Biology subjects

Takeuchi, H.

Publications and source records attributed to Takeuchi, H..

30 records · Page 2Linked to original sources

bioRxiv2023

Comparative transcriptomics shows the evolutionary origin of acoustic fat bodies through a trade-off with skull muscles in toothed whales

Toothed whales (odontocetes) have developed acoustic fat bodies, which include forehead melon, extra-mandibular fat body and intra-mandibular fat body. These contribute to the sound transmission pathways in the unique echolocation process of toothed whales. The acoustic fat bodies of Odontocetes accumulate unusual fatty acids, making them novel traits with unique functional anatomy and chemistry. This study provides new insights into the evolutionary origin and lipid utilisation of acoustic fat bodies in harbour porpoise (Phocoena phocoena) and Pacific white-sided dolphin (Lagenorhynchus obliquidens) using comparative transcriptomics. Comprehensive gene expression analyses indicated that the acoustic fat bodies of toothed whales are composites of muscle and adipose tissues, mainly composed of intramuscular fat. The extra-mandibular fat body is a homologue of the masseter muscle. Additionally, we demonstrated that gene expression-based functional enrichments for specialised branched-chain amino acid metabolism, endocytosis, lysosomes and peroxisomes contribute to the maintenance of the unique fatty characteristics of the acoustic fat bodies of toothed whales. A trade-off occurred in the evolution of acoustic fat bodies as a result of the fatty reorganisation of head muscles involved in aquatic adaptation in toothed whales.

evolutionary biology↗

bioRxiv2023

Optogenetic control of medaka behavior with channelrhodopsin

Optogenetics enables the manipulation of neural activity with high spatiotemporal resolution in genetically defined neurons. The method is widely used in various model animals in the neuroscience and physiology fields. Channelrhodopsins are robust tools for optogenetic manipulation, but they have not yet been used for studies in medaka. In the present study, we used the CRISPR/Cas9-mediated knock-in approach to establish a transgenic medaka strain expressing the Chloromonas oogama channelrhodopsin (CoChR) in the ISL LIM homeobox 1 (isl1) locus. We demonstrated that light stimuli elicited specific behavioral responses such as bending or turning locomotion in the embryos and pectoral fin movements in the larvae and adults. The response probabilities and intensities of these movements could be controlled by adjusting the intensity, duration, or wavelength of each light stimulus. Furthermore, we demonstrated that the pectoral fin movements in the adult stage could be elicited using a laser pointer to irradiate only the hindbrain region. Our results indicate that CoChR allows for manipulation of medaka behaviors by activating targeted neurons, which will further our understanding of the detailed neural mechanisms of social behaviors in medaka.

molecular biology↗

bioRxiv2022

Epigenetically distinct synaptic architecture in clonal compartments in the teleostean dorsal pallium

The dorsal telencephalon (i.e. the pallium) exhibits high anatomical diversity across vertebrate classes. The mammalian dorsal pallium accommodates a six layered-structure, the neocortex, whereas the teleostean dorsal pallium possesses various compartmentalized structures among species. The development, function and evolution of the fish dorsal pallium remain unillustrated. Here, we analyzed the structure and epigenetic landscapes of cell lineages in the telencephalon of medaka fish (Oryzias latipes) which possesses a clearly delineated dorsal pallium (the Dd2 region). We found that different pallial regions, including Dd2, are formed by mutually exclusive clonal units, and that each pallium compartment exhibits a distinct epigenetic landscape. In particular, Dd2 possesses a unique open chromatin pattern that preferentially targets synapse-related genes. Indeed, Dd2 shows a high density of synapses, which might reflect strong plasticity. Finally, we identified several transcription factors as candidate regulators for the Dd2, which are partially shared with the human neocortex and hippocampus.

