The ability to identify patients with Crohn’s disease (CD) at highest risk of surgery would be invaluable in guiding therapy. Genome-wide association (GWA) studies have identified multiple IBD loci with unknown phenotypic consequences.
1) to identify associations between known and novel CD loci with early resective CD surgery2) to develop the best predictive model for time to surgery using a combination of phenotypic, serologic and genetic variables.
Genotyping was performed on 1115 subjects using Illumina-based Genome-wide technology. Univariate and multivariate analyses tested genetic associations with need for surgery within 5 years. Analyses were performed by testing known CD loci (n=71) and by performing a GWA study. Time to surgery was analyzed using Cox regression modeling. Clinical and serologic variables were included along with genotype to build predictive models for time to surgery.
Surgery occurred within 5 years in 239 subjects at a median time of 12 months. Three CD susceptibility loci were independently associated with surgery within 5 years (IL12B, IL23R, C11orf30). GWA identified novel putative loci associated with early surgery; 7q21 (CACNA2D1) and 9q34 (RXRA, COL5A1). The most predictive models of time to surgery included genetic and clinical risk factors. More than a 20% difference in frequency of progression to surgery was seen between the lowest and highest risk groups.
Progression to surgery is faster in CD patients with both genetic and clinical risk factors. IL12B is independently associated with need and time to early surgery in CD patients and justifies the investigation of novel and existing therapies that affect this pathway.
Cigarette smoking is the major cause of chronic obstructive pulmonary disease and emphysema. Recent studies suggest that susceptibility to cigarette smoke may vary by race/ethnicity; however, they were generally small and relied on self-reported race/ethnicity.
To test the hypothesis that relationships of smoking to lung function and percent emphysema differ by genetic ancestry and self-reported race/ethnicity among Whites, African-Americans, Hispanics and Chinese-Americans.
Cross-sectional population-based study of adults age 45-84 years in the United States
Principal components of genetic ancestry and continental ancestry estimated from one-million genome-wide single nucleotide polymorphisms. Pack-years calculated as years smoking cigarettes-per-day/20. Spirometry measured for 3,344 and percent emphysema on computed tomography for 8,224 participants.
The prevalence of ever-smoking was: Whites, 57.6%; African-Americans, 56.4%; Hispanics, 46.7%; and Chinese-Americans, 26.8%. Every 10 pack-years was associated with −0.73% (95% CI −0.90%, −0.56%) decrement in the forced expiratory volume in one second to forced vital capacity (FEV1/FVC) and a 0.23% (95% CI 0.08%, 0.38%) increase in percent emphysema. There was no evidence that relationships of pack-years to the FEV1/FVC, airflow obstruction and percent emphysema varied by genetic ancestry (all p>0.10), self-reported race/ethnicity (all p>0.10) or, among African-Americans, African ancestry. There were small differences in relationships of pack-years to the FEV1 among male Chinese-Americans and to the FEV1/FVC with African and Native American ancestry among male Hispanics only.
In this large cohort, there was little-to-no evidence that the associations of smoking to lung function and percent emphysema differed by genetic ancestry or self-reported race/ethnicity.
cigarette smoke; genetic ancestry; lung function; chronic obstructive pulmonary disease; COPD; emphysema; FVC; Forced Vital Capacity; FEV1; Forced Expiratory Volume in 1 second
In classifying Crohn’s disease (CD) location, proximal (L4) disease includes esophagogastroduodenal (EGD) and jejunal disease. Our aim was to determine the influence of proximal disease on outcomes of behavior and need for surgery and to determine if there was significant clinical heterogeneity between EGD and jejunal disease.
We performed a cross-sectional query of the NIDDK IBD Genetics Consortium (IBDGC) database of patients with a confirmed diagnosis of CD and phenotyped per the IBDGC manual. Presence of any L4, L4-EGD, L4-jejunal and non-L4 disease (L1-ileal, L2-colonic, and L3-ileocolonic) was compared with demographic features including age, race, ethnicity, smoking and IBD family history, diagnosis age, disease duration, clinical outcomes of inflammatory, stricturing or penetrating behavior, and CD abdominal surgeries. Univariate and multivariable analyses were performed with R.
Among 2105 patients with complete disease location data, 346 had L4 disease (175 L4-EGD, 115 L4-jejunal, and 56 EGD and jejunal) with 321 having concurrent L1-L3 disease. 1759 had only L1-L3 disease. L4 vs. non-L4 patients were more likely (p<0.001) to be younger at diagnosis, non-smokers, have co-existing ileal involvement and have stricturing disease. L4- jejunal vs. L4-EGD patients were at least twice as likely (p<0.001) to have had ileal disease, stricturing behavior, and any or multiple abdominal surgeries. Remarkably, L4-jejunal patients had more (p<0.001) stricturing behavior and multiple abdominal surgeries than non-L4 ileal disease patients. Logistic regression showed stricturing risks were ileal (without proximal) site (OR 3.18; 95% CI 2.23-4.64), longer disease duration (OR 1.33/decade; 1.19-1.49), jejunal site (OR 2.90; 1.89-4.45), and older age at diagnosis (OR 1.21/decade; 1.10-1.34). Multiple surgeries risks were disease duration (OR 3.74/decade; 3.05-4.64), penetrating disease (OR 2.60; 1.64-4.21), and jejunal site (OR 2.39; 1.36-4.20), with short duration from diagnosis to first surgery protective (OR 0.87/decade to 1st surgery; 0.84-0.90).
