Chromosome Misalignment Research Articles

Use of confocal microscopy and intracytoplasmic sperm injection (ICSI) to assess viability of equine oocytes from young and old mares after vitrification.

The impact of vitrification on oocyte developmental competence as a function of donor age remains an important issue in assisted reproductive technologies (ARTs). Equine germinal vesicle (GV) or metaphase II (M(II) oocytes were vitrified using the Cryotop® method. Spindle organization and chromosome alignment were evaluated from confocal imaging data sets of in vivo (IVO) or in vitro (IVM) matured oocytes subjected to vitrification or not. Intracytoplasmic sperm injection (ICSI) from the same groups was used to assess developmental potential. An increase in chromosome misalignment was observed in spindles from older mares when compared to those of younger mares (P < 0.05). When MII oocytes subjected to vitrification were examined following warming, there was no difference in the percentage of oocytes displaying chromosome misalignment. Next, GV oocytes, collected from the ovaries of younger and older mares, were compared between fresh IVM and IVM following vitrification and warming. For nonvitrified samples, an age difference was again noted for spindle organization and chromosome alignment, with a higher (P < 0.05) percentage of normal bipolar meiotic spindles with aligned chromosomes observed in nonvitrified oocytes from young versus older mares. Vitrification led to a reduction of spindle length (P < 0.05) for oocytes from old mares, whether vitrified at GV or MII stages, whereas this effect was not observed in oocytes from young mares except those vitrified at GV and subjected to IVM. Oocyte developmental potential after vitrification was evaluated after ICSI of vitrified and warmed MII or GV oocytes from young mares. From 25 MII oocytes, 18 oocytes were injected with sperm, and six blastocysts were produced, which, upon transfer to mares' uteri, resulted in four pregnancies. Immature (GV) oocytes collected from live mares were also vitrified, warmed, and matured in vitro before ICSI. In this group, nonvitrified, control, and vitrified oocytes did not differ (P > 0.05) with respect to the incidence of maturation to MII, cleavage after ICSI, or blastocyst development. These findings demonstrate an effect of maternal age in an equine model at the level of meiotic spindle integrity and chromosome positioning that is influenced by both the meiotic stage at which oocytes are vitrified and whether meiotic maturation occurred in vivo or in vitro.

Specc1l deficiency leads to abnormal oocyte meiosis and reduced blastocyst development in mouse.

This study aimed to investigate the potential role of the mouse Specc1l (Sperm antigen with calponin homology and coiled-coil domains 1 like), a microtubule and actin cytoskeleton-associated protein during oocyte meiotic maturation and its potential effects on preimplantation development. This study shows that the transcriptional levels of Specc1l did not significantly change from the germinal vesicle (GV) stage to the metaphase II (MII) stage, but maternal transcripts rapidly and gradually degraded after fertilization. Specc1l was detected in both the cytoplasm and GV, but not in the nucleolus-like body in the GV intact oocyte. At the MII stages, Specc1l was widely distributed in the cytoplasm but did not co-localize with chromatin. Knockdown of Specc1l expression in oocytes resulted in abnormal spindle morphology and misaligned chromosomes, as well as a decrease in the rate of polar body extrusion and a reduced developmental competence of oocytes, leading to decreased blastocyst formation rate. In conclusion, this study provides evidence that Specc1l plays a critical role in mouse oocyte meiotic maturation and early embryo development, specifically in proper bipolar spindle assembly and extrusion of the first polar body.

Mad2 is dispensable for accurate chromosome segregation but becomes essential when oocytes are subjected to environmental stress.

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.

Generation of Centromere-Associated Protein-E &lt;em&gt;CENP-E&lt;sup&gt;-/-&lt;/sup&gt;&lt;/em&gt; Knockout Cell Lines using the CRISPR/Cas9 System

