%0 Journal Article %J J Alzheimers Dis %D 2016 %T Evaluation of a Genetic Risk Score to Improve Risk Prediction for Alzheimer's Disease. %A Chouraki, Vincent %A Reitz, Christiane %A Maury, Fleur %A Bis, Joshua C %A Bellenguez, Celine %A Yu, Lei %A Jakobsdottir, Johanna %A Mukherjee, Shubhabrata %A Adams, Hieab H %A Choi, Seung Hoan %A Larson, Eric B %A Fitzpatrick, Annette %A Uitterlinden, Andre G %A De Jager, Philip L %A Hofman, Albert %A Gudnason, Vilmundur %A Vardarajan, Badri %A Ibrahim-Verbaas, Carla %A van der Lee, Sven J %A Lopez, Oscar %A Dartigues, Jean-François %A Berr, Claudine %A Amouyel, Philippe %A Bennett, David A %A van Duijn, Cornelia %A DeStefano, Anita L %A Launer, Lenore J %A Ikram, M Arfan %A Crane, Paul K %A Lambert, Jean-Charles %A Mayeux, Richard %A Seshadri, Sudha %X

Effective prevention of Alzheimer's disease (AD) requires the development of risk prediction tools permitting preclinical intervention. We constructed a genetic risk score (GRS) comprising common genetic variants associated with AD, evaluated its association with incident AD and assessed its capacity to improve risk prediction over traditional models based on age, sex, education, and APOEɛ4. In eight prospective cohorts included in the International Genomics of Alzheimer's Project (IGAP), we derived weighted sum of risk alleles from the 19 top SNPs reported by the IGAP GWAS in participants aged 65 and older without prevalent dementia. Hazard ratios (HR) of incident AD were estimated in Cox models. Improvement in risk prediction was measured by the difference in C-index (Δ-C), the integrated discrimination improvement (IDI) and continuous net reclassification improvement (NRI>0). Overall, 19,687 participants at risk were included, of whom 2,782 developed AD. The GRS was associated with a 17% increase in AD risk (pooled HR = 1.17; 95% CI =   [1.13-1.21] per standard deviation increase in GRS; p-value =  2.86×10-16). This association was stronger among persons with at least one APOEɛ4 allele (HRGRS = 1.24; 95% CI =   [1.15-1.34]) than in others (HRGRS = 1.13; 95% CI =   [1.08-1.18]; pinteraction = 3.45×10-2). Risk prediction after seven years of follow-up showed a small improvement when adding the GRS to age, sex, APOEɛ4, and education (Δ-Cindex =  0.0043 [0.0019-0.0067]). Similar patterns were observed for IDI and NRI>0. In conclusion, a risk score incorporating common genetic variation outside the APOEɛ4 locus improved AD risk prediction and may facilitate risk stratification for prevention trials.

%B J Alzheimers Dis %V 53 %P 921-32 %8 2016 Jun 18 %G eng %N 3 %1 http://www.ncbi.nlm.nih.gov/pubmed/27340842?dopt=Abstract %R 10.3233/JAD-150749 %0 Journal Article %J N Engl J Med %D 2013 %T TREM2 variants in Alzheimer's disease. %A Guerreiro, Rita %A Wojtas, Aleksandra %A Bras, Jose %A Carrasquillo, Minerva %A Rogaeva, Ekaterina %A Majounie, Elisa %A Cruchaga, Carlos %A Sassi, Celeste %A Kauwe, John S K %A Younkin, Steven %A Hazrati, Lilinaz %A Collinge, John %A Pocock, Jennifer %A Lashley, Tammaryn %A Williams, Julie %A Lambert, Jean-Charles %A Amouyel, Philippe %A Goate, Alison %A Rademakers, Rosa %A Morgan, Kevin %A Powell, John %A St George-Hyslop, Peter %A Singleton, Andrew %A Hardy, John %K Aged %K Alzheimer Disease %K Animals %K Brain %K Exome %K Genetic Variation %K Genome-Wide Association Study %K Genotype %K Genotyping Techniques %K Heterozygote %K Humans %K Membrane Glycoproteins %K Mice %K Mice, Inbred A %K Mutation %K Receptors, Immunologic %K Risk Factors %K RNA, Messenger %K Sequence Analysis, DNA %X

BACKGROUND: Homozygous loss-of-function mutations in TREM2, encoding the triggering receptor expressed on myeloid cells 2 protein, have previously been associated with an autosomal recessive form of early-onset dementia.

METHODS: We used genome, exome, and Sanger sequencing to analyze the genetic variability in TREM2 in a series of 1092 patients with Alzheimer's disease and 1107 controls (the discovery set). We then performed a meta-analysis on imputed data for the TREM2 variant rs75932628 (predicted to cause a R47H substitution) from three genomewide association studies of Alzheimer's disease and tested for the association of the variant with disease. We genotyped the R47H variant in an additional 1887 cases and 4061 controls. We then assayed the expression of TREM2 across different regions of the human brain and identified genes that are differentially expressed in a mouse model of Alzheimer's disease and in control mice.

RESULTS: We found significantly more variants in exon 2 of TREM2 in patients with Alzheimer's disease than in controls in the discovery set (P=0.02). There were 22 variant alleles in 1092 patients with Alzheimer's disease and 5 variant alleles in 1107 controls (P<0.001). The most commonly associated variant, rs75932628 (encoding R47H), showed highly significant association with Alzheimer's disease (P<0.001). Meta-analysis of rs75932628 genotypes imputed from genomewide association studies confirmed this association (P=0.002), as did direct genotyping of an additional series of 1887 patients with Alzheimer's disease and 4061 controls (P<0.001). Trem2 expression differed between control mice and a mouse model of Alzheimer's disease.

CONCLUSIONS: Heterozygous rare variants in TREM2 are associated with a significant increase in the risk of Alzheimer's disease. (Funded by Alzheimer's Research UK and others.).

%B N Engl J Med %V 368 %P 117-27 %8 2013 Jan 10 %G eng %N 2 %1 http://www.ncbi.nlm.nih.gov/pubmed/23150934?dopt=Abstract %R 10.1056/NEJMoa1211851