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R47H TREM2 variant increases risk of typical early-onset Alzheimer's disease but not of prion or frontotemporal dementia.

ABSTRACT: Rare TREM2 variants are significant risk factors for Alzheimer's disease (AD).We used next generation sequencing of the whole gene (n = 700), exon 2 Sanger sequencing (n = 2634), p.R47H genotyping (n = 3518), and genome wide association study imputation (n = 13,048) to determine whether TREM2 variants are risk factors or phenotypic modifiers in patients with AD (n = 1002), frontotemporal dementia (n = 358), sporadic (n = 2500), and variant (n = 115) Creutzfeldt-Jakob disease (CJD).We confirm only p.R47H as a risk factor for AD (odds ratio or OR = 2.19; 95% confidence interval or CI = 1.04-4.51; P = .03). p.R47H does not significantly alter risk for frontotemporal dementia (OR = 0.81), variant or sporadic CJD (OR = 1.06 95%CI = 0.66-1.69) in our cohorts. Individuals with p.R47H associated AD (n = 12) had significantly earlier symptom onset than individuals with no TREM2 variants (n = 551) (55.2 years vs. 61.7 years, P = .02). We note that heterozygous p.R47H AD is memory led and otherwise indistinguishable from "typical" sporadic AD.We find p.R47H is a risk factor for AD, but not frontotemporal dementia or prion disease.

SUBMITTER: Slattery CF

PROVIDER: S-EPMC4627504 | biostudies-literature | 2014 Nov

REPOSITORIES: biostudies-literature

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R47H TREM2 variant increases risk of typical early-onset Alzheimer's disease but not of prion or frontotemporal dementia.

Slattery Catherine F CF Beck Jonathan A JA Harper Lorna L Adamson Gary G Abdi Zeinab Z Uphill James J Campbell Tracy T Druyeh Ron R Mahoney Colin J CJ Rohrer Jonathan D JD Kenny Janna J Lowe Jessica J Leung Kelvin K KK Barnes Josephine J Clegg Shona L SL Blair Melanie M Nicholas Jennifer M JM Guerreiro Rita J RJ Rowe James B JB Ponto Claudia C Zerr Inga I Kretzschmar Hans H Gambetti Pierluigi P Crutch Sebastian J SJ Warren Jason D JD Rossor Martin N MN Fox Nick C NC Collinge John J Schott Jonathan M JM Mead Simon S

Alzheimer's & dementia : the journal of the Alzheimer's Association 20140823 6

<h4>Background</h4>Rare TREM2 variants are significant risk factors for Alzheimer's disease (AD).<h4>Methods</h4>We used next generation sequencing of the whole gene (n = 700), exon 2 Sanger sequencing (n = 2634), p.R47H genotyping (n = 3518), and genome wide association study imputation (n = 13,048) to determine whether TREM2 variants are risk factors or phenotypic modifiers in patients with AD (n = 1002), frontotemporal dementia (n = 358), sporadic (n = 2500), and variant (n = 115) Creutzfeldt ...[more]

PMID: 25160042

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Project description:ImportanceThe R47H variant in the triggering receptor expressed on myeloid cells 2 gene (TREM2), a modulator of the immune response of microglia, is a strong genetic risk factor for Alzheimer disease (AD) and possibly other neurodegenerative disorders.ObjectiveTo investigate a large family with late-onset AD (LOAD), in which R47H cosegregated with 75% of cases.Design, setting, and participantsThis study includes genetic and pathologic studies of families with LOAD from 1985 to 2014. A total of 131 families with LOAD (751 individuals) were included from the University of Washington Alzheimer Disease Research Center. To identify LOAD genes/risk factors in the LOAD123 family with 21 affected members and 12 autopsies, we sequenced 4 exomes. Candidate variants were tested for cosegregation with the disease. TREM2 R47H was genotyped in an additional 130 families with LOAD. We performed clinical and neuropathological assessments of patients with and without R47H and evaluated the variant's effect on brain pathology, cellular morphology, and expression of microglial markers.Main outcomes and measuresWe assessed the effect of TREM2 genotype on age at onset and disease duration. We compared Braak and Consortium to Establish a Registry for Alzheimer's Disease scores, presence of α-synuclein and TAR DNA-binding protein 43 aggregates, and additional vascular or Parkinson pathology in TREM2 R47H carriers vs noncarriers. Microglial activation was assessed by quantitative immunohistochemistry and morphometry.ResultsTwelve of 16 patients with AD in the LOAD123 family carried R47H. Eleven patients with dementia had apolipoprotein E 4 (ApoE4) and R47H genotypes. We also found a rare missense variant, D353N, in a nominated AD risk gene, unc-5 homolog C (UNC5C), in 5 affected individuals in the LOAD123 family. R47H carriers demonstrated a shortened disease duration (mean [SD], 6.7 [2.8] vs 11.1 [6.6] years; 2-tailed t test; P = .04) and more frequent α-synucleinopathy. The panmicroglial marker ionized calcium-binding adapter molecule 1 was decreased in all AD cases and the decrease was most pronounced in R47H carriers (mean [SD], in the hilus: 0.114 [0.13] for R47H_AD vs 0.574 [0.26] for control individuals; 2-tailed t test; P = .005 and vs 0.465 [0.32] for AD; P = .02; in frontal cortex gray matter: 0.006 [0.004] for R47H_AD vs 0.016 [0.01] for AD; P = .04 and vs 0.033 [0.013] for control individuals; P < .001). Major histocompatibility complex class II, a marker of microglial activation, was increased in all patients with AD (AD: 2.5, R47H_AD: 2.7, and control: 1.0; P < .01).Conclusions and relevanceOur results demonstrate a complex genetic landscape of LOAD, even in a single pedigree with an apparent autosomal dominant pattern of inheritance. ApoE4, TREM2 R47H, and rare variants in other genes, such as UNC5C D353N, are likely responsible for the notable occurrence of AD in this family. Our findings support the role of the TREM2 receptor in microglial clearance of aggregation-prone proteins that is compromised in R47H carriers and may accelerate the course of disease.

Dataset Information

R47H TREM2 variant increases risk of typical early-onset Alzheimer's disease but not of prion or frontotemporal dementia.

Publications

R47H TREM2 variant increases risk of typical early-onset Alzheimer's disease but not of prion or frontotemporal dementia.

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