Maria Schache

Genome-wide meta-analysis of myopia and hyperopia provides evidence for replication of 11 loci

Refractive error (RE) is a complex, multifactorial disorder characterized by a mismatch between the optical power of the eye and its axial length that causes object images to be focused off the retina. The two major subtypes of RE are myopia (nearsightedness) and hyperopia (farsightedness), which represent opposite ends of the distribution of the quantitative measure of spherical refraction. We performed a fixed effects meta-analysis of genome-wide association results of myopia and hyperopia from 9 studies of European-derived populations: AREDS, KORA, FES, OGP-Talana, MESA, RSI, RSII, RSIII and ERF. One genome-wide significant region was observed for myopia, corresponding to a previously identified myopia locus on 8q12 (p = 1.25×10−8), which has been reported by Kiefer et al. as significantly associated with myopia age at onset and Verhoeven et al. as significantly associated to mean spherical-equivalent (MSE) refractive error. We observed two genome-wide significant associations with hyperopia. These regions overlapped with loci on 15q14 (minimum p value = 9.11×10−11) and 8q12 (minimum p value 1.82×10−11) previously reported for MSE and myopia age at onset. We also used an intermarker linkage- disequilibrium-based method for calculating the effective number of tests in targeted regional replication analyses. We analyzed myopia (which represents the closest phenotype in our data to the one used by Kiefer et al.) and showed replication of 10 additional loci associated with myopia previously reported by Kiefer et al. This is the first replication of these loci using myopia as the trait under analysis. “Replication-level” association was also seen between hyperopia and 12 of Kiefer et al.s published loci. For the loci that show evidence of association to both myopia and hyperopia, the estimated effect of the risk alleles were in opposite directions for the two traits. This suggests that these loci are important contributors to variation of refractive error across the distribution.

Role of the hepatocyte growth factor gene in refractive error.

OBJECTIVE Refractive errors such as myopia and hypermetropia are among the leading causes of visual impairment worldwide. Several genetic loci have been associated with myopia but none to date have been reported for hypermetropia. We investigated the hepatocyte growth factor (HGF) as a candidate gene influencing these 2 refractive error states. DESIGN Case-control study. PARTICIPANTS A total of 551 individuals (193 males, 358 females; mean age, 55.41+/-12.65 years) including 117 individuals with high myopia <or= -6.00 diopters (D), 140 individuals with low/moderate myopia (-2.00 to -5.99 D), 148 emmetropic individuals (-0.50 to +0.75 D) and 146 hyperopic individuals (>+2.00 D) were included in the analysis from 3 different Australian population cohorts (The Genes in Myopia Study, the Blue Mountains Eye Study, and the Melbourne Visual impairment project). METHODS Genotyping of 9 tag single nucleotide polymorphisms (SNPs) that encompassed the entire HGF gene and its associated sequences as well as 6 additional SNPs identified through DNA resequencing was undertaken. MAIN OUTCOME MEASURES Genetic association with refraction. RESULTS After correction for multiple testing, the SNPs rs12536657 (odds ratio [OR], 5.53; 95% confidence interval [CI], 1.14-26.76) and rs5745718 (OR, 2.24; 95% CI, 1.30-3.85) showed significant association with hypermetropia. Whereas the SNPs rs1743 (OR, 2.02; 95% CI, 1.19-3.43; P = .009), rs4732402 (OR, 2.03; 95% CI, 1.23-3.36; P = 0.005), rs12536657 (OR, 2.38; 95% CI, 1.40-4.05; P = 0.001), rs10272030 (OR, 2.22; 95% CI, 1.31-3.75; P = 0.003), and rs9642131 (OR, 2.44; 95% CI, 1.43-4.14; P = 0.001) showed significant association with low/moderate myopia. CONCLUSIONS These findings present the HGF gene as the first gene significantly associated with hypermetropia as well as providing evidence of significant association with myopia in a second ethnic population. In addition, it provides insights into the important biological mechanisms that regulate human ocular development (emmetropization), which are currently poorly understood.

