A large-scale mutagenesis screen to identify seizure-resistant zebrafish.
OBJECTIVE
Zebrafish are a vertebrate organism ideally suited to mutagenesis screening strategies. Although a genetic basis for seizure susceptibility and epilepsy is well established, no efforts have been made to study seizure resistance. Here we describe a novel strategy to isolate seizure-resistant zebrafish mutants from a large-scale mutagenesis screen.


METHODS
Seizures were induced with pentylenetetrazole (PTZ). Zebrafish were analyzed between 3 and 7 days postfertilization (dpf). Genome mutations were induced in founders by using N-ethyl-nitrosourea (ENU). Seizure behavior was monitored by using a high-speed camera and quantified by locomotion-tracking software. Electrographic activity was monitored by using a field-recording electrode placed in the optic tectum of agar-immobilized zebrafish.


RESULTS
Short-term PTZ exposure elicited a burst-suppression seizure pattern in 3-dpf zebrafish and more complex activity consisting of interictal- and ictal-like discharges at 7 dpf. Prolonged exposure to PTZ induced status epilepticus-like seizure activity and fatality in wild-type zebrafish larvae. With a PTZ survival assay at 6-7 dpf, we identified six zebrafish mutants in a forward-genetic screen covering nearly 2,000 F(2) families. One mutant (s334) also was shown to exhibit reduced behavioral activity on short-term PTZ exposure and an inability to generate long-duration ictal-like discharge.


CONCLUSIONS
Zebrafish offers a powerful tool for the identification and study of a genetic basis for seizure resistance.
Baraban
Scott C
SC
Epilepsy Research Laboratory in the Department of Neurological Surgery, University of California, San Francisco, California 94143, USA. scott.baraban@ucsf.edu
Dinday
Matthew T
MT
Castro
Peter A
PA
Chege
Sally
S
Guyenet
Stephan
S
Taylor
Michael R
MR
D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects / Q000502:physiology; D004195:Disease Models, Animal; D020022:Genetic Predisposition to Disease / Q000235:genetics; D005820:Genetic Testing; D007814:Larva / Q000235:genetics / Q000502:physiology; D008124:Locomotion / Q000187:drug effects / Q000235:genetics; D016296:Mutagenesis / Q000235:genetics*; D010433:Pentylenetetrazole / Q000494:pharmacology; D012640:Seizures / Q000139:chemically induced / Q000453:epidemiology / Q000517:prevention & control*; D013226:Status Epilepticus / Q000139:chemically induced / Q000517:prevention & control; D013477:Superior Colliculi / Q000502:physiology; D015027:Zebrafish / Q000235:genetics*
D010433:Pentylenetetrazole