Biology subjects

Aiba, I.

Publications and source records attributed to Aiba, I..

8 recordsLinked to original sources

bioRxiv2025

EGR3 Deletion Rescues Developmental and Epileptic Encephalopathy in Kcna1-null Mice

KCNA1 encodes the -subunit of the voltage-gated potassium channel KV1.1. Mutations in KV1.1s pore domain result in developmental and epileptic encephalopathy (DEE), where early life seizures and a culprit lesion synergistically disrupt neurodevelopmental trajectories, resulting in intellectual disability that often presents with disturbances in sleep, sociability and sensory processing. Abnormalities in the subcellular localization of Kv1.1, via mutations in/autoantibodies against LGI1 and CNTNAP2, also give rise to syndromes of epilepsy and neuropsychiatric impairment. Mice with deletions of Kcna1("-/-") display spontaneous seizures at 2-3 weeks of age and premature mortality. In this study, we applied instrumented home-cage monitoring to examine how aberrations in KCNA1 expression may result in pervasive alterations in spontaneous behavior. Compared to wildtype, Kcna1-/- mice displayed a robust multifaceted behavioral syndrome featuring marked nocturnal hyperactivity, insomnia, reduced sheltering, fragmented feeding/drinking rhythms, sensory over-responsivity and diminished wheel-running. In identical recordings, Kcna1+/- mice only displayed increased sheltering, Lgi1+/- mice displayed mild insomnia and Cntnap2-/- mice showed home-cage hypoactivity. Kcna1 loss in parvalbumin-positive interneurons (Pv-Cre) resulted in a subtle phenocopy, with mild insomnia accompanied by reduced sheltering behavior, while similar deletions in forebrain pyramidal neurons (Emx1-Cre) or dopaminergic neurons (DAT-Cre) were asymptomatic. Adult-onset conditional deletions of Kcna1 also produced only mild insomnia 6 weeks later. To survey the molecular landscape in Kcna1-/- mice, we conducted a mass spectrometry proteomic analysis of dissected hippocampal tissue (a predominant seizure onset zone and where astrogliosis is observed). This revealed significant upregulations in BDNF (brain-derived neurotrophic factor) and the immediate early transcription factor EGR3 (early growth response-3), which is necessary for the induction of BDNF following electroconvulsive seizures. Heterozygous or homozygous deletions of Egr3 in Kcna1-/- mice resulted in significant survival prolongation, a partial neurobehavioral rescue, and a significant improvement in the frequency of spontaneous seizures and spreading depolarization events. These clinical improvements were associated with an amelioration of BDNF induction, hippocampal astrogliosis and proteomic disturbances. Together, these data illustrate how an ion channel that governs excitability at millisecond scales also shapes the spatiotemporal structure of spontaneous behavior at meso- or macroscopic time scales. Our results provide a model and a set of precision endpoints to understand how ictal and interictal features of DEE may be ameliorated by inhibiting the long-term downstream transcriptional alterations imparted by early life seizures.

neuroscience↗

bioRxiv2024

Persistent Na+ current couples seizure with Spreading depolarization in Scn8a gain-of-function mice

