Biology subjects

Takahashi, J.

Publications and source records attributed to Takahashi, J..

13 recordsLinked to original sources

bioRxiv2026

Adolescent prodromal phenotypes of psychiatric disorders: insights from a novel DISC1-perturbed monkey model

Neurodevelopmental deficits frequently lead to mild but significant adolescent social and cognitive changes, representing prodromal manifestations of adult-onset psychiatric disorders in a cross-disease manner. Although experimental medicine utilizes animal models to address the mechanisms, rodent brains lack critical structures for human higher brain functions such as the dorsolateral prefrontal cortex. To fill this translational gap, we generated monkeys with an impaired DISC1 gene locus, targeting the multifunctional protein essential for neurodevelopment and involved in transdiagnostic mental health risks. Here we analyze the F0 animals by minimizing mosaicism. At ages equivalent to human adolescence, these monkeys exhibited blunted responsiveness to social stimuli and increased internal drives, mirroring altered social behaviors in the prodromal stage in humans. Resting-state functional MRI data indicated disrupted global functional connectivity and reorganization of network topology, marked by a shift in the dominance of brain hubs from prefrontal regions to sensory areas. This primate model provides a unique platform for studying psychiatric disorders, such as schizophrenia, across the developmental trajectory.

neuroscience↗

bioRxiv2026

Oxygen-permeable microwell plates for high-throughput spheroid culture

Oxygen (O2) transport is a major limitation in high-density cell culture, particularly as three-dimensional (3D) spheroids are increasingly used to better mimic in vivo tissue environments. Here, we developed a poly(4-methyl-1-pentene) (PMP)-based microwell platform, leveraging its lower molecular absorption and greater mechanical stability than the commonly used O2-permeable polydimethylsiloxane (PDMS), while retaining high O2 permeability. We measured O2 permeability in 50-m-thick PMP membranes and found approximately 200-fold greater O2 permeability than the conventional 1-mm polystyrene culture-plate material. PMP membrane-based microwell plates with 350-m-diameter wells maintained spatial separation of pre-formed hepatocyte spheroids while supplying O2 from the plate bottom, synergistically enhancing spheroid oxygenation. Compared with non-O2-permeable plates, the platform reduced localized hypoxia and hypoxia-associated cell injury while improving spheroid viability and growth. Collectively, PMP-based O2-permeable microwell plates provide a promising, scalable, high-throughput platform for spheroid culture with multiple applications in tissue engineering, drug screening and beyond.

bioengineering↗

bioRxiv2026

Modeling interregional propagation of α-synuclein in human striatal-midbrain assembloids

Parkinsons disease is characterized by the progressive degeneration of dopaminergic (DA) neurons in the substantia nigra that project to the striatum. Postmortem studies have found that -synuclein pathology spreads across brain regions in a prion-like manner. Human three-dimensional neural tissues provide experimentally tractable platforms for clarifying the molecular pathology of synucleinopathy that overcome the limitations of postmortem brain studies. In this study, we established a human striatal-midbrain assembloid model enabling spatially and temporally controlled -synuclein induction after formation of the nigrostriatal pathway within hStrMAs. Human induced pluripotent stem cells (hiPSCs) were differentiated into striatal spheroids and midbrain spheroids, which were fused to reconstruct the nigrostriatal pathway in vitro. Histological, electrophysiological, and single-cell RNA sequencing analyses confirmed the generation of region-specific neuronal populations, including striatal GABAergic neurons and midbrain DA neurons, and demonstrated that distinct forebrain and ventral midbrain identities were preserved within assembloids. To model synucleinopathy, we generated a doxycycline-inducible -synuclein hiPSC line, permitting selective induction of -synuclein expression in the striatal region after assembloid formation. Spatially restricted -synuclein induction resulted in the progressive accumulation of phosphorylated and fibrillar -synuclein in midbrain DA neurons, indicating interregional propagation through established neural circuits. Transcriptomic analysis of the midbrain region revealed significant downregulation of DA identity and synaptic function genes, suggesting functional impairment of DA neurons following -synuclein propagation. These findings demonstrate that the human neural circuit architecture contributes to the interregional propagation of -synuclein pathology. Our controllable human assembloid platform provides a powerful experimental framework for dissecting the mechanisms of pathological protein spread and developing therapeutic strategies targeting molecular pathology in neurodegenerative diseases. Significance statementOne pathological feature of Parkinsons disease is the progressive spread of -synuclein pathology across brain regions. However, the molecular mechanisms underlying this process remain poorly understood. In this study, we established a human striatal-midbrain assembloid model in which -synuclein expression can be spatially restricted and temporally induced after the nigrostriatal pathway is formed, thus enabling the experimental dissection of interregional -synuclein propagation across brain regions. We demonstrated that -synuclein pathology initiated in the striatal region propagated to midbrain dopaminergic neurons, leading to disease-relevant molecular and transcriptional alterations. These findings provide direct evidence that human neural circuits contribute to the spread of synucleinopathy and offer a controllable human model for studying disease progression and therapeutic strategies.