The CRISPR (clustered regularly interspaced short palindromic repeats)/Cas9 system has emerged as a powerful tool for precise and efficient gene editing in a variety of organisms. Centromere-associated protein-E (CENP-E) is a plus-end-directed kinesin required for kinetochore-microtubule capture, chromosome alignment, and spindle assembly checkpoint. Although cellular functions of the CENP-E proteins have been well studied, it has been difficult to study the direct functions of CENP-E proteins using traditional protocols because CENP-E ablation usually leads to spindle assembly checkpoint activation, cell cycle arrest, and cell death. In this study, we have completely knocked out the CENP-E gene in human HeLa cells and successfully generated the CENP-E-/- HeLa cells using the CRISPR/Cas9 system. Three optimized phenotype-based screening strategies were established, including cell colony screening, chromosome alignment phenotypes, and the fluorescent intensities of CENP-E proteins, which effectively improve the screening efficiency and experimental success rate of the CENP-E knockout cells. Importantly, CENP-E deletion results in chromosome misalignment, the abnormal location of the BUB1 mitotic checkpoint serine/threonine kinase B (BubR1) proteins, and mitotic defects. Furthermore, we have utilized the CENP-E knockout HeLa cell model to develop an identification method for CENP-E-specific inhibitors. In this study, a useful approach to validate the specificity and toxicity of CENP-E inhibitors has been established. Moreover, this paper presents the protocols of CENP-E gene editing using the CRISPR/Cas9 system, which could be a powerful tool to investigate the mechanisms of CENP-E in cell division. Moreover, the CENP-E knockout cell line would contribute to the discovery and validation of CENP-E inhibitors, which have important implications for antitumor drug development, studies of cell division mechanisms in cell biology, and clinical applications.

P-393 The mitochondrial targeted antioxidant Mitoquinol increases survival of isolated human preantral follicles in vitro

Abstract Study question Does Mitoquinol have a protective effect on survival and mitochondrial oxidative stress in cultured human preantral follicles? Summary answer Mitoquinol significantly increased survival of human preantral follicles cultured for 8 days and significantly decreased expression of genes related to the mitochondrial oxidative stress response. What is known already Culturing human ovarian follicles is a promising new source of mature oocytes for fertility preservation, as well as a key model system to investigate fundamental biology. Nevertheless, only a handful of studies have yielded mature human oocytes from preantral stage follicles and optimizing culture systems is challenging due to the scarcity of human material. Mitoquinol is an antioxidant that contains a form of Coenzyme Q10 called ubiquinone that has been modified to selectively target and protect mitochondria from oxidative damage. In human oocytes, the presence of Mitoquinol in the IVM media increased nuclear maturation and protected against chromosomal misalignment. Study design, size, duration Human preantral follicles (n = 213; mean diameter: 71 µm; range: 26-189 µm) were isolated from ovarian medulla tissue. Preantral follicles were mechanically and enzymatically isolated, encapsulated in 0.5% alginate and cultured for 8 days in three experimental groups: Control (n = 68); 50nM Mitoquinol (n = 71), 250nM Mitoquinol (n = 74). The primary endpoints were follicular growth and survival. Secondary endpoints included follicular gene expression and hormone analysis of the spent culture media. Participants/materials, setting, methods Ovarian medulla tissue was donated by 5 patients (aged 30-37 years) undergoing unilateral oophorectomy for ovarian tissue cryopreservation. Follicular growth and survival were assessed every second day during culture by microscopy. For follicles bigger than 95 µm, AMH and Estradiol concentrations were measured by ELISA in the spent media on day 8. Finally surviving follicles were snap-frozen and gene expression was analysed by qPCR; mitochondrial oxidative stress genes: HSP-60, TFAM and apoptosis genes: BAX/BCL-2. Main results and the role of chance After 8 days in culture, the follicular survival rate in the 50nM Mitoquinol group (68%; n = 51/74) was significantly higher than the control group (49%; n = 32/68; p = 0.0344) and the 250nM Mitoquinol (54%; n = 39/71; p = 0.0443). The protective effect of 50nM Mitoquinol was more pronounced in the subset of small follicles (Day0 &amp;lt; 70 µm, n = 135) in which survival rate of the 50nM Mitoquinol group (65%; n = 31/47) was significantly higher than the control (41%; n = 18/43; p = 0.005) and the 250nM group (44%; n = 20/4; p = 0.019). The average growth of surviving follicles was similar in the three experimental groups (Control: 40.7 ± 17.4 µm; Mitoquinol 50nM: 36.9 ± 19 μm; Mitoquinol 250nM: 36.4 ±16.5 μm). A significant positive association between the diameter of the follicle and the concentration of AMH and Estradiol was observed (AMH: p = 0.0215, R = 0.43 and Estradiol: p = 0.0413, R = 0.38) but no differences were found between the experimental groups. The relative expression of genes involved in mitochondrial oxidative stress response were significantly lower in the 50nM Mitoquinol group compared to the 250mM Mitoquinol group (HSP-60 p = 0.018; TFAM p = 0.013) and similar to the control group (HSP-60 p = 0.056; TFAM p = 0.071). Moreover, the gene expression of the ratio BAX/BCL2 was similar in the three groups. Limitations, reasons for caution A larger sample size is required to confirm the statistical analysis and to extrapolate the results to primordial, primary, and secondary stage follicles. Furthermore, long-term culture studies are required to determine the impact of Mitoquinol on antral follicle development and oocyte maturation Wider implications of the findings Our findings show that Mitoquinol can be used as an antioxidant in the culture of human preantral follicles since it increased follicle survival and reduced gene expression of genes related to mitochondrial oxidative stress response. Trial registration number Not appliclable

