Project description:We compare the brain and fin RNA-seq profiles of wild-type and scn8ab mutant zebrafish, which exhibit locomotion and fin regeneration defects.
Project description:Scn2a encodes voltage-gated sodium channel NaV1.2, a main mediator of neuronal action potential firing. The current paradigm suggests that NaV1.2 gain-of-function variants enhance neuronal excitability resulting in epilepsy, whereas NaV1.2 deficiency impairs excitability contributing to autism. This paradigm, however, does not explain why 20~30% of patients with NaV1.2 deficiency still develop seizures. Here we report a counterintuitive finding that severe NaV1.2 deficiency results in increased neuronal excitability. Using a unique NaV1.2-deficient mouse model, we found enhanced intrinsic excitabilities of principal neurons in the prefrontal cortex and striatum, brain regions known to be involved in Scn2a-related seizures. This increased excitability is autonomous, and is reversible by the genetic restoration of Scn2a expression in adult mice. RNA-sequencing revealed that the downregulation of multiple potassium channels including KV1.1, and KV channel openers alleviated hyperexcitability of NaV1.2-deficient neurons. This unexpected neuronal hyperexcitability may serve as a cellular basis underlying NaV1.2 deficiency-related seizures.
Project description:We investigated the effects of nimodipine, a L-type voltage-gated calcium channel antagonist, on the expression profile of myelin genes in the oligodendrocyte precursor cell (OPC) line Oli-Neu. We performed gene expression profiling analysis using data obtained from RNA-seq of four biological replicates for treatment and four replicates for control condition.
Project description:The voltage-gated sodium channel NaV1.7 plays a critical role in pain pathways. As well as action potential propagation, NaV1.7 regulates neurotransmitter release, integrates depolarizing inputs over long periods and regulates transcription. In order to better understand these functions, we generated an epitope-tagged NaV1.7 mouse that showed normal NaV1.7 channel activity and normal pain behavior. Analysis of NaV1.7 complexes affinity-purified under native conditions by mass spectrometry revealed 267 NaV1.7 associated proteins including known and novel interactors such as sodium channel β3 subunit (Scn3b) and collapsin response mediator protein (Crmp2). Selected NaV1.7 protein interactors, such as Crmp2, membrane-trafficking protein synapototagmin-2 (Syt2), G protein-regulated inducer of neurite outgrowth 1 (Gprin1), L-type amino acid transporter 1 (Lat1) and transmembrane P24 trafficking protein 10 (Tmed10) were validated using co-immunoprecipitation and functional assays. The information provided with this physiologically normal epitope-tagged mouse should provide useful insights into the downstream mechanisms associated with NaV1.7 channel function.
Project description:In multipolar vertebrate neurons, action potentials (AP) initiate close to the soma, at the axonal initial segment (AIS). Invertebrate neurons are typically unipolar with dendrites integrating directly into the axon. Where APs are initiated in the axons of invertebrate neurons is unclear. Voltage-gated sodium (NaV) channels are a functional hallmark of the AIS in vertebrates. We used an intronic MiMIC to determine the endogenous gene expression and subcellular localization of the sole NaV channel in both male and female Drosophila, para. Despite being the only NaV channel in the fly, we show that only 23 ±1% of neurons in the embryonic and larval CNS express para, while in the adult CNS para is broadly expressed. We generated a single-cell transcriptomic atlas of the whole 3rd instar larval brain to identify para expressing neurons and show that it positively correlates with markers of differentiated, actively firing neurons. Therefore only 23 ±1% of larval neurons may be capable of firing NaV-dependent APs. We then show that Para is enriched in an axonal segment, distal to the site of dendritic integration into the axon, which we named the Distal Axonal Segment (DAS). The DAS is present in multiple neuron classes in both the 3rd instar larval and adult CNS. Whole cell patch clamp electrophysiological recordings of adult CNS fly neurons are consistent with the interpretation that Nav-dependent APs originate in the DAS. Identification of the distal NaV localization in fly neurons will enable more accurate interpretation of electrophysiological recordings in invertebrates.
Project description:Using whole-cell patch clamp recording and unbiased gene expression profiling in rat dissociated hippocampal neurons cultured at high density, we demonstrate here that chronic activity blockade induced by the sodium channel blocker tetrodotoxin leads to a homeostatic increase in action potential firing and down-regulation of potassium channel genes. In addition, chronic activity blockade reduces total potassium current, as well as protein expression and current of voltage-gated Kv1 and Kv7 potassium channels, which are critical regulators of action potential firing. Importantly, inhibition of N-Methyl-D-Aspartate receptors alone mimics the effects of tetrodotoxin, including the elevation in firing frequency and reduction of potassium channel gene expression and current driven by activity blockade, whereas inhibition of L-type voltage-gated calcium channels has no effect.
Project description:Developmental and epileptic encephalopathies (DEEs) are a group of rare childhood disorders characterized by severe epilepsy and cognitive deficits. Numerous DEE genes have been discovered thanks to advances in genomic diagnosis, yet putative molecular links between these disorders are unknown. CDKL5 deficiency disorder (CDD, DEE2), one of the most common genetic epilepsies, is caused by loss-of-function mutations in the brain-enriched kinase CDKL5. To elucidate CDKL5 function, we looked for CDKL5 substrates using a SILAC-based phosphoproteomic screen. We identified the voltage-gated Ca2+ channel Cav2.3 (encoded by CACNA1E) as a novel physiological target of CDKL5 in mice and humans. Recombinant channel electrophysiology and interdisciplinary characterization of Cav2.3 phosphomutant mice revealed that loss of Cav2.3 phosphorylation leads to channel gain-of-function via slower inactivation and enhanced cholinergic stimulation, resulting in increased neuronal excitability. Our results thus show that CDD is partly a channelopathy. The properties of unphosphorylated Cav2.3 closely resemble those described for CACNA1E gain-of-function mutations causing DEE69, a disorder sharing clinical features with CDD. We show that these two single-gene diseases are mechanistically related and could be ameliorated with Cav2.3 inhibitors.