Biology subjects

Kato, R.

Publications and source records attributed to Kato, R..

16 recordsLinked to original sources

bioRxiv2026

Loss of the fatty acid β-oxidation gene acaa-2 impairs timely hatching under poor maternal diet in C. elegans

Developmental programs must remain robust despite fluctuations in maternal nutrition, yet the genetic basis of this robustness is incompletely understood. Using an unbiased, diet-dependent forward genetic screen in the nematode Caenorhabditis elegans, we searched for mutants with normal embryogenesis on standard food but defective development when mothers experienced poor nutrition. We isolated a mutation in acaa-2, which encodes an enzyme catalyzing the final step of mitochondrial fatty acid {beta}-oxidation, and confirmed its role using an independent deletion allele. acaa-2 mutant embryos exhibit a marked hatching delay specifically when mothers consume a low-quality diet. Despite remaining motile within the eggshell, mutant embryos are associated with increased unoccupied intra-eggshell space, consistent with impaired late embryonic growth. Our findings reveal a previously unrecognized role for acaa-2 and suggest that mitochondrial fatty acid {beta}-oxidation acts as a metabolic buffer that promotes developmental robustness under maternal nutrient limitation.

developmental biology↗

bioRxiv2026

The mental conflict in risk-taking behavior: Decoding bias between optimism and pessimism

Humans and animals often face risky situations that require decision-making. Such decisions can be high-risk, high-return at some times, and low-risk, low-return at other times, depending on the balance between optimism and pessimism. However, how this optimism-pessimism bias is regulated across contexts remains unclear. Here, we introduced a computational model of decision-making in a risk-taking task based on the free-energy principle, together with a machine-learning framework that inversely estimates cognitive updating and optimism-pessimism bias from behavioral data. Applying this framework to monkey behavioral data, we found that a monkey quickly and accurately recognized the degree of risk, while frequently switching between optimism and pessimism during the task. In addition, we identified a characteristic control rule for optimism-pessimism bias that is distinct from reward-dependent regulation. Our framework provided a principled tool for understanding the latent cognitive processes underlying risky decision-making in animals and humans.

neuroscience↗

bioRxiv2026

Quantitative assessment of sea slugs (Heterobranchia) assemblages along the western coast of Kyushu, Japan: a baseline for long-term biodiversity monitoring

Quantitative information on the seasonal dynamics of heterobranch sea slug assemblages remains limited in warm-temperate coastal regions, despite their ecological importance as benthic consumers and indicators of environmental change. Here, we conducted a standardized, multi-seasonal SCUBA-based survey of sea slug assemblages at two rocky reef sites (Tatsunokuchi and Nomozaki-Akase) along the northwestern coast of Kyushu, Japan, from February 2024 to November 2025. Across the study period, a total of 81 species comprising 892 individuals were recorded. Species richness and total abundance exhibited pronounced seasonal variation at both sites, with higher values in winter-spring and marked declines during summer. Assemblage composition shifted seasonally from relatively even communities in winter-spring to dominance by a few taxa in summer, a pattern reflected by concurrent changes in diversity indices. Water temperature displayed clear seasonal cycles and was negatively correlated with both species richness and total abundance, indicating a close association between thermal conditions and seasonal changes in sea slug assemblages. While causal mechanisms were not explicitly tested, these consistent patterns highlight the importance of temporal environmental variability in structuring heterobranch communities in this region. This study provides one of the few quantitative, multi-seasonal baselines of heterobranch sea slug assemblages in warm-temperate coastal Japan, offering a reference framework for future ecological monitoring and assessments of environmental change.

ecology↗

bioRxiv2025

Oligo DNA-based quantum dot (QD) single-particle tracking for multicolor single-molecule imaging