PARP12 regulates mouse oocyte meiotic maturation.

Poly(ADP-ribosyl)ation (PARylation) is an important post-translational modification of proteins that involves the transfer of ADP-ribose moieties, and plays important roles in many biological processes including DNA repair, gene expression, RNA processing, ribosome biogenesis, and protein translation. Though it is accepted that PARylation is crucial for oocyte maturation, little is known about how Mono(ADP-ribosyl)ation (MARylation) regulates this process. Here, we report that Parp12,a mon(ADP-ribosyl) transferase of poly(ADP-ribosyl) polymerase (PARP) family, was highly expressed at all stages of oocytes during meiotic maturation. At germinal vesicle (GV) stage, PARP12 was mainly distributed in cytoplasm. Interestingly, PARP12 formed granular aggregation near to spindle poles during metaphase I (MI) and metaphase II (MII). PARP12 depletion results in abnormal spindle organization and chromosome misalignment in mouse oocytes. Chromosome aneuploidy frequency in PARP12 knockdown oocytes was significantly increased. Importantly, PARP12 knockdown triggers activation of spindle assembly checkpoint as shown by active BUBR1 in PARP12-KD MI oocytes. Besides, F actin was significantly attenuated in PARP12-KD MI oocytes which may affect the asymmetric division process. Transcriptomic analysis demonstrated that PARP12 depletion disrupts transcriptome homeostasis. Collectively, our results showed that the maternally expressed mono(ADPribosyl) transferases PARP12 was essential for oocyte meiotic maturation in mouse.

Aluminum exposure impairs oocyte quality via subcellular structure disruption and DNA damage-related apoptosis in mice

Aluminum (Al) can lead to an exposure of creature in varieties ways for its universality, and it could disturb normal physiological metabolism, with the damage to multisystem including reproduction. Since the oocyte quality is critical for female reproduction, we inspected the toxicity of Al on mouse oocyte maturation. We constructed in vitro exposure mouse model, and we found that 5 mmol/L Al had adverse effects on oocyte maturation by impairing organelle and cytoskeleton. Aberrant spindle and misaligned chromosomes which might be considered to be caused by elevated levels of acetylation, as well as abnormal distribution of actin dynamics could hinder normal meiosis of oocytes. Organelle dysfunction indicated that Al affected proteins synthesis, transport and digestion, which would further damage oocyte maturation. In order to explore the mechanism of Al toxicity, our further investigation demonstrated that Al caused mitochondrial dysfunction and imbalance calcium homeostasis, resulting in limited energy supply. Moreover, high level of reactive oxygen species, DNA damage and apoptosis caused by oxidative stress were also the manifestation of Al toxicity on oocytes. In conclusion, our study provided the evidence that Al exposure affected oocyte quality through its effects on spindle organization, actin dynamics, organelle function and the induction of DNA damage-related apoptosis with mouse model.

