Robert Wojciechowski

Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, United States

Are you Robert Wojciechowski?

Claim your profile

Publications (32)183.98 Total impact

  • Pirro G Hysi, Robert Wojciechowski, Jugnoo S Rahi, Chris J Hammond
    [Show abstract] [Hide abstract]
    ABSTRACT: The investigation of the genetic basis of refractive error and myopia entered a new stage with the introduction of genome-wide association studies (GWAS). Multiple GWAS on many ethnic groups have been published over the years, providing new insight into the genetic architecture and pathophysiology of refractive error. This is a review of the GWAS published to date, the main lessons learned, and future possible directions of genetic studies of myopia and refractive error.
    Investigative ophthalmology & visual science. 01/2014; 55(5):3344-51.
  • [Show abstract] [Hide abstract]
    ABSTRACT: IMPORTANCE To date, relatively few genes responsible for a fraction of heritability have been identified by means of large genetic association studies of refractive error. OBJECTIVE To explore the genetic mechanisms that lead to refractive error in the general population. DESIGN, SETTING, AND PARTICIPANTS Genome-wide association studies were carried out in 2 British population-based independent cohorts (N = 5928 participants) to identify genes moderately associated with refractive error. MAIN OUTCOMES AND MEASURES Enrichment analyses were used to identify sets of genes overrepresented in both cohorts. Enriched groups of genes were compared between both participating cohorts as a further measure against random noise. RESULTS Groups of genes enriched at highly significant statistical levels were remarkably consistent in both cohorts. In particular, these results indicated that plasma membrane (P = 7.64 × 10-30), cell-cell adhesion (P = 2.42 × 10-18), synaptic transmission (P = 2.70 × 10-14), calcium ion binding (P = 3.55 × 10-15), and cation channel activity (P = 2.77 × 10-14) were significantly overrepresented in relation to refractive error. CONCLUSIONS AND RELEVANCE These findings provide evidence that development of refractive error in the general population is related to the intensity of photosignal transduced from the retina, which may have implications for future interventions to minimize this disorder. Pathways connected to the procession of the nerve impulse are major mechanisms involved in the development of refractive error in populations of European origin.
    Jama Ophthalmology 11/2013; · 3.83 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Refractive error is a complex ocular trait governed by both genetic and environmental factors and possibly their interplay. Thus far, data on the interaction between genetic variants and environmental risk factors for refractive errors are largely lacking. By using findings from recent genome-wide association studies, we investigated whether the main environmental factor, education, modifies the effect of 40 single nucleotide polymorphisms (SNP) on refractive error among 8,461 adults from five studies including ethnic Chinese, Malay and Indian residents of Singapore. Three genetic loci SHISA6-DNAH9, GJD2 and ZMAT4-SFRP1 exhibited a strong association with myopic refractive error in individuals with tertiary or university education (SHISA6-DNAH9: rs2969180 A allele, β=-0.33 diopters (D), P=3.6×10(-6); GJD2: rs524952 A allele, β=-0.31 D, P=1.68×10(-5); ZMAT4-SFRP1: rs2137277 A allele, β=-0.47 D, P=1.68×10(-4)), whereas the association at these loci was non-significant or of borderline significance in those with secondary education or lower (P for interaction: 3.82×10(-3) to 4.78×10(-4)). The evidence for interaction was strengthened when combining the genetic effects of these three loci (P for interaction=4.40×10(-8)), and significant interactions with education were also observed for axial length and myopia. Our study shows that low level of education may attenuate the effect of risk alleles on myopia. These findings further underline the role of gene-environment interactions in the pathophysiology of myopia.
    Human Molecular Genetics 09/2013; · 7.69 Impact Factor
  • Source
    Robert Wojciechowski, Pirro G Hysi
    PLoS Genetics 04/2013; 9(4):e1003442. · 8.52 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Visual refractive errors are complex genetic traits with a largely unknown etiology. To date, genome-wide association studies (GWAS) of moderate size have identified several novel risk markers for refractive error, measured here as mean spherical equivalent. We performed a GWAS using a total of 7,280 samples from 5 cohorts: the Age-Related Eye Disease Study (AREDS); the KORA study ("Cooperative Health Research in the Region of Augsburg"); the Framingham Eye Study (FES); the Ogliastra Genetic Park-Talana (OGP-Talana) Study; and the Multiethnic Study of Atherosclerosis (MESA). Genotyping was performed on Illumina and Affymetrix platforms with additional markers imputed to the HapMap II reference panel. We identified a new genome-wide significant locus on chromosome 16 (rs10500355, p=3.9 x 10-9) in a combined discovery and replication set (26,953 samples). This SNP is located within the RBFOX1 gene which is a neuron-specific splicing factor regulating a wide range of alternative splicing events implicated in neuronal development and maturation, including transcription factors, other splicing factors and synaptic proteins.