neuroscience↗

bioRxiv2022

Collective Decision-making in Response to Visual Looming Stimuli in Medaka Fish

Cohabitation within groups promotes behavioural synchrony and facilitates information transfer. Whether it shapes collective decision-making under predator threat is unknown. Here groups of six medaka (Oryzias latipes) cohabited for one month were used to test whether cohabitation promotes instantaneous collective decision-making in response to a looming stimulus (LS) mimicking a predator attack. Firstly, we analysed behavioural transitions before, during, and after LS in groups composed of six individuals. Individuals showing high-speed swimming in response to LS typically tended to shift to freezing-like behaviour afterwards, whereas non-responders were more likely to maintain normal swimming. Group-level analysis revealed a bimodal distribution in the number of individuals exhibiting freezing-like behaviour, with peaks at zero and six individuals, corresponding to all non-freezing and all-freezing. Importantly, clustering analysis revealed that experimental groups showed consistent collective behavioural characteristics that could be categorised into three profiles: all-freezing, all non-freezing, and partial freezing. In non-cohabited groups assembled immediately before testing, the all-freezing profile was absent, and the distribution in the number of individuals exhibiting freezing-like behaviour shifted to unimodal. In these groups, even at the individual level, responses more often showed a transition from high-speed swimming to normal swimming rather than freezing. The results indicate that cohabitation promotes synchronous freezing-like behaviour and consensus decisions under looming threat. Our study presents a behavioural assay for predator-evoked collective decision-making in a genetic model fish, providing a framework laying the groundwork for future efforts to link behavioural ethology with neuroscience.

animal behavior and cognition↗

bioRxiv2022

F-actin regulates polarized secretion of pollen tube attractants in Arabidopsis synergid cell.

Pollen tube attraction is a key event of sexual reproduction in flowering plants. In the ovule, two synergid cells neighboring the egg cell control pollen tube arrival via the active secretion of attractant peptides such as AtLURE1 and XIUQIU from the filiform apparatus facing toward the micropyle. Distinctive cell polarity together with longitudinal F-actin and microtubules are hallmarks of the synergid cell in various species, though functions of these cellular structures are still unclear. In this study we used genetic and pharmacological approaches to elucidate the roles of cytoskeletal components in filiform apparatus formation and pollen tube guidance in Arabidopsis thaliana. Inhibition of microtubule formation reduced invaginations of the plasma membrane but did not abolish micropylar AtLURE1.2 accumulation. In contrast, the expression of a dominant-negative form of ACTIN8 induced disorganization of the filiform apparatus and loss of polar AtLURE1.2 distribution toward the filiform apparatus. Interestingly, after pollen tube reception, F-actin became unclear for a few hours in the persistent synergid cell, which may be involved in pausing and resuming pollen tube attraction during early polytubey block. Our data propose the central role of F-actin in the maintenance of cell polarity and function of male-female communication in the synergid cell.

plant biology↗

bioRxiv2021

Comprehensive O-GlcNAc glycoproteomics on NOTCH1 EGF repeats refined sequons for O-GlcNAcylation and uncovered unique Lewis X epitopes in mammals

The O-GlcNAc modification of Notch receptors regulates Notch ligand interactions in a manner distinct from other forms of O-glycans on epidermal growth factor-like (EGF) repeats of Notch receptors. Although many proteins, besides Notch receptors, are expected to be O-GlcNAcylated by EGF domain-specific O-GlcNAc transferase (EOGT), only a small number of proteins have been reported to be modified in vivo, and elongated O-GlcNAc glycans have not been extensively explored. To extend our view of the specificity and variety of the glycan modification, we conducted a comprehensive analysis of O-GlcNAc glycans on NOTCH1 in mammals. Mass spectrometric analysis of NOTCH1 fragments expressed in HEK293T cells revealed that several EGF domains with putative O-GlcNAcylation sites were hardly modified with O-GlcNAc. Although amino acid residues before the modification site are preferentially occupied with aromatic residues, Phe and Tyr are preferable to Trp for the apparent modification with O-GlcNAc. Furthermore, a minor form of fucosylated O-GlcNAc glycans was detected in a subset of EGF domains. Fucosylation of O-GlcNAc glycans was enhanced by FUT1, FUT2, or FUT9 expression. The FUT9-dependent Lewis X epitope was confirmed by immunoblotting using an anti-Lewis X antibody. As expected from the similarity in the glycan structures, the Lexis X antigen was detected on O-fucose glycans. Our results refined the putative consensus sequence for the EOGT-dependent extracellular O-GlcNAc modification in mammals and revealed the structural diversity of functional Notch O-glycans.