neuroscience↗

bioRxiv2025

Intrathecal administration of palmitoyl-lysophosphatidylethanolamine reduces secondary injury and improves locomotor recovery following spinal cord injury

Spinal cord injury (SCI) triggers secondary pathophysiological cascades, including glutamate excitotoxicity, that result in neuronal loss and impair functional recovery. We have previously shown that lysophosphatidylethanolamine (LPE), a lysophospholipid, promotes neurite outgrowth and protects against glutamate excitotoxicity in cultured cortical neurons. However, whether these effects extend to spinal cord neurons and occur in vivo has remained unclear. In this study, we compared the effects of different LPE species: myristoyl-LPE (14:0 LPE), palmitoyl-LPE (16:0 LPE), stearoyl-LPE (18:0 LPE), and oleoyl-LPE (18:1 LPE) in cultured spinal commissural neurons, and evaluated their effects in vivo using a mouse model of SCI. In cultured neurons, all LPE species promoted neurite outgrowth. Although several species demonstrated a tendency toward neuroprotection, only 16:0 LPE exhibited a statistically significant protective effect against glutamate-induced excitotoxic cell death. Intrathecal administration of 16:0 LPE after SCI reduced TUNEL-positive cells in the acute phase and attenuated lesion expansion at 8 weeks post-injury. Moreover, 5-HT fluorescence intensity was increased in 16:0 LPE-treated mice, suggesting enhanced serotonergic innervation. Furthermore, administration of 16:0 LPE after SCI significantly improved hind-limb motor performance compared with vehicle controls, as assessed by the Basso Mouse Scale. Collectively, these findings suggest that intrathecal administration of 16:0 LPE reduces secondary injury and promotes functional recovery following SCI. Our findings highlight its potential as a therapeutic candidate for SCI.

neuroscience↗

bioRxiv2025

Induction and long-term maintenance of hindbrain-like neural stem cells in xeno- and basic fibroblast growth factor-free conditions

Neurons exhibit region-specific identities corresponding to functional distinctions across different brain areas. Region-restricted neural stem cells (NSCs) have previously been generated from pluripotent stem cells; however, maintaining their regional identity over extended passages remains challenging. Here, we report the generation of hindbrain-like induced NSCs (Hb-LiNSCs) with upregulated hindbrain-specific markers and downregulated forebrain, midbrain, and spinal cord markers under xeno- and basic fibroblast growth factor-free conditions using three chemicals--CHIR99021 (at a high concentration), a potent activator of the Wnt pathway, A-83-01, a potent inhibitor of the TGF-{beta}/Activin/Nodal pathway, and LDN193189, a potent inhibitor of the bone morphogenetic protein pathway. Hb-LiNSCs maintained their chromosomal integrity, multipotency, and differentiation capacity even after long-term culture for more than 60 weeks. This innovative approach enhances our understanding of neurodevelopmental and neurodegenerative processes in the hindbrain region and paves the way for developing targeted cell-based therapy as well as disease modeling for drug discovery.

cell biology↗

bioRxiv2023

Mammalian circadian clock proteins form dynamic interacting microbodies distinct from phase separation

Liquid-liquid phase separation (LLPS) underlies diverse biological processes. Because most LLPS studies were performed in vitro or in cells that overexpress protein, the physiological relevance of LLPS is unclear. PERIOD proteins are central mammalian circadian clock components and interact with other clock proteins in the core circadian negative feedback loop. Different core clock proteins were previously shown to form large complexes. Here we show that when transgene was stably expressed, PER2 formed nuclear phosphorylation-dependent LLPS condensates that recruited other clock proteins. Super-resolution microscopy of endogenous PER2, however, revealed formation of circadian-controlled, rapidly diffusing microbodies that were resistant to protein concentration changes, hexanediol treatment, and loss of phosphorylation, indicating that they are distinct from the LLPS condensates caused by overexpression. Surprisingly, only a small fraction of endogenous PER2 microbodies transiently interact with endogenous BMAL1 and CRY1, a conclusion that was confirmed in cells and in mice tissues, suggesting an enzyme-like mechanism in the circadian negative feedback process. Together, these results demonstrate that the dynamic interactions of core clock proteins is a key feature of mammalian circadian clock mechanism and the importance of examining endogenous proteins in LLPS and circadian studies.

