Dataset Information

The effects of PPAR? on the regulation of the TOMM40-APOE-C1 genes cluster.

ABSTRACT: Chromosome 19q13.32 is a gene rich region, and has been implicated in multiple human phenotypes in adulthood including lipids traits, Alzheimer's disease, and longevity. Peroxisome Proliferator Activated Receptor Gamma (PPAR?) is a ligand-activated nuclear transcription factor that plays a role in human complex traits that are also genetically associated with the chromosome 19q13.32 region. Here, we study the effects of PPAR? on the regional expression regulation of the genes clustered within chromosome 19q13.32, specifically TOMM40, APOE, and APOC1, applying two complementary approaches. Using the short hairpin RNA (shRNA) method in the HepG2 cell-line we knocked down PPAR? expression and measured the effect on mRNA expression. We discovered PPAR? knock down increased the levels of TOMM40-, APOE-, and APOC1-mRNAs, with the highest increase in expression observed for APOE-mRNA. To complement the PPAR? knockdown findings we also examined the effects of low doses of PPAR? agonists (nM range) on mRNA expression of these genes. Low (nM) concentrations of pioglitazone (Pio) decreased transcription of TOMM40, APOE, and APOC1 genes, with the lowest mRNA levels for each gene observed at 1.5nM. Similar to the effect of PPAR? knockdown, the strongest response to pioglitazone was also observed for APOE-mRNA, and rosiglitazone (Rosi), another PPAR? agonist, produced results that were consistent with these. In conclusion, our results further established a role for PPAR? in regional transcriptional regulation of chr19q13.32, underpinning the association between PPAR?, the chr19q13.32 genes cluster, and human complex traits and disease.

SUBMITTER: Subramanian S

PROVIDER: S-EPMC5285471 | biostudies-literature | 2017 Mar

REPOSITORIES: biostudies-literature

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The effects of PPARγ on the regulation of the TOMM40-APOE-C1 genes cluster.

Subramanian Shobana S Gottschalk William K WK Kim So Young SY Roses Allen D AD Chiba-Falek Ornit O

Biochimica et biophysica acta. Molecular basis of disease 20170106 3

Chromosome 19q13.32 is a gene rich region, and has been implicated in multiple human phenotypes in adulthood including lipids traits, Alzheimer's disease, and longevity. Peroxisome Proliferator Activated Receptor Gamma (PPARγ) is a ligand-activated nuclear transcription factor that plays a role in human complex traits that are also genetically associated with the chromosome 19q13.32 region. Here, we study the effects of PPARγ on the regional expression regulation of the genes clustered within ch ...[more]

PMID: 28065845

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Project description:Apolipoprotein E (APOE) ε genotype has previously been significantly associated with cognitive, brain imaging, and Alzheimer's disease-related phenotypes (e.g., age of onset). In the TOMM40 gene, the rs10524523 ("523") variable length poly-T repeat polymorphism has more recently been associated with similar ph/enotypes, although the allelic directions of these associations have varied between initial reports. Using diffusion magnetic resonance imaging tractography, the present study aimed to investigate whether there are independent effects of apolipoprotein E (APOE) and TOMM40 genotypes on human brain white matter integrity in a community-dwelling sample of older adults, the Lothian Birth Cohort 1936 (mean age = 72.70 years, standard deviation = 0.74, N approximately = 640-650; for most analyses). Some nominally significant effects were observed (i.e., covariate-adjusted differences between genotype groups at p < 0.05). For APOE, deleterious effects of ε4 "risk" allele presence (vs. absence) were found in the right ventral cingulum and left inferior longitudinal fasciculus. To test for biologically independent effects of the TOMM40 523 repeat, participants were stratified into APOE genotype subgroups, so that any significant effects could not be attributed to APOE variation. In participants with the APOE ε3/ε4 genotype, effects of TOMM40 523 status were found in the left uncinate fasciculus, left rostral cingulum, left ventral cingulum, and a general factor of white matter integrity. In all 4 of these tractography measures, carriers of the TOMM40 523 "short" allele showed lower white matter integrity when compared with carriers of the "long" and "very-long" alleles. Most of these effects survived correction for childhood intelligence test scores and vascular disease history, though only the effect of TOMM40 523 on the left ventral cingulum integrity survived correction for false discovery rate. The effects of APOE in this older population are more specific and restricted compared with those reported in previous studies, and the effects of TOMM40 on white matter integrity appear to be novel, although replication is required in large independent samples.

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

The effects of PPAR? on the regulation of the TOMM40-APOE-C1 genes cluster.

Publications

The effects of PPARγ on the regulation of the TOMM40-APOE-C1 genes cluster.

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