft and patient-derived xenograft (PDX) tumour mice.FindingsIn this study, we uncovered that the majority of clinical BRCA1 mutations in breast cancers were in and near the middle of the gene, rather than in essential regions for DNA damage repair. Representative mutations such as R1085I and E1222Q caused transient extra spindle poles during mitosis in cancer cells. PAR, which is synthesized by PARP2 but not PARP1 at mitotic centrosomes, clustered these transient extra poles, independent of DNA damage response. Common PARP inhibitors could effectively suppress PARP2-synthesized PAR and induce cell senescence by abrogating the correction of mitotic extra-pole error.InterpretationOur findings uncover an alternative mechanism by which PARP inhibitors efficiently suppress tumours, thereby pointing to a potential new therapeutic strategy for centrosome error-related tumours.FundingFunded by National Natural Science Foundation of China (NSFC) (T2225006, 82272948, 82103106), Beijing Municipal Natural Science Foundation (Key program Z220011), and the National Clinical Key Specialty Construction Program, P. R. China (2023).

Chemodynamic therapy (CDT), which employs intracellular H2O2 to produce toxic hydroxyl radicals to kill cancer cells, has received great attention due to its specificity to tumors. However, the relatively insufficient endogenous H2O2 and the short-lifetime and limited diffusion distance of •OH compromise the therapeutic efficacy of CDT. Mitochondria, which play crucial roles in oncogenesis, are highly vulnerable to elevated oxidative stress. Herein, we constructed a mitochondria-mediated self-cycling system to achieve high dose of •OH production through continuous H2O2 supply. Cinnamaldehyde (CA), which can elevate H2O2 level in the mitochondria, was loaded in Cu(II)-containing metal organic framework (MOF), termed as HKUST-1. After actively targeting mitochondria, the intrinsic H2O2 in mitochondria of cancer cells could induce degradation of MOF, releasing the initial free CA. The released CA further triggered the upregulation of endogenous H2O2, resulting in the subsequent adequate release of CA and the final burst growth of H2O2. The cycle process greatly promoted the Fenton-like reaction between Cu2+ and H2O2 and induced long-term high oxidative stress, achieving enhanced chemodynamic therapy. In a word, we put forward an efficient strategy for enhanced chemodynamic therapy.

Environmental factors such as diet and lifestyle can influence the health of both mothers and offspring. However, its transgenerational transmission and underlying mechanisms remain largely unknown. Here, using a maternal lactation-period low-protein diet (LPD) mouse model, we show that maternal LPD during lactation causes decreased survival and stunted growth, significantly reduces ovulation and litter size, and alters the gut microbiome in the female LPD-F1 offspring. The transcriptome of LPD-F1 metaphase II (MII) oocytes shows that differentially expressed genes are enriched in female pregnancy and multiple metabolic processes. Moreover, maternal LPD causes early stunted growth and impairs metabolic health, which is transmitted over two generations. The methylome alteration of LPD-F1 oocytes can be partly transmitted to the F2 oocytes. Together, our results reveal that LPD during lactation transgenerationally affects offspring health, probably via oocyte epigenetic changes.

CtBP-interacting protein(CtIP)is known for its multifaceted roles in DNA repair and genomic stability,directing the homologous recombination-mediated DNA double-stranded break repair pathway via DNA end resection,an essential error-free repair process vital for genome stability.Mammalian oocytes are highly prone to DNA damage accumulation due to prolonged G2/prophase arrest.Here,we explore the functions of CtIP in meiotic cell cycle regulation via a mouse oocyte model.Depletion of CtIP by siRNA injection results in delayed germinal vesicle breakdown and failed polar body extrusion.Mechanistically,CtIP deficiency increases DNA damage and decreases the expression and nuclear entry of CCNB1,resulting in marked impairment of meiotic resumption,which can be rescued by exogenous CCNB1 overexpression.Further-more,depletion of CtIP disrupts microtubule-organizing centers coalescence at spindle poles as indicated by failed accumulation of γ-tubulin,p-Aurora kinase A,Kif2A,and TPX2,leading to abnormal spindle as-sembly and prometaphase arrest.These results provide valuable insights into the important roles of CtIP in the G2/M checkpoint and spindle assembly in mouse oocyte meiotic cell cycle regulation.