Ru360 protects against vitrification-induced oocyte meiotic defects by restoring mitochondrial function

Oocyte vitrification has been widely application in female fertility preservation. Recent studies found that vitrification of immature (germinal vesicle stage, GV) oocytes increased the risk of aneuploidy during meiotic maturation; however, the underlying mechanisms and the strategies to prevent this defect remain unexplored. In this study, we found that vitrification of GV oocytes decreased the first polarbody extrusion rate (90.51 ± 1.04% vs. 63.89 ± 1.39%, p < 0.05) and increased the aneuploid rate (2.50% vs. 20.00%, p < 0.05), accompanied with a series of defects during meiotic maturation, including aberrant spindle morphology, chromosome misalignment, incorrect Kinetochore-Microtubule attachments (KT-MTs) and weakened spindle assembly checkpoint protein complex (SAC) function. We also found that vitrification disrupted mitochondrial function by increasing mitochondrial Ca2+ levels. Importantly, inhibition of mitochondrial Ca2+ entry by 1 μM Ru360 significantly restored mitochondrial function and rescued the meiotic defects, indicating that the increase of mitochondrial Ca2+, at least, was a cause of meiotic defects in vitrified oocytes. These results shed light on the molecular mechanisms of oocyte vitrification-induced adverse effects of meiotic maturation and provided a potential strategy to improve oocyte cryopreservation protocols further.

The bisphenol S contamination level observed in human follicular fluid affects the development of porcine oocytes.

Bisphenol S (BPS), the main replacement for bisphenol A (BPA), is thought to be toxic, but limited information is available on the effects of Bisphenol S on ovarian follicles. In our study, we demonstrated the presence of Bisphenol S in the follicular fluid of women at a concentration of 22.4nM. The effect of such concentrations of Bisphenol S on oocyte maturation and subsequent embryo development is still unknown. Therefore, we focused on the effect of Bisphenol S on in vitro oocyte maturation, fertilization, and embryo development. As a model, we used porcine oocytes, which show many physiological similarities to human oocytes. Oocytes were exposed to Bisphenol S concentrations similar to those detected in female patients in the ART clinic. We found a decreased ability of oocytes to successfully complete meiotic maturation. Mature oocytes showed an increased frequency of meiotic spindle abnormalities and chromosome misalignment. Alarming associations of oocyte Bisphenol S exposure with the occurrence of aneuploidy and changes in the distribution of mitochondria and mitochondrial proteins were demonstrated for the first time. However, the number and quality of blastocysts derived from oocytes that successfully completed meiotic maturation under the influence of Bisphenol S was not affected.

Abstract 4896: NF1 (neurofibromatosis 1) controls microtubule dynamics and dictates sensitivity to maytansinoids

Abstract The tumor suppressor NF1 is classically considered a negative RAS regulator, but sparse evidence suggests additional RAS-independent roles. Early studies suggested an interaction with tubulin, which remains poorly characterized to date but may be of particular therapeutic interest as NF1 is somatically mutated across multiple tumor types. We showed that multiple CRISPR-Cas9-engineeerd NF1 KO HER2+ breast cancer cells (BT-474, SK-BR3, HCC1954) become exquisitely sensitive to the Antibody-Drug Conjugate (ADC) Trastuzumab emtansine (T-DM1); we here investigate the underlying mechanism.TDM1 hypersensitivy was specific to the maytansin microtubule-targeting payload, since it was i) replicated by the naked payload but not the naked antibody; ii) absent with other ADCs (T-DxD); iii) not accompanied by increased TDM1 uptake; iv) associated with increased tubulin-maytansin binding in KO cells, as per Cellular Thermal Shift Assay. The mechanism is likely RAS-independent, as KRAS G12V-overexpression did not alter TDM1 sensitivity. RNAseq revealed that KO cells deregulated genes associated with microtubular dynamics and G2-M transition more strongly upon TDM1-treatement. Multiple KO cells investigated by static and live imaging exhibited marked signs of altered mitosis, with longer G2/M, supernumerary centrosomes, chromosome misalignment and frequent aneuploidy, which could also be inferred in multiple public sequencing datasets (TCGA, MSK IMPACT, AACR GENIE). Based on this, we explored NF1 role on microtubule dynamics. We found several lines of evidence for a direct and mitosis-selective interaction between NF1 and tubulin: i) in Immunofluorescence (IF), NF1 was upregulated in mitosis and colocalized with the mitotic spindle; ii) NF1 co-Immunoprecipitated with tubulin in mitosis-enriched but not asynchronous cells; iii) purified NF1 co-eluted with tubulin in size-selection chromatography; iv) in silico modeling with AlphaFold2 predicted an interaction between NF1 central domains and the alpha-beta tubulin dimer. Crucially, KO cells exhibited severe microtubule hypodynamism in cold-induced depolymerization-repolymerization assays, replicated in multiple cell types and accompanied by imbalanced levels of plus/minus-end microtubule-associated proteins. By IF on cocultured WT/KO live cells, KO cells showed significantly higher GTP-tubulin, known to cause microtubular hyperstability, suggesting the intriguing possibility that NF1 may directly regulate tubulin intrinsic GTP-hydrolyzing activity, similar to its role on RAS. In conclusion, we provide extensive mechanistic evidence for a direct and previously underappreciated role of NF1 in microtubular dynamics, which reshapes our understanding of its tumor-suppressive activity and provides a rationale for pharmacological targeting of NF1-mutated tumors. Citation Format: Bruno A. Duso, Eleonora Messuti, Emanuele Bonetti, Giulia Tini, Alessia Castiglioni, Giuseppe Ciossani, Silvia Monzani, Chiara Soriani, Simona Rodighiero, Luigi Scietti, Costantino Jemos, Luca Mazzarella. NF1 (neurofibromatosis 1) controls microtubule dynamics and dictates sensitivity to maytansinoids. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4896.

