| 1. |
- Almqvist, E, et al.
(författare)
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Risk reversals in predictive testing for Huntington disease.
- 1997
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Ingår i: American Journal of Human Genetics. - : Elsevier BV. - 0002-9297 .- 1537-6605. ; 61:4, s. 945-52
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Tidskriftsartikel (refereegranskat)abstract
- The first predictive testing for Huntington disease (HD) was based on analysis of linked polymorphic DNA markers to estimate the likelihood of inheriting the mutation for HD. Limits to accuracy included recombination between the DNA markers and the mutation, pedigree structure, and whether DNA samples were available from family members. With direct tests for the HD mutation, we have assessed the accuracy of results obtained by linkage approaches when requested to do so by the test individuals. For six such individuals, there was significant disparity between the tests. Three went from a decreased risk to an increased risk, while in another three the risk was decreased. Knowledge of the potential reasons for these changes in results and impact of these risk reversals on both patients and the counseling team can assist in the development of strategies for the prevention and, where necessary, management of a risk reversal in any predictive testing program.
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| 2. |
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| 3. |
- Almqvist, E W, et al.
(författare)
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A worldwide assessment of the frequency of suicide, suicide attempts, or psychiatric hospitalization after predictive testing for Huntington disease.
- 1999
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Ingår i: American Journal of Human Genetics. - 0002-9297 .- 1537-6605. ; 64:5, s. 1293-304
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Tidskriftsartikel (refereegranskat)abstract
- Prior to the implementation of predictive-testing programs for Huntington disease (HD), significant concern was raised concerning the likelihood of catastrophic events (CEs), particularly in those persons receiving an increased-risk result. We have investigated the frequency of CEs-that is, suicide, suicide attempt, and psychiatric hospitalization-after an HD predictive-testing result, through questionnaires sent to predictive-testing centers worldwide. A total of 44 persons (0.97%) in a cohort of 4,527 test participants had a CE: 5 successful suicides, 21 suicide attempts, and 18 hospitalizations for psychiatric reasons. All persons committing suicide had signs of HD, whereas 11 (52.4%) of 21 persons attempting suicide and 8 (44.4%) of 18 who had a psychiatric hospitalization were symptomatic. A total of 11 (84.6%) of 13 asymptomatic persons who experienced a CE during the first year after HD predictive testing received an increased-risk result. Factors associated with an increased risk of a CE included (a) a psychiatric history
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| 4. |
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| 5. |
- Chong, S S, et al.
(författare)
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Contribution of DNA sequence and CAG size to mutation frequencies of intermediate alleles for Huntington disease : evidence from single sperm analyses.
- 1997
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Ingår i: Human Molecular Genetics. - : Oxford University Press (OUP). - 0964-6906 .- 1460-2083. ; 6:2, s. 301-9
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Tidskriftsartikel (refereegranskat)abstract
- New mutations for Huntington disease (HD) arise from intermediate alleles (IAs) with between 29 and 35 CAG repeats that expand on transmission through the paternal germline to 36 CAGs or greater. Using single sperm analysis, we have assessed CAG mutation frequencies for four IAs in families with sporadic HD (IANM) and IAs ascertained from the general population (IAGP) by analyzing 1161 single sperm from three persons. We show that IANM are more unstable than IAGP with identical size and sequence. Furthermore, comparison of different sized IAs and IAs with different sequences between the CAG and the adjacent CCG tracts indicates that DNA sequence is a major influence on CAG stability. These studies provide estimates of the likelihood of expansion of IANM and IAGP to > or = 36 CAG repeats for these individuals. For an IA with a CAG of 35 in this family with sporadic HD, the likelihood for siblings to inherit a recurrent mutation > or = 36 CAG is approximately 10%. For IAGP of a similar size, the risk of inheriting an expanded allele of > or = 36 CAG through the paternal germline is approximately 6%. These risk estimates are higher than previously reported and provide additional information for counselling in these families. Further studies on persons with IAs will be needed to determine whether these results can be generalized to other families.
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| 6. |
- Goellner, G M, et al.
(författare)
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Different mechanisms underlie DNA instability in Huntington disease and colorectal cancer.
- 1997
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Ingår i: American Journal of Human Genetics. - 0002-9297 .- 1537-6605. ; 60:4, s. 879-90
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Tidskriftsartikel (refereegranskat)abstract
- Two recent lines of evidence raise the possibility that instability in germ-line or somatic cells arises by a common mechanism that involves defective mismatch repair. Mutations in mismatch-repair proteins are known to cause instability in hereditary nonpolyposis colorectal cancer, instability that is physically similar to germ-line instability observed in Huntington disease (HD). Furthermore, both germ-line and somatic-cell instability are likely to be mitotic defects, the former occurring early in embryogenesis. To test the hypothesis that defective repair is a common prerequisite for instability, we have utilized two disease groups that represent different instability "conditions." Germ-line instability within simple tandem repeats (STR) at 10 loci in 29 HD families were compared with somatic instability at the same loci in 26 colon cancer (CC) patients with identified or suspected defects in mismatch-repair enzymes. HD is known to be caused by expansion within the CAG repeat of the locus, but the extent or pattern of STR instability outside this region has not been examined systematically. We find a distinctly different pattern of STR mutation in the two disease groups, suggesting different mechanisms. Instability in HD is generally confined to a single locus, whereas instability is widespread for the same loci in CC. Our data do not support a causative role for defective mismatch-repair enzymes in instability associated with HD; rather, our data are consistent with a model in which DNA structure may inhibit normal mismatch repair at the expansion site.
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| 7. |
- Goldberg, Y P, et al.
(författare)
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Increased instability of intermediate alleles in families with sporadic Huntington disease compared to similar sized intermediate alleles in the general population.
- 1995
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Ingår i: Human Molecular Genetics. - : Oxford University Press (OUP). - 0964-6906 .- 1460-2083. ; 4:10, s. 1911-8
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Tidskriftsartikel (refereegranskat)abstract
- We have directly compared intergenerational stability of intermediate alleles (IAs) derived from new mutation families (IANM) for Huntington disease (HD) with IAs in the general population (IAGP) which occur in approximately 1 in 50 persons. Analysis of meiotic events in blood and sperm reveals that IANM are significantly more unstable than IAGP despite similar size. However, for both IANM and IAGP CAG changes were small and risks for inheriting an expansion into the HD affected range were low. Sequence analysis reveals that the CAG tract is generally interrupted by a penultimate CAA in IAGP, IANM and alleles in the affected range. In one new mutation family, however, two A-->G mutations result in a pure CAG tract which is associated with very marked instability. These mutations alter the predicted DNA hairpin structure with a predicted increase in the likelihood of large expansion, supporting the model that hairpin loop formation plays an important role in trinucleotide instability.
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