title: Frequency of the different mutations causing spinocerebellar ataxia (SCA1, SCA2, MJD/SCA3 and DRPLA) in a large group of Brazilian patients.
abstract: Spinocerebellar ataxia type 1 (SCA1), spinocerebellar ataxia type 2 (SCA2) and Machado-Joseph disease or spinocerebellar ataxia type 3 (MJD/SCA3) are three distinctive forms of autosomal dominant spinocerebellar ataxia (SCA) caused by expansions of an unstable CAG repeat localized in the coding region of the causative genes. Another related disease, dentatorubropallidoluysian atrophy (DRPLA) is also caused by an unstable triplet repeat and can present as SCA in late onset patients. We investigated the frequency of the SCA1, SCA2, MJD/SCA3 and DRPLA mutations in 328 Brazilian patients with SCA, belonging to 90 unrelated families with various patterns of inheritance and originating in different geographic regions of Brazil. We found mutations in 35 families (39%), 32 of them with a clear autosomal dominant inheritance. The frequency of the SCA1 mutation was 3% of all patients; and 6% in the dominantly inherited SCAs. We identified the SCA2 mutation in 6% of all families and in 9% of the families with autosomal dominant inheritance. The MJD/SCA3 mutation was detected in 30% of all patients; and in the 44% of the dominantly inherited cases. We found no DRPLA mutation. In addition, we observed variability in the frequency of the different mutations according to geographic origin of the patients, which is probably related to the distinct colonization of different parts of Brazil. These results suggest that SCA may be occasionally caused by the SCA1 and SCA2 mutations in the Brazilian population, and that the MJD/SCA3 mutation is the most common cause of dominantly inherited SCA in Brazil.
authors.affiliation: Centre for Research in Neuroscience, McGill University, Montreal, QC, Canada. bke6@musicb.mcgill.ca
authors.forename: I
authors.initials: I
authors.lastname: Lopes-Cendes
authors.forename: H G
authors.initials: HG
authors.lastname: Teive
authors.forename: M E
authors.initials: ME
authors.lastname: Calcagnotto
authors.forename: J C
authors.initials: JC
authors.lastname: Da Costa
authors.forename: F
authors.initials: F
authors.lastname: Cardoso
authors.forename: E
authors.initials: E
authors.lastname: Viana
authors.forename: J A
authors.initials: JA
authors.lastname: Maciel
authors.forename: J
authors.initials: J
authors.lastname: Radvany
authors.forename: W O
authors.initials: WO
authors.lastname: Arruda
authors.forename: P C
authors.initials: PC
authors.lastname: Trevisol-Bittencourt
authors.forename: P
authors.initials: P
authors.lastname: Rosa Neto
authors.forename: I
authors.initials: I
authors.lastname: Silveira
authors.forename: C E
authors.initials: CE
authors.lastname: Steiner
authors.forename: W
authors.initials: W
authors.lastname: Pinto Júnior
authors.forename: A S
authors.initials: AS
authors.lastname: Santos
authors.forename: Y
authors.initials: Y
authors.lastname: Correa Neto
authors.forename: L C
authors.initials: LC
authors.lastname: Werneck
authors.forename: A Q
authors.initials: AQ
authors.lastname: Araújo
authors.forename: G
authors.initials: G
authors.lastname: Carakushansky
authors.forename: L R
authors.initials: LR
authors.lastname: Mello
authors.forename: L B
authors.initials: LB
authors.lastname: Jardim
authors.forename: G A
authors.initials: GA
authors.lastname: Rouleau
mesh_terms: D000293:Adolescent; D000328:Adult; D001938:Brazil; D002648:Child; D002869:Chromosome Aberrations / Q000235:genetics; D025063:Chromosome Disorders; D004252:DNA Mutational Analysis; D005799:Genes, Dominant; D006801:Humans; D017827:Machado-Joseph Disease / Q000235:genetics; D008875:Middle Aged; D009154:Mutation / Q000235:genetics*; D013132:Spinocerebellar Degenerations / Q000235:genetics*