A rare amyloid precursor protein (APP) gene variant, A673T (rs63750847) was recently reported to protect against Alzheimer’s disease (AD) and age-related cognitive decline among Icelanders and the same rare variant was observed also in Finnish, Norwegian, and Swedish populations. We investigated this variant in 1,674 late-onset AD cases and 2,644 elderly controls, all North American Whites (U.S. Whites). We did not observe any example of the A673T variant in our large sample. Our findings suggest that this rare variant could be specific to the individuals of the origin from the Nordic countries.
Alzheimer’s disease; cognitive decline; cognitive impairment; Amyloid precursor protein; APP; rs63750847; A673T
Genetic variation in lipid regulatory genes, particularly APOE, significantly influences the risk of coronary artery disease (CAD). This study aimed to assess the association between APOE polymorphism and angiographically assessed coronary stenosis in Pakistani population. A total of 695 subjects (22.3% female, mean age = 54 ± 11 years) presenting with chest pain were enrolled after obtaining written informed consent. CAD stenosis/extent was assessed by angiography. Patients were classified as having severe stenosis (≥70%), moderate stenosis (30–69%), and mild stenosis (<30%). CAD patients with ≥70% stenosis (n = 491) were further categorized based on possessing one, two, or three vessel diseases to assess the disease extent. Genomic DNA from leukocytes was isolated with DNA purification kit (Qiagen) and APOE polymorphisms (E2/E3/E4) were determined using TaqMan assays. Six hundred and seventy-two of 695 subjects were successfully genotyped. The frequency of APOE∗4 carriers (3/4 and 4/4 genotypes) was significantly higher in severe stenosis group (≥70%) as compared to mild group (<30%) (22.8% versus 13.01%; P = 0.01). In multiple regression, the odds ratio for APOE∗4 carriers to develop ≥70% stenosis was 2.16 (95% CI: 1.29–3.79; P < 0.005). In conclusion, the presence of APOE∗4 allele is a significant risk factor to develop severe coronary stenosis (>70%) among Pakistanis.
As APOE locus variants contribute to both risk of late-onset Alzheimer disease and differences in age-at-onset, it is important to know if other established late-onset Alzheimer disease risk loci also affect age-at-onset in cases.
To investigate the effects of known Alzheimer disease risk loci in modifying age-at-onset, and to estimate their cumulative effect on age-at-onset variation, using data from genome-wide association studies in the Alzheimer’s Disease Genetics Consortium (ADGC).
Design, Setting and Participants
The ADGC comprises 14 case-control, prospective, and family-based datasets with data on 9,162 Caucasian participants with Alzheimer’s occurring after age 60 who also had complete age-at-onset information, gathered between 1989 and 2011 at multiple sites by participating studies. Data on genotyped or imputed single nucleotide polymorphisms (SNPs) most significantly associated with risk at ten confirmed LOAD loci were examined in linear modeling of AAO, and individual dataset results were combined using a random effects, inverse variance-weighted meta-analysis approach to determine if they contribute to variation in age-at-onset. Aggregate effects of all risk loci on AAO were examined in a burden analysis using genotype scores weighted by risk effect sizes.
Main Outcomes and Measures
Age at disease onset abstracted from medical records among participants with late-onset Alzheimer disease diagnosed per standard criteria.
Analysis confirmed association of APOE with age-at-onset (rs6857, P=3.30×10−96), with associations in CR1 (rs6701713, P=7.17×10−4), BIN1 (rs7561528, P=4.78×10−4), and PICALM (rs561655, P=2.23×10−3) reaching statistical significance (P<0.005). Risk alleles individually reduced age-at-onset by 3-6 months. Burden analyses demonstrated that APOE contributes to 3.9% of variation in age-at-onset (R2=0.220) over baseline (R2=0.189) whereas the other nine loci together contribute to 1.1% of variation (R2=0.198).
Conclusions and Relevance
We confirmed association of APOE variants with age-at-onset among late-onset Alzheimer disease cases and observed novel associations with age-at-onset in CR1, BIN1, and PICALM. In contrast to earlier hypothetical modeling, we show that the combined effects of Alzheimer disease risk variants on age-at-onset are on the scale of, but do not exceed, the APOE effect. While the aggregate effects of risk loci on age-at-onset may be significant, additional genetic contributions to age-at-onset are individually likely to be small.
