Biology subjects

Kawata, M.

Publications and source records attributed to Kawata, M..

8 recordsLinked to original sources

bioRxiv2026

How Fisherian runaway halts: Genomic architecture determines the long-term evolutionary consequences of sexual selection.

Sexual selection explains the evolution of exaggerated sexual displays, but less obvious is why biased mate preferences--a requirement for sexual selection--evolve. Fisher (1930) proposed that biased mate preferences can spark self-reinforcing evolutionary process (runaway) that drives their own evolution. This occurs because mate choice imposes sexual selection on sexual displays and links them genetically to mate preferences, producing indirect selection on the preferences themselves. While mathematical models have demonstrated the plausibility of the runaway theory, they rely on several idealized assumptions. Consequently, it remains poorly understood how runaway halts once populations deviate from these idealized conditions as a consequence of evolution via runaway, and how the genetic architecture underlying sexual displays influences the resulting evolutionary dynamics. Here, we address these gaps using two complementary approaches. First, we review and synthesize existing theories to classify the mechanisms that halt runaway into four categories, based on which idealized assumptions of Lande's (1981) classic model are violated during evolution via runaway. Second, we conduct individual-based evolutionary simulations varying the genetic architecture of sexual displays from conventional additive to omnigenic inheritance models. Our results show that genetic architecture determines how runaway process halts, thereby governing long-term evolutionary dynamics under sexual selection.

evolutionary biology↗

bioRxiv2026

Monoaminergic variation, cortical structure, and disaster trauma interact to shape emotional vulnerability

Emotional vulnerability arises from the interplay of genetic variation, cortical network capacity, and subjective processing of adverse experiences, yet these components are rarely examined together in population-scale datasets. Monoaminergic signaling offers an opportunity for understanding such interactions because variation in related genes shapes sensitivity to environmental inputs. Among them, the vesicular monoamine transporter 1 (VMAT1) Thr136Ile variant is notable for its functional effects and its long-term maintenance at intermediate frequencies, a pattern consistent with context-dependent selection. These properties make it an informative marker for investigating how genetic sensitivity interacts with neurobiological and experiential factors to shape affective functioning. Using data from up to 9,625 participants in the Tohoku Medical Megabank Project, a cohort established after the 2011 Great East Japan Earthquake, we investigated how monoaminergic variation, cortical morphology, and traumatic memory shape affective functioning. We found associations between the Thr136Ile variant and negative affectivity and depressive symptoms, consistent with prior reports of heightened emotional reactivity associated with the 136Thr allele. However, magnitude of these effects was substantially amplified in specific experiential and neurobiological contexts. Subjective trauma sensitivity, capturing the discrepancy between earthquake disruption and current traumatic memory, displayed a genotype-dependent association with depressive symptoms, and this relationship was strongest when parietal or insular cortical surface area was smaller. Together, these results identify a multilevel pathway through which monoaminergic variation contributes to emotional vulnerability by interacting with both cortical network capacity and trauma processing. The context-dependent influence of monoaminergic variation may further contribute to maintenance of affective diversity in human populations.

neuroscience↗

bioRxiv2025

NT5DC2 downregulation suppresses monoamine oxidase activity and increases catecholamine levels in PC12D cells

Back groundGenome-wide association studies have revealed the involvement of 5-nucleotidase domain-containing protein 2 (NT5DC2) in neuropsychiatric disorders such as schizophrenia and bipolar disorder; however, its function remains unclear. Recently, we found that NT5DC2 downregulation in PC12D cells increases catecholamine synthesis by promoting the activity of tyrosine hydroxylase and that monoamine oxidase A (MAO A) might bind to NT5DC2 using Affinity Purification-Mass Spectroscopy. Methods and ResultsWe investigated the role of NT5DC2 for MAO A activity in PC12D cells. Western blot analysis revealed that NT5DC2 primarily binds to the non-phosphorylated form of MAO A. siRNA-mediated NT5DC2 downregulation reduced MAO A activity, leading to decreased dopamine metabolism and increased noradrenaline synthesis. ConclusionOur findings suggest that NT5DC2 could affect both tyrosine hydroxylase and MAO A activity to control catecholamine synthesis. Therefore, our study provides valuable insights into disorders associated with catecholamine dysregulation, such as Parkinsons disease and neuropsychiatric disorders.