Women with germline BRCA1 mutations face an increased risk of developing breast and ovarian cancers. BARD1 (BRCA1 associated RING domain 1) is an essential heterodimeric partner of BRCA1, and mutations in BARD1 are also associated with these cancers. While BARD1 mutations are recognized for their cancer susceptibility, the exact roles of numerous BARD1 missense mutations remain unclear. In this study, we conducted functional assays to assess the homology-directed DNA repair (HDR) activity of all BARD1 missense substitutions identified in 55 breast and ovarian cancer samples, using the real-world data from the COSMIC and cBioPortal databases. Seven BARD1 variants (V85M, P187A, G491R, R565C, P669L, T719R, and Q730L) were confirmed to impair DNA damage repair. Furthermore, cells harboring these BARD1 variants exhibited increased sensitivity to the chemotherapeutic drugs, cisplatin, and olaparib, compared to cells expressing wild-type BARD1. These findings collectively suggest that these seven missense BARD1 variants are likely pathogenic and may respond well to cisplatin-olaparib combination therapy. This study not only enhances our understanding of BARD1's role in DNA damage repair but also offers valuable insights into predicting therapy responses in patients with specific BARD1 missense mutations.

Cancer stem cells (CSCs), accounting for only a minor cell proportion (< 1%) within tumors, have profound implications in tumor initiation, metastasis, recurrence, and treatment resistance due to their inherent ability of self-renewal, multi-lineage differentiation, and tumor-initiating potential. In recent years, accumulating studies indicate that CSCs and tumor immune microenvironment act reciprocally in driving tumor progression and diminishing the efficacy of cancer therapies. Extracellular vesicles (EVs), pivotal mediators of intercellular communications, build indispensable biological connections between CSCs and immune cells. By transferring bioactive molecules, including proteins, nucleic acids, and lipids, EVs can exert mutual influence on both CSCs and immune cells. This interaction plays a significant role in reshaping the tumor immune microenvironment, creating conditions favorable for the sustenance and propagation of CSCs. Deciphering the intricate interplay between CSCs and immune cells would provide valuable insights into the mechanisms of CSCs being more susceptible to immune escape. This review will highlight the EV-mediated communications between CSCs and each immune cell lineage in the tumor microenvironment and explore potential therapeutic opportunities.

ABSTRACTBackgroundThe role of solute carrier family 35 member F3 (SLC35F3) in lung adenocarcinoma (LUAD) remains unclear. To address this gap, we conducted a study employing bioinformatics analysis and experimental validation.MethodsThis study aimed to examine the expression patterns of SLC35F3 in various cancer types, particularly focusing on LUAD, by analyzing data from the Cancer Genome Atlas (TCGA) database to evaluate its clinical relevance. The research also explored potential regulatory mechanisms of SLC35F3, including its interactions with immune infiltration, tumor mutational burden (TMB), and drug sensitivity in LUAD. The investigation included analyzing SLC35F3 expression in single‐cell sequencing of LUAD cells, examining genetic variations of SLC35F3 in LUAD, and assessing SLC35F3 expression in cell lines using quantitative real‐time PCR (qRT‐PCR).ResultsThe aberrant expression of SLC35F3 was observed in both pan‐cancer and LUAD. In LUAD patients, a statistically significant increase in SLC35F3 expression was correlated with gender (p < 0.001) and was associated with poorer overall survival (OS) (p = 0.020). The expression of SLC35F3 was identified as an independent prognostic determinant in patients with LUAD (p = 0.032). SLC35F3 exhibited associations with various pathways, including cell cycle and more. SLC35F3 expression demonstrated correlations with immune infiltration, TMB, and some drugs in LUAD. Results indicated significant upregulation of SLC35F3 in both LUAD tissues and cell lines.ConclusionsSLC35F3 may serve as a prognostic biomarker and immunotherapeutic target for patients with LUAD.Clinical Trial RegistrationNot applicable.