Jejunal disease is a significantly greater risk factor for stricturing disease and multiple abdominal surgeries than either EGD or ileal (without proximal) disease. The Montreal site classification should be revised to include separate designations for jejunal and EGD disease.
Keratoconus is a genetically heterogeneous corneal dystrophy. Previously, we performed two genome-wide linkage scans in a four generation autosomal dominant pedigree and repeatedly mapped a keratoconus locus to a genomic region located on chromosome 5q overlapping the gene encoding the inhibitor of calpains, calpastatin (CAST). To test whether variants in CAST gene are involved in genetic susceptibility to keratoconus we performed genetic testing of polymorphic markers in CAST gene in family and case-control panels of patients with keratoconus.
We genotyped SNPs (Single Nucleotide Polymorphisms) located in CAST gene in 262 patients in 40 Caucasian keratoconus families and in a Caucasian case-control panel with 304 cases and 518 controls. Generalized estimating equation models accounting for familial correlations implemented in GWAF program were used for association testing in families. Logistic regression models implemented in PLINK were performed to test associations in case-control samples.
Genetic testing of first set of seven SNPs in familial samples revealed two tentative nominally significant markers (rs4869307 p=0.03; rs27654: p=0.07). Additional genotyping of twelve tightly spaced SNPs identified CAST SNP rs4434401 to be associated with keratoconus in both familial and case-control panels with p values of 0.005 and 0.05, respectively; and with combined meta p value of familial and case-control cohorts of 0.002, or, after Bonferroni correction, 0.04.
Linkage analysis and genetic association support involvement of CAST gene in the genetic susceptibility to keratoconus. In-silico analysis of CAST expression suggests differential regulation of calpain/calpastatin system in cornea as a potential mechanism of functional defect.
Linkage analysis; genetic association; common variation; keratoconus; calpains; calpastatin
Mutations in the nucleotide oligomerization domain-2 (NOD2) gene and positive antibodies to microbial antigens have been found to be associated with the Crohn’s disease (CD) phenotype, fibrostenosis. The aim of this study was to confirm these relationships in a large cohort of CD patients and to determine the correlation between the presence of NOD2 variants and antibodies to oligomannan, CBir, outer membrane porin-C (OmpC), and I2 in CD patients with fibrostenosis.
Sera and DNA from 731 unrelated CD patients were tested for NOD2 variants (SNP 8, 12, and 13) and the antibodies. The results were correlated with CD phenotypes, fibrostenosis, internal penetrating, perianal penetrating, and ulcerative colitis (UC)-like as well as other clinical features.
The presence of NOD2 allelic variants was primarily associated with fibrostenosis, secondarily with small bowel disease and small bowel surgery, and was inversely associated with UC-like disease. This association was present in patients with a fibrostenosis only (Vienna B2) and those with both stricturing and penetrating disease. The presence and level of antibodies to microbial antigens was also associated with the fibrostenosis phenotype. In the 316 patients with fibrostenosis the prevalence of NOD2 variants was significantly correlated with the antibody titer by quartile sum score. Further, when these patients with fibrostenosis were clustered by quartile sum score, the odds ratio for fibrostenosis was significantly higher in the patients with NOD2 variant alleles within each cluster, indicating synergy.
Defects of innate (NOD2 variants) and adaptive (antibodies to microbial antigens) immunity act synergistically to increase the risk of the fibrostenosis phenotype.
NOD2; Crohn’s disease; fibrostenosis; phenotype
Background & Aims
African Americans (AA) are an admixed population of West African (WA) and European ancestry (EA). Crohn's disease (CD) susceptibility genes have not been established. We therefore evaluated the contribution of European admixture and major established risk genes to AA CD.
Ninety-seven admixture informative markers were genotyped for ancestry estimates using STRUCTURE. 354 AA CD cases and 354 ethnicity-matched controls were genotyped for total 21 SNPs in ATG16L1, NOD2, IBD5, IL23R and IRGM by TaqMan or direct sequencing. Association was evaluated by logistic regression, adjusted for ancestry.
