[5] "Voltage-dependent calcium channels mediate the entry of calcium ions into excitable cells, and are also involved in a variety of calcium-dependent processes, including muscle contraction, hormone or neurotransmitter release, and gene expression.

Calcium channels are multisubunit complexes composed of alpha-1, beta, alpha-2/delta, and gamma subunits.

In one set of transcript variants, the (CAG)n-repeats occur in the 3' UTR, and are not associated with any disease.

However, in another set of variants, an insertion extends the coding region to include the (CAG)n-repeats which encode a polyglutamine tract.

Expansion of the (CAG)n-repeats from the normal 4-16 to 21-28 in the coding region is associated with spinocerebellar ataxia 6.