Quantum dot single-particle tracking (QD-SPT), a powerful tool for analyzing membrane domains that are critical to various cellular processes, is widely used in membrane molecular dynamics research. QDs, which possess both a broad excitation range and a narrow emission bandwidth, are inherently suited for multicolor imaging at various wavelengths. However, applying multicolor QD-SPT with multiple biomolecular targets has been challenging due to the limited methods for specifically conjugating QDs to biomolecules. Here, we propose a DNA hybridization-based QD labeling method that generates several specific interactions based on sequence. QD fused with 20-mer oligo DNA specifically labeled membrane lipid 1,2-dipalmitoyl-sn-glycero-3-phosphatidylethanolamine (DPPE) covalently bound to complementary oligo DNA, forming a stable label that is suitable for SPT. The combination of polyA-polyT sequence as the linker oligo caused more QDs to fuse to DPPE compared with a random sequence linker. Oligo DNA-based QD-SPT accurately reflected the diffusion dynamics of DPPE measured using the single-fluorescence tracking technique and was compatible with conventional QD-SPT utilizing secondary antibody Fab. Using different pairs of oligo DNA sequences, we successfully achieved multicolor QD-SPT that distinguishes the lateral diffusion of DPPE and a membrane protein, GABAA receptor (GABAAR), within the same cell. The oligo DNA-based QD labeling method developed in this study is anticipated to substantially advance simultaneous multicolor QD-SPT of different living cell membrane molecules specific to DNA sequences.

biophysics↗

bioRxiv2025

A different world: temporal changes in nudibranch community structure over a half-century

Understanding long-term changes in marine biodiversity is essential for evaluating effects of climate change on coastal ecosystems. In this study, we compared nudibranch assemblages in northwestern Kyushu, Japan, during three time periods (1960-1980, 2001-2003, and 2023-2024), based on underwater surveys and historical records. In all, 47 nudibranch species were recorded during 27 diving surveys conducted in 2023 and 2024. Species diversity indices (Shannon-Wiener H and Simpson D) showed higher values during this survey than in 2001-2003. Comparative analysis of species composition revealed significant shifts, with 15 species exhibiting statistically significant differences in relative abundance from the past to the present. Notably, several species common in the past, such as Aplysia kurodai, were rarely observed in the recent survey, while many tropical-subtropical species appeared for the first time. The proportion of tropical-subtropical species increased markedly, whereas subarctic species were no longer detected. Similarity indices (Jaccards coefficient and Sorensen-Dice index) indicated that the current community differs markedly from those in earlier periods. These findings suggest a major community reorganization, potentially driven by rising sea water temperatures and other environmental changes. This study highlights the importance of long-term monitoring using multiple indicators to detect and interpret climate-driven biodiversity shifts in coastal marine ecosystems. HighlightsO_LILong-term changes in nudibranch assemblages were investigated using visual census surveys spanning 6 decades. C_LIO_LISpecies richness and tropical species have increased markedly in recent decades. C_LIO_LISubtropical species expanded their ranges, while some cold-water species declined. C_LIO_LIFindings suggest that community-level tropicalization is likely driven by ocean warming. C_LI Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=113 SRC="FIGDIR/small/668013v1_ufig1.gif" ALT="Figure 1"> View larger version (42K): org.highwire.dtl.DTLVardef@9d0182org.highwire.dtl.DTLVardef@1ce002borg.highwire.dtl.DTLVardef@16d3830org.highwire.dtl.DTLVardef@183ff06_HPS_FORMAT_FIGEXP M_FIG C_FIG

ecology↗

bioRxiv2025

Intraspecific differences in habitat depth in a deep-sea isopod, Bathynomus doederleini (Crustacea: Isopoda: Cirolanidae), off the west coast of Kyushu, Japan

The giant deep-sea isopod, Bathynomus doederleini, is a benthic scavenger distributed in the northwestern Pacific. Despite its ecological importance, little is known about its habitat use and intraspecific variation in body size in relation to depth. In this study, we examined the habitat depth, size structure, and distributional limits of B. doederleini off the western coast of Kyushu, Japan, using baited traps deployed at depths ranging from 151 to 821 m. A total of 1,152 individuals were collected, with the highest catch per unit effort (CPUE) observed between 300 and 500 m. CPUE declined sharply below 700 m, likely due to thermal constraints and interspecific competition. Body size distribution varied significantly with depth: minimum body size increased with depth, while maximum body size remained constant. Smaller individuals were more abundant in shallower, warmer waters, suggesting ontogenetic habitat segregation possibly driven by metabolic and competitive factors. No brooding individuals were captured, supporting previous findings that reproductive females avoid baited traps. These results suggest that B. doederleini forms a reproductively active population in the East China Sea, with ecological adaptations to thermal conditions and depth-related niche partitioning. This study highlights the importance of trap type and environmental gradients in understanding deep-sea species ecology.

