Biology subjects

Hori, K.

Publications and source records attributed to Hori, K..

26 records · Page 2Linked to original sources

bioRxiv2023

Structural polymorphism of the nucleic acids in pentanucleotide repeats associated with CANVAS

Short tandem repeats are highly unstable, depending on repeat length, and the expansion of the repeat length in the human genome is responsible for repeat expansion disorders. Pentanucleotide AAGGG and ACAGG repeat expansions in intron 2 of the gene encoding replication factor C subunit 1 (RFC1) cause cerebellar ataxia, neuropathy, vestibular areflexia syndrome (CANVAS) and other phenotypes of late-onset cerebellar ataxia. Herein, we reveal the structural polymorphism of the RFC1 repeat sequences associated with CANVAS in vitro. Single-stranded AAGGG repeat DNA formed a hybrid-type G-quadruplex, whereas its RNA formed a parallel-type G-quadruplex with three layers. The RNA of the ACAGG repeat sequence formed double helical hairpin structures comprising C-G and G-C base pairs with A:A and GA:AG mismatched repeats. Furthermore, both pathogenic repeat RNAs formed more rigid structures than those of the non-pathogenic sequences. These findings provide novel insights into the structural polymorphism of the RFC1 repeat sequences, which may be closely related to the disease mechanism of CANVAS.

biophysics↗

bioRxiv2023

RNA G-quadruplexes forming scaffolds for alpha-synuclein aggregation lead to progressive neurodegeneration

Synucleinopathies, including Parkinsons disease, dementia with Lewy bodies, and multiple system atrophy, are triggered by the aggregation of -synuclein, leading to progressive neurodegeneration1,2,3,4,5,6,7,8. However, the intracellular mechanism of -synuclein aggregation remains unclear. Here we show that assembly of RNA G-quadruplexes forming scaffolds for -synuclein aggregation, contributing to neurodegeneration. Purified -synuclein binds RNA G-quadruplexes directly through the N-terminus. RNA G-quadruplex itself undergoes phase separation and assembly by Ca2+, accelerating the sol-gel phase transition of -synuclein. In -synuclein preformed fibrils-treated neurons, RNA G-quadruplexes assembly composed of synaptic mRNAs co-aggregates with -synuclein upon Ca2+ excess influx into cytoplasm, eliciting synaptic dysfunction. Forced assembly of RNA G-quadruplexes using an optogenetic approach evokes -synuclein aggregation, neuronal dysfunction and neurodegeneration. Administration of 5-aminolevulinic acid, a prodrug of protoporphyrin IX that prevents phase separation of RNA G-quadruplexes9, attenuating -synuclein aggregation, neurodegeneration, and progressive motor deficits in -synuclein preformed fibrils-injected synucleinopathy mice. Together, assembly of RNA G-quadruplexes due to dysregulation of intracellular Ca2+ homeostasis accelerates -synuclein phase transition and aggregation may contribute to pathogenesis of synucleinopathies.

molecular biology↗

bioRxiv2021

Hidden pathway for cytokine receptor activation: Structural insights into a marine sponge-derived lectin that activates the thrombopoietin receptor via recognition of the fucose moiety

N-glycan-mediated activation of the thrombopoietin receptor (MPL) under pathological conditions has been implicated in myeloproliferative neoplasms induced by mutant calreticulin, which forms an endogenous receptor-agonist complex that constitutively activates the receptor. However, the molecular basis for this mechanism has not been studied because no external agonists existed. We describe the structure and function of a marine sponge-derived MPL agonist, thrombocorticin (ThC), a homodimerized lectin with calcium-dependent fucose-binding properties. ThC-induced activation persists due to limited receptor internalization. The strong synergy between ThC and thrombopoietin suggests that ThC catalyzes the formation of receptor dimers on the cell surface. MPL is subject to sugar-mediated activation, where the kinetics differ from those of cytokines. This result suggests the presence of diverse receptor activation pathways in human thrombopoiesis. One-sentence summaryA marine sponge lectin catalyzes thrombopoietin receptor dimerization and activation, exhibiting strong synergy with thrombopoietin, and modulates internalization of the receptor.

cell biology↗

bioRxiv2021

ZomB is essential for chemotaxis of Vibrio alginolyticus by the rotational direction control of the polar flagellar motor

Bacteria exhibit chemotaxis by controlling flagellar rotation to move toward preferred places or away from non-preferred places. The change in rotation is triggered by the binding of the chemotaxis signaling protein CheY to the C-ring in the flagellar motor. Some specific bacteria, including Vibrio spp. and Shewanella spp. have a single transmembrane protein called ZomB. ZomB is essential for controlling the flagellar rotational direction in Shewanella putrefaciens and Vibrio parahaemolyticus. In this study, we confirmed that the zomB deletion results only in the counterclockwise (CCW) rotation of the motor in Vibrio alginolyticus as previously reported in other bacteria. We found that ZomB is not required for the clockwise (CW) rotation-fixing phenotype caused by mutations in fliG and fliM, and that ZomB is essential for CW rotation induced by overproduction of CheY. Purified ZomB proteins form multimers, indicating that ZomB functions as a complex. ZomB may interact with a protein involved in the flagellar rotation, stator proteins or rotor proteins. We found that ZomB is a new player in chemotaxis and is required for the rotational control in addition to CheY in Vibrio alginolyticus. ImportanceBacterial chemotaxis is performed by the control of the flagellar rotation. CheY and ZomB control the rotational direction of the flagellar motor in Vibrio spp. and Shewanella spp. In this study, we characterized ZomB in Vibrio alginolyticus, which is essential for the clockwise rotation of the motor.

