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1.  Association Between Celiac Disease and Iron Deficiency in Caucasians, but not Non-Caucasians 
Background & Aims
Celiac disease is an increasingly recognized disorder in Caucasian populations of European origin. Little is known about its prevalence in non-Caucasians. Although it is thought to be a cause of iron deficiency anemia, little is known about the extent to which celiac disease contributes to iron deficiency in Caucasians, and especially non-Caucasians. We analyzed samples collected from participants in the Hemochromatosis and Iron Overload Screening (HEIRS) study to identify individuals with iron deficiency and assess the frequency of celiac disease.
We analyzed serum samples from white men (25 y old or older) and women (50 y old or older) who participated the HEIRS study; cases were defined as individuals with iron deficiency (serum level of ferritin ≤12 mg/L) and controls were those without (serum level of ferritin >100 mg/L in men and >50 mg/L in women). All samples were also analyzed for human recombinant tissue transglutaminase immunoglobulin A; positive results were confirmed by an assay for endomysial antibodies. Patients with positive results from both celiac disease tests were presumed to have untreated celiac disease, and those with a positive result from only 1 test were excluded from analysis. We analyzed HLA genotypes and frequencies of celiac disease between Caucasians and non-Caucasians with iron deficiency.
Celiac disease occurred in 14 of 567 of cases (2.5%) and in only 1 of 1136 controls (0.1%; Fisher’s exact test, P=1.92 × 10−6). Celiac disease was more common in Caucasian cases (14/363, 4%) than non-Caucasian cases (0/204; P=.003). Only 1 Caucasian control and no non-Caucasian controls had celiac disease. The odds of celiac disease in individuals with iron deficiency was 28-fold (95% confidence interval, 3.7–212.8) that of controls; 13/14 cases with celiac disease carried the DQ2.5 variant of the HLA genotype.
Celiac disease is associated with iron deficiency of Caucasians. Celiac disease is rare among non-Caucasians—even among individuals with features of celiac disease, such as iron deficiency. Celiac disease is also rare among individuals without iron deficiency. Men and post-menopausal women with iron deficiency should be tested for celiac disease.
PMCID: PMC3843318  PMID: 23416278
SNP; risk factor; gluten allergy; intestine; absorption
2.  Implementation of Cloud based Next Generation Sequencing data analysis in a clinical laboratory 
BMC Research Notes  2014;7:314.
The introduction of next generation sequencing (NGS) has revolutionized molecular diagnostics, though several challenges remain limiting the widespread adoption of NGS testing into clinical practice. One such difficulty includes the development of a robust bioinformatics pipeline that can handle the volume of data generated by high-throughput sequencing in a cost-effective manner. Analysis of sequencing data typically requires a substantial level of computing power that is often cost-prohibitive to most clinical diagnostics laboratories.
To address this challenge, our institution has developed a Galaxy-based data analysis pipeline which relies on a web-based, cloud-computing infrastructure to process NGS data and identify genetic variants. It provides additional flexibility, needed to control storage costs, resulting in a pipeline that is cost-effective on a per-sample basis. It does not require the usage of EBS disk to run a sample.
We demonstrate the validation and feasibility of implementing this bioinformatics pipeline in a molecular diagnostics laboratory. Four samples were analyzed in duplicate pairs and showed 100% concordance in mutations identified. This pipeline is currently being used in the clinic and all identified pathogenic variants confirmed using Sanger sequencing further validating the software.
PMCID: PMC4036707  PMID: 24885806
Next generation sequencing; Cloud computing; Variant detection; Molecular diagnostics
3.  Genome-wide association study identifies multiple susceptibility loci for pulmonary fibrosis 
Nature genetics  2013;45(6):613-620.
We performed a genome-wide association study in non-Hispanic white subjects with fibrotic idiopathic interstitial pneumonias (N=1616) and controls (N=4683); replication was assessed in 876 cases and 1890 controls. We confirmed association with TERT and MUC5B on chromosomes 5p15 and 11p15, respectively, the chromosome 3q26 region near TERC, and identified 7 novel loci (PMeta = 2.4×10−8 to PMeta = 1.1×10−19). The novel loci include FAM13A (4q22), DSP (6p24), OBFC1 (10q24), ATP11A (13q34), DPP9 (19p13), and chromosomal regions 7q22 and 15q14-15. Our results demonstrate that genes involved in host defense, cell-cell adhesion, and DNA repair contribute to the risk of fibrotic IIP.
