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- Bennet, Anna M, et al.
(författare)
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Pleiotropy in the Presence of Allelic Heterogeneity: Alternative Genetic Models for the Influence of APOE on Serum LDL, CSF Amyloid-β42, and Dementia.
- 2010
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Ingår i: Journal of Alzheimer's disease : JAD. - 1875-8908. ; 22:1, s. 129-134
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Tidskriftsartikel (refereegranskat)abstract
- The two genetic polymorphisms, rs7412 and rs429358, that collectively form the ε2, ε3, and ε4 alleles of apolipoprotein E (APOE) are among the most widely studied sequence variants in the genome. The predominant model for testing APOE involves the haplotype combinations of ε2, ε3, and ε4 and has been basis of associations with dementia, atherosclerosis, and serum lipid levels. Here, we demonstrate the functional independence of these two component sites, with rs7412 contributing to the majority of variance in serum LDL (p=10-20), whereas rs429358 alone influences variance in CSF amyloid-β42 (Aβ42) (p=10-17). This latter relationship is also reflected in the association of APOE with dementia, where rs429358 strongly influences disease (p=10-67), but rs7412 does not. Models based upon ε2, ε3, and ε4 explained less variance for both dementia risk and CSF Aβ42 than did rs429358 alone. When adjusted for CSF Aβ42, the association of rs429358 with dementia is greatly reduced but remains significant indicating that APOE polymorphism influences disease by additional mechanisms distinct from Aβ42 metabolism. We reach four principal conclusion from this study: 1) rs429358 alone is responsible for the association of APOE with dementia; 2) The association of APOE with dementia is substantially mediated by its effect on CNS Aβ42 levels; 3) The association of APOE with dementia is not mediated by its impact on peripheral lipid metabolism; and 4) The dichotomy of effects of rs429358 and rs7412 represents one of the best examples of genetic pleiotropy for complex traits known and illustrates the importance of allelic heterogeneity in APOE.
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| 2. |
- Reynolds, Chandra A, et al.
(författare)
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Sequence variation in SORL1 and dementia risk in Swedes.
- 2010
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Ingår i: Neurogenetics. - : Springer Science and Business Media LLC. - 1364-6753 .- 1364-6745. ; 11:1, s. 139-42
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Tidskriftsartikel (refereegranskat)abstract
- The gene encoding the neuronal sortilin-related receptor SORL1 has been claimed to be associated with Alzheimer's disease (AD) by independent groups and across various human populations. We evaluated six genetic markers in SORL1 in a sample of 1,558 Swedish dementia cases (including 1,270 AD cases) and 2,179 controls. For both single-marker-based and haplotype-based analyses, we found no strong support for SORL1 as a dementia or AD risk-modifying gene in our sample in isolation nor did we observe association with AD/dementia-related traits, including cerebrospinal fluid beta-amyloid(1-42), tau levels, or age at onset. However, meta-analyses of markers in this study together with previously published studies on SORL1 encompassing in excess of 13,000 individuals does suggest significant association with AD (best odds ratio = 1.097; 95% confidence interval = 1.038-1.158, p = 0.001). All six markers were significant in meta-analyses and it is notable that they occur in two distinct linkage disequilibrium blocks. These data are consistent with either allelic heterogeneity or the existence of as yet untested functional variants and these will be important considerations in further attempts to evaluate the importance of sequence variation in SORL1 with AD risk.
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