biochemistry↗

bioRxiv2021

Macrophages in the reticuloendothelial system inhibit the propagation phase of mouse apolipoprotein A-II amyloidosis

Amyloidosis refers to a group of degenerative diseases that are characterized by the deposition of misfolded protein fibrils in various organs. Deposited amyloid may be removed by a phagocyte-dependent innate immune system; however, the precise mechanisms during disease progression remain unclear. We herein investigated the properties of macrophages that contribute to amyloid degradation and disease progression using transmissible apolipoprotein A-II amyloidosis model mice. Intravenously injected AApoAII amyloid was efficiently engulfed by reticuloendothelial macrophages in the liver and spleen and disappeared by 24 h. While cultured murine macrophages degraded AApoAII via the endosomal-lysosomal pathway, AApoAII fibrils reduced cell viability and phagocytic capacity. Furthermore, the depletion of reticuloendothelial macrophages prior to the induction of AApoAII markedly increased hepatic and splenic AApoAII deposition. These results highlight the physiological role of reticuloendothelial macrophages against inter-individual amyloid propagation and suggest the maintenance of phagocytic integrity as a therapeutic strategy to inhibit disease progression.

molecular biology↗

bioRxiv2020

Interleukin-19 alleviates experimental autoimmune encephalomyelitis by attenuating antigen-presenting cell activation

Interleukin-19 (IL-19) acts as an anti-inflammatory cytokine in various inflammatory diseases. Multiple sclerosis (MS) is a major neuroinflammatory disease in the central nervous system, but it remains uncertain how IL-19 contributes to MS pathogenesis. Here, we demonstrate that IL-19 deficiency aggravates experimental autoimmune encephalomyelitis (EAE), a mouse model of MS, by promoting IL-17-producing helper T cell (Th17 cell) infiltration into the central nervous system. In addition, IL-19-deficient splenic macrophages expressed elevated levels of major histocompatibility complex class II, co-stimulatory molecules, and Th17 cell differentiation-associated cytokines such as IL-1{beta}, IL-6, IL-23, TGF-{beta}1, and TNF-. These observations indicated that IL-19 plays a critical role in suppression of MS pathogenesis by inhibiting macrophage antigen presentation, Th17 cell expansion, and subsequent inflammatory responses. Furthermore, treatment with IL-19 significantly abrogated EAE. Our data suggest that IL-19 could provide significant therapeutic benefits in patients with MS.

immunology↗

bioRxiv2020

Functional analysis of the chromosomal passenger complex in Arabidopsis

A key regulator of cell division in all eukaryotes is the kinase Aurora B, which is encoded by the Aurora 3 (AUR3) gene in Arabidopsis. Aurora B has at least two central functions during cell division. On the one hand, it is essential for the correct, i.e. balanced, segregation of chromosomes in mitosis and meiosis by controlling kinetochore function. On the other hand, Aurora B acts at the division plane, where it is necessary to complete cytokinesis. To accomplish these two spatially distinct functions, Aurora B in animals is guided to its sites of action by Borealin, INCENP, and Survivin that build together with Aurora B the chromosome passenger complex (CPC). However, besides Aurora homologs, only a candidate gene with restricted homology to INCENP has so far been described in Arabidopsis raising the question whether there exists a full complement of the CPC in plants and how Aurora homologs are targeted subcellularly. Here, we have identified and functionally characterized a Borealin homolog, BOREALIN RELATED (BORR), in Arabidopsis. This, together with detailed localization studies including the putative Arabidopsis INCENP homolog, supports the existence of a CPC in plants.

