Biology subjects

Shimizu, Y.

Publications and source records attributed to Shimizu, Y..

At least 19 recordsLinked to original sources

bioRxiv2026

KDM6A Haploinsufficiency Is Insufficient to Disrupt Cochlear Structure and Auditory Function in Mouse Models of Kabuki Syndrome Type 2

Objective: Kabuki syndrome type 2 (KS2) is a rare X-linked disorder caused by pathogenic variants in KDM6A and is frequently associated with hearing impairment. Because auditory phenotypes include sensorineural, conductive, and mixed hearing loss, we examined whether Kdm6a deficiency directly impairs cochlear morphology or auditory function in mice. Methods: We generated Nestin-Cre; Kdm6a conditional mutants and a germline-derived global Kdm6a deletion model using Sox2-Cre-mediated germline recombination. Auditory function and cochlear morphology were assessed by auditory brainstem responses (ABRs), distortion product otoacoustic emissions (DPOAEs), and histological analyses. Results: Whole-body hemizygous or homozygous Kdm6a deletion resulted in embryonic lethality. Analyses therefore focused on Nestin-Cre; Kdm6aflox/Y males and females carrying a germline-derived heterozygous Kdm6a deletion. In Nestin-Cre mutants, ABR thresholds, wave I amplitudes and latencies, and DPOAE measures at 8, 16, and 32 kHz were comparable with littermate controls at 4 and 8 weeks. In heterozygous deletion females, ABR thresholds, wave I amplitudes and latencies at 4-64 kHz and DPOAE measures at 8, 16, and 32 kHz were comparable with male and female wild-type controls. No overt cochlear pathology was observed in either model. Conclusion: Kdm6a deficiency in the viable mouse models examined did not produce overt cochlear pathology or baseline auditory dysfunction. These findings suggest that partial Kdm6a loss alone is insufficient to produce a robust primary cochlear phenotype in young mice and highlight the potential contributions of non-cochlear, developmental, central, and later-onset mechanisms to hearing impairment in KS2. Clinically, these findings support careful evaluation for potentially treatable middle-ear disease.

developmental biology↗

bioRxiv2026

Protective effects of heat shock protein 70 induction against global warming by using oriental bezoar and ginseng

The interest in compounds that protect against heat stress-induced damage has been heightened due to world global warming. We found the protective effects of a Japanese natural drug named BG, containing oriental bezoar and ginseng, against heat stress in Drosophila. BG suppressed the heat-induced shortened lifespan and reduced fertility in Drosophila. Interestingly, the protective effects of BG against heat stress were abolished in heat shock protein 70 (HSP70) mutant flies. To see the protective effects in humans, we applied BG on the cytotoxicity in heat-stressed human hepatic cell line, HepG2. BG suppressed heat stress-induced cytotoxicity at 43{degrees}C, and increased HSP70 and heat shock factor 1 (HSF1) mRNA expression in HepG2 cells. These findings indicate that BG protects against heat stress-induced damage via the HSF1/HSP70 pathway and has potential as a therapeutic agent for heat stress-induced disorders, including heatstroke even in human.

pharmacology and toxicology↗

bioRxiv2026

Characterization of a maintainable human myeloid model of VEXAS syndrome with enhanced TNF-induced cell death and DAMP release

