Genetic association of insulin-like growth factor-1 polymorphisms with high-grade myopia in an international family cohort

Association between weight-adjusted waist index and myopia in adolescents and young adults: results from NHANES 1999-2008

BACKGROUND

Previous studies have indicated a possible link between obesity and myopia, although the results have varied. The objective of this study was to investigate the correlation between a new measure of obesity, the weight-adjusted waist index (WWI), and myopia.

METHOD

This cross-sectional study included individuals between the ages of 12 and 25 who participated in a noncycloplegic vision examination as part of the National Health and Nutrition Examination Survey (NHANES) conducted from 1999 to 2008. WWI was calculated as waist circumference divided by the square root of body weight. Myopia was characterized by a spherical equivalent (SE) of ≤ - 0.5 diopters (D) and further categorized into mild (-3.00D < SE≤-0.50 D), moderate (-6.00D < SE ≤-3.00 D), or high (SE≤-6.00 D). We utilized a weighted multivariable logistic regression and a generalized additive model to evaluate the correlation between WWI and myopia. Threshold effects were analyzed, and we performed subgroup analysis and interaction tests.

RESULTS

A grand total of 11,180 individuals were registered for the study. Decreased myopia severity was observed with higher WWI, as evidenced by elevated SE (β = 0.098, 95% CI: 0.028-0.167). Individuals in the top tertile of WWI experienced a 19.8% decrease in risk compared to those in the lowest group (OR = 0.802, 95% CI: 0.800-0.804; P for trend < 0.001). Similar associations were observed for high myopia. Gender-specific nonlinear associations were found, with different breakpoints for males (10.774) and females (10.025). In males, a significant positive association was found on the right side of the breakpoint (OR = 1.398, 95% CI: 1.038-1.884), while no significant association was found on the left side. Conversely, among females, a negative association was observed on the left side of the breakpoint (OR = 0.679, 95% CI: 0.512-0.899), whereas no notable correlation was detected on the right side.

CONCLUSION

Increased WWI level was linked to a lower risk of myopia and high myopia in the overall sample, with gender-specific variations.

Lipid Metabolism Regulators Are the Possible Determinant for Characteristics of Myopic Human Scleral Stroma Fibroblasts (HSSFs)

The purpose of the current investigation was to elucidate what kinds of responsible mechanisms induce elongation of the sclera in myopic eyes. To do this, two-dimensional (2D) cultures of human scleral stromal fibroblasts (HSSFs) obtained from eyes with two different axial length (AL) groups, <26 mm (low AL group, n = 2) and >27 mm (high AL group, n = 3), were subjected to (1) measurements of Seahorse mitochondrial and glycolytic indices to evaluate biological aspects and (2) analysis by RNA sequencing. Extracellular flux analysis revealed that metabolic indices related to mitochondrial and glycolytic functions were higher in the low AL group than in the high AL group, suggesting that metabolic activities of HSSF cells are different depending the degree of AL. Based upon RNA sequencing of these low and high AL groups, the bioinformatic analyses using gene ontology (GO) enrichment analysis and ingenuity pathway analysis (IPA) of differentially expressed genes (DEGs) identified that sterol regulatory element-binding transcription factor 2 (SREBF2) is both a possible upstream regulator and a causal network regulator. Furthermore, SREBF1, insulin-induced gene 1 (INSIG1), and insulin-like growth factor 1 (IGF1) were detected as upstream regulators, and protein tyrosine phosphatase receptor type O (PTPRO) was detected as a causal network regulator. Since those possible regulators were all pivotally involved in lipid metabolisms including fatty acid (FA), triglyceride (TG) and cholesterol (Chol) biosynthesis, the findings reported here indicate that FA, TG and Chol biosynthesis regulation may be responsible mechanisms inducing AL elongation via HSSF.

Whole-Exome Sequencing Among School-Aged Children With High Myopia

Importance

High myopia (HM) is one of the leading causes of visual impairment worldwide. Genetic factors are known to play an important role in the development of HM.

Objective

To identify risk variants in a large HM cohort and to examine the implications of genetic testing of schoolchildren with HM.