Alzheimer Disease; Alzheimer Disease Genetics; Alzheimer’s Disease - Pathophysiology; Genetics of Alzheimer Disease; Aging
There is a strong genetic basis for late-onset of Alzheimer’s disease (LOAD); thus far 22 genes/loci have been identified that affect the risk of LOAD. However, the relationships among the genetic variations at these loci and clinical progression of the disease have not been fully explored. In the present study, we examined the relationships of 22 known LOAD genes to the progression of AD in 680 AD patients recruited from the University of Pittsburgh Alzheimer’s Disease Research Center. Patients were classified as “rapid progressors” if the MMSE changed ≥3 points in 12 months and “slow progressors” if the MMSE changed ≤2 points. We also performed a genome-wide association study in this cohort in an effort to identify new loci for AD progression. Association analysis between SNPs and the progression status of the AD cases was performed using logistic regression model controlled for age, gender, dementia medication use, psychosis, and hypertension. While no significant association was observed with either APOE*4 (p=0.94) or APOE*2 (p=0.33) with AD progression, we found multiple nominally significant associations (p<0.05) either within or adjacent to seven known LOAD genes (INPP5D, MEF2C, TREM2, EPHA1, PTK2B, FERMT2 and CASS4) that harbor both risk and protective SNPs. Genome-wide association analyses identified four suggestive loci (PAX3, CCRN4L, PIGQ and ADAM19) at p<1E-05. Our data suggest that short-term clinical disease progression in AD has genetic basis. Better understanding of these genetic factors could help to improve clinical trial design and potentially affect the development of disease modifying therapies.
LOAD; GWAS; MMSE; AD progression
Although common APOE genetic variation has a major influence on plasma LDL-cholesterol, its role in affecting HDL-cholesterol and triglycerides is not well established. Recent genome-wide association studies suggest that APOE also affects plasma variation in HDL-cholesterol and triglycerides. It is thus important to resequence the APOE gene to identify both common and uncommon variants that affect plasma lipid profile. Here, we have sequenced the APOE gene in 190 subjects with extreme HDL-cholesterol levels selected from two well-defined epidemiological samples of U.S. non-Hispanic Whites (NHWs) and African Blacks followed by genotyping of identified variants in the entire datasets (623 NHWs, 788 African Blacks) and association analyses with major lipid traits. We identified a total of 40 sequence variants, of which 10 are novel. A total of 32 variants, including common tagSNPs (≥5% frequency) and all uncommon variants (<5% frequency) were successfully genotyped and considered for genotype-phenotype associations. Other than the established associations of APOE*2 and APOE*4 with LDL-cholesterol, we have identified additional independent associations with LDL-cholesterol. We have also identified multiple associations of uncommon and common APOE variants with HDL-cholesterol and triglycerides. Our comprehensive sequencing and genotype-phenotype analyses indicate that APOE genetic variation impacts HDL-cholesterol and triglycerides in addition to affecting LDL-cholesterol.
Epidemiological and genetic studies suggest that schizophrenia and autism may share genetic links. Besides common single nucleotide polymorphisms, recent data suggest that some rare copy number variants (CNVs) are risk factors for both disorders. Because we have previously found that schizophrenia and psychosis in Alzheimer's disease (AD+P) share some genetic risk, we investigated whether CNVs reported in schizophrenia and autism are also linked to AD+P. We searched for CNVs associated with AD+P in 7 recurrent CNV regions that have been previously identified across autism and schizophrenia, using the Illumina HumanOmni1-Quad BeadChip. A chromosome 16p11.2 duplication CNV (chr16: 29,554,843-30,105,652) was identified in 2 of 440 AD+P subjects, but not in 136 AD subjects without psychosis, or in 593 AD subjects with intermediate psychosis status, or in 855 non-AD individuals. The frequency of this duplication CNV in AD+P (0.46%) was similar to that reported previously in schizophrenia (0.46%). This duplication CNV was further validated using the NanoString nCounter CNV Custom CodeSets. The 16p11.2 duplication has been associated with developmental delay, intellectual disability, behavioral problems, autism, schizophrenia (SCZ), and bipolar disorder. These two AD+P patients had no personal of, nor any identified family history of, SCZ, bipolar disorder and autism. To the best of our knowledge, our case report is the first suggestion that 16p11.2 duplication is also linked to AD+P. Although rare, this CNV may have an important role in the development of psychosis.
