Genetic heterogeneity has been demonstrated for ADCA, with four cloned genes (SCA1, SCA2, SCA3/MJD, and SCA6) and three mapped loci (SCA4, SCA5 and SCA7).
Spinocerebellar ataxia type 6 (SCA6) was recently identified as a form of autosomal dominant cerebellar ataxia associated with small expansions of the trinucleotide repeat (CAG)n in the gene CACNL1A4 on chromosome 19p13, which encodes the alpha1 subunit of a P/Q-type voltage-gated calcium channel.
To identify various subtypes of spinocerebellar ataxias (SCAs) among autosomal dominant cerebellar ataxia (ADCA) patients referred to our research center, SCA1, SCA2, SCA3/MJD (Machado-Joseph disease), SCA6, SCA7, SCA8 and SCA12 loci were assessed for expansion of trinucleotide repeats.
In Nagano, 16q22-linked ADCA appears to be much more prevalent than either SCA6 or dentatorubral-pallidoluysian atrophy (DRPLA), and may explain the high frequency of spinocerebellar ataxia.
Spinocerebellar ataxia type 6 (SCA 6) is an autosomal dominant cerebellar ataxia caused by CAG repeat expansion in the SCA6 gene, a alpha 1A voltage-dependent calcium channel subunit gene on chromosome 19p13.