Mutations in the brain-specific P/Q type Ca2+ channel alpha1 subunit gene, CACNA1A, have been identified in three clinically distinct disorders, spinocerebellar ataxia type 6 (SCA6), episodic ataxia type 2 (EA2), and familial hemiplegic migraine type 1 (FHM1).
Mutations in the calcium channel voltage dependent P/Q-type alpha-1A subunit (CACNA1A) can cause different neurological disorders which share a wide range of symptoms, including episodic ataxia type 2 (EA2), familial hemiplegic migraine (FHM1) and progressive spinocerebellar ataxia (SCA6).
Spinocerebellar ataxia type 6 (SCA 6) is an autosomal dominant cerebellar degeneration that shares neuropathological findings with late-onset cortical cerebellar atrophy (CCA).
Spinocerebellar ataxia type 6 (SCA6) is due to small expansions of a CAG repeat at the 3' end of the CACNA1A gene, coding for the alpha(1A) subunit of voltage-gated calcium channels type P/Q, expressed in the cerebellar Purkinje and granule cells.
In view of the known role of p62 in protein degradation as well as aggresome/sequestosome formation, the p62 aggregate formation observed in the present study suggests that SCA6not only is associated with an impairment of the calcium channel function and an elongated polyglutamine stretch in CACNA1A, but also with a defective protein handling by the protein quality control system.
Apart from spinocerebellar ataxia type 6 and 12 (SCA6 and SCA12), these CAG-repeat diseases, as well as Huntington disease-like 2 (HDL2) and SCA8, can be neuropathologically identified using 1C2 polyglutamine antibodies.
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.