Genome-wide association studies (GWAS) have identified several risk
variants for late-onset Alzheimer's disease (LOAD)1,2. These
common variants have replicable but small effects on LOAD risk and generally do
not have obvious functional effects. Low-frequency coding variants, not detected
by GWAS, are predicted to include functional variants with larger effects on
risk. To identify low frequency coding variants with large effects on LOAD risk,
we performed whole exome-sequencing (WES) in 14 large LOAD families and
follow-up analyses of the candidate variants in several large case-control
datasets. A rare variant in PLD3 (phospholipase-D family,
member 3, rs145999145; V232M) segregated with disease status in two independent
families and doubled risk for AD in seven independent case-control series (V232M
meta-analysis; OR= 2.10, CI=1.47-2.99; p= 2.93×10-5, 11,354
cases and controls of European-descent). Gene-based burden analyses in 4,387
cases and controls of European-descent and 302 African American cases and
controls, with complete sequence data for PLD3, indicate that
several variants in this gene increase risk for AD in both populations (EA: OR=
2.75, CI=2.05-3.68; p=1.44×10-11, AA: OR= 5.48, CI=1.77-16.92;
p=1.40×10-3). PLD3 is highly expressed in
brain regions vulnerable to AD pathology, including hippocampus and cortex, and
is expressed at lower levels in neurons from AD brains compared to control
brains (p=8.10×10-10). Over-expression of PLD3 leads to a
significant decrease in intracellular APP and extracellular Aβ42 and
Aβ40, while knock-down of PLD3 leads to a significant increase in
extracellular Aβ42 and Aβ40. Together, our genetic and functional
data indicate that carriers of PLD3 coding variants have a
two-fold increased risk for LOAD and that PLD3 influences APP
processing. This study provides an example of how densely affected families may
be used to identify rare variants with large effects on risk for disease or
other complex traits.
Late-onset Alzheimer's disease (LOAD) is a multifactorial disorder with over twenty loci associated with disease risk. Given the number of genome-wide significant variants that fall outside of coding regions, it is possible that some of these variants alter some function of gene expression rather than tagging coding variants that alter protein structure and/or function. RegulomeDB is a database that annotates regulatory functions of genetic variants. In this study, we utilized RegulomeDB to investigate potential regulatory functions of lead single nucleotide polymorphisms (SNPs) identified in five genome-wide association studies (GWAS) of risk and age-at onset (AAO) of LOAD, as well as SNPs in LD (r2≥0.80) with the lead GWAS SNPs. Of a total 614 SNPs examined, 394 returned RegulomeDB scores of 1–6. Of those 394 variants, 34 showed strong evidence of regulatory function (RegulomeDB score <3), and only 3 of them were genome-wide significant SNPs (ZCWPW1/rs1476679, CLU/rs1532278 and ABCA7/rs3764650). This study further supports the assumption that some of the non-coding GWAS SNPs are true associations rather than tagged associations and demonstrates the application of RegulomeDB to GWAS data.
The risk of Alzheimer’s disease (AD) is strongly determined by genetic factors and recent genome-wide association studies (GWAS) have identified several genes for the disease risk. In addition to the disease risk, age-at-onset (AAO) of AD has also strong genetic component with an estimated heritability of 42%. Identification of AAO genes may help to understand the biological mechanisms that regulate the onset of the disease. Here we report the first GWAS focused on identifying genes for the AAO of AD. We performed a genome-wide meta analysis on 3 samples comprising a total of 2,222 AD cases. A total of ~2.5 million directly genotyped or imputed SNPs were analyzed in relation to AAO of AD. As expected, the most significant associations were observed in the APOE region on chromosome 19 where several SNPs surpassed the conservative genome-wide significant threshold (P<5E-08). The most significant SNP outside the APOE region was located in the DCHS2 gene on chromosome 4q31.3 (rs1466662; P=4.95E-07). There were 19 additional significant SNPs in this region at P<1E-04 and the DCHS2 gene is expressed in the cerebral cortex and thus is a potential candidate for affecting AAO in AD. These findings need to be confirmed in additional well-powered samples.
Genome-wide association study; age-at-onset; Alzheimer’s disease; single-nucleotide polymorphisms; meta analysis
Psychotic symptoms occur in approximately 40% of subjects with Alzheimer’s disease (AD) and are associated with more rapid cognitive decline and increased functional deficits. They show heritability up to 61% and have been proposed as a marker for a disease subtype suitable for gene mapping efforts. We undertook a combined analysis of three genome-wide association studies (GWAS) to identify loci that a) increase susceptibility to an AD and subsequent psychotic symptoms; or b) modify risk of psychotic symptoms in the presence of neurodegeneration caused by AD. 1299 AD cases with psychosis (AD+P), 735 AD cases without psychosis (AD-P) and 5659 controls were drawn from GERAD1, the NIA-LOAD family study and the University of Pittsburgh ADRC GWAS. Unobserved genotypes were imputed to provide data on > 1.8 million SNPs. Analyses in each dataset were completed comparing a) AD+P to AD-P cases, and b) AD+P cases with controls (GERAD1, ADRC only). Aside from the APOE locus, the strongest evidence for association was observed in an intergenic region on chromosome 4 (rs753129; ‘AD+PvAD-P’ P=2.85 × 10−7; ‘AD+PvControls’ P=1.11 × 10−4). SNPs upstream of SLC2A9 (rs6834555, P=3.0×10−7) and within VSNL1 (rs4038131, P=5.9×10−7) showed strongest evidence for association with AD+P when compared to controls. These findings warrant further investigation in larger, appropriately powered samples in which the presence of psychotic symptoms in AD has been well characterised.