Mean EA was similar among the CD cases and controls (20.9% and 20.4, respectively, p=0.58). No significant admixture differences were observed among cases (211 to 227) stratified by phenotypic sub-classifications including onset, surgery, site, and behavior. CD was associated with NOD2 carrier (6.93% CD, 2.15% Controls, p = 0.007), ATG16L1 Thr300Ala (36.1% CD, 29.3% Controls, p=0.003), SLC22A4 and SLC22A5 (IBD5 locus) functional SNPs (L503F [10.6% CD, 7.6% Controls, p=0.05] and g-207c [41.3% CD, 35.7% Controls, p=0.03], respectively) and IL23R rs2201841 (18.2% CD, 13.8% Controls, p=0.03), but not IRGM variants nor three African ancestral NOD2 nonsynonymous variants. IBD5 risk was recessive. An all-minor allele IBD5 haplotype from EA was associated (p=0.05), whereas a more common haplotype isolating g-207c was not.
Specific functional gene variations significantly contribute to AA CD risk. Established NOD2, SLC22A4-A5, and ATG16L1 variants show increased CD risk, with IBD5 in recessive. Although CD is more common in whites, European admixture is similar among AA cases and controls.
genetics; epidemiology; Crohn's disease
Central corneal thickness (CCT) is a clinically important risk factor for primary open-angle glaucoma and keratoconus. Genetic factors controlling CCT in Latinos, the most populous minority population in the United States, are unclear. Here we describe the first genome-wide association study (GWAS) report of CCT in Latinos.
We performed a GWAS for CCT on 1768 Latinos recruited in the Los Angeles Latino Eye Study (LALES) using Illumina's HumanOmniExpress BeadChip (∼730K markers). To discover additional associated single-nucleotide polymorphisms (SNPs), we imputed SNPs based on the 1000 Genomes Project reference panels. All subjects were 40 years of age and older. We used linear regression with adjustment for age, sex, and principal components of genetic ancestry.
We replicated the involvement of several previously reported loci, such as RXRA-COL5A1, FOXO1, and ZNF469, for CCT in Latinos (P < 0.002). Moreover, we discovered novel SNPs, rs3118515, rs943423, rs3118594, and rs3132307, that reached GWAS significance (P < 5 × 10−8) in the uncharacterized LOC100506532 (gene type: miscRNA) for CCT in Latinos. By conditional analysis, we demonstrate that rs3118515 in this gene is responsible for the GWAS signal in the chromosome 9 RXRA-COL5A1 region in Latinos. Moreover, multiple sources of ENCODE evidence suggest that rs3118515 is in a regulatory region. Reverse-transcription PCR products indicated that transcripts of LOC100506532 surrounding rs3118515 were expressed in human corneas.
We discovered novel SNPs for CCT in Latinos and provided the first reported evidence of the corneal expression of LOC100506532. These results help to further increase our understanding of the genetic architecture of CCT.
In this first GWAS of central corneal thickness in Latinos, we discovered the involvement of novel SNPs, both directly genotyped and imputed, that reached genome-wide significance. This study provided the first reported evidence of the corneal expression of LOC100506532.
central corneal thickness; Latino; GWAS; rs3118515; LOC100506532
Single nucleotide polymorphisms (SNPs) located near or within the COL5A1 gene, at 9q34.2-q34.3 chromosomal region have been reported in association with central corneal thickness (CCT). Using family linkage analysis, we identified a keratoconus susceptibility locus at 9q34. These findings led us to perform an association study between COL5A1 variation and keratoconus susceptibility.
A Caucasian case–control cohort of 222 keratoconus patients and 3324 controls was selected as the discovery panel. An independent case–control panel of 304 cases and 518 controls and a family panel of 186 subjects were replicated for genotyping and association. Forty-four SNPs (21 for discovery and 23 for fine-mapping) spanning 300 kilobases in and around COL5A1 were genotyped and tested for genetic association. Logistic regression models implemented in PLINK were used to test for association in case controls. Generalized estimating equation models accounting for familial correlations implemented in genome-wide interaction analyses with family data were used for association testing in families.
Two CCT associated SNPs (rs1536482 and rs7044529 near and within COL5A1) were identified in the keratoconus discovery cohort (P values of 6.5 × 10−3 and 7.4 × 10−3). SNP rs1536482 was replicated in the second case–control sample (P = 0.02), and SNP rs7044529 was replicated in a keratoconus family panel (P = 0.03). Meta P values of rs1536482 and rs7044529 in the keratoconus cohorts were 1.5 × 10−4 (odds ratio [OR] = 1.30) and 2.9 × 10−3 (OR = 1.39). After Bonferroni correction, the association of SNP rs1536482 remained significant (P = 6.5 × 10−3).
SNPs in the COL5A1 region, which regulate normal variation in CCT, may play a role in the thinning associated with keratoconus.
Variants in the COL5A1 gene may contribute to genetic susceptibility to corneal thinning associated with keratoconus, in addition to their role in genetic regulation of normal variation in central corneal thickness.
keratoconus; association; COL5A1
Candidate gene and genome-wide association studies have identified ∼60 susceptibility loci for type 2 diabetes. A majority of these loci have been discovered and tested only in European populations. The aim of this study was to assess the presence and extent of trans-ethnic effects of these loci in an East Asian population.