genetics↗

bioRxiv2023

State-dependent role of interhemispheric pathway for motor recovery in primates

Whether and how the interhemispheric pathway is involved in post-injury motor recovery is controversial. Unidirectional chemogenetic blockade of the interhemispheric pathway from the contralesional to ipsilesional premotor cortex impaired dexterous hand movements during the early recovery stage after lesioning the lateral corticospinal tract in macaques. Furthermore, electrocorticographical recording showed that the low frequency band activity of the ipsilesional premotor cortex around the movement onset was decreased by the blockade during the early recovery stage, while it was increased by blockade during the intact state and the late recovery stage. These results demonstrate that the action of the interhemispheric pathway changed from inhibition to facilitation, leading to the involvement of the ipsilesional sensorimotor cortex in hand movements during the early recovery stage. The present study offers new insights into the state-dependent role of the interhemispheric pathway and a therapeutic target in the early recovery stage after lesioning of the corticospinal tract.

neuroscience↗

bioRxiv2023

Global disinhibition and corticospinal plasticity for drastic recovery after spinal cord injury

The induction of large-scale plasticity in the adult brain should be key for recovery from severe damage of the central nervous system. Here, drastic motor recovery was observed after subhemisection spinal cord injury in macaques that received intensive training and cortical electrical stimulation. During recovery, movement-related activity increased in ipsilesional sensorimotor areas and functional connectivity from ipsilesional to contralesional areas was strengthened. Electrical stimulation applied widely across bilateral sensorimotor areas induced muscle twitches in affected and intact forelimbs. The interhemispheric inhibition observed before injury was switched to facilitation. Furthermore, massive re-routing occurred in corticospinal axons from the contralesional motor cortex. Such global disinhibition and massive plasticity would open the workspace for the reorganization of motor networks to recruit novel areas for recovery. One Sentence SummaryGlobal disinhibition and corticospinal plasticity for drastic recovery after spinal cord injury in macaque monkeys.

neuroscience↗

bioRxiv2023

Visuomotor activity associated with conditioned hand movements in premotor cortex of blindsight macaques

Some patients with damage to the primary visual cortex (V1) can respond to visual stimuli in their affected visual field, even though they report loss of visual awareness. This phenomenon is termed blindsight. To clarify the visuomotor transformation for hand movement control in the blindsight condition, we conducted multichannel electrocorticographical recordings from the ipsilesional frontal cortex including the frontal eye field, premotor, primary motor, and somatosensory areas during a delayed conditioned two-alternative forced choice manual response task with arbitrary assignment of push-pull manual responses in relation to the visual target cue locations before and after unilateral V1 lesioning in macaque monkeys. Before lesioning, the activity in the dorsal premotor cortex (PMd) showed short latency task-related {theta} ~ band responses that were significantly higher in the successful trials than in the error/miss trials at approximately 200 ms after target cue onset. At 2-3 months after lesioning, the monkeys regained a >80% success rate in response to appearance of the target cue in the lesion-affected visual field. At this stage, similar task-related {theta} ~ band target cue responses were observed in the PMd. Further, Granger causality from the PMd to the primary motor cortex was enhanced in the {theta} ~ , {gamma}, and high-{gamma} bands during the delay period of the task. These results suggested that the PMd plays a crucial role in mediating the visual signals for execution of hand movements in blindsight monkeys. Significant StatementBlindsight is a curious phenomenon in which the patients with damage to the primary visual cortex can still respond to visual stimulus in their blinded visual field despite loss of awareness. Previously we clarified the critical circuits for visually guided saccadic eye movements in blindsight macaques, however, those for the control of hand movements are still unclear. Here, we have recorded the multichannel electrocorticography in the frontal cortices during the conditioned manual response task and found that the dorsal premotor cortex exhibits task-related {theta} ~ band target cue responses at approximately 200 ms after the visual cue onset, similarly to the intact state. This is the first report of electrophysiological recordings in the frontal lobe of the blindsight subjects.

neuroscience↗

bioRxiv2022

Laccaria bicolor pectin methylesterases are involved in ectomycorrhiza development with Populus tremula x Populus tremuloides

O_LIThe development of ectomycorrhizal (ECM) symbioses between soil fungi and tree roots requires modification of root cell-walls. The pectin-mediated adhesion between adjacent root cells loosens to accommodate fungal hyphae in the Hartig Net, facilitating nutrient exchange between partners. We investigated the role of fungal pectin modifying enzymes in Laccaria bicolor for ECM formation with Populus tremula x Populus tremuloides. C_LIO_LIWe combine transcriptomics of cell-wall related enzymes in both partners during ECM formation, immunolocalization of pectin (Homogalacturonan, HG) epitopes in different methylesterification states, pectin methylesterase (PME) activity assays and functional analyses of transgenic L. bicolor to uncover pectin modification mechanisms and the requirement of fungal pectin methylesterases (LbPMEs) for ECM formation. C_LIO_LIImmunolocalization identified remodelling of pectin towards de-esterified HG during ECM formation, which was accompanied by increased LbPME1 expression and PME activity. Overexpression or RNAi of the ECM-induced LbPME1 in transgenic L. bicolor lines led to reduced ECM formation. Hartig Nets formed with LbPME1 RNAi lines were shallower, whereas those formed with LbPME1 over-expressors were deeper. C_LIO_LIThis suggests that LbPME1 plays a role in ECM formation potentially through HG-de-esterification, which initiates loosening of adjacent root cells to facilitate Hartig Net formation. C_LI

