Biology subjects

Hibi, Y.

Publications and source records attributed to Hibi, Y..

6 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

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↗

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↗

bioRxiv2018

High prevalence of the antibody against Syncytin-1 in schizophrenia

Both genetic and environmental factors have been considered causative agents for schizophrenia (SZ). However, no single gene has been shown responsible for the development of SZ. Furthermore, the pathophysiological roles of environmental factors including psychological stress, autoimmunity, and microbial infection have not been fully understood. Previous studies have suggested the involvement of one of the human endogenous retroviruses (HERVs), HERV-W, in SZ. In this study, prevalence of antibodies against the HERV-W Syncytin-1 protein was examined using a newly developed ELISA test. Fifty percent of patients with SZ (24 out of 48 cases) were antibody-positive, with a specificity of greater than 95% (less than 5% of control cases, 3 out of 79). No significant effect of medication was evident, nor did any SZ cases become seropositive after diagnosis. These findings indicate a possible involvement of HERV-W expression in the development of SZ and support its applicability to laboratory diagnoses.

neuroscience↗