PMCID: PMC3677861  PMID: 23583980
4.  Genetic and environmental predictors of serum 25(OH)D concentrations among middle-aged and elderly Chinese in Singapore 
The British journal of nutrition  2012;109(3):493-502.
Vitamin D is known for maintaining calcium homeostasis and bone structure, and may also decrease susceptibility to chronic and infectious diseases. However, data on vitamin D status and its predictors among Southeast Asian populations is limited. We evaluated the distribution and determinants (genetic and environmental) of serum 25-hydroxyvitamin D (25(OH)D) concentrations among 504 middle-aged and elderly participants (aged 45–74 years) in the Singapore Chinese Health Study. Data on dietary and other lifestyle factors were collected by trained interviewers. Serum 25(OH)D concentrations and genetic polymorphisms in vitamin D metabolism pathway enzymes [cytochrome P450 (CYP) 2R1, 3A4, 27B1, 24A1; vitamin D binding protein (GC); and vitamin D receptor (VDR)] were measured using stored biospecimens. Mean 25(OH)D concentration was 68.8 nmol/L. Serum 25(OH)D concentrations were positively associated with dietary vitamin D intake, and inversely associated with hours sitting at work. BMI was not associated with 25(OH)D concentrations. CYP2R1 rs10741657, rs12794714, rs1993116; CYP3A4 rs2242480; and GC rs4588, rs7041, rs16847015, rs2298849 were statistically significantly associated with 25(OH)D concentrations. Individuals with the Gc2-2 haplotype (rs4588AA/rs7041TT) had statistically significantly lower 25(OH)D concentrations compared to all other Gc haplotypes (p-trend<0.001). The majority of participants (86%) had 25(OH)D concentrations ≥50 nmol/L, which is consistent with the 2011 Institute of Medicine (United States) recommendation for bone health, and 32% had concentrations of ≥75 nmol/L that are thought to be required for broader health effects. Dietary vitamin D intake, hours spent indoors at work, and genetic variation in CYP2R1, CYP3A4 and GC are significant predictors of 25(OH)D concentrations among Singapore Chinese.
PMCID: PMC3442149  PMID: 22583563
25-hydroxyvitamin D; CYP2R1; CYP3A4; GC
5.  The rs4774 CIITA missense variant is associated with risk of systemic lupus erythematosus 
Genes and Immunity  2011;12(8):667-671.
The major histocompatibility complex (MHC) class II transactivator gene (CIITA) encodes an important transcription factor required for HLA class II MHC-restricted antigen presentation. MHC genes, including the HLA class II DRB1*03:01 allele, are strongly associated with systemic lupus erythematosus (SLE). Recently the rs4774 CIITA missense variant (+1632G/C) was reported to be associated with susceptibility to multiple sclerosis. In the current study, we investigated CIITA, DRB1*03:01 and risk of SLE using a multi-stage analysis. In stage 1, 9 CIITA variants were tested in 658 cases and 1,363 controls (N = 2,021). In stage 2, rs4774 was tested in 684 cases and 2,938 controls (N = 3,622). We also performed a meta-analysis of the pooled 1,342 cases and 4,301 controls (N = 5,643). In stage 1, rs4774*C was associated with SLE (odds ratio [OR] = 1.24, 95% confidence interval [95% CI] = 1.07–1.44, P = 4.2 × 10−3). Similar results were observed in stage 2 (OR = 1.16, 95% CI = 1.02–1.33, P = 8.5×10−3) and the meta-analysis of the combined dataset (OR = 1.20, 95% CI = 1.09–1.33, Pmeta = 2.5×10−4). In all three analyses, the strongest evidence for association between rs4774*C and SLE was present in individuals who carried at least one copy of DRB1*03:01 (Pmeta= 1.9×10−3). Results support a role for CIITA in SLE, which appears to be stronger in the presence of DRB1*03:01.
