Spindle Structure Research Articles

PAK4 is Required for Meiotic Resumption, Spindle Assembly, and Cortical Migration in Mouse Oocytes During Meiotic Maturation.

Oocyte meiotic errors can cause infertility, miscarriage, and birth defects. Here the role and the underlying mechanism of p21 activated kinase 4 (PAK4) in mouse oocyte meiosis is evaluated. It is found that PAK4 expression and its phosphorylation are detected in high level at germinal vesicle (GV) stage, and gradually decreased after meiotic resumption in oocytes. PAK4 has direct physical interaction with both mitogen-activated protein kinases 1/2 (MEK1/2) and Paxillin, they are colocalized on the spindle structure during metaphases I and II. Phospho-PAK4 is distributed beneath the cytoplasmic membrane and on the chromosomes, and colocalized with the microtubule organizing center (MTOC) proteins, Pericentrin and γ-tubulin, as well as phosphor-MEK1/2 and phosphor-Paxillin on spindle poles. PAK4 inhibition by chemical inhibitor LCH-7749944, specific Pak4 morpholino oligo or the dominant negative mutant Pak4K350, 351M influence the meiotic resumption, spindle assembly and its cortical migration, and associated with the downregulation in the dephosphorylation of cyclin dependent kinase 1 (CDK1) and the levels of Cyclin B1, MEK1/2, Paxillin, g-tubulin, acetylated a-tubulin, Arp3, and Cofilin phosphorylation in oocytes. In sum, PAK4 functions to sustain the rational levels of Cyclin B1, MEK1/2, Paxillin, y-tubulin, acetylated a-tubulin, Arp3, and phosphor-Cofilin in mouse oocytes, thereby promotes the meiotic resumption, spindle assembly, and migration during meiotic maturation.

Flavopiridol inhibits oocyte maturation, reduces oocyte quality and blocks cumulus cell function

Flavopiridol (FP) is a plant-derived flavonoidis and used to treat cancers, fungal infections and inflammation-related diseases. However, it is not clear whether it has side effects on the female reproductive system. In this study, we aimed to investigate the toxic effects and potential underlying mechanisms of FP on oocyte maturation and cumulus cell expansion in mice. Cumulus-oocyte complexes (COCs) were cultured in vitro with FP of gradient concentration (50–1000 nM), according to the plasma concentration of FP in the clinical trial. The maturation rate and cumulus expansion index of oocytes were counted and studied by immunofluorescence staining, qRT-PCR, oocyte chromosome preparation and so on. The results showed that the FP-exposed COCs inhibited the oocyte maturation and cumulus cell expansion, leading to cell apoptosis in a dose dependent way. Oocytes exposed to 500 nM FP showed abnormalities in the spindle structure and chromosome arrangement, ultimately leading to the oocyte maturation arrest and aneuploidy. This may be due to the excessive oxidative stress caused by mitochondrial membrane potential damage and mislocalization. Therefore, when FP is used for cancer treatment, its side effects on the female reproductive system should be seriously considered.

Predicting mechanical properties of mitotic spindles with a minimal constitutive model

The mitotic spindle, crucial for precise chromosome segregation and cytoplasmic partitioning during cell division, demands stability against forces arising from chromosomal movements and thermal fluctuations. Despite its central role, the mechanical properties of spindles remain largely elusive. In this study, we delve into the mechanical properties of spindles through a comprehensive model encompassing interactions among centrosomes, microtubules, chromosomes, and molecular motors. Our model successfully reproduces the 3D self–assembly of spindles and their responses to mechanical forces. We find that the spindle exhibits viscoelastic properties, responding distinctively to stretch and compression. Rapid stretch induces transient softening of the spindle, while compression leads to temporary hardening. Based on the viscoelastic responses of spindles under constant–force and constant–displacement loadings, we propose a minimal constitutive model for the spindle structure. This constitutive model can not only accurately recapture the viscoelastic responses of spindles under stretch and compression but also predict the mechanical behaviors of spindles under constant–rate loadings and cyclic loadings, which are further verified by simulations. Therefore, our validated constitutive model can replace complex simulations, providing more interesting predictions and guidance for future experiments.

Reduced anti-Müllerian hormone action in cumulus-oocyte complexes is beneficial for oocyte maturation without affecting oocyte competence.

