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ADMIXTURE MAPPING IDENTIFIES NOVEL ALZHEIMER DISEASE RISK REGIONS IN AFRICAN AMERICANS
Abstract
Aims
African American (AA) population with the admixed genetic ancestry provides a unique opportunity to identify novel genetic factors associated with Alzheimer's disease (AD) related to genetic ancestry. Admixture mapping provides a complementary and sometimes more powerful approach to SNP-based genome-wide association studies in admixed populations. This study used admixture mapping to prioritize the genetic regions associated with AD in AA individuals, followed by ancestry-aware regression analysis to fine-map the prioritized regions.
Methods
We analyzed 10,271 individuals from 17 different AA datasets. We performed admixture mapping and meta-analyzed the results. We then used regression analysis, adjusting for local ancestry main effects and interactions with genotype, to refine the regions identified from admixture mapping. Finally, we leveraged in silico annotation and differential gene expression data to prioritize AD-related variants and genes.
Results
Admixture mapping identified two genome-wide significant loci on chromosomes 17p13.2 (p=2.2 x10-5) and 18q21.33 (p=1.2x10-5). The ancestry-aware regression model identified a significant interaction term on chromosome 17p13.2 (p-value=7.93x10-5; parametric bootstrap FDR < 0.05). Our ancestry-aware regression approach showed that AA individuals have a lower risk of AD if they inherited 17p13.2 locus from their African ancestors.
Conclusions
We identified two novel AD risk genetic loci in AAs; however, the 17p13.2 region was identified as genome-wide significant in three previous meta-analysis studies in non-Hispanic White populations. Our fine-mapping of the chromosome 17p13.2 and 18q21.33 regions revealed several interesting genes, some of which have been implicated in AD risk, such as the MINK1, KIF1C, and BCL2.