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Mol Med. 1996 January; 2(1): 77–85.
PMCID: PMC2230032

Mutation detection in Machado-Joseph disease using repeat expansion detection.


BACKGROUND: Several neurological disorders have recently been explained through the discovery of expanded DNA repeat sequences. Among these is Machado-Joseph disease, one of the most common spinocerebellar ataxias (MJD/SCA3), caused by a CAG repeat expansion on chromosome 14. A useful way of detecting repeat sequence mutations is offered by the repeat expansion detection method (RED), in which a thermostable ligase is used to detect repeat expansions directly from genomic DNA. We have used RED to detect CAG expansions in families with either MJD/SCA3 or with previously uncharacterized spinocerebellar ataxia (SCA). MATERIALS AND METHODS: Five MJD/SCA3 families and one SCA family where linkage to SCA1-5 had been excluded were analyzed by RED and polymerase chain reaction (PCR). RESULTS: An expansion represented by RED products of 180-270 bp segregated with MJD/SCA3 (p < 0.00001) in five families (n = 60) and PCR products corresponding to 66-80 repeat copies were observed in all affected individuals. We also detected a 210-bp RED product segregating with disease (p < 0.01) in a non-SCA1-5 family (n = 16), suggesting involvement of a CAG expansion in the pathophysiology. PCR analysis subsequently revealed an elongated MJD/SCA3 allele in all affected family members. CONCLUSIONS: RED products detected in Machado-Joseph disease families correlated with elongated PCR products at the MJD/SCA3 locus. We demonstrate the added usefulness of RED in detecting repeat expansions in disorders where linkage is complicated by phenotyping problems in gradually developing adult-onset disorders, as in the non-SCA1-5 family examined. The RED method is informative without any knowledge of flanking sequences. This is particularly useful when studying diseases where the mutated gene is unknown. We conclude that RED is a reliable method for analyzing expanded repeat sequences in the genome.

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Selected References

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  • Lima L, Coutinho P. Clinical criteria for diagnosis of Machado-Joseph disease: report of a non-Azorena Portuguese family. Neurology. 1980 Mar;30(3):319–322. [PubMed]
  • Takiyama Y, Nishizawa M, Tanaka H, Kawashima S, Sakamoto H, Karube Y, Shimazaki H, Soutome M, Endo K, Ohta S, et al. The gene for Machado-Joseph disease maps to human chromosome 14q. Nat Genet. 1993 Jul;4(3):300–304. [PubMed]
  • Stevanin G, Le Guern E, Ravisé N, Chneiweiss H, Dürr A, Cancel G, Vignal A, Boch AL, Ruberg M, Penet C, et al. A third locus for autosomal dominant cerebellar ataxia type I maps to chromosome 14q24.3-qter: evidence for the existence of a fourth locus. Am J Hum Genet. 1994 Jan;54(1):11–20. [PubMed]
  • Kawaguchi Y, Okamoto T, Taniwaki M, Aizawa M, Inoue M, Katayama S, Kawakami H, Nakamura S, Nishimura M, Akiguchi I, et al. CAG expansions in a novel gene for Machado-Joseph disease at chromosome 14q32.1. Nat Genet. 1994 Nov;8(3):221–228. [PubMed]
  • Schalling M, Hudson TJ, Buetow KH, Housman DE. Direct detection of novel expanded trinucleotide repeats in the human genome. Nat Genet. 1993 Jun;4(2):135–139. [PubMed]
  • Maciel P, Gaspar C, DeStefano AL, Silveira I, Coutinho P, Radvany J, Dawson DM, Sudarsky L, Guimarães J, Loureiro JE, et al. Correlation between CAG repeat length and clinical features in Machado-Joseph disease. Am J Hum Genet. 1995 Jul;57(1):54–61. [PubMed]
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