Anti-Müllerian hormone (AMH) is a key paracrine/autocrine factor regulating folliculogenesis in the postnatal ovary. As antral follicles mature to the preovulatory stage, AMH production tends to be limited to cumulus cells. Therefore, the present study investigated the role of cumulus cell-derived AMH in supporting maturation and competence of the enclosed oocyte. Cumulus-oocyte complexes (COCs) were isolated from antral follicles of rhesus macaque ovaries for in vitro maturation with or without AMH depletion. Oocyte meiotic status and embryo cleavage after in vitro fertilization were assessed. In vitro maturation with AMH depletion was also performed using COCs from antral follicles of human ovarian tissue. Oocyte maturation and morphology were evaluated. The direct AMH action on mural granulosa cells of the preovulatory follicle was further assessed using human granulosa cells cultured with or without AMH supplementation. More macaque COCs produced metaphase II oocytes with AMH depletion than those of the control culture. However, preimplantation embryonic development after in vitro fertilization was comparable between oocytes derived from COCs cultured with AMH depletion and controls. Oocytes resumed meiosis in human COCs cultured with AMH depletion and exhibited a typical spindle structure. The confluency and cell number decreased in granulosa cells cultured with AMH supplementation relative to the control culture. AMH treatment did not induce cell death in cultured human granulosa cells. Data suggest that reduced AMH action in COCs could be beneficial for oocyte maturation. Cumulus cell-derived AMH is not essential for supporting oocyte competence or mural granulosa cell viability.

Ceria Nanoparticle Systems Alleviate Degenerative Changes in Mouse Postovulatory Aging Oocytes by Reducing Oxidative Stress and Improving Mitochondrial Functions.

Postovulatory aging oocytes usually feature diminished potential for fertilization and poor embryonic development due to enhanced oxidative damage to the subcellular organelles and macromolecules, which stands as a formidable obstacle in assisted reproductive technologies (ART). Here, we developed lipoic acid (LA) and polyethylene glycol (PEG)-modified CeO2 nanoparticles (LA-PEG-CeNPs) with biocompatibility, enzyme-like autocatalytic activity, and free radical scavenging capacity. We further investigated the LA-PEG-CeNPs effect in mouse postovulatory oocytes during in vitro aging. The results showed that LA-PEG-CeNPs dramatically reduced the accumulation of ROS in aging oocytes, improving mitochondrial dysfunction; they also down-regulated the pro-apoptotic activity by rectifying cellular caspase-3, cleaved caspase-3, and Bcl-2 levels. Consistently, this nanoenzyme prominently alleviated the proportion of abnormalities in spindle structure, chromosome alignment, microtubule stability, and filamentous actin (F-actin) distribution in aging oocytes, furthermore decreased oocyte fragmentation, and improved its ability of fertilization and development to blastocyst. Taken together, our finding suggests that LA-PEG-CeNPs can alleviate oxidative stress damage on oocyte quality during postovulatory aging, implying their potential value for clinical practice in assisted reproduction.

PLD1 promotes spindle assembly and migration through regulating autophagy in mouse oocyte meiosis