High mortality of ovarian cancer (OC) is primarily attributed to the lack of effective early detection methods. Uterine fluid, pooling molecules from neighboring ovaries, presents an organ -specific advantage over conventional blood samples. Here, we present a protocol for identifying metabolite biomarkers in uterine fluid for early OC detection. We describe steps for uterine fluid collection from patients, metabolite extraction, metabolomics experiments, and candidate metabolite biomarker screening. This standardized workflow holds the potential to achieve early OC diagnosis in clinical practice. For complete details on the use and execution of this protocol, please refer to Wang et al.1

Sperm-induced Ca2+ rise is critical for driving oocyte activation and subsequent embryonic development, but little is known about how lasting Ca2+ oscillations are regulated. Here it is shown that NLRP14, a maternal effect factor, is essential for keeping Ca2+ oscillations and early embryonic development. Few embryos lacking maternal NLRP14 can develop beyond the 2-cell stage. The impaired developmental potential of Nlrp14-deficient oocytes is mainly caused by disrupted cytoplasmic function and calcium homeostasis due to altered mitochondrial distribution, morphology, and activity since the calcium oscillations and development of Nlrp14-deficient oocytes can be rescued by substitution of whole cytoplasm by spindle transfer. Proteomics analysis reveal that cytoplasmic UHRF1 (ubiquitin-like, containing PHD and RING finger domains 1) is significantly decreased in Nlrp14-deficient oocytes, and Uhrf1-deficient oocytes also show disrupted calcium homeostasis and developmental arrest. Strikingly, it is found that the mitochondrial Na+ /Ca2+ exchanger (NCLX) encoded by Slc8b1 is significantly decreased in the Nlrp14mNull oocyte. Mechanistically, NLRP14 interacts with the NCLX intrinsically disordered regions (IDRs) domain and maintain its stability by regulating the K27-linked ubiquitination. Thus, the study reveals NLRP14 as a crucial player in calcium homeostasis that is important for early embryonic development.

Introduction: Chronic rhinosinusitis with nasal polyps (CRSwNP) is a serious inflammatory condition. Nasal fluids (NFs) present a non-invasive alternative to nasal biopsy for studying CRSwNP pathogenesis. We aimed to compare the protein and mRNA inflammation signature between nasal polyps (NPs) and NFs. Method: The performance of polyvinyl alcohol (PVA) sponges and NFs absorbable device (NFAD) for collecting NFs from 20 patients with CRSwNP was compared using the Luminex assay. The other group consisted of four healthy controls and an additional 21 CRSwNP patients (including eosinophilic CRSwNP [ECRSwNP] and non-eosinophilic CRSwNP [NECRSwNP]) for protein quantification by Olink platform and gene expression evaluation by RNA-sequencing. Spearman’s analysis was performed to detect correlations between protein expression levels in NFs and clinical assessment variables. Results: NFAD-collected NFs contained at least a 2-fold higher concentration of cytokines than that obtained using PVA sponge, and these cytokines levels are significantly associated with NPs (ρ > 0.45, P < 0.05). Differentially expressed proteins between NFs and NPs were significantly correlated in the ECRSwNP subgroup compared with controls (ρ = 0.41, P < 0.01). Levels of Th2/IL-13, MCP4, and CCL4, characteristic of eosinophilic infiltration, were increased in ECRSwNP patients. A significant correlation between gene and protein expression was observed (ρ = 0.34, P < 0.01). PDL2 levels in NFs were positively correlated with ECRSwNP postoperative recurrence, the nasal VAS and SNOT-22 scores (ρ > 0.68, P < 0.05 for all). Conclusion: Our study revealed similarities and discrepancies in inflammatory signatures between NPs and NFs in the same CRSwNP patient.

