Background & Aims
Genetic susceptibility loci for Crohn’s disease (CD) are numerous, complex, and likely interact with undefined components of the environment. It has been a challenge to link the effects of particular loci to phenotypes of cells associated with pathogenesis of CD, such as Paneth cells. We investigated whether specific phenotypes of Paneth cells associated with particular genetic susceptibility loci can be used to define specific subtypes of CD.
We performed a retrospective analysis of 119 resection specimens collected from patients with CD at 2 separate medical centers. Paneth cell phenotypes were classified as normal or abnormal (with disordered, diminished, diffuse, or excluded granule phenotypes) based on lysozyme-positive secretory granule morphology. To uncover the molecular basis of the Paneth cell phenotypes, we developed methods to determine transcriptional profiles from whole-thickness and laser-capture microdissected, formalin-fixed, paraffin-embedded tissue sections.
The proportion of abnormal Paneth cells was associated with the number of CD-associated NOD2 risk alleles. The cumulative number of NOD2 and ATG16L1 risk alleles had an additive effect on the proportion of abnormal Paneth cells. Unsupervised clustering analysis of demographic and Paneth cell data divided patients into 2 principal subgroups, defined by high and low proportions of abnormal Paneth cells. The disordered and diffuse abnormal Paneth cell phenotypes were associated with an altered transcriptional signature of immune system activation. We observed an inverse correlation between abnormal Paneth cells and the presence of granuloma. Moreover, high proportions of abnormal Paneth cells were associated with shorter time to disease recurrence after surgery.
Histologic analysis of Paneth cell phenotypes can be used to divide patients with CD into subgroups with distinct pathognomonic and clinical features.
pathogenesis; prognostic factor; diagnosis; inflammatory bowel disease
The IL-23 pathway plays a pivotal role in the development of chronic mucosal inflammation seen in the inflammatory bowel diseases. Multiple studies have now established the contribution of the interleukin 23 receptor gene (IL23R) to Crohn’s Disease (CD) risk in general and of the IL23R R381Q variant in particular. The aim of this work was to estimate the total contribution of this gene to CD risk test using a haplotype approach.
763 CD subjects and 254 controls were genotyped for single nucleotide polymorphisms in the IL23R gene using Illumina and ABI methods. Haplotypes were assigned using PHASEv2 and tested for association with CD by chi-square and permutation.
Haplotypes with both increased and decreased risk for CD were observed in 2 of the 4 observed blocks (Block 2 H1: 55.4% control, 64% CD, p=0.019; H2: 64.5% control, 54.4% CD, p=0.006; Block 3 H1: 55.8% control, 64.4% CD, p=0.013; H2: 47.0% control, 36.6% CD, p=0.001). The population attributable risk for these haplotypes was substantially larger than that estimated for the IL23R R381Q variant (Block 2 H1 and block 3 H1 ~20%, compared with ~4% for Block 3 H6, containing the variant).
These observations suggest that IL23R makes a substantial contribution to Crohn’s disease susceptibility, larger than that estimated from the population frequency of the R381Q variant. These observations also support the expectation that finding “hits” from genome wide association studies will be but an important chapter in the story of unraveling the genetic contribution to Crohn’s disease, rather than the final chapter that brings clarity to all the plot twists of a complicated story.
Statins effectively lower LDL cholesterol levels in large studies and the observed interindividual response variability may be partially explained by genetic variation. Here we perform a pharmacogenetic meta-analysis of genome-wide association studies (GWAS) in studies addressing the LDL cholesterol response to statins, including up to 18,596 statin-treated subjects. We validate the most promising signals in a further 22,318 statin recipients and identify two loci, SORT1/CELSR2/PSRC1 and SLCO1B1, not previously identified in GWAS. Moreover, we confirm the previously described associations with APOE and LPA. Our findings advance the understanding of the pharmacogenetic architecture of statin response.
Statins are effectively used to prevent and manage cardiovascular disease, but patient response to these drugs is highly variable. Here, the authors identify two new genes associated with the response of LDL cholesterol to statins and advance our understanding of the genetic basis of drug response.
To describe the relationships of selected candidate genes to the prevalence of early age-related macular degeneration (AMD) in a cohort of whites, blacks, Hispanics, and Chinese Americans.