Design, Setting, and Participants

This cohort study retrospectively reviewed whole-exome sequencing (WES) results in 6215 schoolchildren with HM who underwent genetic testing between September 2019 and July 2020 in Wenzhou City, China. HM is defined as a spherical equivalent refraction (SER) of -6.00 diopters (D) or less. The study setting was a genetic testing laboratory and a multicenter school census. Data were analyzed from July 2021 to June 2022.

Main Outcomes and Measures

The frequency and distribution of positive germline variants, the percentage of individuals with HM in both eyes, and subsequent variant yield for common high myopia (CHM; -8.00 D ≤ SER ≤ -6.00 D), ultra myopia (UM; -10.00 D ≤ SER < -8.00 D), and extreme myopia (EM; SER < -10.00 D).

Results

Of the 6215 schoolchildren with HM, 3278 (52.74%) were male. Their mean (SD) age was 14.87 (2.02) years, including 355 students in primary school, 1970 in junior high school, and 3890 in senior high school. The mean (SD) SER was -7.51 (-1.36) D for the right eye and -7.46 (-1.34) D for the left eye. Among schoolchildren with HM, genetic testing yielded 271 potential pathogenic variants in 75 HM candidate genes in 964 diagnoses (15.52%). A total of 36 known variants were found in 490 HM participants (7.88%) and 235 protein-truncating variants (PTVs) in 506 participants (8.14%). Involved variant yield was significantly positively associated with SER (Cochran-Armitage test for trend Z = 2.5492; P = .01), which ranged from 7.66% in the CHM group, 8.70% in the UM group, to 11.90% in the EM group. We also found that primary school students with EM had the highest variant yield of PTVs (8 of 35 students [22.86%]), which was 1.77 and 4.78 times that of the UM and CHM, respectively.

Conclusions and Relevance

In this cohort study of WES for HM, several potential pathogenic variants were identified in a substantial number of schoolchildren with HM. The high variation frequency in younger students with EM can provide clues for genetic screening and clinical examinations of HM to promote long-term follow-up assessment.

Differential methylation of microRNA encoding genes may contribute to high myopia

Introduction: High myopia (HM), an eye disorder with a refractive error ≤-6.0 diopters, has multifactorial etiology with environmental and genetic factors involved. Recent studies confirm the impact of alterations in DNA methylation and microRNAs (miRNAs) on myopia. Here, we studied the combined aspects evaluating to the role of methylation of miRNA encoding genes in HM. Materials and Methods: From the genome-wide DNA methylation data of 18 Polish children with HM and 18 matched controls, we retrieved differentially methylated CG dinucleotides localized in miRNA encoding genes. Putative target genes of the highest-ranked miRNAs were obtained from the miRDB and included in overrepresentation analyses in the ConsensusPathDB. Expression of target genes was assessed using the RNA sequencing data of retinal ARPE-19 cell line. Results: We identified differential methylation of CG dinucleotides in promoter regions of MIR3621, MIR34C, MIR423 (increased methylation level), and MIR1178, MIRLET7A2, MIR885, MIR548I3, MIR6854, MIR675, MIRLET7C, MIR99A (decreased methylation level) genes. Several targets of these miRNAs, e.g. GNAS, TRAM1, CTNNB1, EIF4B, TENM3 and RUNX were previously associated with myopia/HM/refractive error in Europeans in genome-wide association studies. Overrepresentation analyses of miRNAs' targets revealed enrichment in pathways/processes related to eye structure/function, such as axon guidance, transcription, focal adhesion, and signaling pathways of TGF-β, insulin, MAPK and EGF-EGFR. Conclusion: Differential methylation of indicated miRNA encoding genes might influence their expression and contribute to HM pathogenesis via disrupted regulation of transcription of miRNAs' target genes. Methylation of genes encoding miRNAs may be a new direction in research on both the mechanisms determining HM and non-invasive indicators in diagnostics.

Association of IGF1 polymorphisms with exotropia in a Pakistani cohort

PURPOSE

Strabismus (STBMS) is a multifactorial ocular disorder in children that leads to misalignment of the eyes. Insulin-like growth factor 1 (IGF1) has been shown to be involved in the development of extraocular muscles and myopia; however, data are limited on the genetic associations of IGF1 with STBMS in Pakistan.