Background: VEXAS syndrome is an adult-onset autoinflammatory disorder caused by somatic UBA1 mutations. UBA1-mutated myeloid cells have been reported to exhibit increased susceptibility to inflammatory cell death; however, the mechanisms underlying this phenotype and the extracellular consequences of enhanced cell death remain incompletely understood. Methods: Disease-associated UBA1 M41 mutations were introduced into U937 cells by CRISPR/Cas9-mediated genome editing. The resulting cells were characterized by genomic, molecular, and functional analyses, with particular focus on UBA1-associated cellular phenotypes, cell death signaling, and extracellular release of damage-associated molecular patterns (DAMPs). Results: Genome editing yielded UBA1-mutated cells that could be maintained under standard culture conditions while recapitulating multiple molecular and cellular features associated with VEXAS syndrome. Long-read sequencing revealed the intended UBA1 M41 mutation on one allele and a CRISPR/Cas9-induced on-target genomic deletion on the other. The mutant cells exhibited reduced UBA1b and increased UBA1c expression, prominent cytoplasmic vacuolization, reduced proliferative capacity, and increased basal cell death. They also showed enhanced susceptibility to TNF-induced cell death under conditions favoring either apoptosis or necroptosis. Mechanistic analyses demonstrated enhanced apoptotic and necroptotic signaling, together with increased basal abundance of RIPK1, RIPK3, and MLKL. Pharmacological inhibition of RIPK1, RIPK3, or MLKL attenuated membrane permeabilization under caspase-inhibited conditions. Enhanced cell death was accompanied by increased extracellular release of ATP, HMGB1, and S100A8/A9. Conclusions: We characterized a maintainable UBA1-mutated human myeloid model that recapitulates multiple molecular and cellular features associated with VEXAS syndrome. Using this model, we showed that UBA1 dysfunction is associated with heightened susceptibility to TNF-dependent apoptotic and necroptotic cell death and increased extracellular release of multiple DAMPs. These findings provide insight into the cellular consequences of UBA1 dysfunction and establish a tractable experimental platform for further mechanistic studies of VEXAS syndrome.

immunology↗

bioRxiv2026

Clonal memory in human embryonic stem cells biases fate potential during endoderm differentiation

Cell fate decisions during development are shaped not only by extrinsic signals but also by heritable intrinsic states passed on across cell division. The extent to which this phenomenon, termed clonal memory, can explain the persistent heterogeneity observed from directed differentiation of human embryonic stem cells is unclear. Here, we combine lineage tracing with single-cell transcriptomics and chromatin accessibility profiling to track clonal behaviour across human embryonic stem cell differentiation towards definitive endoderm. Using a lentiviral barcoding system coupled with a split-well sampling strategy, we find that clonally related cells exhibit reproducible, probabilistic fate outcomes that cannot be explained by signalling environment alone. Fate-biased clones are transcriptionally indistinguishable at the pluripotent stage yet display distinct chromatin accessibility landscapes at lineage-specific cis-regulatory elements. Pre-existing accessibility at these lineage-specific regulatory regions distinguish clones that undergo successful endoderm differentiation from those that generate off-target mesoderm derivatives. Together, these findings provide an explanation for how off-target populations arise during directed differentiation, identifying heritable chromatin states within pluripotent cultures as a source of variability relevant to stem cell-derived in vitro models and cell therapies.

developmental biology↗

bioRxiv2026

Ire1-triggered hxl1 mRNA splicing coordinates stress tolerance and virulence in the pathogenic fungus Trichosporon asahii

The pathogenic fungus Trichosporon asahii causes severe mycoses in immunocompromised hosts, such as neutropenic patients. In Cryptococcus neoformans, the unfolded protein response (UPR) sensor Ire1 induces hxl1 mRNA splicing and contributes to stress responses and virulence. The function of Ire1-triggered hxl1 mRNA splicing in stress tolerance and virulence of T. asahii, however, remains unclear. Here, we demonstrated that ire1- and hxl1 gene-deficient T. asahii mutants are sensitive to dithiothreitol (DTT), an inducer of endoplasmic reticulum stress, and exhibit reduced virulence in a silkworm infection model. DTT treatment induced hxl1 mRNA splicing in the wild-type strain, whereas ire1 gene-deficient mutants did not undergo hxl1 mRNA splicing. The ire1 gene-deficient mutants were more sensitive than the parent strain to DTT, H2O2, Congo red, and SDS, and showed reduced virulence in silkworms. Similarly, hxl1 gene-deficient mutants exhibited increased sensitivity to these stressors and reduced virulence. Both the ire1 gene-deficient and hxl1 gene-deficient mutants showed decreased expression of reactive oxygen species-detoxifying related genes CAT2, SOD1, and SOD2, compared with the parent strain. Together, these findings suggest that Ire1-triggered hxl1 mRNA splicing contributes to stress resistance and virulence in T. asahii.