Despite the initiation of tumor arises from tumorigenic transformation signaling in cancer cells, cancer cell survival, invasion, and metastasis also require a dynamic and reciprocal association with extracellular signaling from tumor microenvironment (TME). Primary cilia are the antenna‐like structure that mediate signaling sensation and transduction in different tissues and cells. Recent studies have started to uncover that the heterogeneous ciliation in cancer cells and cells from the TME in tumor growth impels asymmetric paracellular signaling in the TME, indicating the essential functions of primary cilia in homeostasis maintenance of both cancer cells and the TME. In this review, we discussed recent advances in the structure and assembly of primary cilia, and the role of primary cilia in tumor and TME formation, as well as the therapeutic potentials that target ciliary dynamics and signaling from the cells in different tumors and the TME.

Background. CircRNA has a covalently closed circular conformation and a stable structure. However, the exact role of circRNA in esophageal squamous cell carcinoma (ESCC) remains uncertain. The purpose of this study was to explore the role of hsa_circ_0000277 (circ_PDE3B) in ESCC.Methods. The expression levels of circ_PDE3B, miR-136-5p and mitogen-activated protein kinase kinase kinase 2 (MAP3K2) in ESCC tissues and cells were detected by quantitative real-time polymerase chain reaction (qRT-PCR) or western blot. The proliferation ability of EC9706 and KYSE30 cells was detected by clonal formation, 5-ethynyl-2'-deoxyuridine (EdU) and 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-Htetrazolium bromide (MTT) assays. Flow cytometry was used to detect the apoptosis rate of cells. Transwell assay was used to detect the invasion ability of EC9706 and KYSE3 cells. The relationship between miR-136-5p and circ_PDE3B or MAP3K2 was verified by dual-luciferase reporter assay and RNA pull-down, and the effect of circ_PDE3B on tumor growth in vivo was explored through tumor transplantation experiment. Immunohistochemistry (IHC) assay was used to detect MAP3K2 and Ki67 expression in mice tumor tissues.Results. The results showed that circ_PDE3B was highly expressed in ESCC tissues and cells. Down regulated circ_PDE3B expression in ESCC cells significantly reduced cell proliferation, migration and invasion. Circ_PDE3B served as a sponge for miR-1365p, and miR-136-5p inhibition reversed the roles of circ_PDE3B knockdown in ESCC cells. MAP3K2 was a direct target of miR-136-5p, and miR-136-5p targeted MAP3K2 to inhibit the malignant behaviors of ESCC cells. Furthermore, circ_PDE3B regulated MAP3K2 expression by sponging miR-136-5p. Importantly, circ_PDE3B knockdown inhibited tumor growth in vivo.Conclusions. In conclusion, circ_PDE3B acted as oncogenic circRNA in ESCC and accelerated ESCC progression by adsorption of miR-136-5p and activation of MAP3K2, supporting circ_PDE3B as a potential therapeutic target for ESCC.

Accurate chromosome segregation, monitored by the spindle assembly checkpoint (SAC), is crucial for the production of euploid cells. Previous in vitro studies by us and others showed that Mad2, a core member of the SAC, performs a checkpoint function in oocyte meiosis. Here, through an oocyte-specific knockout approach in mouse, we reconfirmed that Mad2-deficient oocytes exhibit an accelerated metaphase-to-anaphase transition caused by premature degradation of securin and cyclin B1 and subsequent activation of separase in meiosis I. However, it was surprising that the knockout mice were completely fertile and the resulting oocytes were euploid. In the absence of Mad2, other SAC proteins, including BubR1, Bub3 and Mad1, were normally recruited to the kinetochores, which likely explains the balanced chromosome separation. Further studies showed that the chromosome separation in Mad2-null oocytes was particularly sensitive to environmental changes and, when matured in vitro, showed chromosome misalignment, lagging chromosomes, and aneuploidy with premature separation of sister chromatids, which was exacerbated at a lower temperature. We reveal for the first time that Mad2 is dispensable for proper chromosome segregation but acts to mitigate environmental stress in meiotic oocytes.