Genes to Cells

Microtubule-dependent pronuclear migration and mitotic spindle positioning are fundamental processes during the first embryonic division in many animals. In the one-cell embryo of Caenorhabditis elegans, these events are regulated by well-characterized pulling forces acting on astral microtubules, including cortical forces mediated by the G-GPR-LIN-5 dynein complex. Although the overall framework of these dynamics is conserved, recent studies have revealed substantial interspecies variation in their regulation. Here, we investigated nuclei and mitotic spindle behaviors in one-cell embryos of Caenorhabditis inopinata, the closest known relative of C. elegans, using live-cell imaging and functional perturbation. We found that C. inopinata embryos exhibit altered pronuclear migration, reduced anaphase spindle oscillations, and slower centrosome diffusion during telophase compared with C. elegans. These differences suggest weaker cortical pulling forces. Functional analyses using RNA interference showed that GPR retains its essential role in force generation, whereas the contribution of the microtubule depolymerizing kinesin KLP-7 is reduced in C. inopinata. Our results point to evolutionary changes in microtubule-regulated spindle dynamics, and provide insight into how conserved cellular processes can diversify through subtle changes in their underlying mechanisms.

Meiosis is a fundamental process in producing both sperm and eggs, yet recombination landscapes often exhibit sexual differences, known as heterochiasmy. Since meiotic proteins are generally expressed in both sexes, the molecular mechanism driving heterochiasmy remains elusive. The -kleisin subunit gene of meiotic cohesin, Rec8, is expressed bisexually in mammals, while its putative teleost ortholog, rec8a, is expressed in a female-biased manner, presumably due to the presence of its paralog originating from the teleost-specific whole-genome duplication (TGD). Here, we elucidated the evolutionary history and expression dynamics of -kleisin genes across teleost lineages. Through comprehensive phylogenetic and synteny analyses, we revealed that major teleost lineages retain two copies of rec8 and rad21, with rec8 loci experiencing drastic chromosomal rearrangements immediately after the TGD. Using in situ hybridization and single-cell transcriptome data in medaka and zebrafish, we demonstrated a conserved sexually biased expression pattern: rec8a is predominantly female-biased, whereas rec8b exhibits male-biased expression during gametogenesis. Furthermore, comparative epigenetic analyses revealed that the conserved sexually biased expression is driven by lineage-specific cis-regulatory elements, rather than conserved ones. Motif analyses imply that regulatory rewiring by transcription factors, including foxl2l in particular, might have played a crucial role in the establishment and maintenance of this paralog divergence. Our findings highlight how whole-genome duplication and subsequent genomic and epigenetic rewiring subdivided the bisexual function of rec8, offering insights into sexually distinct meiotic regulation. HighlightsO_LITeleosts possess a unique -kleisin repertoire originating from the TGD. C_LIO_LITeleost rec8 paralogs exhibit conserved sex-biased expression during meiosis. C_LIO_LIDrastic genomic rearrangements after the duplication rewired the teleost rec8 loci. C_LIO_LIThe conserved expression pattern is governed by lineage-specific CREs. C_LIO_LIThose CREs harbor similar types of TFBSs such as Fox-family TFs. C_LI Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=94 SRC="FIGDIR/small/731870v1_ufig1.gif" ALT="Figure 1"> View larger version (22K): org.highwire.dtl.DTLVardef@c8c84dorg.highwire.dtl.DTLVardef@1d65668org.highwire.dtl.DTLVardef@c2d732org.highwire.dtl.DTLVardef@1be54a2_HPS_FORMAT_FIGEXP M_FIG C_FIG

Limited oxygen supply or hypoxia can impair fetal development and lead to developmental disorders, but the molecular mechanism underlying this phenomenon remains poorly understood. It is also well known that hypoxia results in transcriptomic alterations and epigenetic reprogramming. Drosophila melanogaster (fruit fly) has been used for decades as a powerful model to dissect the molecular mechanisms regulating development. To better understand the role of early hypoxic stress on development, we performed single-cell joint analysis of chromatin accessibility and transcriptome to characterize the influence of hypoxia on Drosophila embryonic development. We identified hypoxia-induced alterations in both gene expression and chromatin accessibility across 22 cell groups, especially in the genes regulating organogenesis and development of neuronal, tracheal, and muscular systems, including a reduction of germ cells, suggesting a long-lasting influence of hypoxic stress at an early embryonic stage on development and reproduction. In summary, this study demonstrates that early embryonic hypoxia induces cell type- and dose-dependent changes in chromatin accessibility and gene expression, leading to distinct developmental phenotypic responses, such as reduced number of germ cells under both 3% and 5% O2. We further conclude that the tramtrack (ttk) gene is critical in germ cell development and reproduction in Drosophila melanogaster.