2456 persons aged 45–84 years with genotype information and fundus photographs.
Twelve of 2862 single nucleotide polymorphisms (SNPs) from 11 of 233 candidate genes for cardiovascular disease were selected for analysis based on screening with marginal unadjusted P value <0.001 within 1 or more racial/ethnic groups. Logistic regression models tested for association in case-control samples.
Main Outcome Measure
Prevalence of early AMD.
Early AMD was present in 4.0% of the cohort and varied from 2.4% in blacks to 6.0% in whites. The odds ratio increased from 2.3 for one to 10.0 for four risk alleles in a joint effect analysis of Age-Related Maculopathy Susceptibility 2 rs10490924 and Complement Factor H Y402H (P for trend=4.2×10−7). Frequencies of each SNP varied among the racial/ethnic groups. Adjusting for age and other factors, few statistically significant associations of the 12 SNPs with AMD were consistent across all groups. In a multivariate model, most candidate genes did not attenuate the comparatively higher odds of AMD in whites. The higher frequency of risk alleles for several SNPs in Chinese Americans may partially explain their AMD frequency approaching that of whites.
The relationships of 11 candidate genes to early AMD varied among 4 racial/ethnic groups, and partially explained the observed variations in early AMD prevalence among them.
How 9p21 variation affects risk of cardiovascular disease is unclear, so we assessed whether 9p21 variants are associated with arterial elasticity or retinal microvascular findings.
In the prospective Multi-Ethnic Study of Atherosclerosis (MESA) we assessed 378 SNPs in the 9p21 locus. Within four ethnic groups, we used an additive genetic model to relate the 9p21 SNPs to five vascular phenotypes: small and large elasticity derived from radial diastolic pulse contour analysis; Young’s elastic modulus from carotid artery ultrasound measurements; and the diameter of the central retinal arteries and veins.
In neither ethnic-specific nor pooled data was there any statistically significant association between any of the 9p21 SNPs and any of the five vascular phenotypes.
Our study does not support an association of 9p21 variation with arterial elasticity or retinal microvascular abnormalities.
Prospective study; 9p21 SNP; retinal microvascular abnormalities; arterial elasticity
The Puerto Rico population may be modeled as an admixed population with contributions from three continents: Sub-Saharan Africa, Ancient America, and Europe. Extending the study of the genetics of inflammatory bowel disease (IBD) to an admixed population such as Puerto Rico has the potential to shed light on IBD genes identified in studies of European populations, find new genes contributing to IBD susceptibility, and provide basic information on IBD for the care of US patients of Puerto Rican and Latino descent. In order to study the association between immune-related genes and Crohn’s disease (CD) and ulcerative colitis (UC) in Puerto Rico, we genotyped 1159 Puerto Rican cases, controls, and family members with the ImmunoChip. We also genotyped 832 subjects from the Human Genome Diversity Panel to provide data for estimation of global and local continental ancestry. Association of SNPs was tested by logistic regression corrected for global continental descent and family structure. We observed the association between Crohn’s disease and NOD2 (rs17313265, 0.28 in CD, 0.19 in controls, OR 1.5, p = 9×10−6) and IL23R (rs11209026, 0.026 in CD, 0.0.071 in controls, OR 0.4, p = 3.8×10−4). The haplotype structure of both regions resembled that reported for European populations and “local” continental ancestry of the IL23R gene was almost entirely of European descent. We also observed suggestive evidence for the association of the BAZ1A promoter SNP with CD (rs1200332, 0.45 in CD, 0.35 in controls, OR 1.5, p = 2×10−6). Our estimate of continental ancestry surrounding this SNP suggested an origin in Ancient America for this putative susceptibility region. Our observations underscored the great difference between global continental ancestry and local continental ancestry at the level of the individual gene, particularly for immune-related loci.
Estimates of the heritability of plasma fibrinogen concentration, an established predictor of cardiovascular disease (CVD), range from 34 to 50%. Genetic variants so far identified by genome-wide association (GWA) studies only explain a small proportion (< 2%) of its variation.
