Lina Keller

BACKGROUND: Alzheimer's disease is a common debilitating dementia with known heritability, for which 20 late onset susceptibility loci have been identified, but more remain to be discovered. This study sought to identify new susceptibility genes, using an alternative gene-wide analytical approach which tests for patterns of association within genes, in the powerful genome-wide association dataset of the International Genomics of Alzheimer's Project Consortium, comprising over 7 m genotypes from 25,580 Alzheimer's cases and 48,466 controls. PRINCIPAL FINDINGS: In addition to earlier reported genes, we detected genome-wide significant loci on chromosomes 8 (TP53INP1, p = 1.4×10-6) and 14 (IGHV1-67 p = 7.9×10-8) which indexed novel susceptibility loci. SIGNIFICANCE: The additional genes identified in this study, have an array of functions previously implicated in Alzheimer's disease, including aspects of energy metabolism, protein degradation and the immune system and add further weight to these pathways as potential therapeutic targets in Alzheimer's disease.

BACKGROUND: Late-onset Alzheimer's disease (AD) is heritable with 20 genes showing genome-wide association in the International Genomics of Alzheimer's Project (IGAP). To identify the biology underlying the disease, we extended these genetic data in a pathway analysis. METHODS: The ALIGATOR and GSEA algorithms were used in the IGAP data to identify associated functional pathways and correlated gene expression networks in human brain. RESULTS: ALIGATOR identified an excess of curated biological pathways showing enrichment of association. Enriched areas of biology included the immune response (P = 3.27 × 10(-12) after multiple testing correction for pathways), regulation of endocytosis (P = 1.31 × 10(-11)), cholesterol transport (P = 2.96 × 10(-9)), and proteasome-ubiquitin activity (P = 1.34 × 10(-6)). Correlated gene expression analysis identified four significant network modules, all related to the immune response (corrected P = .002-.05). CONCLUSIONS: The immune response, regulation of endocytosis, cholesterol transport, and protein ubiquitination represent prime targets for AD therapeutics.

The FTO gene has been shown to have a small but robust effect on body mass index (BMI) and to increase the risk for diabetes. Both high BMI and diabetes are vascular risk factors that might play a role in the development of Alzheimer's disease (AD) and dementia. Thus, our aim was to explore the impact of FTO on AD and dementia risk. Nine years of follow-up data was gathered from the Kungsholmen project, a prospective population-based study on 1,003 persons without dementia. Cox-regression models were used to assess the relative risks of developing AD and dementia (DSM-III-R criteria) according to FTO genotypes (rs9939609), taking into account APOE, physical inactivity, BMI, diabetes, and cardiovascular disease (CVD). Compared to carriers of the FTO TT-genotype, AA-carriers had a higher risk for AD (RR 1.58, 95% CI: 1.11-2.24) and for dementia (RR 1.48, 95% CI: 1.09-2.02) after adjustment for age, gender, education, and APOE genotype. This effect remained after additional adjustment for physical inactivity, BMI, diabetes, and CVD. An interaction between FTO and APOE was found, with increased risk for dementia for those carrying both FTO AA and APOE ϵ4. Importantly, the effect of the AA-genotype on dementia/AD risk seems to act mostly through the interaction with APOE ϵ4. Our findings suggest that the FTO AA-genotype increases the risk for dementia, and in particular AD, independently of physical inactivity, BMI, diabetes, and CVD measured at baseline. Our results are in line with the recently reported association between FTO and reduced brain volume in cognitively healthy subjects.