Phenotypic Characterization of Larval Zebrafish (Danio rerio) with Partial Knockdown of the cacna1a Gene.
The CACNA1A gene encodes the pore-forming α1 subunit of voltage-gated P/Q type Ca2+ channels (Cav2.1). Mutations in this gene, among others, have been described in patients and rodents suffering from absence seizures and episodic ataxia type 2 with/without concomitant seizures. In this study, we aimed for the first time to assess phenotypic and behavioral alterations in larval zebrafish with partial cacna1aa knockdown, placing special emphasis on changes in epileptiform-like electrographic discharges in larval brains. Whole-mount in situ hybridization analysis revealed expression of cacna1aa in the optic tectum and medulla oblongata of larval zebrafish at 4 and 5 days post-fertilization. Next, microinjection of two antisense morpholino oligomers (individually or in combination) targeting all splice variants of cacna1aa into fertilized zebrafish eggs resulted in dose-dependent mortality and decreased or absent touch response. Over 90% knockdown of cacna1aa on protein level induced epileptiform-like discharges in the optic tectum of larval zebrafish brains. Incubation of morphants with antiseizure drugs (sodium valproate, ethosuximide, lamotrigine, topiramate) significantly decreased the number and, in some cases, cumulative duration of epileptiform-like discharges. In this context, sodium valproate seemed to be the least effective. Carbamazepine did not affect the number and duration of epileptiform-like discharges. Altogether, our data indicate that cacna1aa loss-of-function zebrafish may be considered a new model of absence epilepsy and may prove useful both for the investigation of Cacna1a-mediated epileptogenesis and for in vivo drug screening.
['Gawel|Kinga|K|http://orcid.org/0000-0001-8857-847X', 'Turski|Waldemar A|WA|http://orcid.org/0000-0002-5805-5106', 'van der Ent|Wietske|W|http://orcid.org/0000-0003-2165-9624', 'Mathai|Benan J|BJ|http://orcid.org/0000-0002-9549-2073', 'Kirstein-Smardzewska|Karolina J|KJ|', 'Simonsen|Anne|A|http://orcid.org/0000-0003-4711-7057', 'Esguerra|Camila V|CV|http://orcid.org/0000-0002-2271-8094']
D000818:Animals D001522:Behavior, Animal D001921:Brain D015220:Calcium Channels D004569:Electroencephalography D018507:Gene Expression Regulation, Developmental D055785:Gene Knockdown Techniques D006801:Humans D007814:Larva D060172:Morpholinos D009043:Motor Activity D010641:Phenotype D014110:Touch D015027:Zebrafish D029961:Zebrafish Proteins
Zebrafish CACNA1A gene Touch response Antiseizure drugs Epilepsy Loss of function