Independent and epistatic effects of variants in VPS10-d receptors on Alzheimer disease risk and processing of the amyloid precursor protein (APP)
TRANSLATIONAL PSYCHIATRY
Authors: Reitz, C.; Tosto, G.; Vardarajan, B.; Rogaeva, E.; Ghani, M.; Rogers, R. S.; Conrad, C.; Haines, J. L.; Pericak-Vance, M. A.; Fallin, M. D.; Foroud, T.; Farrer, L. A.; Schellenberg, G. D.; George-Hyslop, P. S.; Mayeux, R.
Abstract
Genetic variants in the sortilin-related receptor (SORL1) and the sortilin-related vacuolar protein sorting 10 (VPS10) domain-containing receptor 1 (SORCS1) are associated with increased risk of Alzheimer's disease (AD), declining cognitive function and altered amyloid precursor protein (APP) processing. We explored whether other members of the (VPS10) domain-containing receptor protein family (the sortilin-related VPS10 domain-containing receptors 2 and 3 (SORCS2 and SORCS3) and sortilin (SORT1)) would have similar effects either independently or together. We conducted the analyses in a large Caucasian case control data set (n=11 840 cases, 10 931 controls) to determine the associations between single nucleotide polymorphisms (SNPs) in all the five homologous genes and AD risk. Evidence for interactions between SNPs in the five VPS10 domain receptor family genes was determined in epistatic statistical models. We also compared expression levels of SORCS2, SORCS3 and SORT1 in AD and control brains using microarray gene expression analyses and assessed the effects of these genes on gamma-secretase processing of APP. Several SNPs in SORL1, SORCS1, SORCS2 and SORCS3 were associated with AD. In addition, four specific linkage disequilibrium blocks in SORCS1, SORCS2 and SORCS3 showed additive epistatic effects on the risk of AD (P <= 0.0006). SORCS3, but not SORCS2 or SORT1, showed reduced expression in AD compared with control brains, but knockdown of all the three genes using short hairpin RNAs in HEK293 cells caused a significant threefold increase in APP processing (from P<0.001 to P<0.05). These findings indicate that in addition to SORL1 and SORCS1, variants in other members of the VPS10 domain receptor family (that is, SORCS1, SORCS2, SORCS3) are associated with AD risk and alter APP processing. More importantly, the results indicate that variants within these genes have epistatic effects on AD risk.
Influence of Coding Variability in APP-A beta Metabolism Genes in Sporadic Alzheimer's Disease
PLOS ONE
Authors: Sassi, Celeste; Ridge, Perry G.; Nalls, Michael A.; Gibbs, Raphael; Ding, Jinhui; Lupton, Michelle K.; Troakes, Claire; Lunnon, Katie; Al-Sarraj, Safa; Brown, Kristelle S.; Medway, Christopher; Lord, Jenny; Turton, James; Morgan, Kevin; Powell, John F.; Kauwe, John S.; Cruchaga, Carlos; Bras, Jose; Goate, Alison M.; Singleton, Andrew B.; Guerreiro, Rita; Hardy, John
Abstract
The cerebral deposition of A beta(42), a neurotoxic proteolytic derivate of amyloid precursor protein (APP), is a central event in Alzheimer's disease (AD)(Amyloid hypothesis). Given the key role of APP-A beta metabolism in AD pathogenesis, we selected 29 genes involved in APP processing, A beta degradation and clearance. We then used exome and genome sequencing to investigate the single independent (single-variant association test) and cumulative (gene-based association test) effect of coding variants in these genes as potential susceptibility factors for AD, in a cohort composed of 332 sporadic and mainly late-onset AD cases and 676 elderly controls from North America and the UK. Our study shows that common coding variability in these genes does not play a major role for the disease development. In the single-variant association analysis, the main hits, none of which statistically significant after multiple testing correction (1.9e(-4)