Document Detail

Expanded CAG repeats in spinocerebellar ataxia (SCA1) segregate with distinct haplotypes in South african families.
MedLine Citation:
PMID:  9225982     Owner:  NLM     Status:  MEDLINE    
The autosomal dominant late onset spinocerebellar ataxias (SCAs) are genetically heterogeneous. Three genes, SCA1 on 6p, SCA2 on 12q and MJD1 on 14q, have been isolated for SCA1, SCA2 and Machado-Joseph disease (MJD), respectively. In these three autosomal dominant disorders the mutation is an expanded CAG repeat. Evidence for heterogeneity in families not linked to the SCA1, SCA2 and MJD loci is provided by the mapping of SCA loci to chromosomes 16q, 11cen and 3p. A total of 14 South African kindreds and 22 sporadic individuals with SCA were investigated for the expanded SCA1 and MJD repeats. None of the families nor the sporadic individuals showed expansion of the MJD repeat. Expanded SCA1 and CAG repeats were found to cosegregate with the disorder in six of the families tested and were also observed in one sporadic individual with a negative family history of SCA. The use of the microsatellite markers D6S260, D6S89 and D6S274 provided evidence that the expanded SCA1 repeats segregated with three distinct haplotypes in the six families. Use of the highly polymorphic tightly linked microsatellite markers is still important as this stage, particularly where this coincides with the possibility of a homozygous genotype with the trinucleotide repeat marker. Importantly, our molecular findings indicate: (1) an absence of MJD expanded repeats underlying SCA; (2) the major disease in this group is due to mutations in the SCA1 gene; and (3) the familial disorder in the majority population group (i.e. mixed ancestry) in the Western Cape region of South Africa is most likely to be the result of two distinct founder events.
R S Ramesar; S Bardien; P Beighton; A Bryer
Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Human genetics     Volume:  100     ISSN:  0340-6717     ISO Abbreviation:  Hum. Genet.     Publication Date:  1997 Jul 
Date Detail:
Created Date:  1997-07-31     Completed Date:  1997-07-31     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  7613873     Medline TA:  Hum Genet     Country:  GERMANY    
Other Details:
Languages:  eng     Pagination:  131-7     Citation Subset:  IM    
Department of Human Genetics, University of Cape Town Medical School, Observatory, South Africa.
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MeSH Terms
Chromosomes, Human, Pair 14
Chromosomes, Human, Pair 6
Founder Effect
Lod Score
Machado-Joseph Disease / genetics
Microsatellite Repeats
Recombination, Genetic
South Africa
Spinocerebellar Degenerations / ethnology,  genetics*
Trinucleotide Repeats*

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