ecology↗

bioRxiv2025

Floating offshore wind farms cause Japanese horse mackerel to congregate

Floating offshore wind farms (F-OWFs) are becoming key components of renewable energy production, yet their ecological impacts on marine ecosystems remain largely unexplored. Using environmental DNA (eDNA) analysis in the East China Sea, this study investigated the tendency for Japanese horse mackerel (Trachurus japonicus) to congregate beneath F-OWFs. Water samples were collected at stations near an F-OWF and control stations farther away at various depths and seasons. A total of 115 samples were analyzed, and eDNA of T. japonicus was detected in 83% of all samples. eDNA concentrations were significantly higher near an F-OWF (F-OWF stations) than at control stations. The highest recorded eDNA concentration reached 2,280 copies/L at an F-OWF station, whereas the maximum concentration at control stations was 783 copies/L. Seasonal variations were also observed, with lower concentrations in summer and higher concentrations from autumn to spring. Generalized linear model (GLM) analysis further revealed that wind turbines had a significant influence on eDNA concentration, whereas other environmental variables, such as water temperature and depth, were not significant. These findings suggest that F-OWFs may function as artificial reefs, providing habitat for commercially important fish and influencing fish distributions at both spatial and temporal scales. However, potential conflicts with fisheries due to spatial restrictions, displacement of fishery resources, and increased navigation costs necessitate further long-term ecological and socio-economic assessments. Integrating eDNA monitoring with traditional survey methods, such as acoustic surveys and ROV observations, is crucial for coexistence of adaptive offshore wind farm management and sustainable fisheries. Future research should also explore the long-term effects of F-OWFs on fish assemblages and biodiversity to support evidence-based decision-making for offshore energy development.

ecology↗

bioRxiv2024

Laboratory evolution in Novosphingobium aromaticivorans enables rapid catabolism of a model lignin-derived aromatic dimer

Lignin contains a variety of interunit linkages, which leads to a range of potential decomposition products that can be used as carbon sources by microbes. {beta}-O-4 linkages are the most common in native lignin and associated catabolic pathways have been well characterized. However, the fate of the mono-aromatic intermediates that result from {beta}-O-4 dimer cleavage has not been fully elucidated. Here, we used experimental evolution to identify mutant strains of Novosphingobium aromaticivorans with improved catabolism of a model aromatic dimer containing a {beta}-O-4 linkage, guaiacylglycerol-{beta}-guaiacyl ether (GGE). We identified several parallel causal mutations, including a single nucleotide mutation in the promoter of an uncharacterized gene that roughly doubled the growth yield with GGE. We characterized the associated enzyme and demonstrated that it oxidizes an intermediate in GGE catabolism, {beta}-hydroxypropiovanillone, to vanilloyl acetaldehyde. Identification of this enzyme and its key role in GGE catabolism furthers our understanding of catabolic pathways for lignin-derived aromatic compounds. ImportanceLignin degradation is a key step for both carbon cycling in nature and biomass conversion to fuels and chemicals. Bacteria can catabolize lignin-derived aromatic compounds, but the complexity of lignin means that full mineralization requires numerous catabolic pathways and often results in slow growth. Using experimental evolution, we identified a new enzyme for catabolism of a lignin-derived aromatic monomer, {beta}-hydroxypropiovanillone. A single mutation in the promoter of the associated gene significantly increased bacterial growth with either {beta}-hydroxypropiovanillone or a related lignin-derived aromatic dimer. This work expands the repertoire of known aromatic catabolic genes and demonstrates that slow catabolism of lignin-derived aromatic compounds may be due to misregulation under laboratory conditions rather than inherent catabolic challenges.

microbiology↗

bioRxiv2024

Synthetic spider silk forming highly-aligned nanoarchitectures on 2D-material surfaces