ABSTRACT PLD1 has been implicated in cytoskeletal reorganization and vesicle trafficking in somatic cells; however, its function remains unclear in oocyte meiosis. Herein, we found PLD1 stably expresses in mouse oocytes meiosis, with direct interaction with spindle, RAB11A+ vesicles and macroautophagic/autophagic vacuoles. The genetic or chemical inhibition of PLD1 disturbed MTOC clustering, spindle assembly and its cortical migration, also decreased PtdIns(4,5)P2, phosphorylated CFL1 (p-CFL1 [Ser3]) and ACTR2, and their local distribution on MTOC, spindle and vesicles. Furthermore in PLD1-suppressed oocytes, vesicle size was significantly reduced while F-actin density was dramatically increased in the cytoplasm, the asymmetric distribution of autophagic vacuoles was broken and the whole autophagic process was substantially enhanced, as illustrated with characteristic changes in autophagosomes, autolysosome formation and levels of ATG5, BECN1, LC3-II, SQSTM1 and UB. Exogenous administration of PtdIns(4,5)P2 or overexpression of CFL1 hyperphosphorylation mutant (CFL1S3E) could significantly improve polar MTOC focusing and spindle structure in PLD1-depleted oocytes, whereas overexpression of ACTR2 could rescue not only MTOC clustering, and spindle assembly but also its asymmetric positioning. Interestingly, autophagy activation induced similar defects in spindle structure and positioning; instead, its inhibition alleviated the alterations in PLD1-depleted oocytes, and this was highly attributed to the restored levels of PtdIns(4,5)P2, ACTR2 and p-CFL1 (Ser3). Together, PLD1 promotes spindle assembly and migration in oocyte meiosis, by maintaining rational levels of ACTR2, PtdIns(4,5)P2 and p-CFL1 (Ser3) in a manner of modulating autophagy flux. This study for the first time introduces a unique perspective on autophagic activity and function in oocyte meiotic development. Abbreviations: ACTR2/ARP2: actin related protein 2; ACTR3/ARP3: actin related protein 3; ATG5: autophagy related 5; Baf-A1: bafilomycin A1; BFA: brefeldin A; GAPDH: glyceraldehyde-3-phosphate dehydrogenase; GOLGA2/GM130: golgin A2; GV: germinal vesicle; GVBD: germinal vesicle breakdown; IVM: in vitro maturation; MAP1LC3/LC3: microtubule-associated protein 1 light chain 3; MI: metaphase of meiosis I; MII: metaphase of meiosis II; MO: morpholino; MTOC: microtubule-organizing center; MTOR: mechanistic target of rapamycin kinase; PB1: first polar body; PLA: proximity ligation assay; PLD1: phospholipase D1; PtdIns(4,5)P2/PIP2: phosphatidylinositol 4,5-bisphosphate; RAB11A: RAB11A, member RAS oncogene family; RPS6KB1/S6K1: ribosomal protein S6 kinase B1; SQSTM1/p62: sequestosome 1; TEM: transmission electron microscopy; TUBA/α-tubulin: tubulin alpha; TUBG/γ-tubulin: tubulin gamma; UB: ubiquitin; WASL/N-WASP: WASP like actin nucleation promoting factor

A deep multi-branch attention model for histopathological breast cancer image classification

Since the impressive superior performance demonstrated by deep learning methods is widely used in histopathological image analysis and diagnosis, existing work cannot fully extract the information in the breast cancer images due to the limited high resolution of histopathological images. In this study, we construct a novel intermediate layer structure that fully extracts feature information and name it DMBANet, which can extract as much feature information as possible from the input image by up-dimensioning the intermediate convolutional layers to improve the performance of the network. Furthermore, we employ the depth-separable convolution method on the Spindle Structure by decoupling the intermediate convolutional layers and convolving them separately, to significantly reduce the number of parameters and computation of the Spindle Structure and improve the overall network operation speed. We also design the Spindle Structure as a multi-branch model and add different attention mechanisms to different branches. Spindle Structure can effectively improve the performance of the network, the branches with added attention can extract richer and more focused feature information, and the branch with residual connections can minimize the degradation phenomenon in our network and speed up network optimization. The comprehensive experiment shows the superior performance of DMBANet compared to the state-of-the-art method, achieving about 98% classification accuracy, which is better than existing methods. The code is available at https://github.com/Nagi-Dr/DMBANet-main.

Ran-GTP assembles a specialized spindle structure for accurate chromosome segregation in medaka early embryos

Despite drastic cellular changes during cleavage, a mitotic spindle assembles in each blastomere to accurately segregate duplicated chromosomes. Mechanisms of mitotic spindle assembly have been extensively studied using small somatic cells. However, mechanisms of spindle assembly in large vertebrate embryos remain little understood. Here, we establish functional assay systems in medaka (Oryzias latipes) embryos by combining CRISPR knock-in with auxin-inducible degron technology. Live imaging reveals several unexpected features of microtubule organization and centrosome positioning that achieve rapid, accurate cleavage. Importantly, Ran-GTP assembles a dense microtubule network at the metaphase spindle center that is essential for chromosome segregation in early embryos. This unique spindle structure is remodeled into a typical short, somatic-like spindle after blastula stages, when Ran-GTP becomes dispensable for chromosome segregation. We propose that despite the presence of centrosomes, the chromosome-derived Ran-GTP pathway has essential roles in functional spindle assembly in large, rapidly dividing vertebrate early embryos, similar to acentrosomal spindle assembly in oocytes.