The plasmodium of Myxogastoria (a group of amoeboid protists) species often crawls around the forest floor to feed while searching for places to form fruiting bodies for reproduction (sporulation). Certain environmental factors that trigger sporulation have been reported; however, other unknown factors are also expected. In this study, we reported field observations of Physarum rigidum and Fuligo septica. Inspired by the field observation, we examined the effects of multiple factors on sporulation in laboratory experiments using Physarum polycephalum. We found that:(1) there was a critical body size below which sporulation did not occur under our experimental conditions and (2) the plasmodium selected its sporulation sites from the available landscape of the experimental arena: dry and low sites for the majority and dry and high sites for the minority. Further analysis revealed that they preferred the edge area at the high site. We discuss the possible ecological importance of the threshold and location preference

Cisplatin and its analogues are valuable anti-cancer drugs that target the genome, block DNA replication, and induce apoptosis. As a counteractive response, cancer cells activate several mechanisms to maintain uninterrupted DNA replication, and those are yet to be fully elucidated. This study using head and neck squamous carcinoma cells (HNSCC) demonstrated the involvement of DNA polymerase Kappa (Pol{kappa}), a trans-lesion DNA synthesis (TLS) polymerase that primarily functions as a mismatch extender, in cisplatin resistance. Interestingly, the catalytic activity of Pol{kappa} plays a minimal role in adduct bypass; rather, tripartite interactions involving it, rewire and stabilize the stalled replication fork. While the Pol{kappa}-PCNA-Pol{delta} axis facilitates efficient proliferation of cisplatin-resistant cells, the Pol{kappa}-PCNA-USP18 axis stabilizes critical proteins of ATM-ATR, and HR and NHEJ pathways to protect replication fork, repair damage, and restart DNA synthesis under cisplatin-induced stress. In resistant cells, the efficiency of ubiquitin-mediated proteasomal degradation is low, which is further diminished by Pol{kappa}-recruited USP18 deubiquitinase, maintaining a cellular homeostasis. In conclusion, for the first time, we uncovered two critical Pol{kappa} axes crucial for regulating cisplatin toxicity in cells and provided foundation for future drug discovery against advance HNSCC by targeting this non-essential DNA polymerase.

Intergroup conflict is one of the most significant issues in human society. In the 1950s, Sherif et al. reported that intergroup conflict could be artificially induced in boys through intergroup competition with tug-of-war and ball games. Since this iconic study, researchers have developed various experimental methods to replicate intergroup competition and/or conflicts. However, although intergroup conflicts in wild animals are often reported, it has been difficult to establish a situation of intergroup conflict in laboratory rodents that is discriminable from aggressive behavior individually. In this study, we established a novel experimental paradigm for intergroup competition in mice in which the members of each group shared objectives and tasks. Adult male ICR/Jcl mice were housed in groups of six, divided into two teams of three and repeatedly performed a competitive Tsunahiki task (tsunahiki means tug-of-war in Japanese). The competitive Tsunahiki task was conducted in an open field divided into two experimental fields, with three ropes stuck to a wall separating the fields. The mice were required to pull two ropes out faster than their opponent team to win, and only the winners could proceed to the reward area separated by a guillotine door. We demonstrated that the experience of the competitive Tsunahiki task induced attack bites selectively toward members of the other team (out-group members). Our findings suggest that intergroup competition induces intergroup conflict in mice, providing a technical breakthrough in elucidating the detailed neuroscientific mechanisms underlying intergroup conflict.

