Identification of rare coding variants associated with Alzheimer’s disease.

Abstract

AbstractBackgroundPrevious whole exome sequencing (WES) studies of Alzheimer’s disease (AD) have identified genome‐wide significant associations with rare variants in several novel genes and highlighted the need for investigations in larger samples. We combined WES and whole genome sequencing (WGS) data assembled by the Alzheimer Disease Sequencing Project (ADSP) to increase the power for detecting associations of AD with rare variants in gene coding regions.MethodWe developed an efficient computational pipeline to perform both pre‐merging and post‐merging genotype, variant and sample‐level quality control (QC) on WGS data containing 16,905 individuals and WES data for 20,504 individuals. The resultant sample included participants from European (EA, 11,279 AD cases, 8,924 controls), African American (AA, 2,757 AD cases, 4,336 controls), and Caribbean Hispanic (CH 1,438 AD cases, 3,256 controls) ancestries. We employed GENESIS to test association of AD with 250,465 bi‐allelic QC’d variants using a logistic model including covariates for age, sex, exome capture kit, read length, and ancestry principal components (PCs).ResultIn the total sample, variants from APOE and other known AD genes including SORL1 (P = 5.30×10‐7), NECTIN2 (P = 6.94×10‐7), and TREM2 R47H (P = 2.34×10‐13) crossed or neared the study‐wide significance (SWS) threshold of P = 2.00×10‐7 (0.05/250,465). SWS or borderline significant associations were also found with variants in several novel loci including TKTL2 (P = 2.35×10‐8), D2HGDH, (P = 1.09×10‐7), CECR1 (P = 4.02×10‐7), PDHA2 (P = 2.76×10‐7), GOLGA1 (P = 1.72×10‐7), CYLD (P = 1.84×10‐7), and RP11‐243M5.4 (P = 1.37×10‐7). PSEN1 missense mutation G206A (rs63750082) previously associated with early onset AD in the CH group, was significantly associated with late onset AD in the same population (P = 1.58×10‐13). SWS association of AD with APOE was observed in all groups. Significant associations were also observed with variants in SERPINB8 (P = 3.77×10‐9) and FAM171A (P = 7.20×10‐7) in EAs and TLR4 (P = 4.58×10‐7) in CH. Associations with several top‐ranked variants were replicated in the Alzheimer’s Disease Genetics Consortium GWAS dataset that were imputed using the TOPMed reference panel and ADSP 5K WGS dataset.ConclusionWe demonstrated that merging WGS and WES datasets can increase power to detect associations with rare coding variants in genes including ones previously implicated in AD (CYLD and TLR4) and early‐onset stroke (CECR1).