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Functional analysis of APOE locus genetic variation implicates regional enhancers in the regulation of both TOMM40 and APOE.

ABSTRACT: Genetic variation within the apolipoprotein E gene (APOE) locus is associated with late-onset Alzheimer's disease risk and quantitative traits as well as apoE expression in multiple tissues. The aim of this investigation was to explore the influence of APOE locus cis-regulatory element enhancer region genetic variation on regional gene promoter activity. Luciferase reporter constructs containing haplotypes of APOE locus gene promoters; APOE, APOC1 and TOMM40, and regional putative enhancers; TOMM40 intervening sequence (IVS)2-4, TOMM40 IVS6 poly-T, as well as previously described enhancers; multienhancer 1 (ME1), or brain control region (BCR), were evaluated for their effects on luciferase activity in three human cell lines. Results of this investigation demonstrate that in SHSY5Y cells, the APOE promoter is significantly influenced by the TOMM40 IVS2-4 and ME1, and the TOMM40 promoter is significantly influenced by the TOMM40 IVS6 poly-T, ME1 and BCR. In HepG2 cells, theTOMM40 promoter is significantly influenced by all four enhancers, whereas the APOE promoter is not influenced by any of the enhancers. The main novel finding of this investigation was that multiple APOE locus cis-elements influence both APOE and TOMM40 promoter activity according to haplotype and cell type, suggesting that a complex transcriptional regulatory structure modulates regional gene expression.

SUBMITTER: Bekris LM

PROVIDER: S-EPMC3266441 | biostudies-literature | 2012 Jan

REPOSITORIES: biostudies-literature

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Functional analysis of APOE locus genetic variation implicates regional enhancers in the regulation of both TOMM40 and APOE.

Bekris Lynn M LM Lutz Franziska F Yu Chang-En CE

Journal of human genetics 20111117 1

Genetic variation within the apolipoprotein E gene (APOE) locus is associated with late-onset Alzheimer's disease risk and quantitative traits as well as apoE expression in multiple tissues. The aim of this investigation was to explore the influence of APOE locus cis-regulatory element enhancer region genetic variation on regional gene promoter activity. Luciferase reporter constructs containing haplotypes of APOE locus gene promoters; APOE, APOC1 and TOMM40, and regional putative enhancers; TOM ...[more]

PMID: 22089642

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Project description:The TOMM40-APOE variants are known for their strong, antagonistic associations with Alzheimer's disease and body weight. While a stronger role of the APOE than TOMM40 variants in Alzheimer's disease was suggested, comparative contribution of the TOMM40-APOE variants in the regulation of body weight remains elusive. We examined additive effects of rs2075650 and rs157580 TOMM40 variants and rs429358 and rs7412 APOE variants coding the ?2/?3/?4 polymorphism on body mass index (BMI) in age-aggregated and age-stratified cohort-specific and cohort-pooled analysis of 27,863 Caucasians aged 20-100 years from seven longitudinal studies. Minor alleles of rs2075650, rs429358, and rs7412 were individually associated with BMI (? = -1.29, p = 3.97 × 10-9 ; ? = -1.38, p = 2.78 × 10-10 ; and ? = 0.58, p = 3.04 × 10-2 , respectively). Conditional analysis with rs2075650 and rs429358 identified independent BMI-lowering associations for minor alleles (? = -0.63, p = 3.99 × 10-2 and ? = -0.94, p = 2.17 × 10-3 , respectively). Polygenic mega-analysis identified additive effects of the rs2075650 and rs429358 heterozygotes (? = -1.68, p = 3.00 × 10-9 ), and the strongest BMI-lowering association for the rs2075650 heterozygous and rs429358 minor allele homozygous carriers (? = -4.11, p = 2.78 × 10-3 ). Conditional analysis with four polymorphisms identified independent BMI-lowering (rs2075650, rs157580, and rs429358) and BMI-increasing (rs7412) associations of heterozygous genotypes with BMI. Age-stratified conditional analysis revealed well-powered support for a differential and independent association of the rs429358 heterozygote with BMI in younger and older individuals, ? = 0.58, 95% confidence interval (CI) = -1.18, 2.35, p = 5.18 × 10-1 for 3,068 individuals aged ?30 years and ? = -4.28, CI = -5.65, -2.92, p = 7.71 × 10-10 for 6,052 individuals aged >80 years. TOMM40 and APOE variants are independently and additively associated with BMI. The APOE ?4-coding rs429358 polymorphism is associated with BMI in older individuals but not in younger individuals.

Dataset Information

Functional analysis of APOE locus genetic variation implicates regional enhancers in the regulation of both TOMM40 and APOE.

Publications

Functional analysis of APOE locus genetic variation implicates regional enhancers in the regulation of both TOMM40 and APOE.

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