Biology subjects

Kawashima, T.

Publications and source records attributed to Kawashima, T..

28 records · Page 2Linked to original sources

bioRxiv2021

Voltage imaging identifies spinal circuits that modulate locomotor adaptation in zebrafish

Motor systems must continuously adapt their output to maintain a desired trajectory. While the spinal circuits underlying rhythmic locomotion are well described, little is known about how the network modulates its output strength. A major challenge has been the difficulty of recording from spinal neurons during behavior. Here, we use voltage imaging to map the membrane potential of glutamatergic neurons throughout the spinal cord of the larval zebrafish during fictive swimming in a virtual environment. We mapped the spiking, subthreshold dynamics, relative timing, and sub-cellular electrical propagation across large populations of simultaneously recorded cells. We validated the approach by confirming properties of known sub-types, and we characterized a yet undescribed sub-population of tonic-spiking ventral V3 neurons whose spike rate correlated with swimming strength and bout length. Optogenetic activation of V3 neurons led to stronger swimming and longer bouts but did not affect tail-beat frequency. Genetic ablation of V3 neurons led to reduced locomotor adaptation. The power of voltage imaging allowed us to identify V3 neurons as a critical driver of locomotor adaptation in zebrafish.

neuroscience↗

bioRxiv2020

Comparative transcriptomic analysis reveals conserved transcriptional programs underpinning organogenesis and reproduction in land plants

The evolution of plant organs, including leaves, stems, roots, and flowers, mediated the explosive radiation of land plants, which shaped the biosphere and allowed the establishment of terrestrial animal life. Furthermore, the fertilization products of angiosperms, seeds serve as the basis for most of our food. The evolution of organs and immobile gametes required the coordinated acquisition of novel gene functions, the co-option of existing genes, and the development of novel regulatory programs. However, our knowledge of these events is limited, as no large-scale analyses of genomic and transcriptomic data have been performed for land plants. To remedy this, we have generated gene expression atlases for various organs and gametes of 10 plant species comprising bryophytes, vascular plants, gymnosperms, and flowering plants. Comparative analysis of the atlases identified hundreds of organ- and gamete-specific gene families and revealed that most of the specific transcriptomes are significantly conserved. Interestingly, the appearance of organ-specific gene families does not coincide with the corresponding organs appearance, suggesting that co-option of existing genes is the main mechanism for evolving new organs. In contrast to female gametes, male gametes showed a high number and conservation of specific genes, suggesting that male reproduction is highly specialized. The expression atlas capturing pollen development revealed numerous transcription factors and kinases essential for pollen biogenesis and function. To provide easy access to the expression atlases and these comparative analyses, we provide an online database, www.evorepro.plant.tools, that allows the exploration of expression profiles, organ-specific genes, phylogenetic trees, co-expression networks, and others.

evolutionary biology↗

bioRxiv2019

Atypical spatial frequency dependence of visual metacognition among schizophrenia patients

Although altered early stages of visual processing have been reported among schizophrenia patients, how such atypical visual processing may affect higher-level cognition remains largely unknown. Here we tested the hypothesis that metacognitive performance may be atypically modulated by spatial frequency (SF) of visual stimuli among individuals with schizophrenia, given their altered magnocellular function. To study the effect of SF on metacognitive performance, we asked patients and controls to perform a visual detection task on gratings with different SFs and report confidence, and analyzed the data using the signal detection theoretic measure meta-d. Control subjects showed better metacognitive performance after yes- (stimulus-presence) than after no- (stimulus-absence) responses ( yes-response advantage) for high SF (HSF) stimuli but not for low SF (LSF) stimuli. The patients, to the contrary, showed a yes-response advantage not only for HSF but also for LSF stimuli, indicating atypical SF dependency of metacognition. An fMRI experiment using the same task revealed that the dorsolateral prefrontal cortex (DLPFC), known to be crucial for metacognition, shows activity mirroring the behavioral results: decoding accuracy of perceptual confidence in DLPFC was significantly higher for HSF than for LSF stimuli in controls, whereas this decoding accuracy was independent of SF in patients. While individuals without schizophrenia may flexibly adapt metacognitive computations across SF ranges, patients may employ a different mechanism that is independent of SF. Because visual stimuli of low SF have been linked to top-down processing in predictive coding, this may reflect atypical functioning in these processes in schizophrenia. HighlightsO_LIVisual metacognition of controls was dependent on spatial frequency. C_LIO_LIVisual metacognition of schizophrenia patients was independent of spatial frequency. C_LIO_LIPatients and controls differently rely on the dorsolateral prefrontal cortex. C_LIO_LISensory inputs may reach metacognitive circuits in an atypical manner among patients. C_LI

neuroscience↗

bioRxiv2019

Estrogenic action by tris(2,6-dimethylphenyl) phosphate, an impurity in resorcinol bis flame retardant formulations, impairs the development of female reproductive functions

