SCN1A Variant Database

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The SCN1A gene is located on chromosome 2q24 and encodes the pore-forming alpha-subunit of the neuronal voltage-gated sodium channel Nav1.1. The gene is composed of 26 coding exons located in a region of approximately 85 kb.

The Nav1.1 protein is a neuronal voltage-gated sodium channel composed of four domains, DI-DIV. Each domain has 6 transmembrane segments (S1-S6). The S4 segment is positively charged and is the voltage-sensor of the protein. S5 and S6 delineate the pore of the channel, and the loop between S5 and S6, the pore loop, is important for ion specificity.

Nav1.1 plays an important role in the initiation and propagation of action potentials. When mutated, it predisposes to epilepsy. The phenotypic spectrum associated with variations in SCN1A (OMIM entry 182389) ranges from the mild epilepsy syndrome 'generalized epilepsy with febrile seizures plus' (GEFS+, OMIM entry 604233) to the severe Dravet syndrome or 'severe myoclonic epilepsy in infancy' (SMEI, OMIM entry 607208). This spectrum has recently been expanded to other phenotypes like familial hemiplegic migraine (FHM3, OMIM entry 609634) and infantile epileptic encephalopathies amongst which cryptogenic epilepsy and Lennox-Gastaut syndrome (LGS, OMIM entry 606369).

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