Api5 is elevated in a number of cancers and is associated with many hallmarks of cancer, including resistance to apoptosis, immune escape, stemness, chemotherapy resistance, high proliferation, and cell-cycle dysregulation. In this study, we identified the DNA and chromatin-binding activities of Api5 in tumorigenic cells, as well as its association with genomic instability and chemotherapy resistance. Knockdown of Api5 resulted in reduced nuclear volume, DNA content, and chromosome number, and increased sensitivity to DNA damage. The survival of Api5-knockdown cells decreased following UV and cisplatin treatments due to the accumulation of damaged DNA and inefficient nucleotide excision repair. Interestingly, Api5 knockdown cells also exhibited low pChk1 levels following UV damage. Further, we confirmed the chemotherapy resistance phenotype in cancers with elevated Api5 levels, demonstrating that xenograft tumours with Api5 knockdown responded better to cisplatin, with significant tumour regression. SummaryApoptosis inhibitor 5 (Api5) contributes to chemotherapy resistance by conferring a survival advantage and promoting efficient DNA repair following genotoxic stress through regulation of Chk1 activation.

Bacterial survival after ultraviolet (UV) exposure is shaped not only by the extent of DNA damage but also by the physiological state-dependent capacity for DNA repair. Here, we examined the mechanisms underlying growth phase-dependent UV resistance in Escherichia coli K-12 exposed to 262 nm UV irradiation. Stationary-phase cells required higher UV fluence for log inactivation than exponential-phase cells, whereas the levels of UV-induced DNA damage, assessed by cyclobutane pyrimidine dimer staining and real-time PCR, did not differ markedly between the two growth phases. Deletion of nucleotide excision repair (NER) genes, including uvrA, uvrB, uvrC, and uvrD, markedly reduced survival after UV irradiation, indicating that NER is essential for the high UV resistance of stationary-phase cells. Quantitative real-time reverse transcription PCR showed stronger UV-induced expression of several DNA repair and UV resistance genes, including uvrA, uvrB, cho, umuC, and umuD, in stationary-phase cells than in exponential-phase cells. Furthermore, deletion of the DNA cytosine methyltransferase gene dcm increased UV resistance and enhanced the expression of uvrB, cho, umuC, umuD, and sulA in stationary-phase cells. These findings suggest that DNA cytosine methylation modulates UV resistance in E. coli, at least in part by influencing NER- and SOS-associated gene expression.

A fraction of patients treated with radiotherapy are known to be more sensitive to ionizing radiations. Skin fibroblasts from such radiosensitive individuals exhibit a higher cellular toxicity after irradiation and a delay in DNA repair. Deciphering the molecular mechanisms underlying these cellular defects is thus of major importance. We previously observed that the transcription factor NFATc2 is expressed at a reduced level in fibroblasts from radiosensitive patients. The present work aimed to elucidate the role of NFATc2 in the regulation of DNA repair, particularly the repair of radiation-induced double-strand breaks. We demonstrate an interaction of NFATc2 with the NHEJ repair protein Ku80 and observe that the NFATc2 RHD domain is necessary and sufficient for this interaction. Moreover, we show that NFATc2-Ku80 complexes are not colocalized to DNA double-strand breaks sites suggesting an involvement upstream of the DNA repair pathway. The silencing of NFATc2 impairs the NHEJ repair activities by delaying Ku70-Ku80 interaction in the early steps of this pathway. Finally, stable over-expression of NFATc2 in patients fibroblasts partially rescues their defective DNA repair phenotype, especially in the most radiosensitive cells. Altogether, our data reveal that NFATc2 is a regulator of DNA repair in skin fibroblasts and therefore a potential modulator of cellular radiosensitivity.

Microtubule-destabilizing agents (MDAs) and microtubule-stabilizing agents (MSAs) are commonly used chemotherapeutic agents due to its activity to induce cell death by compromising the dynamics of spindles during mitosis. Ewing sarcoma, the second most common pediatric bone cancer, is known to selectively respond to MDAs as a first-line treatment, but not to MSAs. Ewing sarcoma cells carry an aberrant EWSR1-FLI1 fusion gene and only one wildtype EWSR1 allele. To investigate the origin of this MDA sensitivity, we used an (AID-EWSR1/wt: EWSR1-FLI1-mCherry/wt) cell line that enables conditional induction of EWSR1-FLI1 expression (Tet-On system) and EWSR1 knockdown derived from one EWSR1 allele (auxin-degron system). A combination of EWSR1-FLI1 expression and EWSR1 knockdown induces apoptosis upon nocodazole treatment, a type of MDA. Our study revealed that the mitotic spindles of Ewing sarcoma cells (A673, RD-ES and SK-ES1) contain elevated levels of tubulin damage, visualized with GTP-tubulin, compared to mesenchymal stem cells (MSC). Consistently, the combination of EWSR1-FLI1 expression and EWSR1 knockdown in (AID-EWSR1/wt: EWSR1-FLI1-mCherry/wt) cell line also leads to an increased incidence of damage in mitotic spindles. Together, we propose that the sensitivity of Ewing sarcoma cells is derived from the increased levels of damage to mitotic spindles caused by EWSR1-FLI1 expression and EWSR1 knockdown.

