Biology subjects

Yamakawa, K.

Publications and source records attributed to Yamakawa, K..

12 recordsLinked to original sources

bioRxiv2026

CRISPR-mediated Stxbp1 gene activation ameliorates epileptic and aggressive phenotypes in Stxbp1-haploinsufficient mice

Mutations in the syntaxin-binding protein 1 (STXBP1) gene, which encodes the presynaptic protein Munc18-1, cause a spectrum of severe epileptic encephalopathies and neurodevelopmental disorders, including Ohtahara syndrome, for which no curative treatment is currently available. Because the disease pathomechanism is thought to be driven by haploinsufficiency, restoring expression of the wild-type allele to physiological levels could provide therapeutic benefit. Here, we evaluated CRISPR-mediated transcriptional activation (CRISPR-ON), based on a dCas9-VPR transcriptional activator, as a strategy to upregulate endogenous Stxbp1 expression in a Stxbp1-haploinsufficient (Stxbp1+/-) mouse model. Screening of guide RNAs (gRNAs) targeting the Stxbp1 promoter in Neuro2A cells identified a multiplexed four-gRNA cassette that elevated Stxbp1 mRNA approximately six-fold. AAV-PHP.eB vectors co-expressing this 4xgRNA cassette and Cre recombinase under the EF1a promoter were administered intracerebroventricularly to neonatal Stxbp1+/-/dCas9-VPRfl/+ mice. CRISPR-ON treatment restored not only brain Stxbp1 mRNA but also Munc18-1 protein levels to those of wild-type controls. Electrocorticographic recordings revealed an approximately 50% reduction in the frequency of spike-wave discharges in CRISPR-ON-treated Stxbp1+/- mice compared with untreated Stxbp1+/- controls, and aggressive behavior in the resident-intruder test was also partially attenuated. In contrast, locomotor activity remained unaffected, indicating that CRISPR-ON treatment achieves selective rescue of disease-related phenotypes without inducing motor side effects. Together, these findings demonstrate that CRISPR-ON-mediated activation of endogenous Stxbp1 is a promising therapeutic strategy for STXBP1-related encephalopathies and support endogenous gene activation as a broadly applicable platform for haploinsufficiency disorders.

neuroscience↗

bioRxiv2026

Reduction of Nav1.1 in the dorsal striatum preferentially increases hyperthermia-induced generalized seizures compared with the neocortex and nucleus accumbens

Mutations in SCN1A, which encodes the voltage-gated sodium channel Nav1.1 (I subunit), are the major cause of Dravet syndrome, a severe developmental and epileptic encephalopathy. Although Nav1.1 haploinsufficiency preferentially impairs inhibitory interneuron function, the region-specific contributions of distributed brain circuits to seizure susceptibility, particularly in subcortical structures that have received less attention than the neocortex and hippocampus, remain unclear. Here, we examined the effects of region-specific Nav1.1 deficiency on hyperthermia-induced seizures by selectively deleting Scn1a in the neocortex, nucleus accumbens (NAc), and dorsal striatum (caudate-putamen, CPu) of adult mice using an adeno-associated virus-mediated Cre-loxP approach. Contrary to expectations based on prior cortical studies, homozygous Scn1a deletion in the neocortex produced only modest effects on seizure generalization. In contrast, homozygous deletion in the NAc and CPu induced generalized seizures to varying degrees. Notably, heterozygous Scn1a deletion in the CPu alone was sufficient to trigger generalized seizures, whereas similar manipulations in the neocortex or NAc were not. Seizure threshold temperatures were largely comparable across regions. These findings identify the dorsal striatum as particularly vulnerable to partial Nav1.1 loss and reveal functional heterogeneity within striatal circuits. Our results underscore a previously underappreciated role of striatal inhibitory networks in hyperthermia-induced seizure susceptibility and provide new insights into the circuit mechanisms underlying Dravet syndrome.

neuroscience↗

bioRxiv2026

Reduced cortico-accumbal excitatory input due to Nav1.2 haploinsufficiency impairs sociability independently of dopamine

