Unknown,Transcriptomics,Genomics,Proteomics

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Drug screening for Dravet syndrome using Scn1a zebrafish mutants

ABSTRACT: Severe myoclonic epilepsy of infancy (SMEI), or Dravet syndrome (DS), is a catastrophic pediatric epilepsy with severe intellectual disability, impaired social development, and persistent drug-resistant seizures. One of its primary monogenic causes is a mutation in SCN1A (Nav1.1), a type I voltage-gated sodium channel. In mice, Nav1.1 mutation is associated with reduced sodium current, altered interneuron firing, cognitive deficits, autistic-like traits and seizures. Here we describe a larval zebrafish Nav1.1 mutant that recapitulates salient features of the human SCN1A mutation phenotype. Between three and seven days post-fertilization, Nav1.1 mutants exhibit spontaneous abnormal electrographic activity, hyperactivity and convulsive behaviors. Transcriptomic analysis of Nav1.1 mutants was remarkable for the relatively small fraction of genes that were differentially expressed (~2%) and the lack of compensatory changes in expression for other SCN subunits. Pharmacological studies confirmed an antiepileptic action for the ketogenic diet, benzodiazepine, valproate, potassium bromide and stiripentol in Nav1.1 mutants; acetazolamide, phenytoin, ethosuximide had no effect, carbamazepine and vigabatrin made seizures worse. Using this mutant, we screened a chemical library of 320 compounds and identified four compounds that reduced spontaneous seizure-like behavior and one compound (clemizole) that inhibited convulsive behavior and electrographic seizures. Drug-resistant scn1a zebrafish mutants described here represent a new direction in modeling pediatric epilepsy and could be used to identify novel lead compounds for DS patients 4 Control sibling samples (sample= 10 pooled larvae) and 4 Nav1.1 mutants (sample= 10 pooled larvae) were collected at 6 dpf (days post fertilization). The Nav1.1 mutants were selected based on phenotype (dark color).

ORGANISM(S): Danio rerio

SUBMITTER: Andrea Barczak

PROVIDER: E-GEOD-43312 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Epilepsy is a common neurological disease, manifested in unprovoked recurrent seizures. Epileptogenesis may develop due to genetic or pharmacological origins or following injury, but it remains unclear how the unaffected brain escapes this susceptibility to seizures. Here, we report that dynamic changes in forebrain microRNA (miR)-211 in the mouse brain shift the threshold for spontaneous and pharmacologically-induced seizures alongside changes in the cholinergic pathway genes, implicating this miR in the avoidance of seizures. We identified miR-211 as a putative attenuator of cholinergic-mediated seizures by intersecting forebrain miR profiles that were Ago-precipitated, synaptic vesicle target-enriched or differentially expressed under pilocarpine-induced seizures, and validated TGFBR2 and the nicotinic anti-inflammatory acetylcholine receptor nAChRa7 as murine and human miR-211 targets, respectively. To explore the link between miR-211 and epilepsy, we engineered dTg-211 mice with doxycycline-suppressible forebrain overexpression of miR-211. These mice reacted to doxycycline exposure by spontaneous electrocorticography-documented non-convulsive seizures, accompanied by forebrain accumulation of the convulsive seizures-mediating miR-134. RNA-sequencing demonstrated in doxycycline-treated dTg-211 cortices over-representation of synaptic activity, Ca2+ transmembrane transport, TGFβR-II signaling and cholinergic synapse pathways. Additionally, a cholinergic dis-regulated mouse model over-expressing a miR-refractory acetylcholinesterase-R splice variant showed a parallel propensity for convulsions, miR-211 decreases and miR-134 elevation. Our findings demonstrate that in mice, dynamic miR-211 decreases induce hyper-synchronization, non-convulsive and convulsive seizures, accompanied by expression changes in cholinergic and TGFBR2 pathways as well as in miR-134. Realizing the importance of miR-211 dynamics opens new venues for translational diagnosis of and interference with epilepsy.

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Drug screening for Dravet syndrome using Scn1a zebrafish mutants

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