METHODS

Two hundred seventy-four STBMS cases and 272 unaffected controls were recruited, and their DNA was extracted. Two IGF1 single nucleotide polymorphisms, rs6214 and rs5742632, were genotyped using PCR-restriction fragment length polymorphism. Univariate logistic regression analysis was performed to determine the association of these single nucleotide polymorphisms with STBMS, and the results were adjusted for age and sex. In addition, 26 extraocular muscle tissues were collected from patients with STBMS undergoing squint correction surgery, along with 3 deceased control samples. IGF1 mRNA expression was measured by quantitative PCR; the Mann-Whitney U test was applied, and fold change was calculated. Logistic regression analysis was applied to determine the association of RNA expression and fold change with genotype.

RESULTS

Multivariate logistic regression analysis revealed that rs5742632 (odds ratio [95% confidence interval] = 1.05[1.01-1.06], p = 0.03) is associated with STBM. Moreover, rs6214 (1.03[1.01-1.05], p = 0.03) and rs5742632 (1.09[1.04-1.11], p = 0.04) were associated with exotropia. Statistically, no significant difference in IGF1 mRNA expression in the extraocular muscles between the STBMS cases and the controls was observed.

CONCLUSIONS

IGF1 polymorphisms rs5742632 (A>G) and rs6214 (C>T) are plausible risk factors for the development of exotropia. However, the physiologic mechanism requires further evaluation.

Myopia and BMI: a nationwide study of 1.3 million adolescents

OBJECTIVE

This study analyzed the association between adolescent BMI and myopia severity.

METHODS

This cross-sectional study comprised 1,359,153 adolescents who were medically examined before mandatory military service. Mild-to-moderate and high myopia were defined based on right-eye refractive data. BMI was categorized based on the US age- and sex-matched percentiles. Logistic regression models were applied separately for women and men to estimate odds ratios (ORs) for myopia per BMI category.

RESULTS

A total of 318,712 adolescents had mild-to-moderate myopia and 23,569 had high myopia. Compared with low-normal BMI (reference group), adjusted ORs for mild-to-moderate and high myopia increased with increasing BMI status, reaching 1.39 (95% CI: 1.23-1.57) and 1.73 (95% CI: 1.19-2.51) for men with severe obesity, respectively, and 1.19 (95% CI: 1.12-1.27) and 1.38 (95% CI: 1.14-1.65) for women with mild obesity, respectively. ORs for mild-to-moderate and high myopia were also higher in men with underweight (OR = 1.20; 95% CI: 1.18-1.23 and OR = 1.39; 95% CI: 1.30-1.47) and women with underweight (OR = 1.06; 95% CI: 1.03-1.09 and OR = 1.12; 95% CI: 1.04-1.22). The overall size effect was greater for men than women (p_interaction  < 0.001), in whom the group with severe obesity did not reach statistical significance.

CONCLUSIONS

BMI was associated with myopia in a J-shaped pattern, with the size effect being greater for adolescent men than women. This study indicates that both low BMI and high BMI are associated with mild-to-moderate and severe myopia.

The G allele of the IGF1 rs2162679 SNP is a potential protective factor for any myopia: Updated systematic review and meta-analysis

Background

The insulin-like growth factor 1 (IGF1) gene is located within the myopia-associated MYP3 interval, which suggests it may play an important role in the progression of myopia. However, the association between IGF1 SNPs and any myopia is rarely reported.

Methods

A comprehensive literature search was conducted on studies published up to July 22, 2021 in PubMed, EMBASE, CBM, COCHRANE, CNKI, WANFANG and VIP databases. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated for single-nucleotide polymorphisms (SNPs) that have been evaluated in at least three studies.