microbiology↗

bioRxiv2026

Elucidating the Bell-Shaped Dependence of Protein Translation Activity on EF-Tu Concentration in a Reconstituted Cell-Free System Using a Mechanistic Model

Protein synthesis in cell-free protein synthesis systems often exhibits non-intuitive input-output relationships. In the PURE system, a reconstituted cell-free system, protein production peaked at low elongation factor Tu (EF-Tu) concentrations and decreased at higher concentrations, resulting in a characteristic bell-shaped profile. Here, we investigated the origin of this behavior using a detailed mechanistic model of translation in the PURE system, designated as ePURE, which describes reaction dynamics of hundreds of molecular species and reactions. Our computational analysis suggested that excess EF-Tu sequesters the initiator tRNA (tRNAfMet) into non-productive EF-Tu{middle dot}GTP{middle dot}Met-tRNAfMet complexes, thereby depleting the pool of initiator tRNA available for translation initiation. This suppression arises from competition for a limited molecular resource rather than from direct inhibition. Based on this mechanism, we predicted that increasing the concentrations of tRNAfMet and methionyl-tRNA formyl-transferase would eliminate the bell-shaped dependence, and experimentally confirmed this prediction. Under these modified conditions, the bell-shaped response disappeared and protein production was enhanced. These findings demonstrate how mechanistic computational models can reveal hidden constraints underlying non-intuitive input-output relationships in complex biochemical networks and guide the rational optimization of cell-free protein synthesis systems.

synthetic biology↗

bioRxiv2025

Actin Counters Geometry to Guide Plant Cell Division

In multicellular organisms, cell division shapes tissue architecture, cell identity, and function. In walled organisms like plants, division plane orientation irreversibly defines tissue topology and is tightly regulated. While divisions often follow the shortest path enclosing cell volume, certain cells deviate, dividing perpendicular to the growth axis. Tissue-scale mechanical stress has been proposed to guide such orientation, but how these cues are integrated remains unclear. Here, we re-examine the role of the actin cytoskeleton in orienting cell division in Arabidopsis root epidermis. Combining cell biology, genetics, pharmacological treatments, 3D segmentation, and modelling, we show that actin is a central molecular actor required to establish cell division orientation against the geometrical rules, highlighting its role in integrating spatial information.

plant biology↗

bioRxiv2025

Kinetic scheme of myosin phosphorylation by ZIP kinase

Zipper-interacting protein kinase (ZIPK) is a ubiquitous serine/threonine protein kinase that plays pivotal roles in regulating cell motility, division, and smooth muscle contractility through phosphorylation of myosin. In this study, we systematically investigated the phosphorylation reactions of smooth muscle myosin (SMM) by ZIPK. We found that ZIPK phosphorylates MRLC sequentially, first at Ser19 and then at Thr18, determined by quantitative mass spectrometry analysis on wild-type MRLC. Analysis on phosphomimic and unphosphorylatable MRLC mutants indicates that the phosphorylation rate at Ser19 on unphosphorylated MRLC is 1.5 times faster than that at Thr18 on Ser19-phosphorylated MRLC. Comparison between SMM and isolated MRLC revealed that the phosphorylation rate of SMM is slower than that of isolated MRLC. To dissect the molecular mechanism responsible for this difference, we measured interactions between ZIPK and SMM by co-sedimentation assay. The result suggests that the C-terminal domain of ZIPK interacts with the heavy chain of SMM, and as a result, competitive binding of ZIPK to MRLC and the myosin heavy chain suppresses phosphorylation of SMM compared to isolated MRLC. By incorporating the kinetic and dissociation constants obtained from mutant analysis and co-sedimentation assays, respectively, a simple kinetic model accurately reproduced the time courses of phosphorylation for both isolated MRLC and SMM. This provides systemic insight into the regulatory mechanism of myosin contractility by ZIPK.

biochemistry↗

bioRxiv2025

Temporal orchestration of transcriptional and epigenomic programming underlying maternal embryonic diapause in a cricket model