    Human Molecular Genetics 03/2013; · 7.69 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Refractive error is the most common eye disorder worldwide and is a prominent cause of blindness. Myopia affects over 30% of Western populations and up to 80% of Asians. The CREAM consortium conducted genome-wide meta-analyses, including 37,382 individuals from 27 studies of European ancestry and 8,376 from 5 Asian cohorts. We identified 16 new loci for refractive error in individuals of European ancestry, of which 8 were shared with Asians. Combined analysis identified 8 additional associated loci. The new loci include candidate genes with functions in neurotransmission (GRIA4), ion transport (KCNQ5), retinoic acid metabolism (RDH5), extracellular matrix remodeling (LAMA2 and BMP2) and eye development (SIX6 and PRSS56). We also confirmed previously reported associations with GJD2 and RASGRF1. Risk score analysis using associated SNPs showed a tenfold increased risk of myopia for individuals carrying the highest genetic load. Our results, based on a large meta-analysis across independent multiancestry studies, considerably advance understanding of the mechanisms involved in refractive error and myopia.
    Nature Genetics 03/2013; 45(3):314-318. · 35.21 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Refractive error is the most common eye disorder worldwide and is a prominent cause of blindness. Myopia affects over 30% of Western populations and up to 80% of Asians. The CREAM consortium conducted genome-wide meta-analyses, including 37,382 individuals from 27 studies of European ancestry and 8,376 from 5 Asian cohorts. We identified 16 new loci for refractive error in individuals of European ancestry, of which 8 were shared with Asians. Combined analysis identified 8 additional associated loci. The new loci include candidate genes with functions in neurotransmission (GRIA4), ion transport (KCNQ5), retinoic acid metabolism (RDH5), extracellular matrix remodeling (LAMA2 and BMP2) and eye development (SIX6 and PRSS56). We also confirmed previously reported associations with GJD2 and RASGRF1. Risk score analysis using associated SNPs showed a tenfold increased risk of myopia for individuals carrying the highest genetic load. Our results, based on a large meta-analysis across independent multiancestry studies, considerably advance understanding of the mechanisms involved in refractive error and myopia.
    Nature Genetics 02/2013; · 35.21 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Refractive error is a complex trait with multiple genetic and environmental risk factors, and is the most common cause of preventable blindness worldwide. The common nature of the trait suggests the presence of many genetic factors that individually may have modest effects. To achieve an adequate sample size to detect these common variants, large, international collaborations have formed. These consortia typically use meta-analysis to combine multiple studies from many different populations. This approach is robust to differences between populations; however, it does not compensate for the different haplotypes in each genetic background evidenced by different alleles in linkage disequilibrium with the causative variant. We used the Age-Related Eye Disease Study (AREDS) cohort to replicate published significant associations at two loci on chromosome 15 from two genome-wide association studies (GWASs). The single nucleotide polymorphisms (SNPs) that exhibited association on chromosome 15 in the original studies did not show evidence of association with refractive error in the AREDS cohort. This paper seeks to determine whether the non-replication in this AREDS sample may be due to the limited number of SNPs chosen for replication. We selected all SNPs genotyped on the Illumina Omni2.5v1_B array or custom TaqMan assays or imputed from the GWAS data, in the region surrounding the SNPs from the Consortium for Refractive Error and Myopia study. We analyzed the SNPs for association with refractive error using standard regression methods in PLINK. The effective number of tests was calculated using the Genetic Type I Error Calculator. Although use of the same SNPs used in the Consortium for Refractive Error and Myopia study did not show any evidence of association with refractive error in this AREDS sample, other SNPs within the candidate regions demonstrated an association with refractive error. Significant evidence of association was found using the hyperopia categorical trait, with the most significant SNPs rs1357179 on 15q14 (p=1.69×10(-3)) and rs7164400 on 15q25 (p=8.39×10(-4)), which passed the replication thresholds. This study adds to the growing body of evidence that attempting to replicate the most significant SNPs found in one population may not be significant in another population due to differences in the linkage disequilibrium structure and/or allele frequency. This suggests that replication studies should include less significant SNPs in an associated region rather than only a few selected SNPs chosen by a significance threshold.