Results

Nine studies involving 4596 subjects with any myopia and 4950 controls examined 25 SNPs in IGF1 gene, among which seven SNPs were included in this meta-analysis. Significant associations were not found in any genetic models between rs6214, rs12423791, rs5742632, rs10860862, rs5742629 and any myopia. Rs2162679 was suggestively associated with any myopia in the codominant model (GA vs. AA: OR = 0.87, 95% CI: 0.76–1.00) and the dominant model (GG+GA vs. AA: OR = 0.88, 95% CI = 0.78–1.00).

Conclusion

Meta-analysis of updated data reveals that the G allele of the IGF1 rs2162679 SNP is a potential protective factor for any myopia, which is worth further researches.

Metabolic characterization of human intraocular fluid in patients with pathological myopia

Pathological myopia (PM) and its associated complications can lead to permanent vision loss. However, the cellular mechanisms underlying PM development remain unclear. To identify the metabolic alterations that may contribute to the pathophysiology of PM, we performed non-targeted metabolomics analysis using ultra-high-performance liquid chromatography with tandem mass spectrometry in age- and sex-matched patients with PM (n = 30) and individuals without myopia as controls (n = 30). Targeted metabolomics and insulin microarray were used to validate the results. We identified 508 metabolites in the aqueous humour (AH) and 601 in the vitreous humour (VH). Statistical evaluation revealed that 104 metabolites in AH and 114 metabolites in VH were significantly different between the two groups (variable important for the projection >1, fold change >1.5, or < 0.667, and P < 0.05). The four metabolic pathways enriched in both AH and VH identified to be associated with PM were: bile secretion, insulin secretion, thyroid hormone synthesis, and cGMP-PKG signaling pathway. The concentration of 10 amino acids was significantly higher in the PM than in the controls. Insulin microarray analysis showed that insulin, insulin-like growth factor 2 (IGF-2), IGF-2R, insulin-like growth factor binding protein 1 (IGFBP-1), IGFBP-2, IGFBP-3, IGFBP-4, and IGFBP-6 levels were significantly higher in PM patients compared to that in the controls. Thus, this study identified potential metabolite biomarkers for PM and provided novel insights into the mechanisms underlying this disorder.

Sex Disparity in Myopia Explained by Puberty Among Chinese Adolescents From 1995 to 2014: A Nationwide Cross-Sectional Study

Importance

Girls in East Asia have a higher myopia prevalence than boys. Less research has been done on whether girls' earlier puberty could explain this sex difference.

Objective

The purpose of this study was to evaluate the association between myopia and puberty and the role of puberty in explaining the sex disparity in adolescent myopia prevalence.

Design, Setting, and Participants

In this nationwide cross-sectional study, data came from five consecutive national surveys from 1995 to 2014 in China. We included 338,896 boys aged 11–18 and 439,481 girls aged 9–18.

Main Outcomes and Measures

Myopia was defined according to unaided distance visual acuity and subjective refraction; puberty status was defined dichotomously as menarche or spermarche status. The association between myopia and puberty was evaluated by robust Poisson GEE regression. Mediation analyses were used to quantify how much of the sex disparity in myopia could be explained by puberty.

Results

Post-menarche girls and post-spermarche boys showed 29–41% and 8–19% higher risk of myopia than pre-menarche girls and pre-spermarche boys, respectively. The association remained significant in girls [prevalence ratio (PR) = 1.07, 95%CI:1.04–1.10] but disappeared in boys (p > 0.05) after adjusting for potential confounders. Girls had a 12–23% higher risk of myopia than boys. A total of 16.7% of the sex disparity in myopia could be explained by girls' earlier puberty, whereas 11.1% could be explained by behavioral factors.

Conclusion and Relevance

Puberty status is independently associated with myopia in girls but not in boys. A significant proportion of the sex disparity in adolescent myopia could be explained by girls' earlier puberty, suggesting the need to consider sex-differentiated strategies for myopia prevention and treatment.