Mutations in SCN2A, which encodes the voltage-gated sodium channel Nav1.2, are associated with a wide spectrum of neurodevelopmental and neuropsychiatric disorders, including epilepsy, autism spectrum disorder (ASD), and schizophrenia. Although dysfunction of SCN2A-dependent neural circuits has been implicated in these disorders, the circuit mechanisms underlying social behavioral abnormalities remain poorly understood. Here, we investigated the neural circuit basis of social behavioral deficits associated with Scn2a dysfunction, focusing on the nucleus accumbens (NAc), a key hub in cortico-limbic circuits that regulates emotional and motivational behaviors. Using conditional genetic and chemogenetic approaches in mice, we examined the roles of dorsal telencephalic excitatory neurons, including those in the cerebral cortex, hippocampus, and amygdala, as well as parvalbumin-positive fast-spiking interneurons (PV FSIs) in the NAc. Mice with Scn2a haploinsufficiency in dorsal telencephalic excitatory neurons (Scn2afl/+/Emx1-Cre) exhibited reduced sociability in the three-chamber social interaction test. Similarly, chemogenetic inhibition of NAc PV FSIs decreased sociability without affecting locomotor activity or anxiety-like behavior. Scn2afl/+/Emx1-Cre mice also showed a trend toward reduced prepulse inhibition of the acoustic startle response. Notably, dopamine release into the NAc in the Scn2afl/+/Emx1-Cre and systemic Scn2a heterozygous knockout (Scn2a+/-) mice was largely comparable to that in control mice. Together, these findings indicate that reduced activity of dorsal telencephalic excitatory neurons or NAc PV FSIs is sufficient to impair sociability independently of mesolimbic dopamine hypofunction. Our results highlight a potential role of cortico-accumbal circuits in social behavioral deficits associated with SCN2A dysfunction.

neuroscience↗

bioRxiv2026

Parallel analysis of voltage-gated sodium channel subunits reveals preferential colocalizations of beta-1/Nav1.1 and beta-2/Nav1.2

Voltage-gated sodium channels (VGSCs) are conventionally described as heterotrimers composed of one alpha and two beta subunits. However, the patterns of co-expression of alpha- and beta-subunits in neurons remain unclear. In the present study, we report that alpha- (Nav1.1, Nav1.2, and Nav1.6) and beta- (beta-1 and beta-2) subunits are densely expressed in axon initial segments (AISs) of neurons in the neocortex, hippocampus and cerebellum at postnatal days 14-15 (P14-15) and 8-9 weeks (8-9W). These distributions are largely unique and partially overlapping among brain regions. Notably, in the neocortex and hippocampus, AISs of presumptive parvalbumin-positive inhibitory neurons are positive for Nav1.1 and beta-1, whereas those of excitatory ones are positive for Nav1.2 and beta-2. Similarly, AISs of cerebellar basket cells, which are inhibitory neurons, are positive for Nav1.1 and beta-1, whereas those of granule cells, which are excitatory neurons, are positive for Nav1.2 and beta-2. Nav1.6 is expressed in many of these neurons. Some subunits exhibited distinct distribution patterns at the two postnatal stages analyzed, possibly because of their developmental changes of subcellular localizations. Taken together, these results indicate that combinations of VGSC subunits are largely unique among different neuronal subpopulations. These findings provide a useful reference for understanding the distribution and interactions of VGSC subunits in the brain.

neuroscience↗

bioRxiv2026

Reduced activity of nucleus accumbens parvalbumin-expressing fast- spiking inhibitory neurons causes convulsive seizures

Pathogenic mutations in STXBP1, which encodes Munc18-1, a synaptic protein essential for synaptic vesicle exocytosis and neurotransmission, and in SCN2A, which encodes the voltage-gated sodium channel Nav1.2 (II subunit), have been identified in patients with epilepsy. Although haploinsufficiency of either Stxbp1 or Scn2a in cortical excitatory neurons induces epileptic phenotypes in mice and a reduction of cortico-striatal, especially cortico-striatal parvalbumin-expressing fast-spiking interneurons (FSIs), excitatory transmission has been suggested to be the basis, the subcortical circuits remain poorly understood. In this study, we investigated which striatal subregions FSIs are responsible for the epileptic seizures. Using chemogenetic approach, we selectively suppressed FSI activity in either the nucleus accumbens (NAc) or the dorsal striatum (caudate-putamen, CPu) of mice. Suppression of FSIs in the NAc induced outwardly-recognized convulsive seizures accompanied by epileptiform discharges in the electrocorticographic (ECoG) analysis, whereas inhibition of FSIs in the CPu resulted in epileptiform discharges without overt convulsions. Notably, focal suppression of FSIs in either the anterior or medial region of the NAc shell (NAcSh), but not in other NAc subregions, was sufficient to trigger convulsive seizures. These findings identify FSIs in the anteromedial shell of the NAc as a critical hub for convulsive seizure generation and provide new insights into the striatal circuit mechanisms underlying STXBP1- or SCN2A-associated epilepsies.