Abstract 301: CENP-E inhibitors activate cGAS-STING pathway by inducing chromosome misalignment and micronucleation after mitotic slippage

Abstract Background: cGAS-STING, which monitors cytosolic DNA and triggers innate immune response, has recently attracted attention as a molecular target to sensitize cancer immune therapies. Since DNAs enclosed in micronucleus frequently leak into cytoplasm, micronucleus generated by centromere-associated protein-E (CENP-E) inhibition is expected to activate cGAS-STING pathways. We validated that small-molecule CENP-E inhibitors profoundly generate micronucleus through misaligned chromosomes. The aim of this study is to elucidate the possibility that micronucleus formation by CENP-E inhibitors activates the cGAS-STING pathway in cancer cells and induces immunological conversion of the tumor microenvironment from cold to hot. Material and Methods: GSK923295 and Cmpd-A were used as CENP-E inhibitors. HeLa and A549 cells were treated with the CENP-E inhibitors at the indicated concentrations. RNA sequencing data were subjected to gene set enrichment analysis (GSEA) to determine the signaling pathways modulated by Cmpd-A treatment compared to DMSO (control). Reporter assays for IRF and NF-kB were performed in A549 dual-reporter cells. High-throughput screening on IRF3 reporter activity was performed in A549 dual reporter cells in combination with -1,400 kinase inhibitor library and GSK923295. Results: The CENP-E inhibitors, GSK-923295 and Cmpd-A, induced chromosome misalignment, resulting in micronucleus formation after mitotic slippage. Phosphorylations of TBK1 and IRF3, cGAS-STING pathway markers, were remarkably upregulated in Cmpd-A-treated cells concordantly with micronucleus formation. The reporter assays also demonstrated that both IRF and NF-kB pathways were significantly activated in Cmpd-A-treated cells in a time-dependent manner. Transcriptome analysis of GSEA demonstrated that the gene ontologies (GO) for innate immune pathways, such as cytosolic DNA sensing pathway and cytokine-cytokine receptor interaction pathway, were significantly enriched in Cmpd-A-treated cells. The kinase library screening revealed that a series of inhibitors targeting PI3K-AKT-mTOR signaling pathways intensively suppressed CENP-E inhibitor-induced IRF activation, which occupied ~40% of hit compounds. Conclusions: The CENP-E inhibitors generated micronucleus activating the cGAS-STING pathway in multiple cancer cell lines. PI3K-AKT-mTOR signaling pathway may play important roles in the CENP-E inhibitor-induced cGAS-STING pathway activation. We are also initiating AI-based drug discovery, aiming to generate novel CENP-E inhibitors by performing virtual screening and generative molecular design. Citation Format: Ryo Kamata, Hitoshi Saito, Yumi Hakozaki, Yukie Kashima, Tomoko Yamamori. Morita, Pinyi Lu, Akihiro Ohashi. CENP-E inhibitors activate cGAS-STING pathway by inducing chromosome misalignment and micronucleation after mitotic slippage [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 301.

Mitotic DNA damage promotes chromokinesin-mediated missegregation of polar chromosomes in cancer cells.