Genetic susceptibility to high myopia in Han Chinese population

High myopia is a common ocular genetic disease in the world. The study sought to investigate the effect of the Insulin-like growth factor-1 (IGF-1) and Matrix metalloproteinase-9 (MMP-9) genes polymorphisms on high myopia in a Han population of China. This study recruited 216 unrelated Han Chinese subjects, including 103 cases with high myopia and 113 controls. Four tagging single nucleotide polymorphisms (SNPs) of IGF-1 and MMP-9 genes were genotyped using the Sequenom MassARRAY method. The chi-square test showed that the family history was significantly correlated with myopia. The SNP genotypes were all in Hardy–Weinberg equilibrium (P > 0.05). Among the four SNPs, there were statistically significant differences in the genotype and allele frequencies of rs2236416 between the groups (P = 0.024). The significant associations of rs2236416 between cases and controls also appeared after Bonferroni multiple correction (P = 0.024). Then, there were significant differences in the genotypes dominant model and codominant model of rs2236416 between groups (P = 0.007 and P = 0.004, respectively). rs5742632 showed a significant difference between the cases and the controls in the recessive model (P = 0.037). Our findings indicated that rs2236416 of MMP-9 was associated with myopia in the population. The result suggested MMP-9 gene locus may play a role in myopia.

Myopia Genetics and Heredity

Myopia is the most common eye condition leading to visual impairment and is greatly influenced by genetics. Over the last two decades, more than 400 associated gene loci have been mapped for myopia and refractive errors via family linkage analyses, candidate gene studies, genome-wide association studies (GWAS), and next-generation sequencing (NGS). Lifestyle factors, such as excessive near work and short outdoor time, are the primary external factors affecting myopia onset and progression. Notably, besides becoming a global health issue, myopia is more prevalent and severe among East Asians than among Caucasians, especially individuals of Chinese, Japanese, and Korean ancestry. Myopia, especially high myopia, can be serious in consequences. The etiology of high myopia is complex. Prediction for progression of myopia to high myopia can help with prevention and early interventions. Prediction models are thus warranted for risk stratification. There have been vigorous investigations on molecular genetics and lifestyle factors to establish polygenic risk estimations for myopia. However, genes causing myopia have to be identified in order to shed light on pathogenesis and pathway mechanisms. This report aims to examine current evidence regarding (1) the genetic architecture of myopia; (2) currently associated myopia loci identified from the OMIM database, genetic association studies, and NGS studies; (3) gene-environment interactions; and (4) the prediction of myopia via polygenic risk scores (PRSs). The report also discusses various perspectives on myopia genetics and heredity.

Myopia and Early-Onset Type 2 Diabetes: A Nationwide Cohort Study

CONTEXT

A correlation between myopia and insulin resistance has been suggested.

OBJECTIVE

We investigated the association between myopia in adolescence and type 2 diabetes (T2D) incidence in young adulthood.

METHODS

This population-based, retrospective, cohort study comprised 1 329 705 adolescents (579 543 women, 43.6%) aged 16 to 19 years, who were medically examined before mandatory military service during 1993 to 2012, and whose data were linked to the Israel National Diabetes Registry. Myopia was defined based on right-eye refractive data. Cox proportional models were applied, separately for women and men, to estimate hazard ratios (HRs) for T2D incidence per person-years of follow-up.

RESULTS

There was an interaction between myopia and sex with T2D (P < .001). For women, T2D incidence rates (per 100 000 person-years) were 16.6, 19.2, and 25.1 for those without myopia, and with mild-to-moderate and high myopia, respectively. These corresponded to HRs of 1.29 (95% CI, 1.14-1.45) and 1.63 (1.21-2.18) for women with mild-to-moderate and high myopia, respectively, compared to those without myopia, after adjustment for age at study entry, birth year, adolescent body mass index, cognitive performance, socioeconomic status, and immigration status. Results persisted in extensive sensitivity and subgroup analyses. When managed as a continuous variable, every 1-diopter lower spherical equivalent yielded a 6.5% higher adjusted HR for T2D incidence (P = .003). There was no significant association among men.

CONCLUSION

For women, myopia in adolescence was associated with a significantly increased risk for incident T2D in young adulthood, in a severity-dependent manner. This finding may support the role of insulin resistance in myopia pathogenesis.

