Variants regulating ZBTB4 are associated with age-at-onset of Alzheimer's disease

Abstract

The identification of novel genetic modifiers of age-at-onset (AAO) of Alzheimer's disease (AD) could advance our understanding of AD and provide novel therapeutic targets. A previous genome scan for modifiers of AAO among families affected by early-onset AD caused by the PSEN2 N141I variant identified 2 loci with significant evidence for linkage: 1q23.3 and 17p13.2. Here, we describe the fine-mapping of these 2 linkage regions, and test for replication in 6 independent datasets. By fine-mapping these linkage signals in a single large family, we reduced the linkage regions to 11% their original size and nominated 54 candidate variants. Among the 11 variants associated with AAO of AD in a larger sample of Germans from Russia, the strongest evidence implicated promoter variants influencing NCSTN on 1q23.3 and ZBTB4 on 17p13.2. The association between ZBTB4 and AAO of AD was replicated by multiple variants in independent, trans-ethnic datasets. Our results show association between AAO of AD and both ZBTB4 and NCSTN. ZBTB4 is a transcriptional repressor that regulates the cell cycle, including the apoptotic response to amyloid beta, while NCSTN is part of the gamma secretase complex, known to influence amyloid beta production. These genes therefore suggest important roles for amyloid beta and cell cycle pathways in AAO of AD.

Keywords: age-at-onset; amyloid beta; apoptotic response; association; complex traits; dementia; fine-mapping; genetic modifiers; linkage analysis; noncoding variants; survival analysis.

Figure 1. Size of quantitative trait loci at SNPs included as a covariate in measured genotype analyses within the R family

Panel A: chromosome 1, Panel B: chromosome 17. The empty space in the middle of panel A corresponds to the centromere. The topSNPs are highlighted in red. X marks the position of the microsatellite markers included in the linkage analysis. For context, APOE has an average effect size of 5.51 in the chr1 analyses and 5.26 in the chr17 analyses.