PMCID: PMC3387803  PMID: 21614020
systemic lupus erythematosus; autoimmunity; major histocompatibility complex; HLA; CIITA; MHC2TA
6.  European ancestry is positively associated with breast cancer risk in Mexican women 
The incidence of breast cancer is 35% lower in Hispanic women living in the San Francisco Bay Area than in non-Hispanic white women. We have previously described a significant association between genetic ancestry and risk of breast cancer in a sample of US Hispanics/Latinas. We re-tested the association in women residing in Mexico because of the possibility that the original finding may be confounded by US specific unmeasured environmental exposures. We genotyped a set of 106 ancestry informative markers (AIMs) in 846 Mexican women with breast cancer and 1,035 unaffected controls and estimated genetic ancestry using a maximum likelihood method. Odds ratios (OR) and 95% confidence intervals (CI) for ancestry modeled as a categorical and continuous variable were estimated using logistic regression and adjusted for reproductive and other known risk factors. Greater European ancestry was associated with increased breast cancer risk in this new and independent sample of Mexican women residing in Mexico. Compared to women with 0-25% European ancestry, the risk was increased for women with 51-75% and 76-100% European ancestry (OR=1.35, 95% CI: 0.96-1.91 and 2.44, 95% CI: 0.94-6.35 respectively, p for trend=0.044). For every 25% increase in European ancestry (modeled as a continuous variable) there was a 20% increase in risk of breast cancer (95% CI: 1.03-1.41, p=0.019). These results suggest that non-genetic factors play a crucial role in explaining the difference in breast cancer incidence between Latinas and non-Latina white women and it also points out to the possibility of a genetic component to this difference.
PMCID: PMC2852491  PMID: 20332279
Breast cancer; genetic ancestry; Mexican women
7.  Genome-Wide Association Study Identifies Genetic Loci Associated with Iron Deficiency 
PLoS ONE  2011;6(3):e17390.
The existence of multiple inherited disorders of iron metabolism in man, rodents and other vertebrates suggests genetic contributions to iron deficiency. To identify new genomic locations associated with iron deficiency, a genome-wide association study (GWAS) was performed using DNA collected from white men aged ≥25 y and women ≥50 y in the Hemochromatosis and Iron Overload Screening (HEIRS) Study with serum ferritin (SF) ≤ 12 µg/L (cases) and iron replete controls (SF>100 µg/L in men, SF>50 µg/L in women). Regression analysis was used to examine the association between case-control status (336 cases, 343 controls) and quantitative serum iron measures and 331,060 single nucleotide polymorphism (SNP) genotypes, with replication analyses performed in a sample of 71 cases and 161 controls from a population of white male and female veterans screened at a US Veterans Affairs (VA) medical center. Five SNPs identified in the GWAS met genome-wide statistical significance for association with at least one iron measure, rs2698530 on chr. 2p14; rs3811647 on chr. 3q22, a known SNP in the transferrin (TF) gene region; rs1800562 on chr. 6p22, the C282Y mutation in the HFE gene; rs7787204 on chr. 7p21; and rs987710 on chr. 22q11 (GWAS observed P<1.51×10−7 for all). An association between total iron binding capacity and SNP rs3811647 in the TF gene (GWAS observed P = 7.0×10−9, corrected P = 0.012) was replicated within the VA samples (observed P = 0.012). Associations with the C282Y mutation in the HFE gene also were replicated. The joint analysis of the HEIRS and VA samples revealed strong associations between rs2698530 on chr. 2p14 and iron status outcomes. These results confirm a previously-described TF polymorphism and implicate one potential new locus as a target for gene identification.
PMCID: PMC3069025  PMID: 21483845
8.  Development and Initial Characterization of a HAPPY Panel for Mapping the X. Tropicalis Genome 
HAPPY mapping was designed to pursue the analysis of approximately random HAPloid DNA breakage samples using the PolYmerase chain reaction for mapping genomes. In the present study, we improved the method and integrated two other molecular techniques into the process: whole genome amplification and the Sequenom SNP (single nucleotide polymorphism) genotyping assay in order to facilitate whole genome mapping of X. tropicalis. The former technique amplified enough DNA materials to genotype a large number of markers, while the latter allowed for relatively high throughput marker genotyping with multiplex assays on the HAPPY lines. A total of 58 X. tropicalis genes were genotyped on an initial panel of 383 HAPPY lines, which contributed to formation of a working panel of 146 lines. Further genotyping of 29 markers on the working panel led to construction of a HAPPY map for the X. tropicalis genome. We believe that our improved HAPPY method described in the present study has paved the way for the community to map different genomes with a simple, but powerful approach.
PMCID: PMC3164153  PMID: 21912511
HAPPY mapping; whole genome amplification; multiplex genotyping assay; mapping X. tropicalis genome.