Spreading depolarization (SD) is a slowly propagating wave of massive cellular depolarization that transiently impairs the function of affected brain regions. While SD typically arises as an isolated hemispheric event, we previously reported that reducing M-type potassium current (IKM) by ablation of Kcnq2 in forebrain excitatory neurons results in tightly coupled spontaneous bilateral seizure-SD complexes in the awake mouse cortex. Here we find that enhanced persistent Na+ current due to gain-of-function (GOF) mutations in Scn8a (N1768D/+, hereafter D/+) produces a similar compound cortical excitability phenotype. Chronic DC-band EEG recording detected spontaneous bilateral seizure-SD complexes accompanied by seizures with a profound tonic motor component, which occur predominantly during the light phase and were detected at ages between P33-100. Laser speckle contrast imaging of cerebral blood flow dynamics resolved SD as a bilateral wave of hypoperfusion and subsequent hour-lasting hypoperfusion in Scn8aD/+ cortex in awake head-restrained mice evoked by a PTZ injection. Subcortical recordings in freely moving mice revealed that approximately half of the spontaneous cortical seizure-SD complexes arose with a concurrent SD-like depolarization in the thalamus and delayed depolarization in the striatum. In contrast, SD-like DC potential shifts were rarely detected in the hippocampus or upper pons. Consistent with the high spontaneous incidence in vivo, cortical slices from Scn8aD/+ mice showed a raised SD susceptibility, and pharmacological inhibition of persistent Na+ current (INaP), which is enhanced in Scn8aD/+ neurons, inhibited SD generation in cortical slices ex vivo as well as in head-fixed mice in vivo, indicating that INaP contributes to SD susceptibility. Ex vivo Ca2+ imaging studies using acute brain slices expressing genetic Ca2+ sensor (Thy1-GCAMP6s) demonstrated that pharmacological activation of IKM suppressed Ca2+ spikes and SD, whereas an IKM inhibitor strongly increased the frequency of hippocampal Ca2+ spikes in Scn8aD/+, but not WT slices, suggesting that IKM restrains the Scn8a GOF hyperexcitability. Together, our study identifies a cortical SD phenotype in Scn8a GOF mice shared with the Kcnq2-cKO model of developmental epileptic encephalopathy, and reveals that an imbalance of non-inactivating inward and outward tonic membrane currents bidirectionally modulates spatiotemporal SD susceptibility.

neuroscience↗

bioRxiv2024

Spiking GABAergic OPC tumor cells prolong survival in IDH1 mutant glioma

Prior studies have described the complex interplay that exists between glioma cells and neurons, however, the electrophysiological properties endogenous to tumor cells remain obscure. To address this, we employed Patch-sequencing on human glioma specimens and found that one third of patched cells in IDH mutant (IDHmut) tumors demonstrate properties of both neurons and glia by firing single, short action potentials. To define these hybrid cells (HCs) and discern if they are tumor in origin, we developed a computational tool, Single Cell Rule Association Mining (SCRAM), to annotate each cell individually. SCRAM revealed that HCs represent tumor and non-tumor cells that feature GABAergic neuron and oligodendrocyte precursor cell signatures. These studies are the first to characterize the combined electrophysiological and molecular properties of human glioma cells and describe a new cell type in human glioma with unique electrophysiological and transcriptomic properties that are likely also present in the non-tumor mammalian brain.

cancer biology↗

bioRxiv2022

Identification of functional immune and neuronal tumor cells in glioma

Despite advances in molecular profiling, therapeutic development has been hindered by the inability to identify and target tumour-specific mechanisms without consequence to healthy tissue. Correspondingly, a computational framework capable of accurately distinguishing tumour from non-tumour cells has yet to be developed and cell annotation algorithms are unable to assign integrated genomic and transcriptional profiles to single cells on a cell-by-cell basis. To address these barriers, we developed the Single Cell Rule Association Mining (SCRAM) tool that integrates RNA-inferred genomic alterations with co-occurring cell type signatures for individual cells. Applying SCRAM to glioma, we identified tumour cell trajectories recapitulate temporally-restricted developmental paradigms and feature unique co-occurring identities. Specifically, we validated two previously unreported tumour cell populations with immune and neuronal signatures as hallmarks of human glioma subtypes. In vivo modeling revealed a rare immune-like tumour cell population resembling antigen presenting cells can direct CD8+ T cell responses. In parallel, Patch sequencing studies in human tumours confirmed that neuronal-like glioma cells fire action potentials and represent 40% of IDH1 mutant tumor cells. These studies identified new glioma cell types with functional properties similar to their non-tumour analogues and demonstrate the ability of SCRAM to identify these cell types in unprecedented detail.