A total of 9,335 unrelated Chinese Han individuals, including 4,535 with type 2 diabetes and 4,800 non-diabetic ethnically matched controls, were genotyped using the Illumina 200K Metabochip. We tested 50 established loci for type 2 diabetes and related traits (fasting glucose, fasting insulin, 2 h glucose). Disease association with the additive model of inheritance was analysed with logistic regression.
We found that 14 loci significantly transferred to the Chinese population, with two loci (p = 5.7 × 10−12 for KCNQ1; p = 5.0 × 10−8 for CDKN2A/B-CDKN2BAS) reaching independent genome-wide statistical significance. Five of these 14 loci had similar lead single-nucleotide polymorphisms (SNPs) as were found in the European studies while the other nine were different. Further stepwise conditional analysis identified a total of seven secondary signals and an independent novel locus at the 3′ end of CDKAL1.
These results suggest that many loci associated with type 2 diabetes are commonly shared between European and Chinese populations. Identification of population-specific SNPs may increase our understanding of the genetic architecture underlying type 2 diabetes in different ethnic populations.
Electronic supplementary material
The online version of this article (doi:10.1007/s00125-013-3047-1) contains peer-reviewed but unedited supplementary material, which is available to authorised users.
Ethnic difference; Genetic association; Type 2 diabetes
Background and Aim
The ability to identify children with Crohn’s disease who are at highest risk for rapid progression from uncomplicated to complicated phenotypes would be invaluable in guiding initial therapy. Aim: To determine whether immune responses and/or CARD15 variants are associated with complicated disease phenotypes and predict disease progression.
Sera were collected from 796 pediatric CD cases and tested for anti-Cbir1 (flagellin), anti-outer membrane protein C (anti-OmpC), anti-Saccharomyces-cerevisiae (ASCA) and perinuclear anti-neutrophil cytoplasmic antibody (pANCA) using ELISA. Genotyping (TaqmanMGB) was performed for 3 CARD15 variants (SNPs 8, 12, 13). Associations between immune responses (antibody sum (AS) and quartile sum score (QSS), CARD15, and clinical phenotype were evaluated.
32% of patients developed at least one disease complication within a median of 32 months and 18% underwent surgery. The frequency of internal penetrating (IP), stricturing (S) and surgery significantly increased (p trend < 0.0001 for all 3 outcomes) with increasing AS and QSS. 9% of seropositive groups had IP/S vs. 2.9% in the seronegative group (p=0.01). 12% of seropositive groups underwent surgery vs. 2% in the seronegative group (p=0.0001). The highest AS group (3) and QSS group (4) demonstrated the most rapid disease progression (p < 0.0001). Increased hazard ratio was observed for AS group 3 (7.8 [2.2–28.7] p < 0.002 and QSS group 4 (11.0 [1.5,83.0] p < 0.02).
The rate of complicated CD increases in children as the number and magnitude of immune reactivity increases. Disease progression is significantly faster in children expressing immune reactivity.
Hypertension represents a complex heritable disease in which environmental factors may directly affect gene function via epigenetic mechanisms. The aim of this study was to test the hypothesis that dietary salt influences the activity of a histone modifying enzyme, lysine-specific demethylase 1 (LSD-1), which in turn is associated with salt-sensitivity of blood pressure (BP).
Animal and human studies were performed. Salt-sensitivity of LSD-1 expression was assessed in wild-type and LSD-1 heterozygote knockout (LSD-1+/−) mice. Clinical relevance was tested by multivariate associations between single nuclear polymorphisms (SNPs) in the LSD-1 gene and salt-sensitivity of BP, with control of dietary sodium, in a primary African-American hypertensive cohort and two replication hypertensive cohorts (Caucasian and Mexican-American).
LSD1 expression was modified by dietary salt in wild-type mice with lower levels associated with liberal salt intake. LSD-1+/− mice expressed lower LSD-1 protein levels than wild-type mice in kidney tissue. Similar to LSD-1+/− mice, African-American minor allele carriers of two LSD-1 SNPs displayed greater change in systolic BP in response to change from low to liberal salt diet (rs671357, p=0.01; rs587168, p=0.005). This association was replicated in the Hispanic (rs587168, p=0.04) but not the Caucasian cohort. Exploratory analyses demonstrated decreased serum aldosterone concentrations in African-American minor allele carriers similar to findings in the LSD-1+/− mice, decreased alpha-EnaC expression in LSD-1+/− mice, and impaired renovascular responsiveness to salt loading in minor allele carriers.
The results of this translational research study support a role for LSD1 in the pathogenesis of salt-sensitive hypertension.