    Molecular vision 01/2013; 19:2173-86. · 1.99 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: PURPOSE: A previous study of Old Order Amish families showed an association of ocular refraction with markers proximal to matrix metalloproteinase (MMP) genes MMP1 and MMP10 and intragenic to MMP2. A candidate gene replication study of association between refraction and single nucleotide polymorphisms (SNPs) within these genomic regions was conducted. DESIGN: Candidate gene genetic association study. PARTICIPANTS: Two thousand participants drawn from the Age-Related Eye Disease Study (AREDS) were chosen for genotyping. After quality-control filtering, 1912 individuals were available for analysis. METHODS: Microarray genotyping was performed using the HumanOmni 2.5 bead array (Illumina, Inc., San Diego, CA). Single nucleotide polymorphisms originally typed in the previous Amish association study were extracted for analysis. In addition, haplotype tagging SNPs were genotyped using TaqMan assays. Quantitative trait association analyses of mean spherical equivalent refraction were performed on 30 markers using linear regression models and an additive genetic risk model while adjusting for age, sex, education, and population substructure. Post hoc analyses were performed after stratifying on a dichotomous education variable. Pointwise (P(emp)) and multiple-test study-wise (P(multi)) significance levels were calculated empirically through permutation. MAIN OUTCOME MEASURES: Mean spherical equivalent refraction was used as a quantitative measure of ocular refraction. RESULTS: The mean age and ocular refraction were 68 years (standard deviation [SD], 4.7 years) and +0.55 diopters (D; SD, 2.14 D), respectively. Pointwise statistical significance was obtained for rs1939008 (P(emp) = 0.0326). No SNP attained statistical significance after correcting for multiple testing. In stratified analyses, multiple SNPs reached pointwise significance in the lower-education group: 2 of these were statistically significant after multiple testing correction. The 2 highest-ranking SNPs in Amish families (rs1939008 and rs9928731) showed pointwise P(emp)<0.01 in the lower-education stratum of AREDS participants. CONCLUSIONS: This study showed suggestive evidence of replication of an association signal for ocular refraction to a marker between MMP1 and MMP10. Evidence of a gene-environment interaction between previously reported markers and education on refractive error also was shown. Variants in MMP1 through MMP10 and MMP2 regions seem to affect population variation in ocular refraction in environmental conditions less favorable for myopia development. FINANCIAL DISCLOSURE(S): The author(s) have no proprietary or commercial interest in any materials discussed in this article.
    Ophthalmology 10/2012; · 5.56 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Myopia is a complex genetic disorder and a common cause of visual impairment among working age adults. Genome-wide association studies have identified susceptibility loci on chromosomes 15q14 and 15q25 in Caucasian populations of European ancestry. Here, we present a confirmation and meta-analysis study in which we assessed whether these two loci are also associated with myopia in other populations. The study population comprised 31 cohorts from the Consortium of Refractive Error and Myopia (CREAM) representing 4 different continents with 55,177 individuals; 42,845 Caucasians and 12,332 Asians. We performed a meta-analysis of 14 single nucleotide polymorphisms (SNPs) on 15q14 and 5 SNPs on 15q25 using linear regression analysis with spherical equivalent as a quantitative outcome, adjusted for age and sex. We calculated the odds ratio (OR) of myopia versus hyperopia for carriers of the top-SNP alleles using a fixed effects meta-analysis. At locus 15q14, all SNPs were significantly replicated, with the lowest P value 3.87 × 10(-12) for SNP rs634990 in Caucasians, and 9.65 × 10(-4) for rs8032019 in Asians. The overall meta-analysis provided P value 9.20 × 10(-23) for the top SNP rs634990. The risk of myopia versus hyperopia was OR 1.88 (95 % CI 1.64, 2.16, P < 0.001) for homozygous carriers of the risk allele at the top SNP rs634990, and OR 1.33 (95 % CI 1.19, 1.49, P < 0.001) for heterozygous carriers. SNPs at locus 15q25 did not replicate significantly (P value 5.81 × 10(-2) for top SNP rs939661). We conclude that common variants at chromosome 15q14 influence susceptibility for myopia in Caucasian and Asian populations world-wide.