Evaluating the Association Between Keratoconus and the Corneal Thickness Genes in an Independent Australian Population

PURPOSE A recent genome-wide association study (GWAS) identified six loci associated with central corneal thickness that also conferred associated risk of keratoconus (KC). We aimed to assess whether genetic associations existed for these loci with KC or corneal curvature in an independent cohort of European ancestry. METHODS In total, 157 patients with KC were recruited from public and private clinics in Melbourne, Australia, and 673 individuals without KC were identified through the Genes in Myopia study from Australia. The following six single-nucleotide polymorphisms (SNPs) that showed a statistically significant association with KC in a recent GWAS study were selected for genotyping in our cohort: rs4894535 (FNDC3B), rs1324183 (MPDZ-NF1B), rs1536482 (RXRA-COL5A1), rs7044529 (COL5A), rs2721051 (FOXO1), and rs9938149 (BANP-ZNF469). The SNPs were assessed for their association with KC or corneal curvature using logistic or linear regression methods, with age and sex included as covariates. Bonferroni corrections were applied to account for multiple testing. RESULTS Genotyping data were available for five of the SNPs. Statistically significant associations with KC were found for the SNPs rs1324183 (P = 0.001; odds ratio [OR], 1.68) and rs9938149 (P = 0.010; OR, 1.47). Meta-analysis of previous studies yielded genome-wide significant evidence of an association for rs1324183, firmly establishing it as a KC risk variant. None of the SNPs were significantly associated with corneal curvature. CONCLUSIONS The SNPs rs1324183 in the MPDZ-NF1B gene and rs9938149 (between BANP and ZNF4659) were associated with KC in this independent cohort, but their association was via a non-corneal curvature route.

Association of the Hepatocyte Growth Factor Gene with Keratoconus in an Australian Population

Purpose A previous study has indicated suggestive association of the hepatocyte growth factor (HGF) gene with Keratoconus. We wished to assess this association in an independent Caucasian cohort as well as assess its association with corneal curvature. Participants Keratoconus patients were recruited from private and public clinics in Melbourne, Australia. Non-keratoconic individuals were identified from the Genes in Myopia (GEM) study from Australia. A total of 830 individuals were used for the analysis including 157 keratoconic and 673 non keratoconic subjects. Methods Tag single nucleotide polymorphisms (tSNPs) were chosen to encompass the hepatocyte growth factor gene as well as 2 kb upstream of the start codon through to 2 kb downstream of the stop codon. Logistic and linear regression including age and gender as covariates were applied in statistical analysis with subsequent Bonferroni correction. Results Ten tSNPs were genotyped. Following statistical analysis and multiple testing correction, a statistically significant association was found for the tSNP rs2286194 {p = 1.1×10-3 Odds Ratio 0.52, 95% CI - 0.35, 0.77} for keratoconus. No association was found between the 10 tSNPs and corneal curvature. Conclusions These findings provide additional evidence of significant association of the HGF gene with Keratoconus. This association does not appear to act through the corneal curvature route.

Identification of myopia-associated WNT7B polymorphisms provides insights into the mechanism underlying the development of myopia

Myopia can cause severe visual impairment. Here, we report a two-stage genome-wide association study for three myopia-related traits in 9,804 Japanese individuals, which was extended with trans-ethnic replication in 2,674 Chinese and 2,690 Caucasian individuals. We identify WNT7B as a novel susceptibility gene for axial length (rs10453441, Pmeta=3.9 × 10(-13)) and corneal curvature (Pmeta=2.9 × 10(-40)) and confirm the previously reported association between GJD2 and myopia. WNT7B significantly associates with extreme myopia in a case-control study with 1,478 Asian patients and 4,689 controls (odds ratio (OR)meta=1.13, Pmeta=0.011). We also find in a mouse model of myopia downregulation of WNT7B expression in the cornea and upregulation in the retina, suggesting its possible role in the development of myopia.

Genetic association of refractive error and axial length with 15q14 but not 15q25 in the Blue Mountains Eye Study cohort.

PURPOSE Myopia is a common complex condition influenced by genetic and environmental factors. Two recent genome-wide association studies have identified loci on chromosomes 15q25 and 15q14 associated with refractive error in Caucasian populations. Our study aimed to assess the association of these 2 loci with refractive error and ocular biometric measures in an independent ethnically matched Caucasian cohort. DESIGN Genetic association study using unrelated individuals. PARTICIPANTS Blue Mountains Eye Study (BMES) cohort. A total of 1571 individuals were included in this study. METHODS Single nucleotide polymorphism (SNP) genotype data were collected from the BMES cohort as part of the Wellcome Trust Case Control Consortium 2. Imputation was performed using MACH version 1.1.16, and statistical analysis was conducted using PLINK. Association tests were performed at both loci using refractive error (spherical equivalent), axial length, corneal curvature, and anterior chamber depth as the phenotypes. MAIN OUTCOME MEASURES Refractive error, axial length, corneal curvature, and anterior chamber depth. RESULTS A total of 1571 individuals were available from the BMES for analysis. A statistically significant association for refractive error was evident for SNPs at the 15q14 locus, with P values ranging from 1.5 × 10(-2) at rs685352 to 6.4 × 10(-4) at rs560764, whereas association could not be confirmed for SNPs at the 15q25 locus, with P values ranging from 8.0 × 10(-1) to 6.4 × 10(-1). Ocular biometric analysis revealed that axial length was the most likely trait underlying the refractive error association at the 15q14 locus for SNPs rs560766 (P=0.0054), rs634990 (P=0.0086), and rs8032019 (P=0.0081). CONCLUSIONS Our results confirm the association with refractive error at the 15q14 locus but do not support the association observed at the 15q25 locus. Axial length seemed to be a major parameter at the 15q14 locus, underscoring the importance of this locus in myopia and future clinical treatment.

