Biology subjects

Mizukami, H.

Publications and source records attributed to Mizukami, H..

10 recordsLinked to original sources

bioRxiv2026

YY1 Binding Motif at Upstream of Rep/Cap Increases AAV Yield and Full Capsids

Adeno-associated virus (AAV) vectors are widely used in gene therapy, whereas low manufacturing efficiency and a large proportion of empty capsids are major obstacles. This study focused on the Yin Yang 1 (YY1) binding motif (YY1-motif) and investigated the effect of its presence or insertion upstream of the Replicase (Rep)/Capsid (Cap) gene on AAV vector production. We found that the YY1-motif incidentally presented in a Rep/Cap plasmid was associated with high vector production. We then designed several modified Rep/Cap (RC2) constructs. The YY1-motif insertion in front of Rep/Cap gene increased vector yield in a repeat-number-dependent manner, and similar effects were not observed with other promoters insertion. Furthermore, the insertion of the YY1-motif reduced the amount of Cap protein per the same amount of full particle in supernatants on multiple serotypes, indicating the improvement in the empty/full capsid ratio. The YY1-motif insertion did not affect the AAV vector infectivity. These results denote that the YY1-motif has a universal regulatory function that optimizes the Rep/Cap expression balance, and simultaneously improves the production efficiency and full particle formation of AAV vectors. This finding could contribute to the development of highly efficient and high-quality AAV manufacturing processes.

microbiology↗

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

Heterogeneous Sensitivity to Src Inhibitors in Oral Squamous Cell Carcinoma and Its Implications for Combination Therapy with Cisplatin

Purpose: Treatment options of advanced oral squamous cell carcinomas (OSCC) are limited, and cisplatin toxicity and drug resistance are major clinical issues. Src is a central kinase that integrates multiple oncogenic pathways and a promising therapeutic target. However, Src inhibitors have shown suboptimal efficacy as monotherapies and their sensitivity in OSCC remains elusive. Experimental Design: We examined the activation of major oncogenic signaling pathways and the antitumor effects of six Src inhibitors (dasatinib, ponatinib, vandetanib, saracatinib, PP2, bosutinib) in seven human OSCC cell lines (HSC-2, HSC-3, HSC-4, SAS, HO-1-u-1, CAL27, SCC-25). BALB/cAJcl nu/nu mice bearing CAL27 xenografts received dasatinib (30 mg/kg, intraperitoneally, daily), bosutinib (50 mg/kg, intraperitoneally, daily), cisplatin (2 mg/kg or 4 mg/kg, intraperitoneally, weekly), or combinations. Tumor volume, bioluminescence imaging, and body weight were monitored for 17 or 21 days, followed by histopathological assessment. Results: The activation of the key pathways, including Src and MAPK, considerably differed among the cell lines and was linked to heterogeneous sensitivity to Src inhibitors. Effective growth suppression required Src dephosphorylation and downstream MAPK pathway inhibition, which vary depending on the cell line. Additionally, combination treatment with a Src inhibitor and cisplatin showed additive antitumor effects, allowing the reduction of cisplatin doses by half without efficacy loss. Notably, dasatinib alone and in combination with cisplatin decreased tumor burden with characteristic internal tumor death in vivo. Conclusions: These findings elucidate Src signaling dependency on OSCC and the potential of Src inhibition to decrease cisplatin toxicity, paving way for Src targeted therapeutic strategies.

cancer biology↗

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↗

bioRxiv2025

GABA mediates experience-dependent regulation of myelination in the mouse visual pathway.

Myelination in the visual pathway is critical for transmitting visual information from retina to the brain. Reducing visual experience shortens myelin sheath length and slows the conduction velocity of the optic nerve. However, the mechanism underlying such experience-dependent myelination is unclear. Here, we found that closing both eyes, binocular deprivation (BD), during the juvenile period less affects the optic nerve myelination than monocular deprivation (MD) via GABA signaling. RNA-seq analysis of optic nerves from MD and BD mice revealed that GABAergic signaling is downregulated on the deprived side of MD compared to the intact side and BD. Inhibition of GABAergic signaling during the juvenile period resulted in myelin sheath shortening and excessive oligodendrocyte generation in normal mice, similar to the changes observed in MD mice. Enhancing GABAergic signaling rescued the myelin sheath shortening and excessive oligodendrocyte generation in the optic nerve of MD mice. Furthermore, we identified novel GABAergic neurons located within the optic nerve, whose neurites form belt-like presynaptic structures with the oligodendrocyte lineage cells, suggesting a potential source of the GABAergic inputs into oligodendrocytes. Our results indicate that the myelination of visual pathway is maintained by binocular visual inputs via intra-nerve GABA signaling.