Alzheimer’s disease; psychosis; behavioural symptoms; genome-wide association study; genetic
Pancreatitis is a complex, progressively destructive inflammatory disorder. Alcohol was long thought to be the primary causative agent, but genetic contributions have been of interest since the discovery that rare PRSS1, CFTR, and SPINK1 variants were associated with pancreatitis risk. We now report two significant genome-wide associations identified and replicated at PRSS1-PRSS2 (1×10-12) and x-linked CLDN2 (p < 1×10-21) through a two-stage genome-wide study (Stage 1, 676 cases and 4507 controls; Stage 2, 910 cases and 4170 controls). The PRSS1 variant affects susceptibility by altering expression of the primary trypsinogen gene. The CLDN2 risk allele is associated with atypical localization of claudin-2 in pancreatic acinar cells. The homozygous (or hemizygous male) CLDN2 genotype confers the greatest risk, and its alleles interact with alcohol consumption to amplify risk. These results could partially explain the high frequency of alcohol-related pancreatitis in men – male hemizygous frequency is 0.26, female homozygote is 0.07.
Genome-wide association studies (GWAS) have identified a number of loci/SNPs associated with plasma total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), and triglyceride (TG) levels. The purpose of this study was to replicate 40 recent GWAS-identified HDL-C-related new loci in 3 epidemiological samples comprising U.S. non-Hispanic Whites (NHWs), U.S. Hispanics, and African Blacks. In each sample, the association analyses were performed with all 4 major lipid traits regardless of previously reported specific associations with selected SNPs. A total of 22 SNPs showed nominally significant association (p<0.05) with at least one lipid trait in at least one ethnic group, although not always with the same lipid traits reported as genome-wide significant in the original GWAS. The total number of significant loci was 10 for TC, 12 for LDL-C, 10 for HDL-C, and 6 for TG levels. Ten SNPs were significantly associated with more than one lipid trait in at least one ethnic group. Six SNPs were significantly associated with at least one lipid trait in more than one ethnic group, although not always with the same trait across various ethnic groups. For 25 SNPs, the associations were replicated with the same genome-wide significant lipid traits in the same direction in at least one ethnic group; at nominal significance for 13 SNPs and with a trend for association for 12 SNPs. However, the associations were not consistently present in all ethnic groups. This observation was consistent with mixed results obtained in other studies that also examined various ethnic groups.
Background. The persistent presence of antiphospholipid antibodies (APA) may lead to the development of primary or secondary antiphospholipid syndrome. Although the genetic basis of APA has been suggested, the identity of the underlying genes is largely unknown. In this study, we have performed a genome-wide association study (GWAS) in an effort to identify susceptibility loci/genes for three main APA: anticardiolipin antibodies (ACL), lupus anticoagulant (LAC), and anti-β2 glycoprotein I antibodies (anti-β2GPI). Methods. DNA samples were genotyped using the Affymetrix 6.0 array containing 906,600 single-nucleotide polymorphisms (SNPs). Association of SNPs with the antibody status (positive/negative) was tested using logistic regression under the additive model. Results. We have identified a number of suggestive novel loci with P < E − 05. Although they do not meet the conservative threshold of genome-wide significance, many of the suggestive loci are potential candidates for the production of APA. We have replicated the previously reported associations of HLA genes and APOH with APA but these were not the top loci. Conclusions. We have identified a number of suggestive novel loci for APA that will stimulate follow-up studies in independent and larger samples to replicate our findings.
Psychotic symptoms occur in approximately 40% of subjects with Alzheimer’s disease (AD) and are associated with more rapid cognitive decline and increased functional deficits. They show heritability up to 61% and have been proposed as a marker for a disease subtype suitable for gene mapping efforts. We undertook a combined analysis of three genome-wide association studies (GWAS) to identify loci that a) increase susceptibility to an AD and subsequent psychotic symptoms; or b) modify risk of psychotic symptoms in the presence of neurodegeneration caused by AD. 1299 AD cases with psychosis (AD+P), 735 AD cases without psychosis (AD−P) and 5659 controls were drawn from GERAD1, the NIA-LOAD family study and the University of Pittsburgh ADRC GWAS. Unobserved genotypes were imputed to provide data on > 1.8 million SNPs. Analyses in each dataset were completed comparing a) AD+P to AD−P cases, and b) AD+P cases with controls (GERAD1, ADRC only). Aside from the APOE locus, the strongest evidence for association was observed in an intergenic region on chromosome 4 (rs753129; ‘AD+PvAD−P’ P=2.85 × 10−7; ‘AD+PvControls’ P=1.11 × 10−4). SNPs upstream of SLC2A9 (rs6834555, P=3.0×10−7) and within VSNL1 (rs4038131, P=5.9×10−7) showed strongest evidence for association with AD+P when compared to controls. These findings warrant further investigation in larger, appropriately powered samples in which the presence of psychotic symptoms in AD has been well characterised.