The IFN-I (type I interferon) signaling pathway is the first line of defence against foreign pathogens. Stringent control of signalling pathways is necessary to maintain host immune responses and homeostasis. However, the underlying mechanism for its tight regulation is yet completely understood. In this study, we demonstrated that the TRIM family protein tripartite motif-containing 52 (TRIM52) is a novel negative regulator of IFN-{beta} production. Ectopically expressed TRIM52 markedly inhibited the activation of the IFN-{beta} promoter by ectopic expression of cGAS/STING, RIG-IN, or TRIF, MAVS, STING, and TBK1 but not by IRF3/5D, indicating that TRIM52 targets TBK1. TRIM52 also significantly inhibited the IFN-{beta}, ISG54, and ISG56 production, the dimerization of IRF3 and the nuclear localization of IRF3-YFP induced by ectopic expression of TBK1. Co-immunoprecipitation experiment revealed that TRIM52 specifically interacted with TBK1. Furthermore, the TBK1 protein, but not its mRNA, decreased considerably with increasing expression of TRIM52, and TRIM52 did not decrease the expression of the cGAS, STING, or IRF3 proteins. In addition, proteasome inhibitor MG-132 blocked the reduced TBK1 induced by TRIM52, indicating that TRIM52 caused TBK1 degradation via the proteasome pathway. Co-IP and ubiquitination assays demonstrated that TRIM52 promotion of K48-linked ubiquitination of TBK1, which depends on its E3 ubiquitin ligase. Collectively, our findings identify a previously unrecognized role of TRIM52 in regulating the IFN-I signalling pathway through targeting TBK1 for polyubiquitination and degradation.

Light-induced body color changes and direct optical sensing in the skin of amphibians and fishes have been debated for more than half a century. Previously reported chromatophore-mediated photoresponses generally occur on timescales of tens of seconds to minutes and are commonly attributed to intracellular molecular mechanisms, including opsin-dependent signaling pathways. In several invertebrates and amphibians, dermal photoreception has been detected electrophysiologically as rapid neural outputs. Here, I report an ultrafast, nonvisual photoresponse mediated by dermal iridophores in the silverside fish Hypoatherina tsurugae (Atherinidae). Upon exposure of living skin to white LED illumination, the light reflection from iridophores was rapidly quenched within seconds. Spectral analysis revealed that this quenching response was most sensitive to blue light compared with green and red illumination. The reflected light recovered to its original twinkling state within approximately 10 s after cessation of illumination. The speed and reversibility of this response suggest that mechanisms beyond slow intracellular structural rearrangements are involved and raise the possibility of neural modulation in addition to intrinsic photoreceptive processes. These findings uncover an unrecognized mode of dermal light sensing and provide insight into bioinspired design principles for artificial optical sensing skins.

Genome-edited mice are widely used to elucidate molecular mechanisms in vivo and are an indispensable tool, particularly for studies aimed at clarifying gene function at the organismal level. Currently, there is an increasing demand for mice in which multiple genes are simultaneously modified in order to investigate interactions among multiple genes. Notably, generating conditional multiple-gene knockout mice with temporal and spatial specificity requires extensive crossing between multiple Cre-driver mice and floxed mice, resulting in a prolonged time frame for line establishment. To address this limitation, we developed Transposon-Enhanced Multi-Plex Orchestration Editing (TEMPO-editing), a single-step strategy for generating multiple-gene-edited mice. TEMPO-editing enables simultaneous modification of multiple genes through the integration of transposon, Cre-loxP, and CRISPR/Cas9 systems. Using the DNA transposon piggyBac, we constructed a single cassette harboring gRNAs targeting genes of interest together with a conditionally expressed Cas9 (lsl-Cas9). By injecting this cassette into fertilized eggs of Cre mice, we enabled the generation of temporally and spatially specific genome edited mice in the F0 generation. In this study, we generated double-gene-edited mice targeting Hoxa13 and Hoxd13, which are key regulators of embryonic body patterning and are essential for autopod development. The phenotype observed in these mice was consistent with the incomplete autopod phenotype previously reported in mice generated by crossing Hoxa13 knockout and Hoxd13 knockout mice. These results demonstrate the utility of TEMPO-editing for the generation of multiple-gene-edited mice in the F0 generation. Notably, this study establishes a simplified strategy for producing conditional multi-gene-edited mice, a process that has traditionally required substantial time and labor using conventional methods.