The synergy between silk proteins and nanomaterials can lead to novel materials with improved mechanical and electrical properties. Designed peptides have been previously utilised in the functionalisation of two-dimensional material surfaces in a self-assembly manner, including graphite, to develop highly sensitive electrical biosensors. These studies have predominantly focused on functionalising the surfaces with peptides of less than several kDa in size. In this work, we assessed the capability of a [~]35 kDa synthetic spider silk protein to serve as a candidate biomolecular scaffold on a range of two-dimensional materials: graphite, molybdenum disulphide and boron nitride. The structural properties of the synthetic spider silk protein at the 2D material surface were characterised at the nanoscale for the first time using a multi-analysis approach incorporating atomic force microscopy and fluorescence microscopy, in addition to polarised Raman and tip-enhanced Raman spectroscopy. The synthetic spider silk protein was revealed to self-assemble into stable nanowire structures of monolayer thickness. Our findings have demonstrated the feasibility of functionalising 2D materials with spider silk-based proteins and will unlock new possibilities in the development of next-generation high-performance biosensing devices.

biophysics↗

bioRxiv2023

Involvement of the splicing factor SART1 in the BRCA1-dependent homologous recombination repair of DNA double-strand breaks

Although previous studies have reported that pre-mRNA splicing factors (SFs) are involved in the repair of DNA double-strand breaks (DSBs) via homologous recombination (HR), their exact role in promoting HR remains poorly understood. Here, we showed that SART1, an SF upregulated in several types of cancer, promotes DSB end resection, which is an essential step in HR, without affecting the expression of HR factors. In the promotion of resection, SART1 is epistatic with BRCA1, an HR factor known to promote resection. Mechanistically, SART1 cooperates with BRCA1 to counteract the resection blockade posed by 53BP1 and RIF1. Moreover, SART1 is required for recruitment of the HR-promoting portion of BRCA1 to DSBs. Laser microirradiation experiments revealed that SART1 is recruited to DSBs in a BRCA1-dependent manner, and that the arginine/serine (RS)-rich domain is required for SART1 recruitment to DSBs. We also obtained evidence that SART1 is involved in transcription-associated HR together with BRCA1. Furthermore, chromosome analysis demonstrated that SART1 and BRCA1 epistatically suppressed genomic alterations caused by DSB misrepair in the G2 phase. Collectively, these results indicate that SART1 and BRCA1 cooperatively facilitate resection of DSBs arising in transcriptionally active genomic regions, thereby promoting faithful HR repair of such DSBs and suppressing genome instability.

cell biology↗

bioRxiv2023

Structural alterations in the amygdala and impaired social incentive learning in a mouse model of a genetic variant associated with neurodevelopmental disorders

Copy number variants (CNVs) are robustly associated with psychiatric disorders and their dimensions and changes in brain structures and behavior. However, as CNVs contain many genes, the precise gene-phenotype relationship remains unclear. Although various volumetric alterations in the brains of 22q11.2 CNV carriers have been identified in humans and mouse models, it is unknown how the genes in the 22q11.2 region individually contribute to structural alterations and associated mental illnesses and their dimensions. Our previous studies have identified Tbx1, a T-box family transcription factor encoded in 22q11.2 CNV, as a driver gene for social interaction and communication, spatial and working memory, and cognitive flexibility. However, it remains unclear how TBX1 impacts the volumes of various brain regions and their functionally linked behavioral dimensions. In this study, we used volumetric magnetic resonance imaging analysis to comprehensively evaluate brain region volumes in congenic Tbx1 heterozygous mice. Our data show that the volumes of anterior and posterior portions of the amygdaloid complex and its surrounding cortical regions were reduced in Tbx1 heterozygous mice. Moreover, we examined the behavioral consequences of an altered volume of the amygdala. Tbx1 heterozygous mice were impaired for their ability to detect the incentive value of a social partner in a task that depends on the amygdala. Our findings identify the structural basis for a specific social dimension associated with loss-of-function variants of TBX1 and 22q11.2 CNV.

neuroscience↗

bioRxiv2023

Stereoinversion via alcohol dehydrogenases enables complete catabolism of β-1-type lignin-derived aromatic isomers

