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ApoE variant p.V236E is associated with markedly reduced risk of Alzheimer's disease.

ABSTRACT: Recent genome-wide association studies (GWAS) of late-onset Alzheimer's disease (LOAD) have identified single nucleotide polymorphisms (SNPs) which show significant association at the well-known APOE locus and at nineteen additional loci. Among the functional, disease-associated variants at these loci, missense variants are particularly important because they can be readily investigated in model systems to search for novel therapeutic targets. It is now possible to perform a low-cost search for these "actionable" variants by genotyping the missense variants at known LOAD loci already cataloged on the Exome Variant Server (EVS). In this proof-of-principle study designed to explore the efficacy of this approach, we analyzed three rare EVS variants in APOE, p.L28P, p.R145C and p.V236E, in our case control series of 9114 subjects. p.R145C proved to be too rare to analyze effectively. The minor allele of p.L28P, which was in complete linkage disequilibrium (D' = 1) with the far more common APOE ?4 allele, showed no association with LOAD (P = 0.75) independent of the APOE ?4 allele. p.V236E was significantly associated with a marked reduction in risk of LOAD (P = 7.5 × 10???; OR = 0.10, 0.03 to 0.45). The minor allele of p.V236E, which was in complete linkage disequilibrium (D' = 1) with the common APOE ?3 allele, identifies a novel LOAD-associated haplotype (APOE ?3b) which is associated with decreased risk of LOAD independent of the more abundant APOE ?2, ?3 and ?4 haplotypes. Follow-up studies will be important to confirm the significance of this association and to better define its odds ratio. The ApoE p.V236E substitution is the first disease-associated change located in the lipid-binding, C-terminal domain of the protein. Thus our study (i) identifies a novel APOE missense variant which may profitably be studied to better understand how ApoE function may be modified to reduce risk of LOAD and (ii) indicates that analysis of protein-altering variants cataloged on the EVS can be a cost-effective way to identify actionable functional variants at recently discovered LOAD loci.

SUBMITTER: Medway CW

PROVIDER: S-EPMC3995879 | biostudies-literature | 2014 Mar

REPOSITORIES: biostudies-literature

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ApoE variant p.V236E is associated with markedly reduced risk of Alzheimer's disease.

Medway Christopher W CW Abdul-Hay Samer S Mims Tynickwa T Ma Li L Bisceglio Gina G Zou Fanggeng F Pankratz Shane S Sando Sigrid B SB Aasly Jan O JO Barcikowska Maria M Siuda Joanna J Wszolek Zbigniew K ZK Ross Owen A OA Carrasquillo Minerva M Dickson Dennis W DW Graff-Radford Neill N Petersen Ronald C RC Ertekin-Taner Nilüfer N Morgan Kevin K Bu Guojun G Younkin Steven G SG

Molecular neurodegeneration 20140310

Recent genome-wide association studies (GWAS) of late-onset Alzheimer's disease (LOAD) have identified single nucleotide polymorphisms (SNPs) which show significant association at the well-known APOE locus and at nineteen additional loci. Among the functional, disease-associated variants at these loci, missense variants are particularly important because they can be readily investigated in model systems to search for novel therapeutic targets. It is now possible to perform a low-cost search for ...[more]

PMID: 24607147

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Project description:BackgroundThe apolipoprotein E (APOE) genotype provides information on the risk of Alzheimer's disease, but the genotyping of patients and their family members has been discouraged. We examined the effect of genotype disclosure in a prospective, randomized, controlled trial.MethodsWe randomly assigned 162 asymptomatic adults who had a parent with Alzheimer's disease to receive the results of their own APOE genotyping (disclosure group) or not to receive such results (nondisclosure group). We measured symptoms of anxiety, depression, and test-related distress 6 weeks, 6 months, and 1 year after disclosure or nondisclosure.ResultsThere were no significant differences between the two groups in changes in time-averaged measures of anxiety (4.5 in the disclosure group and 4.4 in the nondisclosure group, P=0.84), depression (8.8 and 8.7, respectively; P=0.98), or test-related distress (6.9 and 7.5, respectively; P=0.61). Secondary comparisons between the nondisclosure group and a disclosure subgroup of subjects carrying the APOE epsilon4 allele (which is associated with increased risk) also revealed no significant differences. However, the epsilon4-negative subgroup had a significantly lower level of test-related distress than did the epsilon4-positive subgroup (P=0.01). Subjects with clinically meaningful changes in psychological outcomes were distributed evenly among the nondisclosure group and the epsilon4-positive and epsilon4-negative subgroups. Baseline scores for anxiety and depression were strongly associated with post-disclosure scores of these measures (P<0.001 for both comparisons).ConclusionsThe disclosure of APOE genotyping results to adult children of patients with Alzheimer's disease did not result in significant short-term psychological risks. Test-related distress was reduced among those who learned that they were APOE epsilon4-negative. Persons with high levels of emotional distress before undergoing genetic testing were more likely to have emotional difficulties after disclosure. (ClinicalTrials.gov number, NCT00571025.)

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ApoE variant p.V236E is associated with markedly reduced risk of Alzheimer's disease.

Publications

ApoE variant p.V236E is associated with markedly reduced risk of Alzheimer's disease.

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