Hematopoietic stem cells (HSCs) give rise to all blood cell lineages and possess long-term self-renewal potential. HSCs undergo symmetric division for their expansion and asymmetric division to generate one HSCs and one progenitor cells which contribute to production of mature blood cells. The midbody is a structure which is formed in the center of the intercellular bridge during cytokinesis. However, the midbody is either asymmetrically inherited by one daughter cell or symmetrically released after cell division, whether these distinct patterns of midbody inheritance influence HSC fate remain poorly understood. In this study, we designed a fusion protein hmKO2 and MgcRacGAP which is a component of midbody. We then traced the midbody inheritance during cell division and the future cell fates of HSC daughters after division by time-lapse imaging. As a result, we found that the midbody release correlated with the delay of the time to the next division but not to the lineage potential of HSCs, indicating the possibility that midbody remnant plays some roles in cell cycle progression. HighlightHematopoietic stem cells exhibit a low frequency of midbody inheritance. Midbody inheritance does not affect the lineage potential of daughter cells. Midbody loss is associated with delayed entry into the next cell cycle.

CT83 (KK-LC-1) is a cancer-testis antigen originally identified in human lung cancer cells and has recently attracted attention as a potential target for cancer therapy. Although KK-LC-1 orthologs have been identified in up to 160 animal species, a murine homolog had not previously been identified, hindering in vivo analysis of its physiological function. In this study, we identified the mouse homolog of KK-LC-1 and performed a comparative analysis of its properties in humans and mice, together with an investigation of its biological function using gene knockout (KO) mice. The murine Kk-lc-1 gene is located on the X chromosome and, like its human counterpart, contains an N-terminal transmembrane domain. In both humans and mice, KK-LC-1 is expressed specifically in the testis and localizes to the head and tail regions of sperm. Analysis of Kk-lc-1-deficient mice revealed normal spermatogenesis, and both male and female KO mice were fertile. However, sperm from Kk-lc-1-deficient males exhibited reduced motility caused by decreased flexibility of the midpiece and failed to penetrate the oocyte zona pellucida in vitro. This defect was rescued by artificial insemination using epididymal sperm, suggesting that maternal factors in vivo may compensate for reduced sperm motility. Although impaired sperm motility during in vitro fertilization (IVF) was rescued by murine Kk-lc-1, functional rescue by human KK-LC-1 was not observed. These findings indicate that KK-LC-1 contributes to sperm motility but is not essential for fertility. Moreover, species-specific differences in KK-LC-1-mediated regulation of sperm motility suggest functional divergence during evolution. The role of KK-LC-1 in sperm motility should therefore be considered in the clinical development of cancer therapies targeting KK-LC-1.

Chromosomes in Drosophila melanogaster are organized into distinct topologically associated domains delimited by boundaries bound by insulator proteins. The insulator protein BEAF (Boundary Element-Associated Factor of 32kDa) plays roles in both chromatin organization and transcriptional regulation, yet its precise molecular mechanisms remain elusive. To examine the role of BEAF in insulator function we used yeast 2-hybrid assays, pull-down assays with bacterially expressed proteins, and bimolecular fluorescence complementation assays in S2 cells to characterize interactions between BEAF and three co-insulator proteins: CP190, Pzg, and Chro. Our studies pinpoint minimal regions of CP190, Pzg, and Chro that directly interact with BEAF, as well as parts of BEAF that are crucial for its interactions with these co-insulator proteins. Functional analyses in transfected S2 cells revealed distinct regulatory roles for BEAF in association with CP190, Pzg, and Chro. CP190 showed a weak interaction with BEAF, and CP190 bound 2.3 kb upstream of promoter-proximal BEAF could not loop out the intervening DNA to effectively communicate with BEAF for luciferase reporter gene activation. In contrast, more robust interactions were observed between BEAF and both Pzg and Chro. Both could also effectively interact with BEAF from a distance to activate the reporter gene. It is likely that the role of CP190 in long-range insulator interactions is mediated by insulator proteins other than BEAF, although BEAF could help stabilize interactions. On the other hand, we propose that BEAF can directly collaborate with Pzg and Chro to mediate long-range chromatin interactions.