Maternal perception of environmental conditions can direct offspring developmental trajectories, providing adaptive flexibility across taxa. In the band-legged ground cricket Dianemobius nigrofasciatus, maternal exposure to short days induces embryonic diapause at the cellular blastoderm stage in offspring. Here, we investigate molecular mechanisms underlying this transgenerational adaptation through genome assembly (1.45 Gbp) and time-series transcriptomic analyses of diapause and non-diapause eggs from 12 to 72 hours post-oviposition. Despite morphological similarity, diapause-destined eggs show early upregulation of ATP-dependent chromatin remodeling genes at 24 hours. ATAC-seq reveals reduced chromatin accessibility at neural and cell cycle-related genes. Time-series clustering identifies precocious shifts in RNA processing machinery (peaking at 24 versus 40 hours in non-diapause eggs), followed by metabolic regulation toward amino acid catabolism and gluconeogenesis sustaining long-term survival during developmental arrest. Our findings reveal diapause as actively coordinated molecular programming involving epigenetic, transcriptional, and metabolic remodeling, providing insights into transgenerational environmental adaptation.

developmental biology↗

bioRxiv2025

Calcineurin-responsive zinc finger 1 (Crz1) contributes to stress tolerance and virulence in the pathogenic fungus Trichosporon asahii

The pathogenic fungus Trichosporon asahii causes severe invasive fungal infections in immunocompromised patients with neutropenia. In Cryptococcus neoformans, calcineurin-responsive zinc finger 1 (Crz1) functions as a transcription factor downstream of the calcineurin signaling pathway and regulates the expression of genes involved in stress resistance and virulence. In T. asahii, Cna1 and Cnb1, which are key components of the calcineurin pathway, contribute to various stress responses and virulence. The role of Crz1 in stress tolerance and virulence in T. asahii, however, has remained unclear. Here we demonstrate that a crz1 gene-deficient T. asahii mutant exhibited increased sensitivity to cell wall and endoplasmic reticulum stress. The crz1 gene-deficient mutant was sensitive to Congo red and tunicamycin, but not to dithiothreitol or sodium dodecyl sulfate. Moreover, the virulence of the crz1 gene-deficient mutant in the silkworm infection model was reduced. These phenotypes of the crz1 gene-deficient mutant were restored by reintroducing the crz1 gene, confirming the association between Crz1 and these phenotypes. The half maximal lethal dose of the cnb1 gene-deficient T. asahii mutant was higher than that of the crz1 gene-deficient mutant. These results suggest that Crz1 plays a role in mediating the stress responses and virulence of T. asahii. The involvement of Crz1 in the virulence of T. asahii is small, however, compared to that of the calcineurin.

microbiology↗

bioRxiv2025

Simultaneous in vitro expression of minimal 21 transfer RNAs by tRNA array method

Transfer RNA (tRNA) plays a central role in translation. The simultaneous in vitro synthesis of minimal yet sufficient tRNA species (at least 21) poses a challenge for constructing a self-reproducible artificial cell. A key obstacle is the processing of the 5 and 3 ends, which requires a multi-step reaction in natural cells. In this study, we developed a simplified processing method that allows simultaneous expression of all 21 tRNAs in a reconstituted transcription/translation system (PURE system). We tested three available methods (leader, 5-G variants, and HDVR attachment methods) and one new method (direct tRNA linkage method). Using these methods, we succeeded in simultaneous expression of six non-G-start tRNA from monocistronic six DNA templates in the PURE system. Furthermore, we developed a method that combines the direct tRNA linkage and HDVR attachment methods (termed tRNA array method). Using this method, we succeeded in simultaneous expression of all 21 tRNAs from a single polycistronic DNA template in the PURE system. The tRNA mixture produced by the tRNA array method supported a similar level of translation to the individually synthesized tRNA mixture. Additionally, we demonstrated that the minimal tRNA sets prepared by the tRNA array method can be used for genetic code engineering. This study represents a step toward the realization of self-reproducible artificial cells and also provides an easy method for preparing all tRNAs useful for genetic code engineering.