Hypertension; Salt-sensitivity; LSD1; Genetics; Epigenetic
Genotyping arrays are a cost effective approach when typing previously-identified genetic polymorphisms in large numbers of samples. One limitation of genotyping arrays with rare variants (e.g., minor allele frequency [MAF] <0.01) is the difficulty that automated clustering algorithms have to accurately detect and assign genotype calls. Combining intensity data from large numbers of samples may increase the ability to accurately call the genotypes of rare variants. Approximately 62,000 ethnically diverse samples from eleven Cohorts for Heart and Aging Research in Genomic Epidemiology (CHARGE) Consortium cohorts were genotyped with the Illumina HumanExome BeadChip across seven genotyping centers. The raw data files for the samples were assembled into a single project for joint calling. To assess the quality of the joint calling, concordance of genotypes in a subset of individuals having both exome chip and exome sequence data was analyzed. After exclusion of low performing SNPs on the exome chip and non-overlap of SNPs derived from sequence data, genotypes of 185,119 variants (11,356 were monomorphic) were compared in 530 individuals that had whole exome sequence data. A total of 98,113,070 pairs of genotypes were tested and 99.77% were concordant, 0.14% had missing data, and 0.09% were discordant. We report that joint calling allows the ability to accurately genotype rare variation using array technology when large sample sizes are available and best practices are followed. The cluster file from this experiment is available at www.chargeconsortium.com/main/exomechip.
The role of metabolic disturbance in polycystic ovary syndrome (PCOS) has been well established, with insulin resistance and the resulting compensatory hyperinsulinemia thought to promote hyperandrogenemia. Genome-wide association studies (GWAS) have established a large number of loci for metabolic conditions such as type 2 diabetes and obesity. A subset of these loci has been investigated for a role in PCOS; these studies generally have not revealed a confirmed role for these loci in PCOS risk. However, a large scale investigation of genes related to these pathways has not previously been performed. We conducted a two stage case control association study of 121,715 single nucleotide polymorphisms (SNPs) selected to represent susceptibility loci associated with traits such as type 2 diabetes, obesity measures, lipid levels and cardiovascular function using the Cardio-Metabochip in 847 PCOS cases and 845 controls. Several hypothesis-generating associations with PCOS were observed (top SNP rs2129107, P = 3.8 × 10−6). We did not find any loci definitively associated with PCOS after strict correction for multiple testing, suggesting that cardio-metabolic loci are not major risk factors underlying the susceptibility to PCOS.
Candidate-wide association study; Polycystic ovary syndrome; Cardio-Metabochip; Single nucleotide polymorphism; Genetic association
Recently, a genome-wide association scan was completed in the IRAS (Insulin Resistance Atherosclerosis Study) Family Study (IRASFS) Hispanic-American cohort. Multiple single-nucleotide polymorphisms (SNPs) in the G-protein signaling 6 (RGS6) gene were found to be associated with adiposity phenotypes. RGS6 has shown downstream antagonistic interplay with opioid receptors, targets of fatty/sugary food agonists. The possibility that RGS6 promotes tolerance and tachyphylaxis among the opioid receptor is a plausible pathway for overconsuming fat/sugar-laden food. Therefore, we hypothesized that RGS6 variants are associated with intake of fatty/sugary foods. In 932 Hispanics from San Antonio and San Luis Valley, CO, the following dietary intake variables were assessed using the Block Brief 2000 food frequency questionnaire: total calories, total fat, % calories from fat, % calories from saturated fat, protein, % calories from protein, carbohydrates, % calories from carbohydrates, and daily frequency of servings of fats/oils/sweets. We tested for association between 23 SNPs in RGS6 and dietary intake using a variance components measured genotype approach. All models were adjusted for gender, recruitment site, admixture, BMI, and age. Using an additive genetic model, rs1402064 was associated with higher intake of fats/oils/sweets, total calories, total fat and saturated fat (P = 0.0007, 0.026, 0.023, and 0.024). SNPs rs847330 and rs847354 were associated with higher intake of fats/oils/sweets (P = 0.002 and 0.018), total fat (P = 0.040 and 0.048) and saturated fat (P = 0.044 and 0.041). Finally, rs769148 was associated with higher intake of fats/oils/sweets (P = 0.002). RGS6 is a new candidate gene for adiposity traits that may be associated with a behavioral tendency toward fat-laden food intake.
Narrow arterioles in the retina have been shown to predict hypertension as well as other vascular diseases, likely through an increase in the peripheral resistance of the microcirculatory flow. In this study, we performed a genome-wide association study in 18,722 unrelated individuals of European ancestry from the Cohorts for Heart and Aging Research in Genomic Epidemiology consortium and the Blue Mountain Eye Study, to identify genetic determinants associated with variations in retinal arteriolar caliber. Retinal vascular calibers were measured on digitized retinal photographs using a standardized protocol. One variant (rs2194025 on chromosome 5q14 near the myocyte enhancer factor 2C MEF2C gene) was associated with retinal arteriolar caliber in the meta-analysis of the discovery cohorts at genome-wide significance of P-value <5×10−8. This variant was replicated in an additional 3,939 individuals of European ancestry from the Australian Twins Study and Multi-Ethnic Study of Atherosclerosis (rs2194025, P-value = 2.11×10−12 in combined meta-analysis of discovery and replication cohorts). In independent studies of modest sample sizes, no significant association was found between this variant and clinical outcomes including coronary artery disease, stroke, myocardial infarction or hypertension. In conclusion, we found one novel loci which underlie genetic variation in microvasculature which may be relevant to vascular disease. The relevance of these findings to clinical outcomes remains to be determined.