In TMPRSS2 fusion-positive prostate cancer, ERR is involved in regulation of ERG and promotes the androgen receptor independent signaling in the cancer progression. The ERR binds to the ERREs (estrogen-related receptor response elements) present at -5042 bp of the TMPRSS2- promoter and enhances the ERG overexpression that causes prostate cancer progression. To dissect the structural basis of the ERR recognition to the TMPRSS2 promoter DNA, we have purified the full-length ERR (ERRFL), NTD deleted construct (ERR{Delta}NTD), and the DNA-binding domain (ERRDBD) proteins and performed the binding analysis with 30 bp TMPRSS2-promoter DNA (5' -AGTCCAAGGTCGGTGGATC ACAAGGTCAGG-3'). Circular dichroism analysis showed that all three ERR proteins adopt native secondary structures. DNA binding induced subtle changes in the secondary structures, while enhancing the thermal stability (Tm) of all ERRa proteins. Binding analysis showed that ERRDBD bound weakly to the DNA, whereas ERRFL and ERR{Delta}NTD exhibited substantially higher affinities ~120-fold and ~131-fold than ERRaDBD, respectively. Small-angle X-ray scattering (SAXS) analyses revealed a dimeric ERRFL structure and an ERRFL-DNA complex (2:1) structure in solution and fitted well with Alpha Fold model of apo and DNA bound complex of ERRFL. Furthermore, 100 ns dynamics simulations on apo and DNA-bound ERRa proteins showed that all proteins remained structurally stable, with flexibility largely confined to loop regions of ERRa proteins. Our biophysical, DNA binding and structural analyses have revealed the mechanism involved in ERR recognition of the TMPRSS2- promoter DNA, which provides insight into ERR-mediated transcriptional regulation and development of anticancer drugs against ERR-driven prostate cancer.

The red palm weevil, Rhynchophorus ferrugineus, is the most economically destructive palm pest worldwide, threatening livelihoods, food security, and ecosystems across 49 countries. Weevil management currently relies predominantly on chemical insecticides, raising significant environmental and public health concerns. Despite its global agricultural importance, genetic approaches to pest management and the mechanistic basis of genome-editing strategies in Rhynchophorus remain largely unexplored. Here, we employed CRISPR/Cas9 genome editing to disrupt the R. ferrugineus ommochrome biosynthetic pathway -- a multi-enzymatic metabolic cascade that converts tryptophan into ommochrome pigments, including brown, yellow, and red pigments. We targeted two key pathway components: the ATP-binding cassette transporter white and the heme peroxidase cardinal. Both genes were ubiquitously expressed, with peak expression levels in the gut, fat body, and head. Elevated transcript levels were observed across early, mid, and late pupal stages and in 0-, 1-, and 2-day-old adult males and females, consistent with the progression of eye pigmentation throughout the R. ferrugineus life cycle. Embryonic microinjection of a single guide RNA (sgRNA)-Cas9 ribonucleoprotein complex targeting white produced in the Generation-0 (G0) adults with a distinct, white-eyed phenotype with a brownish outer margin, in contrast to the black eyes of wild-type adults. Genome-edited cardinal mutant adults displayed a translucent, brownish-white-eyed phenotype, with white streaks that gradually transitioned to a persistent translucent reddish-brown eye coloration. Mutations in both genes were confirmed in G0 adults by genomic DNA sequencing. Mutant adults were crossed to generate heterozygous G1 (+/-), G2 (-/-, -/+, and +/+), and G3 lines (-/-) with genotypes verified as carrying 2-, 3-, 9-, and 13-nucleotide deletions. A stable, heritable eye-color phenotype was established in homozygous knockout (-/-) G3 lines for both white and cardinal, confirmed by unambiguous indel (insertions/deletions) genotyping. Inheritance analysis revealed that both genes are X-linked, following a classical Mendelian sex-linked pattern: paternal alleles are transmitted exclusively to daughters, while maternal alleles are inherited equally by both daughters and sons. This study establishes the first fully homozygous knockout strain in R. ferrugineus and, by characterizing sex-linked inheritance in a coleopteran system, advances our understanding of how CRISPR/Cas9 can be efficiently applied to destructive palm weevil species. The present study represents the first report of CRISPR/Cas9 genome editing in any weevil (Curculionidae), using white and cardinal as marker genes. These findings provide a valuable platform for functional genomics and genome engineering in R. ferrugineus and offer a translational framework for genome editing in the invasive South American palm weevil, R. palmarum, laying a solid foundation for the development of gene-drive strategies aimed at sustainable palm weevil population control.