Sphingobium sp. SYK-6 is an efficient aromatic catabolic bacterium that can consume all four stereoisomers of 1,2-diguaiacylpropane-1,3-diol (DGPD), which is a ring-opened {beta}-1-type dimer. Recently, LdpA-mediated catabolism of erythro-DGPD was reported in SYK-6, but the catabolic pathway for threo-DGPD was heretofore unknown. Here we elucidated the catabolism of threo-DGPD, which proceeds through conversion to erythro-DGPD. When threo-DGPD was incubated with SYK-6, the C alcohol groups of threo-DGPD (DGPD I and II) were initially oxidized to produce the C carbonyl form (DGPD-keto I and II). This initial oxidation step is catalyzed by C-dehydrogenases, which belong to the short-chain dehydrogenase/reductase (SDR) family and are involved in the catabolism of {beta}-O-4-type dimers. Analysis of seven candidate genes revealed that NAD+-dependent LigD and LigL are mainly involved in the conversion of DGPD I and II, respectively. Next, we found that DGPD-keto I and II were reduced to erythro-DGPD (DGPD III and IV) in the presence of NADPH. Genes involved in this reduction were sought from C-dehydrogenase and ldpA-neighboring SDR genes. The gene products of SLG_12690 (ldpC) and SLG_12640 (ldpB) catalyzed the NADPH-dependent conversion of DGPD-keto I to DGPD III and DGPD-keto II to DGPD IV, respectively. Mutational analysis further indicated that ldpC and ldpB are predominantly involved in the reduction of DGPD-keto. Together, these results demonstrate that SYK-6 harbors a comprehensive catabolic enzyme system to utilize all four {beta}-1-type stereoisomers through successive oxidation and reduction reactions of the C alcohol group of threo-DGPD with a net stereoinversion using multiple dehydrogenases. IMPORTANCEIn many catalytic depolymerization processes of lignin polymers, aryl-ether bonds are selectively cleaved, leaving carbon-carbon bonds between aromatic units intact, including dimers and oligomers with {beta}-1 linkages. Therefore, elucidating the catabolic system of {beta}-1-type lignin-derived compounds will aid in the establishment of biological funneling of heterologous lignin-derived aromatic compounds to value-added products. In this work, we found that threo-DGPD was converted by successive stereoselective oxidation and reduction at the C-position by multiple alcohol dehydrogenases to erythro-DGPD, which is further catabolized. This system is very similar to that developed to obtain enantiopure alcohols from racemic alcohols by artificially combining two enantiocomplementary alcohol dehydrogenases. The results presented here demonstrate that SYK-6 has evolved to catabolize all four stereoisomers of DGPD by incorporating this stereoinversion system into its native {beta}-1-type dimer catabolic system.

microbiology↗

bioRxiv2021

Construction of transcript regulation mechanism prediction models based on binding motif environment of transcription factor AoXlnR in Aspergillus oryzae

Recent study revealed that there are thousands of genes that remain unaffected by increased AoXlnR expression, despite the presence of one or more AoXlnR-binding motifs in their promoter region. Given this knowledge, we designed this study to construct several predictive models for determining whether a gene can exhibit a differential response to changes in AoXlnR expression. These models were constructed using 3D DNA shape information determined using the sequence around the AoXlnR binding motifs with classification as functional or nonfunctional. These models were created using a support vector machine followed by the evaluations designed to determine whether these DNA shape-based models can correctly classify functional motifs in terms of area under the receiver operating characteristic curve. The results showed that the differential expression levels of genes located downstream of the AoXlnR motif are closely related to specific DNA shape information around the binding motifs. Furthermore, we found that the parameters contributing to differential expressions differed depending on the number of motifs in the promoter region by comparing the prediction models using regions with only one binding DNA motif and those with multiple binding DNA motifs. Author SummaryDNA-binding transcription factors (TFs) play a central role in transcriptional regulation mechanisms, mainly through their specific binding to target sites on the genome and regulation of the expression of downstream genes. Therefore, a comprehensive analysis of the function of these TFs will lead to the understanding of various biological mechanisms. However, the functions of TFs in vivo are diverse and complicated, and the identified binding sites on the genome are not necessarily involved in the regulation of downstream gene expression. In this study, we investigated whether DNA structural information around the binding site of transcription factors can be used to predict the involvement of the binding site in the regulation of the expression of genes located downstream of the binding site. Specifically, we calculated the structural parameters based on the DNA shape around the DNA binding motif located upstream of the gene whose expression is directly regulated by the transcription factor AoXlnR from Aspergillus oryzae, and showed that the presence or absence of expression regulation can be predicted from the sequence information with high accuracy by machine learning incorporating these parameters.

genomics↗

bioRxiv2021

RAP80 suppresses the vulnerability of R-loops during DNA double-strand break repair