Alzheimer’s disease; psychosis; behavioural symptoms; genome-wide association study; genetic
Late-onset Alzheimer’s disease (LOAD) is a complex and multifactorial disease. So far ten loci have been identified for LOAD, including APOE, PICALM, CLU, BIN1, CD2AP, CR1, CD33, EPHA1, ABCA7, and MS4A4A/MS4A6E, but they explain about 50% of the genetic risk and thus additional risk genes need to be identified. Amyloid beta (Aβ) plaques develop in the brains of LOAD patients and are considered to be a pathological hallmark of this disease. Recently 12 new Aβ toxicity modifier genes (ADSSL1, PICALM, SH3KBP1, XRN1, SNX8, PPP2R5C, FBXL2, MAP2K4, SYNJ1, RABGEF1, POMT2, and XPO1) have been identified that potentially play a role in LOAD risk. In this study, we have examined the association of 222 SNPs in these 12 candidate genes with LOAD risk in 1291 LOAD cases and 958 cognitively normal controls. Single site and haplotype analyses were performed using PLINK. Following adjustment for APOE genotype, age, sex, and principal components, we found single nucleotide polymorphisms (SNPs) in PPP2R5C, PICALM, SH3KBP1, XRN1, and SNX8 that showed significant association with risk of LOAD. The top SNP was located in intron 3 of PPP2R5C (P=0.009017), followed by an intron 19 SNP in PICALM (P=0.0102). Haplotype analysis revealed significant associations in ADSSL1, PICALM, PPP2R5C, SNX8, and SH3KBP1 genes. Our data indicate that genetic variation in these new candidate genes affects the risk of LOAD. Further investigation of these genes, including additional replication in other case-control samples and functional studies to elucidate the pathways by which they affect Aβ, are necessary to determine the degree of involvement these genes have for LOAD risk.
Late-onset Alzheimer’s disease (LOAD); risk genes; SNPs; ADSSL1; PICALM; SH3KBP1; XRN1; SNX8; PPP2R5C; FBXL2; MAP2K4; SYNJ1; RABGEF1; POMT2; XPO1
Two F2 functional polymorphisms, rs1799963 (G20210A) and rs3136516 (A19911G), are known to be associated with elevated prothrombin (encoded by F2) levels/activity and thrombosis risk. Since systemic lupus erythematosus (SLE) patients have high risk of thrombosis and accelerated atherosclerosis and also high prevalence of anti-prothrombin antibodies, we hypothesized that these two F2 polymorphisms could affect SLE risk.
We investigated these polymorphisms in 627 women with SLE (84% Caucasian Americans, 16% African Americans) and 657 female controls (78% Caucasian Americans, 22% African Americans).
While the rs1799963 A allele was almost absent in African Americans, it was present at ~2% frequency in Caucasian Americans and showed no significant association with SLE. The rs3136516 G allele frequency was significantly higher in Caucasian SLE cases than controls (48.4% vs. 43.7%) with a covariate-adjusted odds ratio (OR) of 1.22 (95%CI: 1.03–1.46; P = 0.023). The association was replicated in African Americans (rs3136516 G allele frequency: 91.2% in cases vs. 82.2% in controls) with an adjusted OR of 1.96 (95%CI: 1.08–3.58; P = 0.022). Stratification of Caucasian SLE patients based on the presence or absence of cardiac and vascular events (CVE) revealed stronger association with the CVE-positive SLE subgroup than the CVE-negative SLE subgroup (OR: 1.42 vs. 1.20). Prothrombin activity measurements in a subset of SLE cases demonstrated higher activity in the carriers of the rs3136516 G allele.
Our results suggest a potential role for prothrombin and the crosstalk between hemostatic and immune/inflammatory systems in SLE and SLE-associated cardiovascular events, which warrant further investigation in independent samples.