neuroscience↗

bioRxiv2024

An AI-Driven Model of Consciousness, Its Disorders, and Their Treatment

Understanding disorders of consciousness (DOC) remains one of the most challenging problems in neuroscience, hindered by the lack of experimental models for probing mechanisms or testing interventions [1]. To address this, we introduce a generative adversarial AI framework [2] that pits deep neural networks--trained to detect consciousness across over 680,000 neuroelectro-physiology samples and validated on 565 patients, healthy volunteers, and animals--against interpretable, machine learning-driven neural field models [3]. This adversarial architecture produces biologically realistic simulations of both conscious and comatose brains that recapitulate empirical neurophysiological features across humans, monkeys, rats, and bats. Without explicit programming, the AI model retrodicts known DOC responses to brain stimulation and generates testable predictions about unconsciousness mechanisms. Two such predictions are validated here: selective disruption of the basal ganglia indirect pathway, supported by diffusion MRI in 51 DOC patients; and increased cortical inhibitory-to-inhibitory synaptic coupling, supported by RNA sequencing from resected brain tissue in six human coma patients and a rat stroke model. The model also identifies high-frequency subthalamic nucleus stimulation as a promising DOC intervention, supported here using electrophysiology data from human patients. This work introduces an AI framework for causal inference and therapeutic discovery in consciousness research and complex systems more broadly.

neuroscience↗

bioRxiv2024

Epilepsy protein myoclonin1 interacts with inositol 1,4,5-trisphosphate (IP3) receptor and reduces Ca2+ store in endoplasmic reticulum

Mutations of EFHC1 gene have been identified in patients with epilepsies including juvenile myoclonic epilepsy (JME), and mice with Efhc1 deficiency exhibit epileptic phenotypes. Myoclonin1 protein encoded by EFHC1 is not expressed in neurons but in cells with motile cilia including those of choroid plexus and ependymal cells which form an epithelial layer lining brain ventricles. Detailed molecular basis of epilepsies caused by EFHC1 mutations, however, remain unclear. Here we report that myoclonin1 is well co-expressed with inositol 1,4,5-trisphosphate receptor type 1 (IP3R1) at choroid plexus and ependymal cells and these two proteins bind each other. Endoplasmic reticulum (ER) of Efhc1-deficient mouse (Efhc1-/-) cells contains larger levels of calcium ions (Ca2+) than that of wild-type (WT) mice, and IP3-induced Ca2+ release (IICR) from ER is higher in Efhc1-/- cells than that of WT. Furthermore, myoclonin1 revealed to interact with PRKCSH, also known as a protein kinase C substrate 80K-H which interacts with IP3R1. Myoclonin1 further binds to IP3R2 and IP3R3. Thus, our results indicate that myoclonin1 modulates ER-Ca2+ homeostasis through interactions with IP3Rs and PRKCSH, and suggest that myoclonin1 dysfunctions cause impaired intracellular Ca2+ mobilization. Its relevance to the epileptic phenotypes of patients with EFHC1 mutations is now of interest.

physiology↗

bioRxiv2023

Criticality supports cross-frequency cortical-thalamic information transfer during conscious states

Consciousness is thought to be regulated by bidirectional information transfer between the cortex and thalamus, but the nature of this bidirectional communication - and its possible disruption in unconsciousness - remains poorly understood. Here, we present two main findings elucidating mechanisms of corticothalamic information transfer during conscious states. First, we identify a highly preserved spectral channel of cortical-thalamic communication which is present during conscious states but which is diminished during the loss of consciousness and enhanced during psychedelic states. Specifically, we show that in humans, mice, and rats, information sent from either the cortex or thalamus via{delta} /{theta}/ waves (~1.5-13 Hz) is consistently encoded by the other brain region by high{gamma} waves (~50-100 Hz); moroever, unconsciousness induced by propofol anesthesia or generalized spike-and-wave seizures diminishes this cross-frequency communication, whereas the psychedelic 5-methoxy-N,N/-dimethyltryptamine (5-MeO-DMT) enhances this interregional communication. Second, we leverage numerical simulations and neural electrophysiology recordings from the thalamus and cortex of human patients, rats, and mice to show that these changes in cross-frequency cortical-thalamic information transfer are mediated by excursions of low-frequency thalamocortical electrodynamics toward/away from edge-of-chaos criticality, or the phase transition from stability to chaos. Overall, our findings link thalamic-cortical communication to consciousness, and further offer a novel, mathematically well-defined framework to explain the disruption to thalamic-cortical information transfer during unconscious states.