SiRNA-Mediated BmAurora B Depletion Impedes the Formation of Holocentric Square Spindles in Silkworm Metaphase BmN4 Cells.

Silkworm ovary-derived BmN4 cells rely on chromatin-induced spindle assembly to form microtubule-based square mitotic spindles that ensure accurate segregation of holocentric chromosomes during cell division. The chromosome passenger protein Aurora B regulates chromosomal condensation and segregation, spindle assembly checkpoint activation, and cytokinesis; however, its role in holocentric organisms needs further clarification. This study examined the architecture and dynamics of spindle microtubules during prophase and metaphase in BmN4 cells and those with siRNA-mediated BmAurora B knockdown using immunofluorescence labeling. Anti-α-tubulin and anti-γ-tubulin antibodies revealed faint γ-tubulin signals colocalized with α-tubulin in early prophase during nuclear membrane rupture, which intensified as prophase progressed. At this stage, bright regions of α-tubulin around and on the nuclear membrane surrounding the chromatin suggested the start of microtubules assembling in the microtubule-organizing centers (MTOCs). In metaphase, fewer but larger γ-tubulin foci were detected on both sides of the chromosomes. This resulted in a distinctive multipolar square spindle with holocentric chromosomes aligned at the metaphase plate. siRNA-mediated BmAurora B knockdown significantly reduced the γ-tubulin foci during prophase, impacting microtubule nucleation and spindle structure in metaphase. Spatiotemporal BmAurora B expression analysis provided new insights into the regulation of this mitotic kinase in silkworm larval gonads during gametogenesis. Our results suggest that BmAurora B is crucial for the formation of multipolar square spindles in holocentric insects, possibly through the activation of γ-tubulin ring complexes in multiple centrosome-like MTOCs.

Smart lattice light-sheet microscopy for imaging rare and complex cellular events.

Light-sheet microscopes enable rapid high-resolution imaging of biological specimens; however, biological processes span spatiotemporal scales. Moreover, long-term phenotypes are often instigated by rare or fleeting biological events that are difficult to capture with a single imaging modality. Here, to overcome this limitation, we present smartLLSM, a microscope that incorporates artificial intelligence-based instrument control to autonomously switch between epifluorescent inverted imaging and lattice light-sheet microscopy (LLSM). We apply this approach to two unique processes: cell division and immune synapse formation. In each context, smartLLSM provides population-level statistics across thousands of cells and autonomously captures multicolor three-dimensional datasets or four-dimensional time-lapse movies of rare events at rates that dramatically exceed human capabilities. From this, we quantify the effects of Taxol dose on spindle structure and kinetochore dynamics in dividing cells and of antigen strength on cytotoxic T lymphocyte engagement and lytic granule polarization at the immune synapse. Overall, smartLLSM efficiently detects rare events within heterogeneous cell populations and records these processes with high spatiotemporal four-dimensional imaging over statistically significant replicates.

Mito-TEMPO Improves the Meiosis Resumption and Mitochondrial Function of Vitrified Sheep Oocytes via the Recovery of Respiratory Chain Activity.

Vitrification is a crucial method for preserving animal germ cells. Considering the increased oxidative stress and organelle damage incurred, it is still necessary to make the process more efficient for oocytes. As the energy source of oocytes, mitochondria are the most abundant organelle in oocytes and play a crucial role in their maturation. Here, we found that Mito-TEMPO, a mitochondria-targeted antioxidant, could efficaciously improve the oxidative stress injury of vitrified oocytes by recovering mitochondrial function via the mitochondrial respiratory chain. It was observed that Mito-TEMPO not only improves oocyte viability and meiosis but also maintains spindle structure. A subsequent study indicated that Mito-TEMPO effectively rescued mitochondrial dysfunction and attenuated vitrification-induced oxidative stress. Further investigation revealed that Mito-TEMPO regulates vitrified oocytes' intracellular Ca2+ homeostasis and ATP content and provides strong antioxidant properties. Additionally, an analysis of the transcriptome at the single-cell level revealed that the respiratory chain mediates the beneficial effect of Mito-TEMPO on vitrified oocytes. Overall, our findings indicate that supplementing oocytes with Mito-TEMPO is an effective method to shield them from the damage caused by vitrification. In addition, the beneficial effects of Mito-TEMPO on vitrified sheep oocytes could inspire further investigations of the principles underlying oocyte cryobiology in other animals.