cell biology↗

bioRxiv2019

Auxin-mediated rapid degradation of selective proteins in hippocampal neurons

Genetic manipulation of protein levels is a promising approach to identify the function of a specific protein in living organisms. Previous studies demonstrated that the auxin-inducible degron (AID) strategy provides rapid and reversible degradation of various proteins in fungi and mammalian mitotic cells. In this study, we employed this technology to postmitotic neurons to address whether the AID system could be applied to the nervous system. Using adeno-associated viruses, we simultaneously introduced EGFP fused with an AID tag, and an F-box family protein, TIR1 from Oryza sativa (OsTIR1) into hippocampal neurons. In dissociated hippocampal neurons, EGFP fluorescence signals rapidly decreased when adding a plant hormone, auxin. Further, auxin-induced EGFP degradation was also observed in hippocampal acute slices. Taken together, these results open the door for neuroscientists to manipulate protein expression levels by the AID-system in a temporally-controlled manner.

neuroscience↗

bioRxiv2019

Long-read sequencing identifies GGC repeat expansion in human-specific NOTCH2NLC associated with neuronal intranuclear inclusion disease

Neuronal intranuclear inclusion disease (NIID) is a progressive neurodegenerative disease characterized by eosinophilic hyaline intranuclear inclusions in neuronal and somatic cells. The wide range of clinical manifestations in NIID makes ante-mortem diagnosis difficult 1-8, but skin biopsy realized its ante-mortem diagnosis 9,10 and many NIID cases have been diagnosed by skin biopsy11,12. Most cases of NIID are sporadic, but several familial cases are known. Using a large NIID family, we conducted linkage mapping, found a 58.1-Mb linked-region at 1p22.1-q21.3 with a maximum logarithm of odds (LOD) score of 4.21, and successfully identified a GGC repeat expansion in the 5 portion of NOTCH2NLC in all affected members by long-read sequencing, but not in unaffected members. We further found the similar expansions in additional 8 unrelated families with NIID as well as 39 sporadic NIID patients. Repeat-primed PCR consistently detected the GGC repeat expansion in all the familial and sporadic patients diagnosed by skin biopsy, but never in unaffected family members nor 200 controls. This shows that pathogenic changes in a human-specific gene evolutionarily generated by segmental duplication indeed causes a human disease.

genetics↗

bioRxiv2018

Sharp wave-associated activity patterns of olfactory cortical neurons in the mouse piriform cortex

The olfactory piriform cortex is thought to participate in olfactory associative memory. Like the hippocampus, which is essential for episodic memory, it belongs to an evolutionally conserved paleocortex and comprises a three-layered cortical structure. During slow-wave sleep, the olfactory piriform cortex becomes less responsive to external odor stimuli and instead displays sharp wave (SPW) activity similar to that observed in the hippocampus. Neural activity patterns during hippocampal SPW have been intensively studied in terms of memory consolidation; however, little is known about the activity patterns of olfactory cortical neurons during olfactory cortex sharp waves (OC-SPWs). In this study, we recorded multi-unit neural activities in the anterior piriform cortex in urethane-anesthetized mice. We found that the activity patterns of olfactory cortical neurons during OC-SPWs were non-randomly organized. Individual olfactory cortical neurons varied in the timings of their peak firing rates during OC-SPW events. Moreover, specific pairs of olfactory cortical neurons were more frequently activated together than expected by chance. On the basis of these observations, we speculate that coordinated activation of specific subsets of olfactory cortical neurons repeats during OC-SPWs, thereby facilitating synaptic plasticity underlying the consolidation of olfactory associative memories.

neuroscience↗