Gram-negative bacilli causing infective endocarditis (IE) is rare, even in intravenous drug users. This case report underscores several clinically important aspects of Delftia acidovorans IE: the organism's ability to cause rapid destruction of normal native valves and to cause embolic occlusion of large arteries and its resistance to all aminoglycosides.
Recent genome-wide association studies (GWAS) have identified novel loci associated with sudden cardiac death (SCD). Despite this progress, identified DNA variants account for a relatively small portion of overall SCD risk, suggesting that additional loci contributing to SCD susceptibility await discovery. The objective of this study was to identify novel DNA variation associated with SCD in the context of coronary artery disease (CAD).
Methods and Findings
Using the MetaboChip custom array we conducted a case-control association analysis of 119,117 SNPs in 948 SCD cases (with underlying CAD) from the Oregon Sudden Unexpected Death Study (Oregon-SUDS) and 3,050 controls with CAD from the Wellcome Trust Case-Control Consortium (WTCCC). Two newly identified loci were significantly associated with increased risk of SCD after correction for multiple comparisons at: rs6730157 in the RAB3GAP1 gene on chromosome 2 (P = 4.93×10−12, OR = 1.60) and rs2077316 in the ZNF365 gene on chromosome 10 (P = 3.64×10−8, OR = 2.41).
Our findings suggest that RAB3GAP1 and ZNF365 are relevant candidate genes for SCD and will contribute to the mechanistic understanding of SCD susceptibility.
Mild retinopathy (microaneurysms or dot-blot hemorrhages) is observed in persons without diabetes or hypertension and may reflect microvascular disease in other organs. We conducted a genome-wide association study (GWAS) of mild retinopathy in persons without diabetes.
A working group agreed on phenotype harmonization, covariate selection and analytic plans for within-cohort GWAS. An inverse-variance weighted fixed effects meta-analysis was performed with GWAS results from six cohorts of 19,411 Caucasians. The primary analysis included individuals without diabetes and secondary analyses were stratified by hypertension status. We also singled out the results from single nucleotide polymorphisms (SNPs) previously shown to be associated with diabetes and hypertension, the two most common causes of retinopathy.
No SNPs reached genome-wide significance in the primary analysis or the secondary analysis of participants with hypertension. SNP, rs12155400, in the histone deacetylase 9 gene (HDAC9) on chromosome 7, was associated with retinopathy in analysis of participants without hypertension, −1.3±0.23 (beta ± standard error), p = 6.6×10−9. Evidence suggests this was a false positive finding. The minor allele frequency was low (∼2%), the quality of the imputation was moderate (r2 ∼0.7), and no other common variants in the HDAC9 gene were associated with the outcome. SNPs found to be associated with diabetes and hypertension in other GWAS were not associated with retinopathy in persons without diabetes or in subgroups with or without hypertension.
This GWAS of retinopathy in individuals without diabetes showed little evidence of genetic associations. Further studies are needed to identify genes associated with these signs in order to help unravel novel pathways and determinants of microvascular diseases.
Keratoconus is a condition in which the cornea progressively thins over time, and is a major cause for cornea transplantation. To identify keratoconus susceptibility regions, we performed a comprehensive genome-wide association study (GWAS) using a discovery and replication design. A discovery panel of 222 keratoconus Caucasian patients and 3324 Caucasian controls was genotyped using Illumina 370K beadchips. Further associated and fine-mapping single nucleotide polymorphisms (SNPs) (n= 4905) were genotyped in an independent replication case–control panel of 304 cases and 518 controls and a family panel of 307 subjects in 70 families. Logistic regression models implemented in PLINK were performed to test associations in case–control samples with and without principal component (PC) adjustments. Generalized estimation equation models accounting for familial correlations implemented in GWAF were used for association testing in families. No genome-wide associations were identified in the discovery GWAS panel. From the initial testing without adjustments for PCs, the top three SNPs located at 3p26 (rs6442925), 2q21.3 (rs4954218) and 19q13.3 (rs1428642) were identified with unadjusted P-values of 6.5 × 10−8, 2.4 × 10−7 and 3.1 × 10−7, respectively. After adjustments for PCs, rs1428642 became the most significant through the genome with a P-value of 1.4 × 10−6, while rs6442925 and rs4954218 were less significant (P= 1.9 × 10−5 and 2.6 × 10−4). SNP rs4954218 was confirmed in two independent replication panels with P-values of 0.004 and 0.009, respectively. Meta-analysis revealed a highest association at rs4954218 with adjusted P= 1.6 × 10−7 (unadjusted P= 1.2 × 10−9). These findings suggest SNP rs4954218, located near the RAB3GAP1 gene, previously reported to be associated with corneal malformation, is a potential susceptibility locus for keratoconus.