microbiology↗

bioRxiv2021

Systematic analysis of brain lactate and pH levels in 65 animal models related to neuropsychiatric conditions

Increased levels of lactate, an end-product of glycolysis, have been proposed as a potential surrogate marker for metabolic changes during neuronal excitation. These changes in lactate levels can result in decreased brain pH, which has been implicated in patients with various neuropsychiatric disorders. We previously demonstrated that such alterations are commonly observed in five mouse models of schizophrenia, bipolar disorder, and autism, suggesting a shared endophenotype among these disorders rather than mere artifacts due to medications or agonal state. However, there is still limited research on this phenomenon in animal models, leaving its generality across other disease animal models uncertain. Moreover, the association between changes in brain lactate levels and specific behavioral abnormalities remains unclear. To address these gaps, the International Brain pH Project Consortium investigated brain pH and lactate levels in 109 strains/conditions of 2,294 animals with genetic and other experimental manipulations relevant to neuropsychiatric disorders. Systematic analysis revealed that decreased brain pH and increased lactate levels were common features observed in multiple models of depression, epilepsy, Alzheimers disease, and some additional schizophrenia models. While certain autism models also exhibited decreased pH and increased lactate levels, others showed the opposite pattern, potentially reflecting subpopulations within the autism spectrum. Furthermore, utilizing large-scale behavioral test battery, a multivariate cross-validated prediction analysis demonstrated that poor working memory performance was predominantly associated with increased brain lactate levels. Importantly, this association was confirmed in an independent cohort of animal models. Collectively, these findings suggest that altered brain pH and lactate levels, which could be attributed to dysregulated excitation/inhibition balance, may serve as transdiagnostic endophenotypes of debilitating neuropsychiatric disorders characterized by cognitive impairment, irrespective of their beneficial or detrimental nature.

neuroscience↗

bioRxiv2020

AUTS2 Governs Cerebellar Development, Purkinje Cell Maturation, Motor Function and Social Communication

Autism susceptibility candidate 2 (AUTS2), a risk gene for autism spectrum disorders (ASDs), is implicated in telencephalon development. Because AUTS2 is also expressed in the cerebellum where defects have been linked to ASDs, we investigated AUTS2 functions in the cerebellum. AUTS2 is specifically localized in Purkinje cells (PCs) and Golgi cells during postnatal development. Auts2 conditional knockout (cKO) mice exhibited smaller and deformed cerebella containing immature-shaped PCs with reduced expression of Cacna1a. Auts2 cKO and knock-down experiments implicated AUTS2 participation in elimination and translocation of climbing fiber synapses, and restriction of parallel fiber synapse numbers. Auts2 cKO mice exhibited behavioral impairments in motor learning and vocal communications. Because Cacna1a is known to regulate synapse development in PCs, it suggests that AUTS2 is required for PC maturation to elicit normal development of PC synapses and thus the impairment of AUTS2 may cause cerebellar dysfunction related to psychiatric illnesses such as ASDs.

neuroscience↗

bioRxiv2019

AUTS2 regulation of synapses for proper synaptic inputs and social communication.

Impairments in synapse development are thought to cause numerous psychiatric disorders. Autism susceptibility candidate 2 (AUTS2) gene has been associated with various psychiatric disorders, such as autism and intellectual disabilities. Although roles for AUTS2 in neuronal migration and neuritogenesis have been reported, its involvement in synapse regulation remains unclear. In this study, we found that excitatory synapses were specifically increased in the Auts2-deficient primary cultured neurons as well as Auts2 mutant forebrains. Electrophysiological recordings and immunostaining showed increases in excitatory synaptic inputs as well as c-fos expression in Auts2 mutant brains, suggesting that an altered balance of excitatory and inhibitory inputs enhances brain excitability. Auts2 mutant mice exhibited autistic-like behaviors including impairments in social interaction and altered vocal communication. Together, these findings suggest that AUTS2 regulates excitatory synapse number to coordinate E/I balance in the brain, whose impairment may underlie the pathology of psychiatric disorders in individuals with AUTS2 mutations.

neuroscience↗

bioRxiv2019

Inertial Measurement Unit-Based Estimation of Foot Trajectory for Clinical Gait Analysis

Gait analysis is used widely in clinical practice for the evaluation of abnormal gait caused by disease. Conventionally, medical professionals use motion capture systems or make visual observations to evaluate a patients gait. Recent biomedical engineering studies have proposed easy-to-use gait analysis methods involving wearable sensors with inertial measurement units (IMUs). IMUs placed on the shanks just above the ankles allow for the long-term monitoring of gait because the participant can walk with or without shoes during the analysis. As far as the authors know, there is no report of the gait analysis method that estimates stride length, gait speed, stride duration, stance duration, and swing duration at the same time. In this study, we tested a proposed gait analysis method that uses IMUs attached on the shanks to estimate foot trajectory and temporal gait parameters. We evaluated this proposed method by analyzing the gait of 10 able-bodied participants (mean age 23.1 years, nine men and one woman). Wearable sensors were attached to the participants shanks, and we measured three-axis acceleration and three-axis angular velocity with the sensors to estimate foot trajectory during walking. We compared gait parameters estimated from the foot trajectory obtained with the proposed method and those measured with a motion capture system. Mean accuracy (mean {+/-} standard deviation) was -0.046 {+/-} 0.026 m for stride length, -0.036 {+/-} 0.026 m/s for gait speed, -0.002 {+/-} 0.019 s for stride duration, -0.000 {+/-} 0.016 s for stance duration, and -0.002 {+/-} 0.022 s for swing duration. These results suggest that the proposed method is useful for evaluation of clinical gait parameters.

physiology↗