    Human Genetics 06/2012; 131(9):1467-80. · 4.63 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Family-based study designs are again becoming popular as new next-generation sequencing technologies make whole-exome and whole-genome sequencing projects economically and temporally feasible. Here we evaluate the statistical properties of linkage analyses and family-based tests of association for the Genetic Analysis Workshop 17 mini-exome sequence data. Based on our results, the linkage methods using relative pairs or nuclear families had low power, with the best results coming from variance components linkage analysis in nuclear families and Elston-Stewart model-based linkage analysis in extended pedigrees. For family-based tests of association, both ASSOC and ROMP performed well for genes with large effects, but ROMP had the advantage of not requiring parental genotypes in the analysis. For the linkage analyses we conclude that genome-wide significance levels appear to control type I error well but that "suggestive" significance levels do not. Methods that make use of the extended pedigrees are well powered to detect major loci segregating in the families even when there is substantial genetic heterogeneity and the trait is mainly polygenic. However, large numbers of such pedigrees will be necessary to detect all major loci. The family-based tests of association found the same major loci as the linkage analyses and detected low-frequency loci with moderate effect sizes, but control of type I error was not as stringent.
    BMC proceedings 11/2011; 5 Suppl 9:S83.
  • [Show abstract] [Hide abstract]
    ABSTRACT: To investigate age-related trends in refractive, corneal, and internal astigmatism and to assess the association between internal astigmatism and lens opacity in an elderly Chinese population. A population-based study was conducted among 1360 inhabitants aged 65 years and older in Taipei, Taiwan. Participants underwent measurements of refraction, corneal dioptric power, and slit lamp biomicroscopy with lens grading. A total of 2084 eyes were included in power vector analyses of Cartesian astigmatism (J(0)) and oblique astigmatism (J(45)) components of refractive, corneal, and internal astigmatism. The crude prevalence of refractive astigmatism (defined as ≥0.75 diopters) was 73.0% based on the right eyes and 76.4% based on the left eyes. The vector values in both refractive J(0) and corneal J(0) tended to be more negative with increasing age (P < 0.001), indicating the trend toward against-the-rule (ATR) astigmatism. Corneal J(0) alone accounted for 54% of the variability in refractive J(0). Refractive J(45) increased with age in the right eyes (P < 0.001) and decreased slightly with age in the left eyes (P = 0.012). Cortical opacity was associated with internal J(0) (P = 0.025), but the association was weak. Astigmatism affects approximately three quarters of the Chinese population aged 65 years and older in Taiwan. With increasing age, the prevalence of astigmatism increases, and refractive and corneal astigmatism shift toward ATR. Continuous corneal changes appear to be responsible for the age trend in refractive astigmatism. The severity of lens opacity plays only a minor role in the change of internal astigmatism.
    Investigative ophthalmology & visual science 11/2011; 52(13):9651-7. · 3.43 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Despite many years of research, most of the genetic factors contributing to myopia development remain unknown. Genetic studies have pointed to a strong inherited component, but although many candidate regions have been implicated, few genes have been positively identified. We have previously reported 2 genomewide linkage scans in a population of 63 highly aggregated Ashkenazi Jewish families that identified a locus on chromosome 22. Here we used ordered subset analysis (OSA), conditioned on non-parametric linkage to chromosome 22 to detect other chromosomal regions which had evidence of linkage to myopia in subsets of the families, but not the overall sample. Strong evidence of linkage to a 19-cM linkage interval with a peak OSA nonparametric allele-sharing logarithm-of-odds (LOD) score of 3.14 on 20p12-q11.1 (ΔLOD=2.39, empirical p=0.029) was identified in a subset of 20 families that also exhibited strong evidence of linkage to chromosome 22. One other locus also presented with suggestive LOD scores >2.0 on chromosome 11p14-q14 and one locus on chromosome 6q22-q24 had an OSA LOD score=1.76 (ΔLOD=1.65, empirical p=0.02). The chromosome 6 and 20 loci are entirely novel and appear linked in a subset of families whose myopia is known to be linked to chromosome 22. The chromosome 11 locus overlaps with the known Myopia-7 (MYP7, OMIM 609256) locus. Using ordered subset analysis allows us to find additional loci linked to myopia in subsets of families, and underlines the complex genetic heterogeneity of myopia even in highly aggregated families and genetically isolated populations such as the Ashkenazi Jews.
