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Transient knockdown of LIS1 results in seizures, differential gene expression and a neuronal migration disorder in developing zebrafish

ABSTRACT: Mutation or deletion of LIS1 (Lissencephaly-1) underlies classical lissencephaly, a migration disorder resulting in brain malformation, epilepsy and mental retardation. Orthologues for LIS1 genes (lis1a and lis1b) are ubiquitously expressed in developing zebrafish larvae, but the functional consequences of Lis1 knockdown are unknown. Here we used lis1-specific morpholino oligonucleotides (MOs, targeting protein translation or mRNA splicing, respectively) to transiently knockdown Lis1 expression in zebrafish. Injection of lis1 MOs resulted in morphological changes including microcephaly. At four days post-fertilization, lis1 morphants exhibited spontaneous convulsive behavior and abnormal large-amplitude electrographic discharge resembling that seen in acute and genetic zebrafish models of epilepsy. Abnormal brain development and neuronal migration defects were observed when lis1 MO injections were made into fluorescent reporter lines demarcating interneuron distribution (Dlx5a/6a:GFP) and brain structure (GBT0133:mRFP). Microarray analysis for ~44,000 Danio rerio transcripts identified 215 up-regulated and 160 down-regulated genes. Quantitative PCR and whole-mount in situ hybridization were used to validate these results for twenty and seven genes, respectively. These findings in a simple vertebrate model reproducing neuroanatomical and epileptic hallmarks of the human condition represent a novel approach to the study of childhood seizure disorders associated with a single gene mutation

ORGANISM(S): Danio rerio

PROVIDER: GSE47952 | GEO | 2013/06/15

SECONDARY ACCESSION(S): PRJNA208438

REPOSITORIES: GEO

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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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Transient knockdown of LIS1 results in seizures, differential gene expression and a neuronal migration disorder in developing zebrafish

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