plant biology↗

bioRxiv2020

Versatile live-cell activity analysis platform for characterization of neuronal dynamics at single-cell and network level

Chronic imaging of neuronal networks in vitro has provided fundamental insights into mechanisms underlying neuronal function. Existing labeling and optical imaging methods, however, cannot be used for continuous and long-term recordings of the dynamics and evolution of neuronal networks, as fluorescence indicators can cause phototoxicity. Here, we introduce a versatile platform for label-free, comprehensive and detailed electrophysiological live-cell imaging of various neurogenic cells and tissues over extended times. We report on a novel dual-mode high-density microelectrode array, which can simultaneously record in i) full-frame mode with 19,584 recording sites and ii) high-signal-to-noise mode with 246 channels. We set out to demonstrate the capabilities of this platform with recordings from primary and iPSC-derived neuronal cultures and tissue preparations over several weeks, providing detailed morpho-electrical phenotypic parameters at subcellular, cellular and network level. Moreover, we developed reliable analysis tools with drastically increased throughput for extracting axonal morphology and conduction parameters.

neuroscience↗

bioRxiv2019

ELIMAKI locus is required for mechanosensing and proprioception in birch trees

The remarkable vertical and radial growth observed in tree species, encompasses a major physical challenge for wood forming tissues. To compensate with increasing size and weight, cambium-derived radial growth increases the stem width, thereby supporting the aerial body of trees. This feedback appears to be part of a so-called \"proprioception\" (1, 2) mechanism that controls plant size and biomass allocation. Yet, how trees experience or respond to mechanical stress derived from their own vertical loading, remains unknown. Here, we combined two strategies to dissect the proprioceptive response in birch. First, we show that in response to physical loading, trees promote radial growth with different magnitudes along the stem. Next, we identified a mutant cultivar (B. pubescens cv. Elimaki) in which the main stem shows normal vertical development, but collapses after three months. By inducing precocious flowering, we generated a backcrossed population (BC1) by producing two generations in 4 years. In his scheme, we uncovered a recessive trait (eki) that segregates and genetically maps with a Mendelian monogenic pattern. Unlike WT, eki is resistant to vertical mechanical stimulation. However, eki responds normally to the gravitropic stimulus by making tension wood. Before the collapse, cell size in eki is compromised resulting in radial growth defects, depending on stem height. Cell walls of developing xylem and phloem tissues have delayed differentiation in eki, and its tissues are softer compared to WT as indicated by atomic force microscopy (AFM). The transcriptomic profile of eki highlighted the overlap with that of the Arabidopsis response to touch. Taken together, our results suggest that the mechanical environment and cell wall properties of developing woody tissues, can significantly affect the growth responses to vertical loading thereby compromising their proprioceptive capacity. Additionally, we introduce a fast forward genetics strategy to dissect complex phenotypes in trees.

plant biology↗

bioRxiv2018

Mean-Variance QTL Mapping Identifies Novel QTL for Circadian Activity and Exploratory Behavior in Mice

We illustrate, through two case studies, that \"mean-variance QTL mapping\" can discover QTL that traditional interval mapping cannot. Mean-variance QTL mapping is based on the double generalized linear model, which elaborates on the standard linear model by incorporating not only a linear model for the data itself, but also a linear model for the residual variance. Its potential for use in QTL mapping has been described previously, but it remains underutilized, with certain key advantages undemonstrated until now. In the first case study, we use mean-variance QTL mapping to reanalyze a reduced complexity intercross of C57BL/6J and C57BL/6N mice examining circadian behavior and find a mean-controlling QTL for circadian wheel running activity that was not detected by traditional interval mapping. Mean-variance QTL mapping was more powerful than traditional interval mapping at the QTL because it accounted for the fact that mice homozygous for the C57BL/6N allele had less residual variance than the other mice. In the second case study, we reanalyze an intercross between C57BL/6J and C58/J mice examining anxiety-like behaviors, and identify a variance-controlling QTL for rearing behavior. This QTL was not identified in the original analysis because traditional interval mapping does not target variance QTL.

genetics↗