synthetic biology↗

bioRxiv2024

Evolutionary flexibility of ribosome biogenesis in bacteria

Ribosomes are essential for protein synthesis and require ribosome biogenesis factors (RBFs) for assembly. To uncover the evolutionary diversity of ribosome biogenesis, we analyzed over 30,000 bacterial genomes and revealed that Candidate Phyla Radiation (CPR), also known as the phylum Patescibacteria, characterized by reduced genomes and smaller ribosomes, has about half the average number of RBFs compared with non-CPR bacteria. Notably, key RBFs such as der, obgE, and rbfA, considered indispensable, are conserved in only around 20%-70% of CPR genomes. Since such repertoires were not observed in reduced genomes of other phyla, CPR presumably diverged early in bacterial evolution. We further confirmed that ribosomal structural changes correlate with reduced RBFs, evidencing co-evolution between RBFs and the ribosome. These findings suggest that ribosomal biogenesis is more flexible than recognized, and the small cell and genome sizes of CPR bacteria and their early divergence may influence the unusual repertoires of RBFs. TeaserRibosome biogenesis in CPR bacteria was unexpectedly flexible, challenging traditional views of this essential process in evolution.

microbiology↗

bioRxiv2024

PATROL1-mediated H+-ATPase translocation boosts plant growth under drought by optimizing root and leaf functions

Optimizing leaf photosynthesis and root water and mineral uptake in crops during drought is crucial for enhancing agricultural productivity under climate change. Although plasma membrane H+-ATPase plays a key role in plant physiological processes, its overexpression alone does not consistently improve growth. While PROTON ATPASE TRANSLOCATION CONTROL 1 (PATROL1) regulates H+-ATPase translocation in response to various environmental stimuli in leaves, its function in roots remains largely unknown. Here we show that H+-ATPase was coimmunoprecipitated with PATROL1 in roots of Arabidopsis thaliana. Micrografting between wild type and PATROL1 knockout or overexpression lines showed that PATROL1 are indispensable in both shoots and roots, indicating that root uptake and leaf photosynthesis are simultaneous limiting factors for plant growth under drought conditions. PATROL1 overexpression in whole plants resulted in a 41% increase above wild type in shoot dry weight under drought conditions. These findings highlight the potential of H+-ATPase regulation in roots as a new strategy to improve plant productivity, particularly under drought conditions.

plant biology↗

bioRxiv2024

Autonomous biogenesis of the entire protein translation machinery excluding ribosomes

Recreating the conditions for autonomous biogenesis of the protein translation machinery is fundamental to our understanding of living systems and is essential for the assembly of minimal cell models. All components of the translation machinery, including the ribosomes, translation factors and aminoacyl tRNA synthetases, are made of proteins and are therefore involved in their own synthesis, posing a unique challenge for self-biogenesis. Here, we created physicochemical conditions for autonomous biogenesis of all the translation machinery, excluding the ribosome. We surface-immobilized synthetic genes coding for all thirty components as densely packed DNA brushes forming a reaction center that localizes, concentrates and catalyzes their simultaneous synthesis. To demonstrate their activity, we first determined empirically the minimal critical concentration of each translation protein required to initiate its own self-biogenesis in bulk solution. We then assembled a minimal gene expression reaction with all translation proteins at their critical concentrations. Under these dilute conditions, reporter proteins were not synthesized unless the DNA brushes encoded all the translation proteins, thereby demonstrating their co-synthesis, functionality and engagement in their own synthesis. This scenario of a complex biochemical process that amplifies itself can be generalized and extended to impact our understanding toward the design of autonomous self-replicating biological system.

synthetic biology↗

bioRxiv2024

Single-step in vitro ribosome reconstitution mediated by two GTPase factors, EngA and ObgE