Methodology to Create Auxin-Inducible Degron Tagging System to Control Expression of a Target Protein in Mammalian Cell Lines.

The auxin-inducible degron (AID) system is a versatile tool in cell biology and genetics, enabling conditional protein regulation through auxin-induced degradation. Integrating CRISPR/Cas9 with AID expedites tagging and depletion of a required protein in human and mouse cells. The mechanism of AID involves interactions between receptors like TIR1 and the AID tag fused to the target protein. The presence of auxin triggers protein ubiquitination, leading to proteasome-mediated degradation. We have used AID to explore the mitotic functions of the replication licensing protein CDT1. Swift CDT1 degradation via AID upon auxin addition achieves precise mitotic inhibition, revealing defects in mitotic spindle structure and chromosome misalignment. Using live imaging, we found that mitosis-specific degradation of CDT1 delayed progression and chromosome mis-segregation. AID-mediated CDT1 inhibition surpasses siRNA-based methods, offering a robust approach to probe CDT1's mitotic roles. The advantages of AID include targeted degradation and temporal control, facilitating rapid induction and reversal of degradation-contrasting siRNA's delayed RNA degradation and protein turnover. In summary, the AID technique enhances precision, control, and efficiency in studying protein function and regulation across diverse cellular contexts. In this article, we provide a step-by-step methodology for generating an efficient AID-tagging system, keeping in mind the important considerations that need to be adopted to use it for investigating or characterizing protein function in a temporally controlled manner. Key features • The auxin-inducible degron (AID) system serves as a versatile tool, enabling conditional protein regulation through auxin-induced degradation in cell biology and genetics. • Integration of CRISPR/Cas9 knock-in technology with AID expedites the tagging and depletion of essential proteins in mammalian cells. • AID's application extends to exploring the mitotic functions of the replication licensing protein CDT1, achieving precise mitotic inhibition and revealing spindle defects and chromosome misalignment. • The AID system and its diverse applications advance the understanding of protein function and cellular processes, contributing to the study of protein regulation and function.

Cyclophosphamide reduces gene transcriptional activity and embryo in vitro development by inhibiting NF-κB expression through decreasing AcH4K12

Cyclophosphamide (CTX), a widely used chemotherapeutic agent for cancer treatment, has been associated with long-term toxicity and detrimental effects on oocytes and ovaries, resulting in female reproductive dysfunction. This study aimed to investigate the potential impact of CTX on in vitro maturation (IVM) injury of porcine oocytes and subsequent embryonic development, as well as its effects on epigenetic modification and gene activation during early embryonic development. The results demonstrated that CTX treatment caused aberrant spindle structure and mitochondrial dysfunction during oocyte maturation, inducing DNA damage and early apoptosis, which consequently disrupted meiotic maturation. Indeed, CTX significantly reduced the in vitro developmental capacity of porcine embryos, and induced DNA damage and apoptosis in in vitro fertilization (IVF) blastocysts. Importantly, CTX induced abnormal histone modification of AcH4K12 in early porcine embryos. Moreover, addition of LBH589 before zygotic genome activation (ZGA) effectively increased AcH4K12 levels and restored the protein expression of NF-κB, which can effectively enhance the in vitro developmental potential of IVF embryos. The DNA damage and apoptosis induced by CTX compromised the quality of the blastocysts, which were recovered by supplementation with LBH589. This restoration was accompanied by down-regulation of BAX mRNA expression and up-regulation of BCL2, POU5F1, SOX2 and SOD1 mRNA expression. These findings indicated that CTX caused abnormal histone modification of AcH4K12 in early porcine embryos and reduced the protein expression of NF-κB, a key regulator of early embryo development, which may block subsequent ZGA processes.