    Molecular vision 01/2011; 17:1641-51. · 1.99 Impact Factor
  • Source
    R Wojciechowski
    [Show abstract] [Hide abstract]
    ABSTRACT: The refractive errors, myopia and hyperopia, are optical defects of the visual system that can cause blurred vision. Uncorrected refractive errors are the most common causes of visual impairment worldwide. It is estimated that 2.5 billion people will be affected by myopia alone within the next decade. Experimental, epidemiological and clinical research has shown that refractive development is influenced by both environmental and genetic factors. Animal models have showed that eye growth and refractive maturation during infancy are tightly regulated by visually guided mechanisms. Observational data in human populations provide compelling evidence that environmental influences and individual behavioral factors play crucial roles in myopia susceptibility. Nevertheless, the majority of the variance of refractive error within populations is thought to be because of hereditary factors. Genetic linkage studies have mapped two dozen loci, while association studies have implicated more than 25 different genes in refractive variation. Many of these genes are involved in common biological pathways known to mediate extracellular matrix (ECM) composition and regulate connective tissue remodeling. Other associated genomic regions suggest novel mechanisms in the etiology of human myopia, such as mitochondrial-mediated cell death or photoreceptor-mediated visual signal transmission. Taken together, observational and experimental studies have revealed the complex nature of human refractive variation, which likely involves variants in several genes and functional pathways. Multiway interactions between genes and/or environmental factors may also be important in determining individual risks of myopia, and may help explain the complex pattern of refractive error in human populations.
    Clinical Genetics 11/2010; 79(4):301-20. · 4.25 Impact Factor
  • Source
    Robert Wojciechowski, Joan E Bailey-Wilson, Dwight Stambolian
    [Show abstract] [Hide abstract]
    ABSTRACT: Matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) are involved in scleral extracellular matrix remodeling and have shown differential expression in experimental myopia. The genetic association of refractive error and polymorphisms in MMP and TIMP genes in Old Order Amish (AMISH) and Ashkenazi Jewish (ASHK) families was investigated. Individuals from 55 AMISH and 63 ASHK families participated in the study. Ascertainment was designed to enrich the families for myopia; the mean spherical equivalent (MSE) refractive error (SD) was -1.61 (2.72) D in the AMISH, and -3.56 (3.32) D in the ASHK. One hundred forty-six common haplotype tagging SNPs covering 14 MMP and 4 TIMP genes were genotyped in 358 AMISH and 535 ASHK participants. Association analyses of MSE and the spherical component of refraction (SPH) were performed separately for the AMISH and the ASHK. Bonferroni-corrected significance thresholds and local false discovery rates were used to account for multiple testing. After they were filtered for quality-control, 127 SNPs were included in the analyses. No polymorphisms showed statistically significant association to refraction in the ASHK (minimum P = 0.0132). In AMISH, two SNPs showed evidence of association with refractive phenotypes: rs1939008 (P = 0.00016 for SPH); and rs9928731 (P = 0.00026 for SPH). These markers were each estimated to explain <5% of the variance of SPH in the AMISH sample. Statistically significant genetic associations of ocular refraction to polymorphisms near MMP1 and within MMP2 were identified in the AMISH but not among the ASHK families. The results suggest that the MMP1 and MMP2 genes are involved in refractive variation in the AMISH. Genetic and/or environmental heterogeneity most likely contribute to differences in association results between ethnic groups.
