| 1. |
- Andrew, S, et al.
(author)
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DNA analysis of distinct populations suggests multiple origins for the mutation causing Huntington disease.
- 1993
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In: Clinical Genetics. - 0009-9163 .- 1399-0004. ; 43:6, s. 286-94
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Journal article (peer-reviewed)abstract
- Results of association studies can be significantly biased if the ancestry of the control population is not similar to that of the affected population. One approach to overcome such a bias is to use distinct populations where controls and affected individuals are likely to be of similar descent. We have examined homogeneous populations of French, Danish and Swedish ancestry for nonrandom allelic association between Huntington disease (HD) and several markers previously shown to be in association with HD. No evidence for nonrandom allelic association between HD and these markers was shown in these populations. The demonstration of association in a United Kingdom (UK) sample of similar size, and lack of significant differences in allele frequencies between the French, Danish, Swedish and UK populations suggested that the absence of association was not predominantly a consequence of allele frequencies or sample size. To investigate further the number of potential HD chromosomes, DNA haplotypes were constructed for the Danish, French, Swedish and UK populations. The minimum of two HD haplotypes observed in each of the French, Danish and Swedish populations, compared to the one haplotype in the UK population of a similar size, is an important factor accounting for the absence of association between HD and the DNA markers in these populations. Furthermore, these data are in favour of multiple independent origins for the mutation causing HD.
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| 2. |
- Kremer, B, et al.
(author)
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A worldwide study of the Huntington's disease mutation. The sensitivity and specificity of measuring CAG repeats.
- 1994
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In: New England Journal of Medicine. - 0028-4793 .- 1533-4406. ; 330:20, s. 1401-6
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Journal article (peer-reviewed)abstract
- BACKGROUND: Huntington's disease is associated with an expanded sequence of CAG repeats in a gene on chromosome 4p16.3. However, neither the sensitivity of expanded CAG repeats in affected persons of different ethnic origins nor the specificity of such repeats for Huntington's disease as compared with other neuropsychiatric disorders has been determined.METHODS: We studied 1007 patients with diagnosed Huntington's disease from 565 families and 43 national and ethnic groups. In addition, the length of the CAG repeat was determined in 113 control subjects with a family history of Alzheimer's disease (44 patients), schizophrenia (39), major depression (16), senile chorea (5), benign hereditary chorea (5), neuroacanthocytosis (2), and dentatorubropallidoluysian atrophy (2). The number of CAG repeats was also assessed in 1595 control chromosomes, with the size of adjacent polymorphic CCG trinucleotide repeats taken into account.RESULTS: Of 1007 patients with signs and symptoms compatible with a diagnosis of Huntington's disease, 995 had an expanded CAG repeat that included from 36 to 121 repeats (median, 44) (sensitivity, 98.8 percent; 95 percent confidence interval, 97.7 to 99.4 percent). There were no significant differences among national and ethnic groups in the number of repeats. No CAG expansion was found in the 110 control subjects with other neuropsychiatric disorders (specificity, 100 percent; 95 percent confidence interval, 95.2 to 100 percent). In 1581 of the 1595 control chromosomes (99.1 percent), the number of CAG repeats ranged from 10 to 29 (median, 18). In 12 control chromosomes (0.75 percent), intermediate-sized CAG sequences with 30 to 35 repeats were found, and 2 normal chromosomes unexpectedly had expanded CAG sequences, of 39 and 37 repeats.CONCLUSIONS: CAG trinucleotide expansion is the molecular basis of Huntington's disease worldwide and is a highly sensitive and specific marker for inheritance of the disease mutation.
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