Monitoring method of cutting forces and vibrations by using frequency separation of acceleration sensor signals during milling process with small ball end mills

Recently, there has been a further demand for precise monitoring of milling process with a machine tool by a simple and cost-effective method. One of the ways for monitoring is to install acceleration sensors to the tool spindle and estimate cutting forces from the model of the tool spindle structure. This method generally allows stable monitoring of cutting forces for tools with large diameters. However, in case of using tools with small diameters, it is difficult to estimate the cutting force due to higher frequency vibrations generated near the tool center point. Therefore, to solve the problem, we propose a new monitoring method by signal analysis of acceleration sensors in this research. The problem is that the acceleration sensor signals contain two types of signals, such as ‘acceleration change due to mechanical displacement of a tool spindle generated by cutting load’ and ‘high frequency self-excited and forced vibration’. In our method, we separate these two signals by using an approximation of sequential quadratic regression. From the former, cutting forces are estimated from equation of motions which are obtained in advance from frequency responses of the tool spindle, and from the latter, intensities of vibrations due to milling are estimated. This method was tested several milling patterns such as large cutting loads, fluctuations of cutting loads, and cutting during abnormal vibrations. As a result, we have achieved in-process monitoring of milling process not only in the X and Y directions, but also in the Z direction with a small radius ball end mill.

Design and analysis of a novel flexible variable stiffness damping mechanism for grinding electric spindle

The purpose of this research is to design a flexible variable stiffness damping mechanism to solve the load impact problem in the grinding process of permanent magnet electric spindle. Firstly, combined with the structure and usage scene of the grinding permanent magnet electric spindle, according to the design principles and technical indicators, a novel flexible variable stiffness vibration damping joint is proposed. Then the stiffness and energy storage model of the flexible variable stiffness damping mechanism is established, and the stiffness and energy storage characteristics of the mechanism are analyzed. The strength and dynamic characteristics of the flexible variable stiffness mechanism are analyzed by Ansys and Adams, respectively. Finally, an experimental platform for the comprehensive performance verification of the flexible variable stiffness damping mechanism is built to verify the dynamic characteristics and damping effect of the mechanism. The research results show that the designed flexible variable stiffness structure has better vibration damping effect and can improve the grinding performance of the permanent magnet electric spindle.

CTCF is essential for proper mitotic spindle structure and anaphase segregation.

Mitosis is an essential process in which the duplicated genome is segregated equally into two daughter cells. CTCF has been reported to be present in mitosis and has a role in localizing CENP-E, but its importance for mitotic fidelity remains to be determined. To evaluate the importance of CTCF in mitosis, we tracked mitotic behaviors in wild-type and two different CTCF CRISPR-based genetic knockdowns. We find that knockdown of CTCF results in prolonged mitoses and failed anaphase segregation via time-lapse imaging of SiR-DNA. CTCF knockdown did not alter cell cycling or the mitotic checkpoint, which was activated upon nocodazole treatment. Immunofluorescence imaging of the mitotic spindle in CTCF knockdowns revealed disorganization via tri/tetrapolar spindles and chromosomes behind the spindle pole. Imaging of interphase nuclei showed that nuclear size increased drastically, consistent with failure to divide the duplicated genome in anaphase. Long-term inhibition of CNEP-E via GSK923295 recapitulates CTCF knockdown abnormal mitotic spindles with polar chromosomes and increased nuclear sizes. Population measurements of nuclear shape in CTCF knockdowns do not display decreased circularity or increased nuclear blebbing relative to wild-type. However, failed mitoses do display abnormal nuclear morphologies relative to successful mitoses, suggesting that population images do not capture individual behaviors. Thus, CTCF is important for both proper metaphase organization and anaphase segregation which impacts the size and shape of the interphase nucleus likely through its known role in recruiting CENP-E.

High-Valence Metal Doping Induced Lattice Expansion for M-FeNi LDH toward Enhanced Urea Oxidation Electrocatalytic Activities.

The precise design of low-cost, efficient, and definite electrocatalysts is the key to sustainable renewable energy. The urea oxidation reaction (UOR) offers a promising alternative to the oxygen evolution reaction for energy-saving hydrogen generation. In this study, by tuning the lattice expansion, a series of M-FeNi layered double hydroxides (M-FeNi LDHs, M: Mo, Mn, V) with excellent UOR performance are synthesized. The hydrolytic transformation of Fe-MIL-88A is assisted by urea, Ni2+ and high-valence metals, to form a hollow M-FeNi LDH. Owing to the large atomic radius of the high-valence metal, lattice expansion is induced, and the electronic structure of the FeNi-LDH is regulated. Doping with high-valence metal is more favorable for the formation of the high-valence active species, NiOOH, for the UOR. Moreover, the hollow spindle structure promoted mass transport. Thus, the optimal Mo-FeNi LDH showed outstanding UOR electrocatalytic activity, with 1.32V at 10mA cm-2 . Remarkably, the Pt/C||Mo-FeNi LDH catalyst required a cell voltage of 1.38V at 10 mA·cm-2 in urea-assisted water electrolysis. This study suggests a new direction for constructing nanostructures and modulating electronic structures, which is expected to ultimately lead to the development of a class of auxiliary electrocatalysts.