lupus; prothrombin; F2; polymorphism; A19911G; G20210A
The Alzheimer Disease Genetics Consortium (ADGC) performed a genome-wide association study (GWAS) of late-onset Alzheimer disease (LOAD) using a 3 stage design consisting of a discovery stage (Stage 1) and two replication stages (Stages 2 and 3). Both joint and meta-analysis analysis approaches were used. We obtained genome-wide significant results at MS4A4A [rs4938933; Stages 1+2, meta-analysis (PM) = 1.7 × 10−9, joint analysis (PJ) = 1.7 × 10−9; Stages 1–3, PM = 8.2 × 10−12], CD2AP (rs9349407; Stages 1–3, PM = 8.6 × 10−9), EPHA1 (rs11767557; Stages 1–3 PM = 6.0 × 10−10), and CD33 (rs3865444; Stages 1–3, PM = 1.6 × 10−9). We confirmed that CR1 (rs6701713; PM = 4.6×10−10, PJ = 5.2×10−11), CLU (rs1532278; PM = 8.3 × 10−8, PJ = 1.9×10−8), BIN1 (rs7561528; PM = 4.0×10−14; PJ = 5.2×10−14), and PICALM (rs561655; PM = 7.0 × 10−11, PJ = 1.0×10−10) but not EXOC3L2 are LOAD risk loci1–3.
We have examined the association of 14 tagging single nucleotide polymorphisms (tagSNPs) in peroxisome proliferator activated-receptor gamma transcripts 1 and 2 (PPARG1&2) and 5 tagSNPs in adiponectin (ADIPOQ) genes for their effect on type 2 diabetes (T2D) risk in Asian Indian Sikhs. A total of 554 T2D cases and 527 normoglycemic (NG) controls were examined for association with T2D and other sub-phenotypes of T2D. With the exception of a strong association of PPARG2/Pro12Ala with T2D [OR 0.13, 95%CI (0.03–0.56), p=0.0007], no other tagSNP in the PPARG locus revealed any significant association with T2D in this population. Similarly, none of the tagSNPs in the ADIPOQ gene was associated with T2D susceptibility in single-site analysis. However, haplotype analysis provided strong evidence of association of these loci with T2D. Three-site haplotype analysis in the PPARG locus using the two marginally associated SNPs (P/rs11715073 and P/rs3892175) in combination with Pro12 Ala (P/rs1801282) revealed a strong association of one ‘risk’ (CGC) (p=0.003; permutation p=0.015) and one ‘protective’ (CAC) (p =0.001; permutation p=0.005) haplotype associated with T2D. However, the major effect still appears to be driven by Pro12Ala as the association of these haplotypes did not remain significant when analyzed conditional upon Pro12Ala (p = 0.262). Additionally, two-site haplotype analysis in the ADIPOQ locus using only two marginally associated SNPs (AD/rs182052 and AD/rs7649121) revealed a significant protective association of the GA haplotype with T2D (p=0.009; permutation p=0.026). Multiple linear regression analysis also revealed significant association of an ADIPOQ variant (AD/rs12495941) with total body weight (p= 0.010), waist (p=0.024) and hip (p=0.021), although these associations were not significant after adjusting for multiple testing. Our new findings strongly suggest that the genetic variation in PPARG and ADIPOQ loci could contribute to risk for the development of T2D in Indian Sikhs. Identification of causal SNPs in these important biological and positional candidate genes would help determine true physiological significance of these loci in T2D and obesity.
Systemic lupus erythematosus (SLE) is a clinically heterogeneous, systemic autoimmune disease characterized by autoantibody formation. Previously published genome-wide association studies (GWAS) have investigated SLE as a single phenotype. Therefore, we conducted a GWAS to identify genetic factors associated with anti–dsDNA autoantibody production, a SLE–related autoantibody with diagnostic and clinical importance. Using two independent datasets, over 400,000 single nucleotide polymorphisms (SNPs) were studied in a total of 1,717 SLE cases and 4,813 healthy controls. Anti–dsDNA autoantibody positive (anti–dsDNA +, n = 811) and anti–dsDNA autoantibody negative (anti–dsDNA –, n = 906) SLE cases were compared to healthy controls and to each other to identify SNPs associated specifically with these SLE subtypes. SNPs in the previously identified SLE susceptibility loci STAT4, IRF5, ITGAM, and the major histocompatibility complex were strongly associated with anti–dsDNA + SLE. Far fewer and weaker associations were observed for anti–dsDNA – SLE. For example, rs7574865 in STAT4 had an OR for anti–dsDNA + SLE of 1.77 (95% CI 1.57–1.99, p = 2.0E-20) compared to an OR for anti–dsDNA – SLE of 1.26 (95% CI 1.12–1.41, p = 2.4E-04), with pheterogeneity<0.0005. SNPs in the SLE susceptibility loci BANK1, KIAA1542, and UBE2L3 showed evidence of association with anti–dsDNA + SLE and were not associated with anti–dsDNA – SLE. In conclusion, we identified differential genetic associations with SLE based on anti–dsDNA autoantibody production. Many previously identified SLE susceptibility loci may confer disease risk through their role in autoantibody production and be more accurately described as autoantibody propensity loci. Lack of strong SNP associations may suggest that other types of genetic variation or non-genetic factors such as environmental exposures have a greater impact on susceptibility to anti–dsDNA – SLE.