Assessment of the Association of Matrix Metalloproteinases with Myopia, Refractive Error and Ocular Biometric Measures in an Australian Cohort

Extracellular matrix proteins have been implicated in protein remodelling of the sclera in refractive error. The matrix metalloproteinases (MMPs) falling into the collagenase (MMP1, MMP8, MMP13), gelatinase (MMP2, MMP9) and stromelysin (MMP3, MMP10, MMP11) functional groups are particularly important. We wished to assess their association with myopia, refractive error and ocular biometric measures in an Australian cohort. A total of 543 unrelated individuals of Caucasian ethnicity were genotyped including 269 myopes (≤−1.0D) and 274 controls (>−1.0D). Tag single nucleotide polymorphisms (SNPs) (n = 53) were chosen to encompass these eight MMPs. Association tests were performed using linear and logistic regression analysis with age and gender as covariates. Spherical equivalent, myopia, axial length, anterior chamber depth and corneal curvature were the phenotypes of interest. Initial findings indicated that the best p values for each trait were 0.02 for myopia at rs2274755 (MMP9), 0.02 for SE at both rs3740938 (MMP8) and rs131451 (MMP11), 0.01 for axial length at rs11225395 (MMP8), 0.01 for anterior chamber depth at rs498186 (MMP1) and 0.02 at rs10488 (MMP1). However, following correction for multiple testing, none of these SNPs remained statistically significant. Our data suggests that the MMPs in the collagenase, gelatinase and stromelysin categories do not appear to be associated with myopia, refractive error or ocular biometric measures in this cohort.

Recent Patents Relating to Diagnostic Advances in Age Related Macular Degeneration (AMD)

Age Related Macular Degeneration (AMD) is a complex neurodegenerative disorder accounting for 50% of blind registrations in the western world. Its substantial impact on quality of life has been a main driver in research to understand its etiology, which up until recently was mostly unknown. In the last three years our understanding of the molecular pathology of AMD has increased dramatically with the identification of two major AMD loci comprising of, Complement Factor H (CFH) and a chromosome 10q26 locus consisting of the Heat Shock Serine Protease (HTRA1) and LOC387715 genes. These two loci have been described as associated with over 50% of disease in certain ethnicities. The rapid pace in our understanding of the complex biology of this disease has placed a large emphasis on gene patenting, especially with the licensing of the CFH and chromosome 10 patents to a private life science company called Optherion Inc. The patents discussed in this review highlight the important discoveries that have contributed to our understanding of AMD and provide valuable information as to where research in this area will be heading in the future.

Mirror image congenital esotropia and concordant hypermetropia in identical twins.

Purpose To report the occurrence of mirror image congenital esotropia and concordant hypermetropia in a pair of monozygotic twins. Methods A pair of twins was recruited through the Australian Twin Registry. Zygosity was determined by questionnaire, physical appearance, and standard genotyping. Visual acuity was measured using the logMAR chart at 3 m followed by cycloplegic refraction using the Topcon autorefractor. Results Twin 1 developed right eye esotropia at 2 years of age with bilateral hypermetropia (right = +5.75 D, left = +5.75 D). Twin 2 developed left eye esotropia at age 2 years with bilateral hypermetropia (right = +6.75, left = +7.50). Conclusions We describe the first reported case of mirror image congenital esotropia with concordant hypermetropia in monozygotic twins.

The Australian Twin Registry as a resource for genetic studies into ophthalmic traits.

The Australian Twin Registry (ATR) is a not-for-profit organization that coordinates research involving Australian twins and researchers. The ATR is one of the largest volunteer registries of its kind and contains over 33,000 twin pairs. The purpose of this review is to provide a broad overview of recent ophthalmic studies that have utilized the ATR for recruitment purposes. Such studies include the Australian Twin Eye Study (ATES) and the Genes in Myopia (GEM) study. The ATES and GEM studies have undertaken studies into the genetic influences on a number of ophthalmic traits through the use of heritability studies, linkage studies, genome-wide association studies, and candidate gene-based studies. An overview of these studies is provided in this review, as well as a description of the recruitment methodologies for both the ATES and GEM studies.