A Sensitive Electrochemical Sensor Based on Hollow Spindle Ferric Oxide for the Determination of Hydrogen Sulfide

AbstractA one‐step hydrothermal synthesis method was used to synthesize ferric oxide nanoparticles with unique hollow spindle microstructure, which were mixed with conductive carbon black (CCB) to construct an electrochemical sensor to realize the highly sensitive detection of trace hydrogen sulfide (H2S) in biological samples. Our findings suggested that hollow spindle ferric oxide (Hs‐Fe2O3) held good electrocatalytic activity toward H2S, which mainly depended on the coupling effect of Fe (III)/Fe (II) significantly reduced the overpotential of electro‐oxidation reaction of H2S. Importantly, the unique structure of the hollow spindle provided more catalytic active sites and more efficient mass transfer process, which effectively improved the detection performance. The proposed sensor had good sensing performances, with excellent sensitivity (2.4 times of commercial Fe2O3/CCB), low detection limit (1.86 μM), wide linear range (7.6~152 μM) and favorable selectivity. Furthermore, quantitative detection of H2S was achieved in fetal bovine serum samples, which confirmed that the sensor could become a promising strategy for detecting H2S in the pathological study of related diseases.

YAP co-localizes with the mitotic spindle and midbody to safeguard mitotic division in lung-cancer cells.

YES-associated protein (YAP) is a part of the Hippo pathway, with pivotal roles in several developmental processes and dual functionality as both a tumor suppressor and an oncogene. In the present study, we identified YAP activity as a microtubular scaffold protein that maintains the stability of the mitotic spindle and midbody by physically interacting with α-tubulin during mitotic progression. The interaction of YAP and α-tubulin was evident in co-immunoprecipitation assays, as well as observing their co-localization in the microtubular structure of the mitotic spindle and midbody in immunostainings. With YAP depletion, levels of ECT2, MKLP-1, and Aurora B are reduced, which is consistent with YAP functioning in midbody formation during cytokinesis. The concomitant decrease in α-tubulin and increase in acetyl-α-tubulin during YAP depletion occurred at the post-transcriptional level. This suggests that YAP maintains the stability of the mitotic spindle and midbody, which ensures appropriate chromosome segregation during mitotic division. The increase in acetyl-α-tubulin during YAP depletion may provide a lesion-halting mechanism in maintaining the microtubule structure. The depletion of YAP also results in multinuclearity and aneuploidy, which supports its role in stabilizing the mitotic spindle and midbody.

Near-infrared fluorophore IR-61 delays postovulatory aging of mouse oocytes through suppressing oxidative stress mediated by mitochondrial protection.

Postovulatory aging can trigger deterioration of oocyte quality and subsequent embryonic development, and thus reduce the success rates of assisted reproductive technology (ART). The molecular mechanisms underlying postovulatory aging, and preventative strategies, remain to be explored. The near-infrared fluorophore IR-61, a novel heptamethine cyanine dye, has the potential for mitochondrial targeting and cell protection. In this study, we found that IR-61 accumulated in oocyte mitochondria and reduced the postovulatory aging-induced decline in mitochondrial function, including mitochondrial distribution, membrane potential, mtDNA number, ATP levels, and mitochondrial ultrastructure. In addition, IR-61 rescued postovulatory aging-caused oocyte fragmentation, defects in spindle structure, and embryonic developmental potential. RNA sequencing analysis indicated that the postovulatory aging-induced oxidative stress pathway might be inhibited by IR-61. We then confirmed that IR-61 decreased the levels of reactive oxygen species and MitoSOX, and increased GSH content in aged oocytes. Collectively, the results indicate that IR-61 may prevent postovulatory aging by rescuing oocyte quality, promoting successful rate in ART procedure.