Systemic lupus erythematosus (SLE) is a chronic autoimmune disease that can involve virtually any organ system. SLE patients produce antibodies that bind to their own cells and proteins (autoantibodies) which can cause irreversible organ damage. One particular SLE–related autoantibody directed at double-stranded DNA (anti–dsDNA) is associated with kidney involvement and more severe disease. Previous genome-wide association studies (GWAS) in SLE have studied SLE itself, not particular SLE manifestations. Therefore, we conducted this GWAS of anti–dsDNA autoantibody production to identify genetic associations with this clinically important autoantibody. We found that many previously identified SLE–associated genes are more strongly associated with anti–dsDNA autoantibody production than SLE itself, and they may be more accurately described as autoantibody propensity genes. No strong genetic associations were observed for SLE patients who do not produce anti–dsDNA autoantibodies, suggesting that other factors may have more influence in developing this type of SLE. Further investigation of these autoantibody propensity genes may lead to greater insight into the causes of autoantibody production and organ damage in SLE.
This study characterized the human apolipoprotein H (APOH, a.k.a. β2-glycoprotein I) promoter and its variants by in vitro functional experiments and investigated their relation with human plasma β2GPI levels. We examined the individual effects of 12 APOH promoter SNPs in the 5' flanking region of APOH (~1.4 kb) on luciferase activity in COS-1 cells and HepG2 cells and their impact on plasma β2GPI levels in 799 U.S. Whites, the DNA-binding properties of APOH promoter using electrophoretic mobility shift assay (EMSA) in HepG2 cells, the effects of serial deletion analysis of APOH 5' flanking region in COS-1 and HepG2 cells, and cross-species conservation of the APOH promoter sequence. The variant alleles of three SNPs (−1219G>A, −643T>C and −32C>A) showed significantly lower luciferase expression (51%, 40% and 37%, respectively) as compared to the wild-type allele. EMSA demonstrated that these three variants specifically bind with protein(s) from HepG2 cell nuclear extracts. Three-site haplotype analysis (−1219G>A, −643T>C, and −32C>A) revealed one haplotype carrying −32A (allele frequency = 0.075) to be significantly associated with decreased plasma β2GPI levels (P < 0.001). Deletion analysis localized the core APOH promoter to ~160 bp upstream of ATG codon with the presence of critical cis-acting elements between −166 and −65. Cross-species conservation analysis of the APOH promoters of 7 species indicated that basic promoter elements are highly conserved across species. In conclusion, we have characterized the functional promoter of APOH and identified functional variants that affect the transcriptional activity of the APOH promoter.
APOH; β2-glycoprotein I; promoter; polymorphisms; association
Low serum paraoxonase (PON) activity is associated with the risk of coronary artery disease, diabetes and systemic lupus erythematosus (SLE). Our prior studies have shown that the PON1/rs662 (p.Gln192Arg), PON1/rs854560 (p.Leu55Met), PON3/rs17884563 and PON3/rs740264 SNPs (single nucleotide polymorphisms) significantly affect serum PON activity. Since PON1, PON2 and PON3 share high degree of structural and functional properties, in this study, we examined the role of PON2 genetic variation on serum PON activity, risk of SLE and SLE-related clinical manifestations in a Caucasian case-control sample.
PON2 SNPs were selected from HapMap and SeattleSNPs databases by including at least one tagSNP from each bin defined in these resources. A total of nineteen PON2 SNPs were successfully genotyped in 411 SLE cases and 511 healthy controls using pyrosequencing, restriction fragment length polymorphism (RFLP) or TaqMan allelic discrimination methods.
Our pair-wise linkage disequilibrium (LD) analysis, using an r2 cutoff of 0.7, identified 14 PON2 tagSNPs that captured all 19 PON2 variants in our sample, 12 of which were not in high LD with known PON1 and PON3 SNP modifiers of PON activity. Stepwise regression analysis of PON activity, including the known modifiers, identified five PON2 SNPs [rs6954345 (p.Ser311Cys), rs13306702, rs987539, rs11982486, and rs4729189; P = 0.005 to 2.1 × 10-6] that were significantly associated with PON activity. We found no association of PON2 SNPs with SLE risk but modest associations were observed with lupus nephritis (rs11981433, rs17876205, rs17876183) and immunologic disorder (rs11981433) in SLE patients (P = 0.013 to 0.042).
Our data indicate that PON2 genetic variants significantly affect variation in serum PON activity and have modest effects on risk of lupus nephritis and SLE-related immunologic disorder.