cancer biology↗

bioRxiv2022

Febrile seizure unleashes spreading depolarizations in Scn1a deficient mice

Spreading depolarization (SD) is a massive wave of cellular depolarization that slowly migrates across the brain gray matter. Cortical SD is frequently generated following brain injury, while less is understood about its potential contribution to genetic disorders of hyperexcitability, such as SCN1A deficient epilepsy in which febrile seizure often contributes to disease initiation. Here we report that spontaneous SD waves are a predominant EEG abnormality in the Scn1a deficient mouse (Scn1a+/R1407X) and undergo sustained intensification following a single hyperthermic seizure. Chronic DC-band EEG recording detected spontaneous SDs, seizures, and seizure-SD complexes in Scn1a+/R1407X mice but not wild-type littermates. The SD events were infrequent, while a single hyperthermia-induced seizure robustly increased SD frequency over four-fold during the initial postictal week. This prolonged neurological aftermath could be suppressed by memantine administration. Video, electromyogram (EMG), and EEG spectral analysis revealed distinct neurobehavioral patterns; individual seizures were associated with increased motor activities, while SDs were generally associated with immobility. We also identified a stereotypic SD prodrome, detectable over a minute before the onset of the DC potential shift, characterized by increased motor activity and bilateral EEG frequency changes. Our study suggests that cortical SD is a pathological manifestation in SCN1A deficient epileptic encephalopathy.

neuroscience↗

bioRxiv2022

Emx1-Cre is expressed in vagal afferent nerves that regulate central cardiorespiratory functions

The Emx1-IRES-Cre transgenic mouse is commonly used to direct genetic recombination in forebrain excitatory neurons. However, the original study reported that Emx1-Cre is also expressed embryonically in peripheral autonomic ganglia, which could potentially affect the interpretation of targeted circuitry contributing to systemic phenotypes. Here, we report that Emx1-Cre is expressed in the afferent vagus nerve system involved in autonomic cardiorespiratory regulatory pathways. Our imaging studies revealed expression of Emx1-Cre driven tdtomato fluorescence in the afferent vagus nerve innervating the dorsal medulla of brainstem, cell bodies in the nodose ganglion, and their potential target structures at the carotid bifurcation such as the carotid sinus and the superior cervical ganglion. Photostimulation of the afferent terminals in the nucleus tractus solitarius (NTS) in vitro using Emx1-Cre driven ChR2 reliably evoked excitatory postsynaptic currents in the postsynaptic neurons with electrophysiological characteristics consistent with the vagus afferent nerves. In addition, optogenetic stimulation targeting the Emx1-Cre expressing structures identified in this study, such as vagus nerve, carotid bifurcation, and the dorsal medulla surface transiently depressed cardiorespiratory rate in urethane anesthetized mice in vivo. Together, our study demonstrates that Emx1-IRES-Cre is expressed in the key peripheral autonomic nerve system and can modulate the cardiorespiratory function independently of forebrain expression. These results raise caution when interpreting the systemic phenotypes of Emx1-IRES-Cre conditional recombinant mice, and also suggest the utility of this line to investigate the modulators of afferent vagal system. Significance StatementEmx1-IRES-Cre mice are widely used to dissect critical circuitry underlying neurological disorders such as epilepsy. These studies often assume the Cre is expressed selectively in forebrain excitatory neurons. However, earlier work reported that Emx1 is expressed in several peripheral tissues of the developing embryo and thus gene recombination may affect these peripheral structures. In this study, we characterized the expression and physiological functions of Emx1-Cre expressed in the vagus nerve, the critical peripheral autonomic component. Optogenetic stimulation of these Emx1-Cre+ neurons activates the nucleus tractus solitarius neurons within the brainstem in vitro and induces complex cardiorespiratory reflex in vivo. This study confirmed that peripheral Emx1-Cre+ cells are involved in autonomic regulation and potentially affect transgenic mouse phenotypes.

neuroscience↗

bioRxiv2020

Kcnq2/Kv7.2 controls the threshold and bihemispheric symmetry of cortical spreading depolarization

