Evaluation of SCN8A as a candidate gene for autosomal dominant essential tremor.

OBJECTIVES: Essential tremor (ET) is a common inherited movement disorder whose causes remain unknown. The presence of spontaneous tremor in murine mutants may provide clues into the pathogenesis of ET. SCN8A encodes the neuronal voltage gated sodium channel Na(v)1.6 that is widely expressed in the central nervous system. Several mutations of Scn8a in the mouse result in congenital postural tremor of the extremities and head.
METHODS: We screened SCN8A as a candidate gene in a cohort of 95 Caucasian patients with ET and a positive family history, including 48 patients with early onset in the first two decades of life. Early and adult onset ET subgroups did not differ in disease severity, but early onset patients had longer disease duration. Observed sequence variants were also screened in an ethnically matched control group.
RESULTS: We did not detect SCN8A mutations affecting amino acid sequence or splice sites in our cohort of ET patients.
CONCLUSIONS: Although mutations of Scn8a cause congenital tremor in mice, mutations in the sequence of the exons and splice sites of human SCN8A do not appear to be a common cause of autosomal dominant essential tremor in Caucasian patients.