    Investigative ophthalmology & visual science 10/2010; 51(10):4989-95. · 3.43 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: To assess the correlations between retinal nerve fiber layer (RNFL) thickness measured with scanning laser polarimetry and visual field (VF) sensitivity in primary open-angle glaucoma (POAG) and primary angle-closure glaucoma (PACG). Prospective, comparative, observational cases series. Fifty patients with POAG and 56 patients with PACG were examined using scanning laser polarimetry with variable corneal compensation (GDx VCC; Laser Diagnostic Technologies, Inc.) and Humphrey VF analyzer (Carl Zeiss Meditec, Inc.) between August 2005 and July 2006 at Taipei Veterans General Hospital. Correlations between RNFL thickness and VF sensitivity, expressed as mean sensitivity in both decibel and 1/Lambert scales, were estimated by the Spearman rank correlation coefficient (r(s)) and multivariate median regression models (pseudo R(2)). The correlations were determined globally and for 6 RNFL sectors and their corresponding VF regions. The correlation between RNFL thickness and mean sensitivity (in decibels) was weaker in the PACG group (r(s) = 0.38; P = .004; pseudo R(2) = 0.17) than in the POAG group (r(s) = 0.51; P < .001; pseudo R(2) = .31), but the difference in the magnitude of correlation was not significant (P = .42). With Bonferroni correction, the structure-function correlation was significant in the superotemporal (r(s) = 0.62), superonasal (r(s) = 0.56), inferonasal (r(s) = 0.53), and inferotemporal (r(s) = 0.50) sectors in the POAG group (all P < .001), whereas it was significant only in the superotemporal (r(s) = 0.53) and inferotemporal (r(s) = 0.48) sectors in the PACG group (both P < .001). The results were similar when mean sensitivity was expressed as 1/Lambert scale. Both POAG and PACG eyes had moderate structure-function correlations using scanning laser polarimetry. Compared with eyes with POAG, fewer RNFL sectors have significant structure-function correlations in eyes with PACG.
    American journal of ophthalmology 05/2010; 149(5):817-25.e1. · 3.83 Impact Factor
  • Source
    Robert Wojciechowski, Joan E Bailey-Wilson, Dwight Stambolian
    [Show abstract] [Hide abstract]
    ABSTRACT: A previous genome-wide study in Orthodox Ashkenazi Jewish pedigrees showed significant linkage of ocular refraction to a Quantitative Trait Locus (QTL) on 1p34-36.1. We carried out a fine-mapping study of this region in Orthodox Ashkenazi Jewish (ASHK) and Old Order Amish (OOA) families to confirm linkage and narrow the candidate region. Families were recruited from ASHK and OOA American communities. The samples included: 402 individuals in 53 OOA families; and 596 members in 68 ASHK families. Families were ascertained to contain multiple myopic individuals. Genotyping of 1,367 SNPs was carried out within a 35cM (approximately 23.9 Mb) candidate QTL region on 1p34-36. Multipoint variance components (VC) and regression-based (REG) linkage analyses were carried out separately in OOA and ASHK groups, and in a combined analysis that included all families. Evidence of linkage of refractive error was found in both OOA (VC LOD=3.45, REG LOD=3.38 at approximately 59 cM) and ASHK families (VC LOD=3.12, REG LOD=4.263 at ~66 cM). Combined analyses showed three highly significant linkage peaks, separated by approximately 11cM (or 10 Mb), within the candidate region. In a fine-mapping linkage study of OOA and ASHK families, we have confirmed linkage of refractive error to a QTL on 1p. The area of linkage has been narrowed down to a gene-rich region at 1p34.2-35.1 containing ~124 genes.
    Molecular vision 02/2009; 15:1398-406. · 1.99 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: ABSTRACT : Random forests (RF) is one of a broad class of machine learning methods that are able to deal with large-scale data without model specification, which makes it an attractive method for genome-wide association studies (GWAS). The performance of RF and other association methods in the presence of interactions was evaluated using the simulated data from Genetic Analysis Workshop 16 Problem 3, with knowledge of the major causative markers, risk factors, and their interactions in the simulated traits. There was good power to detect the environmental risk factors using RF, trend tests, or regression analyses but the power to detect the effects of the causal markers was poor for all methods. The causal marker that had an interactive effect with smoking did show moderate evidence of association in the RF and regression analyses, suggesting that RF may perform well at detecting such interactions in larger, more highly powered datasets.
    BMC proceedings 01/2009; 3 Suppl 7:S64.