Methods and Results
We conducted a meta-analysis of 28 GWA studies, including more than 90,000 subjects of European ancestry, the first GWA meta-analysis of fibrinogen levels in 7 African Americans studies totaling 8,289 samples, and a GWA study in Hispanic-Americans totaling 1,366 samples. Evaluation for association of SNPs with clinical outcomes included a total of 40,695 cases and 85,582 controls for coronary artery disease (CAD), 4,752 cases and 24,030 controls for stroke, and 3,208 cases and 46,167 controls for venous thromboembolism (VTE). Overall, we identified 24 genome-wide significant (P<5×10−8) independent signals in 23 loci, including 15 novel associations, together accounting for 3.7% of plasma fibrinogen variation. Gene-set enrichment analysis highlighted key roles in fibrinogen regulation for the three structural fibrinogen genes and pathways related to inflammation, adipocytokines and thyrotrophin-releasing hormone signaling. Whereas lead SNPs in a few loci were significantly associated with CAD, the combined effect of all 24 fibrinogen-associated lead SNPs was not significant for CAD, stroke or VTE.
We identify 23 robustly associated fibrinogen loci, 15 of which are new. Clinical outcome analysis of these loci does not support a causal relationship between circulating levels of fibrinogen and CAD, stroke or VTE.
Fibrinogen; cardiovascular disease; genome-wide association study
Diabetic retinopathy (DR) is a leading cause of preventable blindness in adults. To identify genetic contributions in DR, we studied 2071 type 2 diabetics. We first conducted a genome-wide association study of 1007 individuals, comparing 570 subjects with ≥8 years duration without DR (controls) with 437 PDR (cases) in the Chinese discovery cohort. Cases and controls were similar for HbA1c, diabetes duration and body mass index. Association analysis with imputed data identified three novel loci: TBC1D4-COMMD6-UCHL3 (rs9565164, P = 1.3 × 10−7), LRP2-BBS5 (rs1399634, P = 2.0 × 10−6) and ARL4C-SH3BP4 (rs2380261, P = 2.1 × 10−6). Analysis of an independent cohort of 585 Hispanics diabetics with or without DR though did not confirm these signals. These genes are still of particular interest because they are involved in insulin regulation, inflammation, lipid signaling and apoptosis pathways, all of which are possibly involved with DR. Our finding nominates possible novel loci as potential DR susceptibility genes in the Chinese that are independent of the level of HbA1c and duration of diabetes and may provide insight into the pathophysiology of DR.
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
Central corneal thickness (CCT) is associated with eye conditions including keratoconus and glaucoma. We performed a meta-analysis on >20,000 individuals in European and Asian populations that identified 16 new loci associated with CCT at genome-wide significance (P < 5 × 10−8). We further showed that 2 CCT-associated loci, FOXO1 and FNDC3B, conferred relatively large risks for keratoconus in 2 cohorts with 874 cases and 6,085 controls (rs2721051 near FOXO1 had odds ratio (OR) = 1.62, 95% confidence interval (CI) = 1.4–1.88, P = 2.7 × 10−10, and rs4894535 in FNDC3B had OR = 1.47, 95% CI = 1.29–1.68, P = 4.9 × 10−9). FNDC3B was also associated with primary open-angle glaucoma (P = 5.6 × 10−4; tested in 3 cohorts with 2,979 cases and 7,399 controls). Further analyses implicate the collagen and extracellular matrix pathways in the regulation of CCT.
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.
Crohn’s disease (CD) and ulcerative colitis (UC), the two common forms of inflammatory bowel disease (IBD), affect over 2.5 million people of European ancestry with rising prevalence in other populations1. Genome-wide association studies (GWAS) and subsequent meta-analyses of CD and UC2,3 as separate phenotypes implicated previously unsuspected mechanisms, such as autophagy4, in pathogenesis and showed that some IBD loci are shared with other inflammatory diseases5. Here we expand knowledge of relevant pathways by undertaking a meta-analysis of CD and UC genome-wide association scans, with validation of significant findings in more than 75,000 cases and controls. We identify 71 new associations, for a total of 163 IBD loci that meet genome-wide significance thresholds. Most loci contribute to both phenotypes, and both directional and balancing selection effects are evident. Many IBD loci are also implicated in other immune-mediated disorders, most notably with ankylosing spondylitis and psoriasis. We also observe striking overlap between susceptibility loci for IBD and mycobacterial infection. Gene co-expression network analysis emphasizes this relationship, with pathways shared between host responses to mycobacteria and those predisposing to IBD.
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.