Spreading depolarization (SD) is a slowly propagating wave of massive cellular depolarization associated with acute brain injury and migraine aura. Genetic studies link molecular defects in enhanced cytoplasmic Ca2+ flux, glial Na+-K+ ATPase, and interneuronal Na+ current with SD susceptibility, emphasizing the important roles of synaptic activity and extracellular ionic homeostasis in determining SD threshold. In contrast, gene mutations in ion channels that shape intrinsic membrane excitability are frequently associated with epilepsy susceptibility. It is not well known whether epileptogenic mutations in voltage-gated potassium channels that regulate membrane repolarization also modify SD threshold and generation pattern. Here we report that the Kcnq2/Kv7.2 potassium channel subunit, frequently mutated in developmental epilepsy, is an SD modulatory gene with significant control over seizure-SD transition threshold, bilateral cortical expression, and temporal susceptibility. Chronic DC-band cortical EEG recording from awake conditional Kcnq2 deletion mice (Emx2cre/+::Kcnq2flox/flox) revealed spontaneous cortical seizures and SD. In contrast to a related potassium channel deficient model, Kv1.1 KO mice, spontaneous cortical SDs in Kcnq2 cKO mice are tightly coupled to the terminal phase of seizures, arise bilaterally, and are observed predominantly during the dark phase. Administration of the nonselective Kv7.2 inhibitor XE991 to Kv1.1 KO mice reproduced the Kcnq2 cKO-like SD phenotype (tight seizure coupling and bilateral symmetry) in these mice, indicating that Kv7.2 currents directly and actively modulate SD properties. In vitro brain slice studies confirmed that Kcnq2/Kv7.2 depletion or pharmacological inhibition intrinsically lowers the cortical SD threshold, whereas pharmacological activators elevate the threshold to multiple depolarizing and hypometabolic SD triggers. Together these results identify Kcnq2/Kv7.2 as a distinctive SD regulatory gene, and point to SD as a potentially significant pathophysiological component of KCNQ2-linked epileptic encephalopathy syndromes. Our results also implicate KCNQ2/Kv7.2 channel activation as an adjunctive therapeutic target to inhibit SD incidence.

neuroscience↗

bioRxiv2018

Adrenergic activation of cardiac preganglionic neurons in nucleus ambiguous relies on persistent sodium current

Cholinergic vagal nerves projecting from neurons in the brainstem nucleus ambiguus (NAm) play a predominant role in cardiac parasympathetic pacemaking control. Central adrenergic signaling modulates the tone of this vagal output; however the exact excitability mechanisms are not fully understood. We investigated responses of NAm neurons to adrenergic agonists using in vitro mouse brainstem slices. Preganglionic NAm neurons were identified by Chat-tdtomato fluorescence in young adult transgenic mice and their cardiac projection confirmed by retrograde dye tracing. Juxtacellular recordings detected sparse or absent spontaneous action potentials (AP) in NAm neurons. However bath application of epinephrine or norepinephrine strongly and reversibly activated most NAm neurons regardless of their basal firing rate. Epinephrine was more potent than norepinephrine, and this activation largely depends on 1-adrenoceptors. Interestingly, adrenergic activation of NAm neurons does not require an ionotropic synaptic mechanism, since postsynaptic excitatory or inhibitory receptor blockade did not occlude the excitatory effect, and bath-applied adrenergic agonists did not alter excitatory or inhibitory synaptic transmission. Instead, adrenergic agonists significantly elevated intrinsic membrane excitability to facilitate generation of recurrent action potentials. T-type calcium current (ICaT) and hyperpolarization-activated current (Ih) are involved in this excitation pattern, while not required for spontaneous AP induction by epinephrine. In contrast, pharmacological blockade of persistent sodium current (INaP) significantly inhibited the adrenergic effects. Our results demonstrate that central adrenergic signaling enhances the intrinsic excitability of NAm neurons, and persistent sodium current is required for this effect. This central balancing mechanism may counteract excessive peripheral cardiac excitation during increased sympathetic tone.\n\nNew & NoteworthyCardiac preganglionic cholinergic neurons in the Nucleus ambiguus (NAm) are responsible for slowing cardiac pacemaking. This study identified that adrenergic agonists can induce rhythmic action potentials in otherwise quiescent cholinergic NAm preganglionic neurons in brainstem slice preparation. The modulatory influence of adrenaline on central parasympathetic outflow may contribute to both physiological and deleterious cardiovascular regulation.

neuroscience↗