The mouse SCA2 gene: cDNA sequence, alternative splicing and protein expression.

Spinocerebellar ataxia type 2 (SCA2) is caused by expansion of a CAG trinucleotide repeat located in the coding region of the human SCA2 gene. Sequence analysis revealed that SCA2 is a novel gene of unknown function. In order to provide insights into the molecular mechanisms of pathogenesis of SCA2 and to identify conserved domains, we isolated and characterized the mouse homolog of the SCA2 gene. Sequence and amino acid analysis revealed 89% identity at the nucleotide and 91% identity at the amino acid level. However, there was no extended polyglutamine tract in the mouse SCA2 cDNA, suggesting that the normal function of SCA2 is not dependent on this domain. Northern blot analysis of different mouse tissues indicated that the mouse SCA2 gene was expressed in most tissues, but at varying levels. Alternative splicing seen in human SCA2 was conserved in the mouse. By northern blot analysis, SCA2 was expressed during embryogenesis as early as day 8 of gestation (E8). Immunohistochemical staining using affinity-purified antibodies demonstrated that ataxin 2 was expressed in the cytoplasm of Purkinje cells as well as in other neurons of the CNS.