neuroscience↗

bioRxiv2025

Positive selection of a starch synthesis gene and phenotypic differentiation of starch accumulation in symbiotic and free-living coral symbiont dinoflagellate species

Symbiosis is a basis for species diversification through interactions between organisms. In tropical and subtropical oceans, dinoflagellate symbionts belonging to the family Symbiodiniaceae, including the genus Symbiodinium, support the flourishment of cnidarian hosts, including corals, and thereby the ecology of oligotrophic oceans through their photosynthate carbon transfers. Although the genus Symbiodinium includes both free-living and symbiotic species, the detailed genetic background of their lifestyle differences remains unclear. In this study, we identified candidate genes involved in the evolutionary acquisition or maintenance of symbiosis in Symbiodinium spp. by detecting genes that have undergone positive selection during symbiotic and free-living lifestyle diversification. Using multiple Symbiodinium genomes to detect positive selection, 35 genes were identified, including a gene encoding soluble starch synthase SSY1 and genes related to metabolite secretion, which may be preferred for symbiotic lifestyles. In particular, our in silico analyses revealed that the SSY1 gene family has undergone extensive gene duplications in an ancestral dinoflagellate, and that the mutations detected as positive selection have occurred in the intrinsically disordered region of one of the homologs. Consistent with molecular evolution, the phenotypes of intracellular starch synthesis/accumulation were distinct between the symbiotic and free-living species of Symbiodinium when cultured under different pH and nitrogen conditions. These results provide molecular and phenotypic insights into symbiotic Symbiodinium-coral relationships. Significance statementClarifying how coral symbiont algae of the family Symbiodiniaceae are functionally diversified is crucial for understanding the molecular mechanisms of symbiotic relationships and interactions in animal-algal symbioses. However, gene-level molecular evolution that contributes to symbiotic relationships remains unclear. Our genome-wide single-gene analyses of the genus Symbiodinium, comprising both symbiotic and free-living species, successfully detected several dozen protein-coding genes that underwent symbiont-specific positive selection after divergence from the free-living species in the genus. Furthermore, our cultivation experiments demonstrated differences in photosynthate-related phenotypes between the symbiotic and free-living species. Our findings provide a key to illuminating the molecular evolution involved in phenotypic changes that potentially contribute to symbiotic lifestyles in Symbiodinium.

evolutionary biology↗

bioRxiv2022

Environmental pH signals the release of monosaccharides from cell wall in coral symbiotic alga

Reef-building corals thrive in oligotrophic environments due to their possession of endosymbiotic algae. Confined to the low pH interior of the symbiosome within the cell, the algal symbiont provides the coral host with photosynthetically fixed carbon. However, it remains unknown how carbon is released from the algal symbiont for uptake by the host. Here we show, using cultured symbiotic dinoflagellate, Breviolum sp., that decreases in pH directly accelerates the release of monosaccharides, i.e., glucose and galactose, into the ambient environment. Under low pH conditions, the cell surface structures were deformed and genes related to cellulase were significantly upregulated in Breviolum. Importantly, the release of monosaccharides was suppressed by the cellulase inhibitor, glucopyranoside, linking the release of carbon to degradation of the agal cell wall. Our results suggest that the low pH signals the cellulase-mediated release of monosaccharides from the algal cell wall as an environmental response in coral reef ecosystems.

evolutionary biology↗

bioRxiv2022

Draft genome of six Cuban Anolis lizards and insights into genetic changes during the diversification