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Genomewide linkage scans were performed in Caucasian (CAUC) and Old Order Amish (OOA) families to identify genomic regions containing genes responsible for refractive error control. We also performed a meta-analysis by combining these results with our previous linkage results from Ashkenazi Jewish (ASHK) and African American (AFRAM) families. Two hundred seventy-one CAUC and 411 OOA participants (36 and 61 families, respectively) were recruited to participate in the Myopia Family Study. Recruitment criteria were designed to enrich the sample for multiplex myopic families. Genomewide, model-free, multipoint linkage analyses were performed separately for each population by using >370 microsatellite markers. Empirical significance levels were determined via gene-dropping simulations. A meta-analysis was performed by combining linkage results from the CAUC, OOA, AFRAM, and ASHK samples, and results were compared to previously reported loci for myopia and refraction. Suggestive evidence of linkage was found at 12q24 (LOD = 4.583, P = 0.00037) and 4q21 (LOD = 2.72, P = 0.0028) in the CAUC sample and at 5qter (LOD = 3.271, P = 0.0014) in the OOA. Meta-analysis linkage results were largely driven by population-specific signals from ASHK and AFRAM families. The meta-analysis showed suggestive evidence of linkage to 4q21-22 (meta-P = 0.00214) adjacent to the previously reported MYP9 and MYP11 loci. The results showed suggestive evidence of linkage of ocular refraction to 12q24 and 4q21 in CAUC and to 5qter in OOA families. The meta-analysis supports the view that several genes play a role in refractive development across populations. In MFS families, four broad genomic regions (on 1p, 4q, 7p, and 12q) most likely contain genes that influence ocular refraction.
    Investigative ophthalmology & visual science 01/2009; 50(5):2024-32. · 3.43 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: To identify myopia susceptibility genes influencing common myopia in 94 African-American and 36 White families. A prospective study of families with myopia consisting of a minimum of two individuals affected with myopia. Extended families consisting of at least two siblings affected with myopia were ascertained. A genome-wide linkage scan using 387 markers was conducted by the Center for Inherited Disease Research. Linkage analyses were conducted with parametric and nonparametric methods. Model-free linkage analysis was performed maximizing over penetrance and over dominance (that is, fitting a wide range of both dominant and recessive models). Under the model-free analysis, the maximum two point heterogeneity logarithm of the odds score (MALOD) was 2.87 at D6S1009 in the White cohort and the maximum multipoint MALOD was 2.42 at D12S373-D12S1042 in the same cohort. The nonparametric linkage (NPL) maximum multipoint at D6S1035 had a P value of .005. An overall multipoint NPL score was obtained by combining NPL scores from both populations. The highest combined NPL score was observed at D20S478 with a significant P value of .008. Suggestive evidence of linkage in the White cohort mapped to a previously mapped locus on chromosome 11 at D11S1981 (NPL = 2.14; P = .02). Suggestive evidence of linkage to myopia in both African Americans and Whites was seen on chromosome 20 and became more significant when the scores were combined for both groups. The locus on chromosome 11 independently confirms a report by Hammond and associates mapping a myopia quantitative trait locus to this region.
    American journal of ophthalmology 12/2008; 147(3):512-517.e2. · 3.83 Impact Factor

Publication Stats

416 Citations
183.98 Total Impact Points

Institutions

  • 2004–2014
    • Johns Hopkins Bloomberg School of Public Health
      • Department of Epidemiology
      Baltimore, Maryland, United States
  • 2013
    • King's College London
      • Department of Twin Research and Genetic Epidemiology
      Londinium, England, United Kingdom
    • Erasmus MC
      Rotterdam, South Holland, Netherlands
  • 2008–2013
    • National Human Genome Research Institute
      Maryland, United States
    • Pennsylvania College of Optometry
      Philadelphia, Pennsylvania, United States
  • 2007
    • University of Pennsylvania
      • Department of Ophthalmology
      Philadelphia, PA, United States
  • 2006
    • National Institutes of Health
      • Branch of Epidemiology (EPI)
      Bethesda, MD, United States
  • 2004–2005
    • Johns Hopkins University
      Baltimore, Maryland, United States
  • 2003
    • Yukon-Kuskokwim Health Corporation
      Bethel, Alaska, United States