DNA damage response (DDR) during interphase involves active signaling and repair to ensure genomic stability. However, how mitotic cells respond to DNA damage remains poorly understood. Supported by correlative live-/fixed-cell microscopy, it was found that mitotic cells exposed to several cancer chemotherapy compounds acquire and signal DNA damage, regardless of how they interact with DNA. In-depth analysis upon DNA damage during mitosis revealed a spindle assembly checkpoint (SAC)-dependent, but ataxia telangiectasia mutated-independent, mitotic delay. This delay was due to the presence of misaligned chromosomes that ultimately satisfy the SAC and missegregate, leading to micronuclei formation. Mechanistically, it is shown that mitotic DNA damage causes missegregation of polar chromosomes due to the action of arm-ejection forces by chromokinesins. Importantly, with the exception of DNA damage induced by etoposide-a topoisomerase II inhibitor-this outcome was independent of a general effect on kinetochore microtubule stability. Colony formation assays in pan-cancer cell line models revealed that mitotic DNA damage causes distinct cytotoxic effects, depending on the nature and extent of the damage. Overall, these findings unveil and raise awareness that therapeutic DNA damage regimens may contribute to genomic instability through a surprising link with chromokinesin-mediated missegregation of polar chromosomes in cancer cells.

MiR-186 induces tetraploidy in arsenic exposed human keratinocytes

Chronic inorganic arsenic (iAs) exposure in drinking water is a global issue affecting >225 million people. Skin is a major target organ for iAs. miRNA dysregulation and chromosomal instability (CIN) are proposed mechanisms of iAs-induced carcinogenesis. CIN is a cancer hallmark and tetraploid cells can better tolerate increase in chromosome number and aberration, contributing to the evolution of CIN. miR-186 is overexpressed in iAs-induced squamous cell carcinoma relative to iAs-induced hyperkeratosis. Bioinformatic analysis indicated that miR-186 targets mRNAs of important cell cycle regulators including mitotic checkpoint serine/threonine kinase B (BUB1) and cell division cycle 27 (CDC27). We hypothesized that miR-186 overexpression contributes to iAs-induced transformation of keratinocytes by targeting mitotic regulators leading to induction of CIN. Ker-CT cells, a near diploid human keratinocyte cell line, were transduced with miR-186 overexpressing or scrambled control lentivirus. Stable clones were isolated after puromycin selection. Clones transduced with lentivirus expressing either a scrambled control miRNA or miR-186 were maintained with 0 or 100 nM iAs for 4 weeks. Unexposed scrambled control clones were considered as passage matched controls. Chronic iAs exposure increased miR-186 expression in miR-186 clones. miR-186 overexpression significantly reduced CDC27 levels irrespective of iAs exposure. The percentage of tetraploid or aneuploid cells was increased in iAs exposed miR-186 clones. Aneuploidy can arise from a tetraploid intermediate. Suppression of CDC27 by miR-186 may lead to impairment of mitotic checkpoint complex formation and its ability to maintain cell cycle arrest leading to chromosome misalignment. As a result, cells overexpressing miR-186 and chronically exposed to iAs may have incorrect chromosome segregation and CIN. These data suggest that dysregulation of miRNA by iAs mediates tetraploidy, aneuploidy and chromosomal instability contributing to iAs-induced carcinogenesis.

The m6A reader PRRC2A is essential for meiosis I completion during spermatogenesis

N6-methyladenosine (m6A) and its reader proteins YTHDC1, YTHDC2, and YTHDF2 have been shown to exert essential functions during spermatogenesis. However, much remains unknown about m6A regulation mechanisms and the functions of specific readers during the meiotic cell cycle. Here, we show that the m6A reader Proline rich coiled-coil 2A (PRRC2A) is essential for male fertility. Germ cell-specific knockout of Prrc2a causes XY asynapsis and impaired meiotic sex chromosome inactivation in late-prophase spermatocytes. Moreover, PRRC2A-null spermatocytes exhibit delayed metaphase entry, chromosome misalignment, and spindle disorganization at metaphase I and are finally arrested at this stage. Sequencing data reveal that PRRC2A decreases the RNA abundance or improves the translation efficiency of targeting transcripts. Specifically, PRRC2A recognizes spermatogonia-specific transcripts and downregulates their RNA abundance to maintain the spermatocyte expression pattern during the meiosis prophase. For genes involved in meiotic cell division, PRRC2A improves the translation efficiency of their transcripts. Further, co-immunoprecipitation data show that PRRC2A interacts with several proteins regulating mRNA metabolism or translation (YBX1, YBX2, PABPC1, FXR1, and EIF4G3). Our study reveals post-transcriptional functions of PRRC2A and demonstrates its critical role in the completion of meiosis I in spermatogenesis.