Genetic factors explain a majority of risk variance for age-related macular degeneration (AMD). While genome-wide association studies (GWAS) for late AMD implicate genes in complement, inflammatory and lipid pathways, the genetic architecture of early AMD has been relatively under studied. We conducted a GWAS meta-analysis of early AMD, including 4,089 individuals with prevalent signs of early AMD (soft drusen and/or retinal pigment epithelial changes) and 20,453 individuals without these signs. For various published late AMD risk loci, we also compared effect sizes between early and late AMD using an additional 484 individuals with prevalent late AMD. GWAS meta-analysis confirmed previously reported association of variants at the complement factor H (CFH) (peak P = 1.5×10−31) and age-related maculopathy susceptibility 2 (ARMS2) (P = 4.3×10−24) loci, and suggested Apolipoprotein E (ApoE) polymorphisms (rs2075650; P = 1.1×10−6) associated with early AMD. Other possible loci that did not reach GWAS significance included variants in the zinc finger protein gene GLI3 (rs2049622; P = 8.9×10−6) and upstream of GLI2 (rs6721654; P = 6.5×10−6), encoding retinal Sonic hedgehog signalling regulators, and in the tyrosinase (TYR) gene (rs621313; P = 3.5×10−6), involved in melanin biosynthesis. For a range of published, late AMD risk loci, estimated effect sizes were significantly lower for early than late AMD. This study confirms the involvement of multiple established AMD risk variants in early AMD, but suggests weaker genetic effects on the risk of early AMD relative to late AMD. Several biological processes were suggested to be potentially specific for early AMD, including pathways regulating RPE cell melanin content and signalling pathways potentially involved in retinal regeneration, generating hypotheses for further investigation.
The intestinal microflora, typically equated with bacteria, influences diseases such as obesity and inflammatory bowel disease (IBD). Here we show that the mammalian gut contains a rich fungal community that interacts with the immune system through the innate immune receptor Dectin-1. Mice lacking Dectin-1 exhibited increased susceptibility t chemically-induced colitis, which was the result of altered responses to indigenous fungi. In humans we identified a polymorphism in the gene for Dectin-1 (CLEC7A) that is strongly linked to a severe form of ulcerative colitis. Together our findings reveal a novel eukaryotic fungal community in the gut (the “mycobiome”) that coexists with bacteria and substantially expands the repertoire of organisms interacting with the intestinal immune system to influence health and disease.
Genetic studies may help explain abnormalities of fat distribution in HIV-infected patients treated with antiretroviral therapy (ARV).
Subcutaneous adipose tissue (SAT) volume measured by magnetic resonance imaging (MRI) in leg, lower trunk, upper trunk, and arm was examined in 192 HIV-infected Caucasian men, ARV-treated from the Fat Redistribution and Metabolic Change in HIV infection (FRAM) study. Single nucleotide polymorphisms (SNPs) were assayed using the Illumina HumanCNV370-quad beadchip. Multivariate and univariate genome wide association analyses of the four SAT depots were implemented in PLINK software adjusted for age and ARV duration. Functional annotation analysis (FAA) using Ingenuity Systems Pathway Analysis tool (IPA) was carried out for markers with P<10-3 near known genes identified by multivariate analysis.
Loci (rs10504906, rs13267998, rs921231) in or near the anion exchanger solute carrier family 26, member 7 isoform a (SLC26A7) were strongly associated with upper trunk and arm SAT (9.8*10-7≤P<7.8*10-6). Loci (rs193139, rs7523050, rs1761621) in and near a gene rich region including G-protein-signaling modulator 2 (GPSM2) and syntaxin binding protein 3 (STXBP3) were significantly associated with lower body SAT depots (9.9*10-7≤P<9.5*10-6). GPSM2 is associated with cell division and cancer while STXBP3 is associated with glucose metabolism in adipoctyes. IPA identified atherosclerosis, mitochondrial function and T-Cell mediated apoptosis as processes related to SAT volume in HIV-infected individuals (P<5*10-3).
Our results are limited by the small sample size and replication is needed, however this genomic scan uncovered new genes associated with metabolism and inflammatory pathways that may affect SAT volume in ARV-treated HIV-infected patients.