neuroscience↗

bioRxiv2023

Epileptic responses in marmosets induced by knockdown of CREB Regulated Transcription Coactivator 1 (CRTC1)

Animal models have contributed greatly to the development of anticonvulsant drugs. However, 20-30% of epilepsy patients still do not achieve adequate seizure control. It is important to understand the biological mechanisms of epilepsy in order to develop treatments and novel anticonvulsant drugs. Here we report CRTC1 knockdown (KD) induced abnormal cFOS expression beyond the injection sites followed by epileptic response by three local injections of short hairpin RNA (shRNA) in marmoset V1. Longitudinal monitoring of cortical-wide neural activity revealed transient changes in high frequency oscillations by cortical electrocorticography throughout the cortex, and a lesion in the temporal lobe was observed by MRI and postmortem histology. shCRTC1 KD marmosets showed severe lesions surrounding the injection site several months after injection. Glial cell activation may occur simultaneously or prior to IEG induction after shCRTC1 injection. Thus, the epileptic process from seizure onset to remission can be studied in this animal model.

neuroscience↗

bioRxiv2022

Imbalance of circuit plasticity and consolidation in autism model marmosets is adjusted by oxytocin administration

Alterations in the experience-dependent and autonomous elaboration of neural circuits are assumed to underlie autism spectrum disorder (ASD), though it is unclear what synaptic traits are responsible. Here, we used a valproic acid-induced ASD marmoset model, which shares common molecular features with idiopathic ASD, to investigate the structural dynamics of tuft dendrites of upper-layer pyramidal neurons and adjacent axons in the dorsomedial prefrontal cortex using two-photon microscopy. In model marmosets, dendritic spine turnover was upregulated, and spines were actively generated in clusters and subsequently survived more often than in control marmosets. Presynaptic boutons in local axons but not in commissural long-range axons showed hyperdynamic turnover in model marmosets, suggesting alterations in projection-specific plasticity. Intriguingly, nasal administration of oxytocin reduced the clustered spine emergence. Enhanced clustered spine generation, possibly unique to certain presynaptic partners, may be associated with ASD and may be a potential therapeutic target.

neuroscience↗

bioRxiv2022

Connectional architecture of the prefrontal cortex in the marmoset brain

Prefrontal cortex (PFC) has dramatically expanded in primates, but its organization and interactions with other brain regions are only partially understood. We performed high-resolution connectomic mapping of marmoset PFC and found two contrasting corticocortical and corticostriatal projection patterns: "patchy" projections that formed many columns of submillimeter scale in nearby and distant regions and "diffuse" projections that spread widely across the cortex and striatum. Parcellation-free analyses revealed representations of PFC gradients in these projections local and global distribution patterns. We also demonstrated column-scale precision of reciprocal cortico-cortical connectivity, suggesting that PFC contains a mosaic of discrete columns. Diffuse projections showed considerable diversity in the laminar patterns of axonal spread. In mice, columnar projections were much less conspicuous, underscoring the importance of the primate model. Altogether, these fine-grained analyses reveal important principles of local and long-distance PFC circuits in marmosets and provide insights into the functional organization of the primate brain.

neuroscience↗

bioRxiv2020

The Effects of Inter-Individual Biological Differences and Taphonomic Alteration on Human Bone Protein Profiles: Implications for the Development of PMI/AAD Estimation Methods

Bone proteomics studies using animal proxies and skeletonized human remains have delivered encouraging results in the search for potential biomarkers for precise and accurate post-mortem interval (PMI) and the age-at-death (AAD) estimation in medico-legal investigations. At present, however, the effects of inter-individual biological differences and taphonomic alteration on recovered human bone protein profiles are not well understood. This study investigated the human bone proteome in four human body donors studied throughout decomposition outdoors. The effects of ageing phenomena (in vivo and post-mortem), and intrinsic and extrinsic variables on the variety and abundancy of the bone proteome were assessed. Results identified a new potential biomarker for PMI estimation, as well as three potential biomarkers for AAD estimation. The results also suggest that bone mineral density (BMD) may be an important variable affecting the survival and extraction of proteins. Highlights- CO3, CO9, COBA2, CO3A1, MGP, PGS2 and TTHY are potential biomarkers for post-mortem interval estimation in skeletonized human remains - FETUA, ALBU and OLFL3 are potential biomarkers for age-at-death estimation in human remains - Taphonomic and biological variables play a significant role in survival and extraction rates of proteins in bone - Bone mineral density may affect survival of proteins in bone, probably due to the effects of the mineral matrix on the movement of decomposer microbes - Higher bone mineral density may affect the survival and the extraction rate of collagen and mineral-binding proteins

biochemistry↗