Alzheimer's disease (AD) is a complex and multifactorial disease with the possible involvement of several genes. With the exception of the APOE gene as a susceptibility marker, no other genes have been shown consistently to be associated with late-onset AD (LOAD). A recent genome-wide association study of 17,343 gene-based putative functional single nucleotide polymorphisms (SNPs) found 19 significant variants, including 3 linked to APOE, showing association with LOAD (Hum Mol Genet 2007; 16:865–873). We have set out to replicate the 16 new significant associations in a large case-control cohort of American Whites. Additionally, we examined six variants present in positional and/or biological candidate genes for AD. We genotyped the 22 SNPs in up to 1,009 Caucasian Americans with LOAD and up to 1,010 age-matched healthy Caucasian Americans, using 5′ nuclease assays. We did not observe a statistically significant association between the SNPs and the risk of AD, either individually or stratified by APOE. Our data suggest that the association of the studied variants with LOAD risk, if it exists, is not statistically significant in our sample.
Alzheimer's disease; genetics; age-at-onset; disease duration
Sequence variation in gene promoters is often associated with disease risk. In this study, we tested the hypothesis that common promoter variation in the APOH gene (encoding for β2-glycoprotein I) is associated with systemic lupus erythematosus (SLE) risk and SLE-related clinical phenotypes in a Caucasian cohort.
We used a case-control design and genotyped 345 SLE women and 454 healthy control women for 8 APOH promoter single nucleotide polymorphisms (SNPs) (−1284C>G, −1219G>A, −1190G>C, −759 A>G, − 700C>A, −643T>C, −38G>A, and −32C>A). Association analyses were performed on single SNPs and haplotypes. Haplotype analyses were performed using EH (Estimate Haplotype-frequencies) and Haploview programs. In vitro reporter gene assay was performed in COS-1 cells. Electrophoretic mobility shift assay (EMSA) was performed using HepG2 nuclear cells.
Overall haplotype distribution of the APOH promoter SNPs was significantly different between cases and controls (P = 0.009). The −643C allele was found to be protective against carotid plaque formation (adjusted OR = 0.37, P = 0.013) among SLE patients. The −643C allele was associated with a ~ 2-fold decrease in promoter activity as compared to wild-type −643T allele (mean ± standard deviation: 3.94 ± 0.05 vs. 6.99 ± 0.68, P = 0.016). EMSA showed that the −643T>C SNP harbors a binding site for a nuclear factor. The −1219G>A SNP showed a significant association with the risk of lupus nephritis (age-adjusted OR = 0.36, P = 0.016).
Our data indicate that APOH promoter variants may be involved in the etiology of SLE, especially the risk for autoimmune-mediated cardiovascular disease.
APOH; β2-glycoprotein I; promoter; SLE; lupus; polymorphism
A polymorphism in the calcium homeostasis modulator 1 gene (CALHM1) has recently been associated with risk of late-onset Alzheimer disease. We examined this variant (rs2986017) in 945 Caucasian Americans with late-onset Alzheimer disease and 875 age-matched Caucasian American controls. No association with risk of late-onset Alzheimer disease (p = 0.368 for genotypes; p = 0.796 for alleles) was observed in our sample. However, a potential modest association of minor allele homozygosity (TT) with an earlier age-at-onset was seen (p = 0.034).
Alzheimer disease; CALHM1; genetic; association
Lipoprotein Lipase (LPL) plays a pivotal role in lipid metabolism by hydrolyzing triglyceride (TG) rich lipoprotein particles. Abnormalities in normal LPL function are associated with the risk of coronary artery disease (CAD). A number of genetic variants have been identified in the LPL gene that affects different functions of the LPL protein. A common HindIII polymorphism in intron 8 (T/G) of the LPL gene has been found to be associated with altered plasma TG and HDL-cholesterol, and CAD risk in several studies, but its functional significance is unknown. It has been shown that certain intronic sequence contain regulatory elements that are important for transcription and translational regulation of a gene. In this study we tested the hypothesis that this polymorphism affects the binding site of a transcription factor that regulates the transcription of LPL gene. Electrophoretic mobility shift assays revealed that the HindIII site binds to a transcription factor and that the mutant allele has lower binding affinity than the wild type allele. Transcription assays containing the entire intron 8 sequence along with full-length human LPL promoter were carried out in COS-1 and human vascular smooth muscle cells. The mutant allele was associated with significantly decreased luciferase expression level compared to the wild type allele in both the muscle (3.394 ± 0.022 vs. 4.184 ± 0.028; P=4.7 × 10−6) and COS-1 (11.603 ± 0.409 vs. 14.373 ± 1.096; P<0.0001) cells. In conclusion, this study demonstrates for the first time that the polymorphic HindIII site in the LPL gene is functional because it affects the binding of a transcription factor and it also has an impact on LPL expression.
Lipoprotein lipase; HindIII polymorphism; electrophoretic mobility shift assay; luciferase reporter gene assay; coronary artery disease