Bipolar spindle assembly is essential for accurate chromosome segregation. KIFC1, a conserved Ran- regulated minus-end-directed kinesin-14 motor, accumulates in the nucleus during interphase and promotes chromatin-mediated spindle assembly during mitosis and meiosis. In human oocytes, reduced KIFC1 levels destabilize meiotic spindles, a defect that can be rescued by increasing KIFC1 expression. However, how KIFC1 expression levels affect mitotic spindle stability during cleavage divisions in vertebrates remains unclear. Here, we show that whereas an approximately 50% reduction in KIFC1 causes no detectable defects in spindle assembly, approximately 10-fold overexpression of KIFC1 induces monopolar spindle formation, leading to chromosome mis-segregation and embryonic lethality in medaka early embryos. KIFC1 overexpression results in ectopic centrosomal localization during interphase, impairing the separation of duplicated centrosomes before mitotic entry. Analyses of KIFC1 mutants demonstrated that these centrosome separation defects require KIFC1s microtubule-binding and motor activities and are further enhanced by deletion of KIFC1s nuclear localization sequences. Together, our findings demonstrate that tight regulation of KIFC1 expression and its nuclear sequestration is essential for the proper separation and positioning of duplicated centrosomes before mitotic entry, thereby ensuring efficient bipolar spindle assembly during the rapid cleavage divisions of vertebrate embryos. HighlightsO_LIKIFC1 accumulates in the nucleus and at the embryonic spindle midplane via the Ran pathway. C_LIO_LIPartial KIFC1 depletion does not impair spindle assembly in medaka early embryos. C_LIO_LIKIFC1 overexpression induces monopolar spindles by preventing centrosome separation. C_LIO_LICentrosome separation defects require KIFC1 microtubule-binding and motor activity. C_LI

eIF5A is an evolutionarily conserved protein found in all eukaryotes, and in Archaea and bacteria. It functions as a translation factor promoting ribosomal elongation, and it can also bind to genes in the nucleus and to mRNA. eIF5A is encoded by two paralogous genes in most eukaryotes, with one copy (TIF51A in yeast and EIF5A1 in humans) highly expressed and essential, and the other (TIF51B in yeast and EIF5A2 in humans) repressed in most cells and conditions. eIF5A is linked to viral infection, aging, diabetes and neurodevelopmental disorders. Whilst derepression of the duplicated silent gene EIF5A2 is associated with several cancers, promoting metastasis. To expand our knowledge of eIF5As function, we searched for suppressors of yeast temperature-sensitive mutants of TIF51A, which cannot grow at restrictive temperature. All suppressors contained mutations in the transcriptional repressors Rox1 and Mot3, resulting in the upregulation of the paralogous gene TIF51B. Next, we searched for suppressors of TIF51A temperature-sensitive mutants in yeast lacking the TIF51B gene. The frequency of suppression was 20-times lower and all suppressors were revertants or contained intragenic mutations in the Tif51A protein that conferred stability. Our results suggest that the duplicated eIF5A gene serves as a non-conventional backup system that rescues mutations in the first copy, but acting at the population level. Furthermore, our results expand our understanding of the repression mechanisms that keep the second eIF5A gene silent. Lastly, our results demonstrate that eIF5A is an indispensable protein in eukaryotic cells, whose function cannot be substituted by mutations in other proteins or pathways. Article summaryeIF5A is an evolutionary conserved protein encoded by two paralogous genes in eukaryotes: one highly expressed and essential, and the other silent. eIF5A promotes translation elongation, and its deficiency is linked to diabetes, aging and neurodevelopmental disorders; while derepression of the silent gene promotes metastatic cancers. We isolated suppressors of conditional mutants of the first eIF5A gene in yeast cells. Suppressors either up-regulated the second eIF5A gene or reverted first copy mutations, restoring eIF5A protein levels and survival. Our work deepens our understanding of the eIF5A paralogue gene repression, and demonstrates that eIF5A is an indispensable protein for eukaryotic cells.