Characteristics of oocytes that failed to fertilize after intracytoplasmic sperm injection.

We assessed the morphologies of meiotic spindles in oocytes that failed to fertilize following intracytoplasmic sperm injection (ICSI) and identified factors contributing to failed fertilization. A total of 225 unfertilized oocytes were collected after ICSI. Oocytes were fixed and stained for tubulin and chromosomes. Meiotic spindle morphologies, chromosome alignment, and sperm nuclear decondensation were assessed to identify contributing factors to fertilization failure. We identified relationships between several factors and both abnormal spindle morphologies and sperm nuclear decondensation in oocytes that failed to fertilize. Three causes for unfertilized oocytes after ICSI were identified: (I) the absence of a sperm nucleus in the ooplasm; (II) failed oocyte activation; and (III) defects in pronucleus formation or migration. The rate of disarranged polar spindles in oocytes collected from women older than 35 years (73.3%; 33/45 oocytes) was significantly higher than that of those collected from women 35 years and younger (50.4%; 68/135 oocytes; odds ratio [OR]: 2.71, 95% confidence interval [CI]: 1.29-5.69, p = 0.009). The proportion of unfertilized oocytes with abnormal spindles and chromosome misalignment was significantly higher in oocytes collected from women older than 35 years than those from women 35 years and younger (62.2% vs. 41.5%, p = 0.016). The proportion of partially decondensed chromatin in the abnormal sperm morphology group was significantly higher than in the normal sperm morphology group (66.7% versus 52.9%, OR: 1.78, 95% CI: 1.01-3.11, p = 0.044). The main contributor to the failure of oocytes to fertilize after ICSI is failed oocyte activation. The ICSI technique used, the maternal age, and sperm morphology are also contributing factors in fertilization failure after ICSI.

Inhibitory Effects of 3-Methylcholanthrene Exposure on Porcine Oocyte Maturation.

3-methylcholanthrene (3-MC) is a highly toxic environmental pollutant that impairs animal health. 3-MC exposure can cause abnormal spermatogenesis and ovarian dysfunction. However, the effects of 3-MC exposure on oocyte maturation and embryo development remain unclear. This study revealed the toxic effects of 3-MC exposure on oocyte maturation and embryo development. 3-MC with different concentrations of 0, 25, 50, and 100 μM was applied for in vitro maturation of porcine oocytes. The results showed that 100 μM 3-MC significantly inhibited cumulus expansion and the first polar body extrusion. The rates of cleavage and blastocyst of embryos derived from 3-MC-exposed oocytes were significantly lower than those in the control group. Additionally, the rates of spindle abnormalities and chromosomal misalignments were higher than those in the control group. Furthermore, 3-MC exposure not only decreased the levels of mitochondria, cortical granules (CGs), and acetylated α-Tubulin, but also increased the levels of reactive oxygen species (ROS), DNA damage, and apoptosis. The expression of cumulus expansion and apoptosis-related genes was abnormal in 3-MC-exposed oocytes. In conclusion, 3-MC exposure disrupted the nuclear and cytoplasmic maturation of porcine oocytes through oxidative stress.

TPX2 Amplification-Driven Aberrant Mitosis in Culture Adapted Human Embryonic Stem Cells with gain of 20q11.21.

Despite highly effective machinery for the maintenance of genome integrity in human embryonic stem cells (hESCs), the frequency of genetic aberrations during in-vitro culture has been a serious issue for future clinical applications. By passaging hESCs over a broad range of timepoints (up to 6years), the isogenic hESC lines with different passage numbers with distinct cellular characteristics, were established. We found that mitotic aberrations, such as the delay of mitosis, multipolar centrosomes, and chromosome mis-segregation, were increased in parallel with polyploidy compared to early-passaged hESCs (EP-hESCs) with normal copy number. Through high-resolution genome-wide approaches and transcriptome analysis, we found that culture adapted-hESCs with a minimal amplicon in chromosome 20q11.21 highly expressed TPX2, a key protein for governing spindle assembly and cancer malignancy. Consistent with these findings, the inducible expression of TPX2 in EP-hESCs reproduced aberrant mitotic events, such as the delay of mitotic progression, spindle stabilization, misaligned chromosomes, and polyploidy. These studies suggest that the increased transcription of TPX2 in culture adapted hESCs could contribute to an increase in aberrant mitosis due to altered spindle dynamics.