R-loops, consisting of ssDNA and DNA-RNA hybrids, are potentially vulnerable unless they are appropriately processed. Recent evidence suggests that R-loops can form in the proximity of DNA double-strand breaks (DSBs) within transcriptionally active regions. Yet, how the vulnerability of R-loops is overcome during DSB repair remains unclear. Here, we identify RAP80 as a factor suppressing the vulnerability of ssDNA in R-loops and chromosome translocations and deletions during DSB repair. Mechanistically, RAP80 prevents unscheduled nucleolytic processing of ssDNA in R-loops by CtIP. This mechanism promotes efficient DSB repair via transcription-associated end-joining dependent on BRCA1, Pol{theta}, and LIG1/3. Thus, RAP80 suppresses the vulnerability of R-loops during DSB repair, thereby precluding genomic abnormalities in a critical component of the genome caused by deleterious R-loop processing.

molecular biology↗

bioRxiv2020

Maternal approach behaviors toward neonatal calls are impaired by mother's experiences of raising pups with a risk gene variant for autism

How the intrinsic sequence structure of neonatal mouse pup ultrasonic vocalization (USV) and maternal experiences determine maternal behaviors in mice is poorly understood. Our previous work showed that pups with a Tbx1 heterozygous (HT) mutation, a genetic risk for autism spectrum disorder (ASD), emit altered call sequences that do not induce maternal approach behaviors in C57BL6/J mothers. Here, we tested how maternal approach behaviors induced by wild-type and HT USVs are influenced by the mothers experience in raising pups of these two genotypes. The results showed that wild-type USVs were effective in inducing maternal approach behaviors when mothers raised wild-type but not HT pups. The USVs of HT pups were ineffective regardless of whether mothers raised HT or wild-type pups. However, the sequence structure of pup USVs had no effect on the general, non-directional incentive motivation of maternal behaviors. Our data show how the mothers experience with a pup with a genetic risk for ASD alters the intrinsic incentive values of USV sequences in maternal approach behaviors.

developmental biology↗

bioRxiv2018

Refining the application of microbial lipids as tracers of Staphylococcus aureus growth rates in cystic fibrosis sputum

Chronic lung infections in cystic fibrosis (CF) could be treated more effectively if the effect of antimicrobials on pathogens in situ were known. Here, we compared changes in the microbial community composition and pathogen growth rates in longitudinal studies of CF patients undergoing intravenous antibiotic administration during pulmonary exacerbations. Microbial community composition was measured by NanoString DNA analysis and growth rates were obtained by incubating CF sputum with heavy water and tracing incorporation of deuterium into two different anteiso fatty acids (a-C15:0 and a-C17:0) using gas chromatography-mass spectrometry (GC/MS). Prior to this study, both lipids were thought to be specific for Staphylococcaceae and hence their isotopic enrichment was interpreted as a growth proxy for S. aureus. Our experiments revealed, however, that Prevotella is also a relevant microbial producer of a-C17:0 fatty acid in some CF patients, thus deuterium incorporation into these lipids is better interpreted as a more general pathogen growth rate proxy. Even accounting for a small non-microbial background source detected in some patient samples, a-C15:0 fatty acid still appear to be a relatively robust proxy for CF pathogens, revealing a median generation time of ~1.5 days, similar to prior observations. Contrary to our expectations, pathogen growth rates remained relatively stable throughout exacerbation treatment. We suggest two best practices for application of stable isotope probing in CF sputum: (1) parallel determination of microbial community composition in CF sputum using culture-independent tools, and (2) analysis of samples with a minimum a-C15:0 concentration of 0.1 weight percent of saturated fatty acids.\n\nIMPORTANCEIn chronic lung infections, populations of microbial pathogens change and mature in ways that are often unknown, which makes it challenging to identify appropriate treatment options. A promising tool to better understand the physiology of microorganisms in a patient is stable-isotope probing, which we previously developed to estimate the growth rates of S. aureus in cystic fibrosis (CF) sputum. Here, we tracked microbial communities in a cohort of CF patients and found that anteiso fatty acids can also originate from other sources in CF sputum. This awareness led us to develop an new workflow for the application of stable isotope probing in this context, improving our ability to estimate pathogen generation times in clinical samples.

microbiology↗