Meta-analyses of all data provided compelling evidence that ABCA7 (rs3764650, meta P = 4.5 × 10(-17); including ADGC data, meta P = 5.0 × 10(-21)) and the MS4A gene cluster (rs610932, meta P = 1.8 × 10(-14); including ADGC data, meta P = 1.2 × 10(-16)) are new Alzheimer's disease susceptibility loci.
There are other cis-variants that significantly influence brain expression of CLU and ABCA7 (p = 4.01 × 10(-5)-9.09 × 10(-9)), some of which also associate with AD risk (p = 2.64 × 10(-2)-6.25 × 10(-5)).
This work, so far accomplished through single nucleotide polymorphism arrays, has revealed nine new genes implicated in AD risk (ABCA7, BIN1, CD33, CD2AP, CLU, CR1, EPHA1, MS4A4E/MS4A6A, and PICALM).
Besides the previously reported APOE and CR1 loci, we found that the ABCA7 (rs3764650; P = .02) and CD2AP (rs9349407; P = .03) AD susceptibility loci are associated with neuritic plaque burden.
We interpret our findings as suggesting a model wherein increased ABCA7 expression reduces AD risk and that the increased ABCA7 observed in AD reflects an inadequate compensatory change.
Genome-wide association studies have indicated that ABCA7 single nucleotide polymorphisms confer increased risk for late-onset AD; however, the role that ABCA7 plays in the brain in the AD context is unknown.
Genome-wide significance in fully adjusted models (sex, age, APOE genotype, population stratification) was observed for a SNP in ABCA7 (rs115550680, allele = G; frequency, 0.09 cases and 0.06 controls; odds ratio [OR], 1.79 [95% CI, 1.47-2.12]; P = 2.2 × 10(-9)), which is in linkage disequilibrium with SNPs previously associated with Alzheimer disease in Europeans (0.8 < D' < 0.9).
Five genomewide association studies (GWAS) in white populations have recently identified and confirmed 9 novel Alzheimer's disease (AD) susceptibility loci (CLU, CR1, PICALM, BIN1, ABCA7, MS4A gene cluster, CD2AP, CD33, and EPHA1).
There were four significant associations between genotypes and phenotypes of AD patients: CR1 SNP rs11803956 correlated with Mini-Mental State Examination (MMSE) score (β=1.718, Pcorrected=0.002); ABCA7 SNP rs3752232 correlated with Rey Complex Figure Test (RCFT) copy score (β=-6.861, Pcorrected=0.013); APOE SNP rs2075650 correlated with the percentile of RCFT copy score (β=14.005, Pcorrected=0.021) and the percentile of total score in phonemic fluency (β=11.052, Pcorrected=0.035).
We found that loss-of-function variants in ABCA7 confer risk of Alzheimer's disease in Icelanders (odds ratio (OR) = 2.12, P = 2.2 × 10(-13)) and discovered that the association replicated in study groups from Europe and the United States (combined OR = 2.03, P = 6.8 × 10(-15)).