neuroscience↗

bioRxiv2021

CUX2 mutations in temporal lobe epilepsy; increased kainate susceptibility and excitatory input to hippocampus in deficient mice

CUX2 gene encodes a transcription factor that controls neuronal proliferation, dendrite branching and synapse formation, locating at the epilepsy-associated chromosomal region 12q24 that we previously identified by a genome-wide association study (GWAS) in Japanese population. A CUX2 recurrent de novo variant p.E590K has been described in patients with rare epileptic encephalopathies and the gene is a candidate for the locus, however the mutation may not be enough to generate the genome-wide significance in the GWAS and whether CUX2 variants appear in other types of epilepsies and physiopathological mechanisms are remained to be investigated. Here in this study, we conducted targeted sequencings of CUX2, a paralog CUX1 and its short isoform CASP harboring a unique C-terminus on 271 Japanese patients with a variety of epilepsies, and found that multiple CUX2 missense variants, other than the p.E590K, and some CASP variants including a deletion, predominantly appeared in patients with temporal lobe epilepsy (TLE). The CUX2 variants showed abnormal localization in human cell culture analysis. While wild-type CUX2 enhances dendritic arborization in fly neurons, the effect was compromised by some of the variants. Cux2- and Casp-specific knockout mice both showed high susceptibility to kainate, increased excitatory cell number in the entorhinal cortex, and significant enhancement in glutamatergic synaptic transmission to the hippocampus. CASP and CUX2 proteins physiologically bound to each other and co-expressed in excitatory neurons in brain regions including the entorhinal cortex. These results suggest that CUX2 and CASP variants contribute to the TLE pathology through a facilitation of excitatory synaptic transmission from entorhinal cortex to hippocampus.

neuroscience↗

bioRxiv2021

Scn1a-GFP transgenic mouse revealed Nav1.1 expression in neocortical pyramidal tract projection neurons

Expressions of voltage-gated sodium channels Nav1.1 and Nav1.2, encoded by SCN1A and SCN2A genes respectively, have been reported to be mutually exclusive in most brain regions. In juvenile and adult neocortex, Nav1.1 is predominantly expressed in inhibitory neurons while Nav1.2 is in excitatory neurons. Although a distinct subpopulation of layer V (L5) neocortical excitatory neurons were also reported to express Nav1.1, their nature has been uncharacterized. In hippocampus, Nav1.1 has been proposed to be expressed only in inhibitory neurons. By using newly-generated transgenic mouse lines expressing Scn1a promoter-driven green fluorescent protein (GFP), here we confirm the mutually-exclusive expressions of Nav1.1 and Nav1.2 and the absence of Nav1.1 in hippocampal excitatory neurons. We also show that Nav1.1 is expressed in inhibitory and a subpopulation of excitatory neurons not only in L5 but all layers of neocortex. By using neocortical excitatory projection neuron markers including FEZF2 for L5 pyramidal tract (PT) and TBR1 for layer VI (L6) cortico-thalamic (CT) projection neurons, we further show that most L5 PT neurons and a minor subpopulation of layer II/III (L2/3) cortico-cortical (CC) neurons express Nav1.1 while the majority of L6 CT, L5/6 cortico-striatal (CS) and L2/3 CC neurons express Nav1.2. These observations now contribute to the elucidation of pathological neural circuits for diseases such as epilepsies and neurodevelopmental disorders caused by SCN1A and SCN2A mutations.

neuroscience↗

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↗

bioRxiv2017

Enhanced cross-modal activation of sensory cortex in mouse models of autism

SUMMARYSynesthesia is a condition wherein one sense is evoked by another. Recent studies suggested a higher incidence of synesthesia among people with autism. However, the underlying circuit mechanism of the comorbidity remains unknown partly due to lack of animal models. Here, we measured auditory response of primary visual cortex (V1) in mouse models to estimate the mixture level of their senses. We found that the V1 auditory response exhibits bidirectional cross-modal plasticity and depends on the level of GABA-mediated inhibition. Analysis of the V1 auditory response in autistic BTBR strain revealed its contralateral bias as in primary auditory cortex, and the auditory evoked field potential was enhanced at gamma range. Furthermore, early sound-driven spike modulation of V1 was commonly shifted toward enhancement in three different autism models (BTBR, NL3 R451C, SCN1A R1407X). Disruption of excitatory/inhibitory (E/I) circuit balance is prevalent among autistic people and mouse models. Thus, our results suggest that E/I imbalance may be the common circuit dysfunction for both autism and synesthesia.

neuroscience↗