Gene mapping and other tools for discovery

Large-Scale Phenotype-Based Antiepileptic Drug Screening in a Zebrafish Model of Dravet Syndrome

Mutations in a voltage-gated sodium channel (SCN1A) result in Dravet Syndrome (DS), a catastrophic childhood epilepsy. Zebrafish with a mutation in scn1Lab recapitulate salient phenotypes associated with DS, including seizures, early fatality, and resistance to antiepileptic drugs. To discover new drug candidates for the treatment of DS, we screened a chemical library of ∼1000 compounds and identified 4 compounds that rescued the behavioral seizure component, including 1 compound (dimethadione) that suppressed associated electrographic seizure activity. Fenfluramine, but not huperzine A, also showed antiepileptic activity in our zebrafish assays. The effectiveness of compounds that block neuronal calcium current (dimethadione) or enhance serotonin signaling (fenfluramine) in our zebrafish model suggests that these may be important therapeutic targets in patients with DS. Over 150 compounds resulting in fatality were also identified. We conclude that the combination of behavioral and electrophysiological assays provide a convenient, sensitive, and rapid basis for phenotype-based drug screening in zebrafish mimicking a genetic form of epilepsy.

Facioscapulohumeral muscular dystrophy: the impact of genetic research

Recent developments in genetic research have led to the localization and identification of the causative gene defect in a large number of neurological diseases. This paper describes some of the basic principles of molecular genetics and the strategies that have been followed in the search for the gene for facioscapulohumeral muscular dystrophy (FSHD), beginning with the recent localization to chromosome 4q. Many questions remain concerning the pathogenesis and possible genetic heterogeneity of this autosomal dominant myopathy. Hitherto, most evidence favours a genetically homogeneous disorder, but only the isolation and detailed characterization of the FSHD gene will resolve these issues completely.