When bacterial ribosomes are assembled in vitro, manipulation of incubation temperature and magnesium ion concentration have been an essential procedure, which is a crucial step for the assembly of active large subunits. The present study tackles with this issue to develop a single-step procedure, which can be performed in a near-physiological condition, where cell-free protein synthesis is active. We found that GTPase factors EngA and ObgE can complement the changes in temperature and magnesium ion concentrations. In the presence of these factors, both the ribosome assembly and translation processes were successfully integrated in the reconstituted cell-free protein synthesis system. Furthermore, we found that these GTPase factors can reassemble the ribosomes to an active state, whose structure was disrupted by EDTA chelation of magnesium ions, indicating that these two factors can reversibly induce the ribosome structure to an intact state. The findings are essential for the bottom-up construction of synthetic cells.

biochemistry↗

bioRxiv2024

Sustainable Regeneration of 20 Aminoacyl-tRNA Synthetases in a Reconstituted System Toward Self-Synthesizing Artificial Systems

In vitro construction of self-reproducible artificial systems is a major challenge in bottom-up synthetic biology. Here, we developed a reconstituted system capable of sustainably regenerating all 20 aminoacyl-tRNA synthetases (aaRSs), which are major components of the translation system. To achieve this, we needed five types of improvements: 1) optimization of aaRS sequences for efficient translation, 2) optimization of the composition of the translation system to enhance translation, 3) employment of another bacterial AlaRS and SerRS to improve each aminoacylation activity, 4) diminishing the translational inhibition caused by certain aaRS sequences by codon optimization and EF-P addition, and 5) balancing the DNA concentrations of 20 aaRSs to match each requirement. After these improvements, we succeeded in the sustainable regeneration of all 20 aaRSs for up to 20 cycles of 2.5-fold serial dilutions. These methodologies and results provide a substantial advancement toward the realization of self-reproducible artificial systems.

synthetic biology↗

bioRxiv2024

Genome-wide epitope identification with single-amino-acid resolution via high-throughput and unbiased peptide analysis

Antibodies are extensively used in biomedical research, clinical fields, and disease treatment. However, to enhance the reproducibility and reliability of antibody-based experiments, it is crucial to have a detailed understanding of the antibodys target specificity and epitope. In this study, we developed a high-throughput and precise epitope analysis method, DECODE (Decoding Epitope Composition by Optimized-mRNA-display, Data analysis, and Expression sequencing). This method allowed identifying patterns of epitopes recognized by monoclonal or polyclonal antibodies at single amino acid resolution and predicted cross-reactivity against the entire protein database. By applying the obtained epitope information, it has become possible to develop a new 3D immunostaining method that increases the penetration of antibodies deep into tissues. Furthermore, to demonstrated the applicability of DECODE to more complex blood antibodies, we performed epitope analysis using serum antibodies from mice with experimental autoimmune encephalomyelitis (EAE). As a result, we were able to successfully identify an epitope that matched the sequence of the peptide inducing the disease model without relying on existing antigen information. These results demonstrate that DECODE can provide high-quality epitope information, improve the reproducibility of antibody-dependent experiments, diagnostics and therapeutics, and contribute to discover pathogenic epitopes from antibodies in the blood.

bioengineering↗

bioRxiv2024

An allometric study of the contribution of prostrate stems to belowground development of juvenile Fagus crenata

Prostrate stems represent an important morphological component of Fagus crenata (Siebolds beech). This unique stem-bending growth strategy has led to the dominance of this tree species in regions with heavy snowfall along the Sea of Japan. We investigated the early-stage aboveground-belowground dynamics of F. crenata by applying allometric scaling theory to analyze morphological development in saplings (aged 3-20 years). Samples were collected from 25 trees in three forests in Nagano, central Japan. The scaling exponent (b) demonstrated an increase in the fraction of aboveground biomass (i.e., dry mass) in relation to the overall surface area (aboveground, b = 0.748; belowground, b = 0.626) and biomass (aboveground, b = 1.087; belowground, b = 0.983). These values are highly consistent with recent field observations by other researchers. Aboveground biomass growth was supported by the increasing role of prostrate stems in belowground development (b = 1.114). Despite its extension belowground, the growth properties of the prostrate stem may be identical to those of shoots, as both are directly influenced by nutrient sources above the germination point. Our findings highlight the significance of the prostrate stem in supporting beech survival in areas with heavy snowfall.

ecology↗