Post-ovulatory aging is associated with altered patterns for small ubiquitin-like modifier (SUMO) proteins and SUMO-specific proteases.

Mammalian oocytes are ovulated arrested at metaphase of the second meiotic division. If they are not fertilized within a short period, the oocyte undergoes several progressive morphological, structural, and molecular changes during a process called oocyte aging. Herein, we focused on those functional events associated with proper cytoskeleton organization and those that correlate with spindle displacement and chromosome misalignment or scatter. Post-translational modifications by Small Ubiquitin-like Modifier (SUMO) proteins are involved in spindle organization and here we demonstrate that the SUMO pathway is involved in spindle morphology changes and chromosome movements during oocyte aging. SUMO-2/3 as well as the SUMO-specific proteases SENP-2 localization are affected by postovulatory aging in vitro. Consistent with these findings, UBC9 decreases during oocyte aging while differential ubiquitination patterns also correlate with in vitro oocyte aging. These results are consistent with postovulatory aging-related alterations in the posttranslational modifications of the spindle apparatus by SUMO and its SENP proteases. These findings are suggestive that such age-related changes in SUMOylation and the deSUMOylation of key target proteins in the spindle apparatus and kinetochore may be involved with spindle and chromosome alignment defects during mammalian oocyte postovulatory aging. Such findings may have implications for ART-related human oocyte aging in vitro regarding the activities of the SUMO pathway and fertilization success.

Tetraploidy-linked sensitization to CENP-E inhibition in human cells.

Tetraploidy is a hallmark of cancer cells, and tetraploidy-selective cell growth suppression is a potential strategy for targeted cancer therapy. However, how tetraploid cells differ from normal diploids in their sensitivity to anti-proliferative treatments remains largely unknown. In this study, we found that tetraploid cells are significantly more susceptible to inhibitors of a mitotic kinesin (CENP-E) than are diploids. Treatment with a CENP-E inhibitor preferentially diminished the tetraploid cell population in a diploid-tetraploid co-culture at optimum conditions. Live imaging revealed that a tetraploidy-linked increase in unsolvable chromosome misalignment caused substantially longer mitotic delay in tetraploids than in diploids upon moderate CENP-E inhibition. This time gap of mitotic arrest resulted in cohesion fatigue and subsequent cell death, specifically in tetraploids, leading to tetraploidy-selective cell growth suppression. In contrast, the microtubule-stabilizing compound paclitaxel caused tetraploidy-selective suppression through the aggravation of spindle multipolarization. We also found that treatment with a CENP-E inhibitor had superior generality to paclitaxel in its tetraploidy selectivity across a broader spectrum of cell lines. Our results highlight the unique properties of CENP-E inhibitors in tetraploidy-selective suppression and their potential use in the development of tetraploidy-targeting interventions in cancer.

Protocatechuic Acid Delays Postovulatory Oocyte Ageing in Mouse.

Tea is a popular beverage worldwide and has many health functions. Protocatechuic acid (PCA) is an important bioactive component of tea and has benefit to health. In some cases, oocytes after ovulation may miss the optimal fertilization time and enter a postovulatory ageing process. Therefore, to investigate the role of PCA in delaying oocyte ageing is aimed. Metaphase II (MII) oocytes aged in vitro are randomly divided into three groups: control, aged, and aged + PCA. PCA treatment (30µM) reduces the fragmentation rate and the incidence of abnormal spindle morphology and chromosome misalignment of oocytes aged 24h in vitro. The mitochondrial dysfunction of aged oocytes, such as decreased mitochondrial membrane potential and excessive accumulation of reactive oxygen (ROS), is also alleviated by PCA. PCA also delays apoptosis of aged oocytes, and improves the sperm binding capacity. Otherwise, aged oocytes treated with PCA have a higher fertilization rate and blastocyst rate compared with untreated aged oocytes in vitro. PCA is an important bioactive ingredient of tea that improves aged oocyte quality, suggesting that PCA is available to improve the quality of aged oocytes in vitro.