BackgroundDevelopmental exposure to environmental chemicals with estrogen-like activity has been suspected to permanently impair womens health. ObjectivesIn this study, we used a mouse model to evaluate whether a chemical having putative estrogen-like action detected by in vitro study, namely tris(2,6-dimethylphenyl) phosphate (TDMPP) impairs sexual differentiation of the brain. MethodsTo induce developmental exposure, TDMPP was administered subcutaneously to dams from gestational day 14 to parturition and to pups from postnatal day 0 to 9 at two different doses (TDMPP-high and TDMPP-low groups, respectively). To compare the results between TDMPP and typical estrogen exposures, 17{beta}-estradiol was administered at two different doses on the same treatment schedule (E2-low and E2-high groups, respectively). A vehicle control group was formed by administering an equivalent volume of sesame oil to dams and to pups. ResultsAlthough there was no specific impairment in female ovary morphology, precocious puberty, detected by vaginal opening, and irregular estrous cycles, detected by vaginal cytology after sexual maturation, were found in TDMPP- and E2-treated groups, but not in the vehicle control group. In addition, lower lordosis response during reproductive behavioral tests was found in TDMPP- or E2-treated groups. To further clarify whether TDMPP directly affects sexual differentiation of the brain, we evaluated the transfer of TDMPP into the brain and the formation of sexual dimorphic nuclei. We detected a certain amount of TDMPP and its metabolites in the mouse brain after treatment, and masculinization of sexual dimorphic nuclei in the hypothalamus of female mice, suggesting the direct impact of TDMPP in developing brain. DiscussionTaken together, the experimental evidence demonstrates that TDMPP directly enters the fetal and neonatal brain, inducing changes of sex-related brain structures, and impairing female reproductive functions.

pharmacology and toxicology↗

bioRxiv2019

Dissociating orexin-dependent and -independent functions of orexin neurons using novel orexin-Flp knock-in mice

Uninterrupted arousal is important for survival during threatening situations. Activation of orexin/hypocretin neurons is implicated in sustained arousal. However, orexin neurons produce and release orexin as well as several co-transmitters including dynorphin and glutamate. Thus, it is important to disambiguate orexin peptide-dependent and -independent physiological functions of orexin neurons. To attain this, we generated a novel orexin-flippase (Flp) knock-in (KI) mouse line. Crossing with Flp-reporter or Cre-expressing mice showed gene expression exclusively in orexin neurons. Histological studies confirmed that orexin was completely knock-out (KO) in KI/KI homozygous mice. Orexin neurons without orexin showed altered electrophysiological properties, as well as received decreased glutamatergic inputs. Selective chemogenetic activation revealed that both orexin and co-transmitters functioned to increase wakefulness, however, orexin was indispensable to promote sustained arousal. Surprisingly, activation of orexin neurons without orexin caused a significant increase in the total time spent in cataplexy. Taken together, orexin is essential to maintain basic membrane properties and input-output computation of orexin neurons, as well as to exert awake-sustaining aptitude of orexin neurons.

neuroscience↗

bioRxiv2018

Development of the Brief Personal Values Inventory for sense of values in the Japanese general population

The Portrait Values Questionnaire (PVQ) is a widely used questionnaire for assessing sense of values; however, it has limitations, especially for children. Therefore, the present study aims to develop a questionnaire for sense of values, called the Brief Personal Values Inventory (BPVI), consisting of simple questions and a smaller number of items compared to the PVQ. We first created 12 items for the BPVI and then tested their validity and reliability in 167 Japanese general population (81 males, mean age (SD) [range]: 23.4 (8.2) [15-57] years). Each of these items was correlated with one or more values in the PVQ-57. The BPVI items covered all higher-order values in Schwartzs theory (Openness to Change, Self-Enhancement, Conservation, and Self-Transcendence). In sum, the BPVI has an acceptable criterion-related validity and corresponds to higher-order values in Schwartzs value theory. The BPVI is suitable for a reliable and direct comparison of sense of values between children and adults, which may be useful for elucidating the developmental pathway of personal sense of values.

scientific communication and education↗

bioRxiv2018

Bright and photostable chemigenetic indicators for extended in vivo voltage imaging

Imaging changes in membrane potential using genetically encoded fluorescent voltage indicators (GEVIs) has great potential for monitoring neuronal activity with high spatial and temporal resolution. Brightness and photostability of fluorescent proteins and rhodopsins have limited the utility of existing GEVIs. We engineered a novel GEVI, Voltron, that utilizes bright and photostable synthetic dyes instead of protein-based fluorophores, extending the combined duration of imaging and number of neurons imaged simultaneously by more than tenfold relative to existing GEVIs. We used Voltron for in vivo voltage imaging in mice, zebrafish, and fruit flies. In mouse cortex, Voltron allowed single-trial recording of spikes and subthreshold voltage signals from dozens of neurons simultaneously, over 15 minutes of continuous imaging. In larval zebrafish, Voltron enabled the precise correlation of spike timing with behavior.