9.  CpG Methylation of a Silent Controlling Element in the Murine Avy Allele Is Incomplete and Unresponsive to Methyl Donor Supplementation 
PLoS ONE  2010;5(2):e9055.
The viable yellow allele of agouti (Avy) is remarkable for its unstable and partially heritable epigenetic state, which produces wide variation in phenotypes of isogenic mice. In the Avy allele an inserted intracisternal A particle (IAP) acts as a controlling element which deregulates expression of agouti by transcription from the LTR of the IAP; the phenotypic state has been linked to CpG methylation of the LTR. Phenotypic variation between Avy mice indicates that the epigenetic state of the IAP is unstable in the germline.
Principal Findings
We have made a detailed examination of somatic methylation of the IAP using bisulphite allelic sequencing, and find that the promoter is incompletely methylated even when it is transcriptionally silent. In utero exposure to supplementary methyl donors, which alters the spectrum of Avy phenotypes, does not increase the density of CpG methylation in the silent LTR.
Our findings suggest that, contrary to previous supposition, methyl donor supplementation acts through an indirect mechanism to silence Avy. The incomplete cytosine methylation we observe at the somatically silent Avy allele may reflect its unstable germline state, and the influence of epigenetic modifications underlying CpG methylation.
PMCID: PMC2816220  PMID: 20140227
10.  An african-specific functional polymorphism in KCNMB1 shows sex-specific association with asthma severity 
Human Molecular Genetics  2008;17(17):2681-2690.
A highly heritable and reproducible measure of asthma severity is baseline pulmonary function. Pulmonary function is largely determined by airway smooth muscle (ASM) tone and contractility. The large conductance, voltage and calcium-activated potassium (BK) channel negatively regulates smooth muscle tone and contraction in ASM. The modulatory subunit of BK channels, the β1-subunit, is critical for proper activation of BK channels in smooth muscle and has shown sex hormone specific regulation. We hypothesized that KCNMB1 genetic variants in African Americans may underlie differences in bronchial smooth muscle tone and thus pulmonary function, possibly in a sex-specific manner. Through resequencing of the KCNMB1 gene we identified several common variants including a novel African-specific coding polymorphism (C818T, R140W). The C818T SNP and four other KCNMB1 variants were genotyped in two independent groups of African American asthmatics (n = 509) and tested for association with the pulmonary function measure – forced expiratory volume (FEV1) % of predicted value. The 818T allele is associated with a clinically significant decline (−13%) in FEV1 in both cohorts of asthmatics among males but not females (Pcombined = 0.0003). Patch clamp electrophysiology studies of the BK channel expressed with the 140Trp variant of the β1-subunit demonstrated significantly reduced channel openings, predicted by the loss of pulmonary function observed. African American male asthmatics carrying the 818T allele (10% of population) are potentially at risk for greater airway obstruction and increased asthma morbidity. Female asthmatics may be insulated from the deleterious effects of the 818T allele by estrogen-mediated upregulation in BK channel activity.
PMCID: PMC2733805  PMID: 18535015
11.  Comparing Genetic Ancestry and Self-Described Race in African Americans Born in the United States and in Africa 
Genetic association studies can be used to identify factors that may contribute to disparities in disease evident across different racial and ethnic populations. However, such studies may not account for potential confounding if study populations are genetically heterogeneous. Racial and ethnic classifications have been used as proxies for genetic relatedness. We investigated genetic admixture and developed a questionnaire to explore variables used in constructing racial identity in two cohorts – 50 African Americans (AAs) and 40 Nigerians. Genetic ancestry was determined by genotyping 107 ancestry informative markers. Ancestry estimates calculated with maximum likelihood estimation were compared with population stratification detected with principal component analysis. Ancestry was approximately 95% west African, 4% European, and 1% Native American in the Nigerian cohort and 83% west African, 15% European, and 2% Native American in the AA cohort. Therefore, self-identification as AA agreed well with inferred west African ancestry. However, the cohorts differed significantly in mean percentage west African and European ancestries (P < 0.0001) and in the variance for individual ancestry (P ≤ 0.01). Among AAs, no set of questionnaire items effectively estimated degree of west African ancestry, and self-report of a high degree of African ancestry in a three-generation family tree did not accurately predict degree of African ancestry. Our findings suggest that self-reported race and ancestry can predict ancestral clusters, but do not reveal the extent of admixture. Genetic classifications of ancestry may provide a more objective and accurate method of defining homogenous populations for the investigation of specific population-disease associations.