The detection of various type of genomic variants and their accumulation processes during species diversification and adaptive radiation is important for understanding the molecular and genetic basis of evolution. Anolis lizards in the West Indies are good models for studying the mechanism of the evolution because of the repeated evolution of their morphology and the ecology. In this study, we performed de novo genome assembly of six Cuban Anolis lizards with different ecomorphs and thermal habitats (Anolis isolepis, Anolis allisoni, Anolis porcatus, Anolis allogus, Anolis homolechis, and Anolis sagrei). As a result, we obtained six novel draft genomes with relatively long and high gene completeness, with scaffold N50 ranging from 5.56-39.79 Mb, and vertebrate Benchmarking Universal Single-Copy Orthologs completeness ranging from 77.5% to 86.9%. Subsequently, we performed comparative analysis of genomic contents including those of mainland Anolis lizards to estimate genetic variations that had emerged and accumulated during the diversification of Anolis lizards. Comparing the repeat element compositions and repeat landscapes revealed differences in the accumulation process between Cuban trunk-crown and trunk-ground species, LTR accumulation observed only in A. carolinensis, and separate expansions of several families of LINE in each of Cuban trunk-ground species. The analysis of duplicated genes suggested that the proportional difference of duplicated gene number among Cuban Anolis lizards may be associated to the difference of their habitat range. Furthermore, Pairwise Sequentially Markovian Coalescent analysis proposed that the effective population sizes of each species might have been affected by Cubas geohistory. Hence, these six novel draft genome assemblies and detected genetic variations can be a springboard for the further genetic elucidation of the Anolis lizards diversification. SignificanceAnolis lizard in the West Indies is excellent model for studying the mechanisms of speciation and adaptive evolution. Still, due to a lack of genome assemblies, genetic variations and accumulation process of them involved in the diversification remain largely unexplored. In this study, we reported the novel genome assemblies of six Cuban Anolis lizards and analyzed evolution of genome contents. From comparative genomic analysis and inferences of genetic variation accumulation process, we detected species- and lineage-specific transposon accumulation processes and gene copy number evolution, considered to be associated with the adaptation to their habitats. Additionally, we estimated past effective population sizes and the results suggested its relationship to Cubas geohistory.

genomics↗

bioRxiv2021

Humanized substitutions of Vmat1 in mice induce changes in amygdala-dependent behaviors associated with the evolution of anxiety in humans

The human vesicular monoamine transporter 1 (VMAT1) harbors unique substitutions (Asn136Thr/Ile) that affect monoamine uptake into synaptic vesicles. These substitutions are absent in all known mammals, suggesting their contributions to distinct aspects of human behavior modulated by monoaminergic transmission, such as emotion and cognition. To directly test the impact of these human-specific mutations, we introduced the humanized residues into mouse Vmat1 via CRISPR/Cas9-mediated genome editing and examined changes at the behavioral, neurophysiological and molecular levels. Behavioral tests revealed reduced anxiety-related traits of Vmat1Ile mice, consistent with human studies, and electrophysiological recordings showed altered oscillatory activity in the amygdala under anxiogenic conditions. Transcriptome analyses further identified amygdala-specific changes in the expression of genes involved in neurodevelopment and emotional regulation, which may corroborate the observed phenotypes. This knock-in mouse model hence provides compelling evidence that the mutations affecting monoaminergic signaling and amygdala circuits have contributed to the evolution of human socio-emotional behaviors.

evolutionary biology↗

bioRxiv2020

Involvement of the doublesex gene in body color masculinization of the blue-tailed damselfly, Ischnura senegalensis

Odonata (dragonflies and damselflies) display remarkable color pattern diversity including sexual dimorphism and intrasexual polymorphism. We previously found that expression of a sex-determining transcription factor, the doublesex (dsx) gene, is associated with female color polymorphism (gynomorph for female-specific color and andromorph for male mimicking color) in the blue-tailed damselfly, Ischnura senegalensis. Here we investigate the function of dsx gene on thoracic coloration by electroporation-mediated RNA interference (RNAi). RNAi of the dsx common region changed color patterns of males and andromorphic females to patterns of gynomorphic females. Further, gynomorphic color pattern was not affected by dsx RNAi. The long isoform of dsx RNAi produced no effects, suggesting that the short isoform of dsx is important for body color masculinization in both males and andromorphic females. Expression pattern changes were also examined in five genes with different expression levels between sexes and female morphs. Among these genes are two melanin suppressing genes, black and ebony, that were upregulated in the dsx-RNAi region compared to a control region. Upregulation coincides with a gynomorphic orange color instead of the black stripe observed in males and andromorphic females. dsx may regulate male color differentiation by suppressing black and ebony in the thoracic region of I. senegalensis. Results add to the understanding of molecular mechanisms underlying the evolution of female polymorphism in Odonata.

genetics↗