The Association Between Genetic Variants in SORL1 and Alzheimer Disease in an Urban, Multiethnic, Community-Based Cohort

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Abstract
Objective To investigate the association between Alzheimer disease (AD) and variant alleles inSORL1using a series of single nucleotide polymorphisms (SNPs) in an urban, multiethnic, community-based population. Design We used a nested case-control analysis in a population-based, prospective study of aging and dementia in Medicare recipients, 65 years and older. Setting Northern Manhattan, NY. Participants There were 296 patients with probable AD and 428 healthy, elderly controls. The participants were African American (34%), Caribbean Hispanic (51%), or non-Hispanic white (15%). Main Outcome Measures We genotyped all 29 SNPs inSORL1that were examined in the earlier report. We assessed allelic association with AD using standard case-control methods, which included apolipoprotein E genotype as a covariate. Results Several individual SNPs and SNP haplotypes were significantly associated with AD in this prospectively collected community-based cohort, confirming the previously reported positive association ofSORL1with AD. Single nucleotide polymorphism 12, near the 5′ region, was associated with AD in African American and Hispanic individuals. Two SNPs in the 3′ region were also associated with AD in African American (SNP 26) and non-Hispanic white (SNP 20) individuals. A single haplotype in the 3′ region was associated with AD in Hispanic individuals. However, several different haplotypes were associated with AD in African American and white individuals, including the TTC haplotypes at SNPs 23 through 25 (P = .035), which was significantly associated with AD in the North European white individuals in our previous report. Conclusions This study confirms the association between genetic variants inSORL1and AD. While the associations observed in these data sets overlap with those previously reported, the finding of novel SNP and haplotype associations suggests that there may be extensive allelic heterogeneity inSORL1. Broad regions of theSORL1gene will therefore need to be scrutinized for functional pathogenic variants.