PMCID: PMC2507870  PMID: 18559547
African American; race; ancestry; genetic admixture
12.  Ethnicity-specific Gene–Gene Interaction between IL-13 and IL-4Rα among African Americans with Asthma 
Rationale: Genes in the interleukin (IL)-4/IL-13/IL-4Rα pathway have been shown to be associated with asthma and related phenotypes in some populations, but not in others. Furthermore, interaction between these genes has been shown to affect asthma in white and Chinese populations.
Objectives: To determine whether there are IL-4/IL-13 and IL-4Rα gene–gene interactions that are associated with asthma in African Americans.
Methods: Eighteen single-nucleotide polymorphisms (SNPs) in IL-4, IL-13, and IL-4Rα genes were genotyped in 264 African Americans with asthma and 176 healthy control subjects. We tested the SNPs for genetic associations and gene–gene interactions with asthma, baseline lung function, bronchodilator drug response, and total serum IgE levels.
Measurements and Main Results: We identified 94 SNPs in IL-4, IL-13, and IL-4Rα genes by directly sequencing these genes in 24 African-American subjects with asthma. Seventeen SNPs were analyzed for association with asthma and related phenotypes. We found no evidence of association in the IL-4 gene. One SNP in the IL-13 gene (A−646G, rs2069743) and two SNPs in the IL-4Rα gene (A+4679G, rs1805010, and C+22656T, rs1805015) showed association with lung function (both baseline and post-bronchodilator). Although the association between individual SNPs and asthma-related phenotypes differed from previous studies performed in white and Chinese populations, significant gene–gene interaction was found between the IL-13 (A−646G) and IL-4Rα (A+4679G) SNPs for baseline lung function among African-American subjects with asthma.
Conclusions: Gene–gene interaction between the IL-13 and IL-4Rα genes may play an important role in asthma among African Americans.
PMCID: PMC1899298  PMID: 17303794
asthma; African Americans; gene–gene interaction
13.  Using DNA pools for genotyping trios 
Nucleic Acids Research  2006;34(19):e129.
The genotyping of mother–father–child trios is a very useful tool in disease association studies, as trios eliminate population stratification effects and increase the accuracy of haplotype inference. Unfortunately, the use of trios for association studies may reduce power, since it requires the genotyping of three individuals where only four independent haplotypes are involved. We describe here a method for genotyping a trio using two DNA pools, thus reducing the cost of genotyping trios to that of genotyping two individuals. Furthermore, we present extensions to the method that exploit the linkage disequilibrium structure to compensate for missing data and genotyping errors. We evaluated our method on trios from CEPH pedigree 66 of the Coriell Institute. We demonstrate that the error rates in the genotype calls of the proposed protocol are comparable to those of standard genotyping techniques, although the cost is reduced considerably. The approach described is generic and it can be applied to any genotyping platform that achieves a reasonable precision of allele frequency estimates from pools of two individuals. Using this approach, future trio-based association studies may be able to increase the sample size by 50% for the same cost and thereby increase the power to detect associations.
PMCID: PMC1636483  PMID: 17020923
14.  Dramatic age-related changes in nuclear and genome copy number in the nematode Caenorhabditis elegans 
Aging Cell  2007;6(2):179-188.
The nematode Caenorhabditis elegans has become one of the most widely used model systems for the study of aging, yet very little is known about how C. elegans age. The development of the worm, from egg to young adult has been completely mapped at the cellular level, but such detailed studies have not been extended throughout the adult lifespan. Numerous single gene mutations, drug treatments and environmental manipulations have been found to extend worm lifespan. To interpret the mechanism of action of such aging interventions, studies to characterize normal worm aging, similar to those used to study worm development are necessary. We have used 4′,6′-diamidino-2-phenylindole hydrochloride staining and quantitative polymerase chain reaction to investigate the integrity of nuclei and quantify the nuclear genome copy number of C. elegans with age. We report both systematic loss of nuclei or nuclear DNA, as well as dramatic age-related changes in nuclear genome copy number. These changes are delayed or attenuated in long-lived daf-2 mutants. We propose that these changes are important pathobiological characteristics of aging nematodes.
PMCID: PMC2049047  PMID: 17286610
aging; C. elegans; genome; nematode; oldest old; variability

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