neuroscience↗

bioRxiv2018

A genetically encoded fluorescent sensor for in vivo imaging of GABA

Current techniques for monitoring GABA, the primary inhibitory neurotransmitter in vertebrates, cannot follow ephemeral transients in intact neural circuits. We applied the design principles used to create iGluSnFR, a fluorescent reporter of synaptic glutamate, to develop a GABA sensor using a protein derived from a previously unsequenced Pseudomonas fluorescens strain. Structure-guided mutagenesis and library screening led to a usable iGABASnFR ({Delta}F/Fmax ~ 2.5, Kd ~ 9 M, good specificity, adequate kinetics). iGABASnFR is genetically encoded, detects single action potential-evoked GABA release events in culture, and produces readily detectable fluorescence increases in vivo in mice and zebrafish. iGABASnFR enabled tracking of: (1) mitochondrial GABA content and its modulation by an anticonvulsant; (2) swimming-evoked GABAergic transmission in zebrafish cerebellum; (3) GABA release events during inter-ictal spikes and seizures in awake mice; and (4) GABAergic tone decreases during isoflurane anesthesia. iGABASnFR will permit high spatiotemporal resolution of GABA signaling in intact preparations.

neuroscience↗

bioRxiv2018

A shared cis-regulatory module activates transcription in the suspensor of plant embryos

The mechanisms controlling the transcription of gene sets in specific regions of a plant embryo shortly after fertilization remain unknown. Previously, we showed that G564 mRNA, encoding a protein of unknown function, accumulates to high levels in the giant suspensor of both Scarlet Runner Bean (SRB) and Common Bean embryos, and a cis-regulatory module containing three unique DNA sequences, designated as the 10-bp, Region 2, and Fifth motifs, is required for G564 suspensor-specific transcription [Henry, K. F. et al., Plant Mol. Biol. 88(3):207-217 (2015); Kawashima, T. et al., Proc. Natl. Acad. Sci USA 106(9):3627-3632 (2009)]. We tested the hypothesis that these motifs are also required for transcription of the SRB GA 20-oxidase gene, which encodes a gibberellic acid hormone biosynthesis enzyme and is co-expressed with G564 at a high level in giant bean suspensors. We used deletion and gain-of-function experiments in transgenic tobacco embryos to show that two GA 20-oxidase DNA regions are required for suspensor-specific transcription - one in the 5 untranslated region (UTR) (+119 to +205) and another in the 5 upstream region (-341 to -316). Mutagenesis of sequences in these two regions determined that the cis-regulatory motifs required for G564 suspensor transcription are also required for GA 20-oxidase transcription within the suspensor, although the motif arrangement differs. Our results demonstrate the flexibility of motif positioning within a cis-regulatory module that activates gene transcription within giant bean suspensors, and suggest that G564 and GA 20-oxidase comprise part of a suspensor gene regulatory network.\n\nSignificanceLittle is known about how genes are expressed in different plant embryo regions. We tested the hypothesis that shared cis-regulatory motifs control the transcription of genes specifically in the suspensor. We carried out functional studies with the Scarlet Runner Bean (SRB) GA 20-oxidase gene that encodes a gibberellic acid (GA) hormone biosynthesis enzyme, and is expressed specifically within the suspensor. We show that cis-regulatory motifs required for GA 20-oxidase transcription within the suspensor are the same as those required for suspensor-specific transcription of the SRB G564 gene, although motif number, spacing and order differ. These cis-elements constitute a control module that is required to activate genes in the SRB suspensor and may form part of a suspensor regulatory network.

plant biology↗

bioRxiv2017

Collaborative environmental DNA sampling from petal surfaces of flowering cherry Cerasus ×- yedoensis 'Somei-yoshino' across the Japanese archipelago

Recent studies have shown that environmental DNA is found almost everywhere. Flower petal surfaces are an attractive tissue to use for investigation of the dispersal of environmental DNA in nature as they are isolated from the external environment until the bud opens and only then can the petal surface accumulate environmental DNA. Here, we performed a crowdsourced experiment, the \"Ohanami Project\", to obtain environmental DNA samples from petal surfaces of Cerasus x yedoensis Somei-yoshino across the Japanese archipelago during spring 2015. C. x yedoensis is the most popular garden cherry species in Japan and clones of this cultivar bloom simultaneously every spring. Data collection spanned almost every prefecture and totaled 577 DNA samples from 149 collaborators. Preliminary amplicon-sequencing analysis showed the rapid attachment of environmental DNA onto the petal surfaces. Notably, we found DNA of other common plant species in samples obtained across a wide distribution; this DNA likely originated from pollen of the Japanese cedar. Our analysis supports our belief that petal surfaces after blossoming are a promising target to reveal the dynamics of environmental DNA in nature. The success of our experiment also shows that crowdsourced environmental DNA analyses have considerable value in ecological studies.

microbiology↗