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- Lindholm, Eva, et al.
(författare)
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Reconstruction of ancestral haplotypes in a 12-generation schizophrenia pedigree
- 2004
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Ingår i: Psychiatric Genetics. - Philadelphia : Lippincott Williams & Wilkins. - 0955-8829 .- 1473-5873. ; 14:1, s. 1-8
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Tidskriftsartikel (refereegranskat)abstract
- We searched for candidate chromosomal regions inherited identical by descent in 19 patients suffering from schizophrenia or schizoaffective disorder that are related 12 generations back, to an ancestral couple born in the middle of the seventeenth century. To accomplish this goal, we constructed complete chromosomal haplotypes for each patient using genotype data from 450 markers. In total, 12 haplotype regions (with sizes ranging from 0.6 to 10.9 cM) constituted by three markers each were identical in three or more of the affected individuals. The largest genomic segment was located on 6q25, a region previously shown to be significantly more frequent in patients than controls, and proposed to contain a schizophrenia susceptibility locus. For the remaining 11 candidate haplotypes, we estimated haplotype frequencies from all the 43 affected members collected from the same family and 46 unrelated control individuals. This analysis indicated that at least four of the 11 candidate haplotypes are ancestral, since the frequencies were significantly higher in patients than in controls. Five additional haplotypes showed higher estimated frequencies in the patients but the differences were not significant. Interestingly, five of these 11 genomic regions are located in, or close to, candidate regions previously suggested to contain susceptibility genes for schizophrenia. The regions are 5q21-23, 8p21-22, 1 0p13-15, 13q12-13 and 22q12-13. Several of these haplotypes are probably ancestral linkage disequilibrium blocks inherited from the original couple. There exists, however, the possibility that one or more of these regions harbour schizophrenia susceptibility loci that may have epistatic interactions among them.
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| 2. |
- Visscher, Peter M., et al.
(författare)
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Genetic survival analysis of age-at-onset of bipolar disorder : evidence for anticipation or cohort effect in families
- 2001
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Ingår i: Psychiatric Genetics. - : Lippincott Williams & Wilkins. - 0955-8829 .- 1473-5873. ; 11:3, s. 129-137
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Tidskriftsartikel (refereegranskat)abstract
- Age-at-onset (AAO) in a number of extended families ascertained for bipolar disorder was analysed using survival analysis techniques, fitting proportional hazards models to estimate the fixed effects of sex, year of birth, and generation, and a random polygenic genetic effect. Data comprised the AAO (for 171 affecteds) or age when last seen (ALS) for 327 unaffecteds, on 498 individuals in 27 families. ALS was treated as the censored time in the statistical analyses. The majority of individuals classified as affected were diagnosed with bipolar I and II (n = 103) or recurrent major depressive disorder (n = 68). In addition to the significant effects of sex and year of birth, a fitted ‘generation’ effect was highly significant, which could be interpreted as evidence for an anticipation effect. The risk of developing bipolar or unipolar disorder increased twofold with each generation descended from the oldest founder. However, although information from both affected and unaffected individuals was used to estimate the relative risk of subsequent generations, it is possible that the results are biased because of the ‘Penrose effect’. Females had a twofold increased risk in developing depressive disorder relative to males. The risk of developing bipolar or unipolar disorder increased by approximately 4% per year of birth. A polygenic component of variance was estimated, resulting in a ‘heritability’ of AAO of approximately 0.52. In a family showing strong evidence of linkage to chromosome 4p (family 22), the ‘affected haplotype’ increased the relative risk of being affected by a factor of 46. In this family, there was strong evidence of a time trend in the AAO. When either year of birth or generation was fitted in the model, these effects were highly significant, but neither was significant in the presence of the other. For this family, there was no increase in trinucleotide repeats measured by the repeat expansion detection method in affected individuals compared with control subjects. Proportional hazard models appear appropriate to analyse AAO data, and the methodology will be extended to map quantitative trait loci (QTL) for AAO.
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