HIV; HAART; GWAS; Subcutaneous Fat; SAT
Keratoconus is a bilateral noninflammatory progressive corneal disorder with complex genetic inheritance and a common cause for cornea transplantation in young adults. A genomewide linkage scan in keratoconus families identified a locus at 5q23.2, overlapping the gene coding for the lysyl oxidase (LOX). LOX encodes an enzyme responsible for collagen cross-linking in a variety of tissues including the cornea. Corneal collagen cross-linking with long-wave ultraviolet light and riboflavin is a promising new treatment for keratoconus. To determine whether LOX is a genetic determinant of the pathogenesis of keratoconus, we analyzed association results of LOX polymorphisms in two independent case-control samples and in keratoconus families.
Association results were analyzed of single-nucleotide polymorphisms (SNPs) in the LOX gene from a Genome-Wide Association Study (GWAS) investigation in two independent panels of patients with keratoconus and controls and in keratoconus families.
Evidence of association was found at SNPs rs10519694 and rs2956540 located in intron 4 of LOX in the GWAS discovery case-control panel with P values of 2.3 × 10−3 and 7 × 10−3, respectively. The same two SNPs were found to be associated with keratoconus by family-based association testing with P values of 2.7 × 10−3 and 7.7 × 10−4, respectively. Meta P values of 4.0 × 10−5 and 4.0 × 10−7 were calculated for SNPs rs10519694 and rs2956540 by analyzing case-control and family samples simultaneously. Sequencing of LOX exons in a subset of keratoconus patients identified two polymorphisms, rs1800449 and rs2288393, located in LOX transcripts I and II, associated with keratoconus in case-control and family samples with a meta P value of 0.02.
Results provided strong genetic evidence that LOX variants lead to increased susceptibility to developing of keratoconus.
Keratoconus is a progressive disorder of the cornea with complex genetic inheritance, which can lead to severe visual impairment or blindness. Here we describe the association between variation in the lysyl oxidase gene and keratoconus susceptibility in case-control and family studies.
Circulating adiponectin has been associated with both clinical and subclinical cardiovascular disease (CVD). Variants of the adiponectin gene (ADIPOQ) are associated with clinical CVD, but little is known about associations with subclinical CVD. We studied the association of 11 ADIPOQ SNPs with common and internal carotid intima media thickness (cIMT), presence of coronary artery calcification (CAC), and CAC scores (in those with CAC) in 2847 participants in the Multi-Ethnic Study of Atherosclerosis (MESA). Participants were Caucasian (n=712), African-American (n=712), Chinese (n=718), and Hispanic (n=705). All models were adjusted for age, sex, and field site, and stratified by race/ethnic group. African-Americans with genotypes AG/GG of rs2241767 had 36% greater (95% CI (16%, 59%), p=0.0001) CAC prevalence; they also had a larger common cIMT (p=0.0043). Also in African-Americans, genotypes AG/AA of rs1063537 were associated with a 35% (95% CI (14%, 59%), p=0.0005) greater CAC prevalence. Hispanics with the AA genotype of rs11711353 had a 37% (95% CI (14%, 66%), p=0.0011), greater CAC prevalence compared to those with the GG genotype. Additional adjustment for ancestry in African-American and Hispanic participants did not change the results. No single SNP was associated with subclinical CVD phenotypes in Chinese or Caucasian participants. There appears to be an association between ADIPOQ SNPs and subclinical CVD in African-American and Hispanics. Replication as well as assessment of other ADIPOQ SNPs appears warranted.
A recent large-scale meta-analysis of genome-wide studies has identified 95 loci, 59 of them novel, as statistically significant predictors of blood lipid traits; we tested whether the same loci explain the observed heterogeneity in response to lipid-lowering therapy with fenofibrate. Using data from the Genetics of Lipid Lowering Drugs and Diet Network (GOLDN, n = 861) we fit linear mixed models with the genetic markers as predictors and high-density lipoprotein (HDL) cholesterol, low-density lipoprotein (LDL) cholesterol, total cholesterol, and triglyceride concentrations as outcomes. For all four traits, we analyzed both baseline levels and changes in response to treatment with fenofibrate. For the markers that were significantly associated with fenofibrate response, we fit additional models evaluating potential epistatic interactions. All models were adjusted for age, sex, and study center as fixed effects, and pedigree as a random effect. Statistically significant associations were observed between the rs964184 polymorphism near APOA1 (P-value≤0.0001) and fenofibrate response for HDL and triglycerides. The association was replicated in the Pharmacogenetics of Hypertriglyceridemia in Hispanics study (HyperTG, n = 267). Suggestive associations with fenofibrate response were observed for markers in or near PDE3A, MOSC1, FLJ36070, CETP, the APOE-APOC1-APOC4-APOC2, and CILP2. Finally, we present strong evidence for epistasis (P-value for interaction = 0.0006 in GOLDN, 0.05 in HyperTG) between rs10401969 near CILP2 and rs4420638 in the APOE-APOC1-APOC4-APOC2 cluster with total cholesterol response to fenofibrate. In conclusion, we present evidence linking several novel and biologically relevant genetic polymorphisms to lipid lowering drug response, as well as suggesting novel gene-gene interactions in fenofibrate pharmacogenetics.