Digital Therapeutics: Exploring the Possibilities of Digital Intervention for Myopia

Pediatric myopia is increasing globally and has become a major public health issue. However, the mechanism of pediatric myopia is still poorly understood, and there is no effective treatment to prevent its progression. Based on results from animal and clinical studies, certain neuronal–humoral factors (NHFs), such as IGF-1, dopamine, and cortisol may be involved in the progression of pediatric myopia. Digital therapeutics uses evidence-based software as therapeutic interventions and it has the potential to offer innovative treatment strategies for pediatric myopia beyond conventional treatment methods. In this perspective article, we introduce digital therapeutics SAT-001, a software algorithm that modulates the level of NHFs to reduce the progression of pediatric myopia. The proposed mechanism is based on a theoretical hypothesis derived from scientific research and clinical studies and will be further confirmed by evidence generated from clinical studies involving pediatric myopia.

Variants in FLRT3 and SLC35E2B identified using exome sequencing in seven high myopia families from Central Europe

PURPOSE

High myopia (HM) is an eye disorder with both environmental and genetic factors involved. Many genetic factors responsible for HM were recognized worldwide, but little is known about genetic variants underlying HM in Central Europe. Thus, the aim of this study was to identify rare sequence variants involved in HM in families from Central Europe to better understand the genetic basis of HM.

MATERIALS AND METHODS

We assessed 17 individuals from 7 unrelated Central European families with hereditary HM using exome sequencing (ES). Segregation of selected variants in other available family members was performed using Sanger sequencing.

RESULTS

Detected 73 rare variants were selected for verification. We observed 2 missense variants, c.938C>T in SLC35E2B - encoding solute carrier family 35 member E2B, and c.1642G>C in FLRT3 - encoding fibronectin leucine rich transmembrane protein, segregating with HM in one family.

CONCLUSIONS

FLRT3 ​and/or ​SLC35E2B ​could represent disease candidate genes and identified sequence variants might be responsible for HM in the studied family.

The association between menarche and myopia and its interaction with related risk behaviors among Chinese school-aged girls: a nationwide cross-sectional study

Nearly 80% of new cases of myopia arise between 9 and 13 years old when puberty development also progresses rapidly. However, little is known about the association between myopia and puberty. We aim to evaluate the association between myopia and menarche, the most important puberty indicator for girls, and to test whether menarche could modify the effects of myopia-related behaviors. The participants came from two consecutive national surveys conducted in 30 provinces in mainland China in 2010 and 2014. We included 102,883 girls (61% had experienced menarche) aged 10-15 years. Risk behaviors for myopia which included sleep duration, homework time, and outdoor activity were measured by self-administrated questionnaire. Myopia was defined according to a validated method, and its relationships with menarche status and behaviors were evaluated by robust Poisson regression models based on generalized estimated equation adjusting for cluster effect of school. We found that postmenarche girls were at 13% (95% confidence interval: 11%-16%) higher risk of myopia than premenarche girls, after adjusting for exact age, urban-rural location, survey year, and four behavioral covariates. Short sleep duration (<7 h/d), long homework time (>1 h/d) and low frequency of weekend outdoor activity tended to be stronger (with higher prevalence ratios associated with myopia) risk factors for myopia in postmenarche girls than in premenarche girls, and their interaction with menarche status was all statistically significant (P < 0.05). Overall, our study suggests that menarche onset may be associated with increased risk of myopia among school-aged girls and could also enhance girls' sensitivity to myopia-related risk behaviors.

DNA methylation and mRNA expression of IGF-1 and MMP-2 after form-deprivation myopia in guinea pigs

PURPOSE

The molecular mechanism of form-deprivation myopia is unclear. This study was aimed to investigate the roles of scleral DNA methylation and mRNA expression of IGF-1 and MMP-2 in a guinea pig model of form-deprivation myopia.

METHODS

Seventy 2-week-old male guinea pigs were assigned to three groups: (1) zero week group that was used to collect baseline data; (2) monocular deprivation treatment (MDT) group, in which a thin slice of opaque latex glove was placed over the right eyes of the animals for four weeks, and the left eyes were untreated and served as the monocular contralateral control (MCC) group; (3) control group (CG), in which the animals grew four weeks, but received no manipulation. Animals in each group were evenly divided for DNA methylation assay and quantitative PCR (qPCR). After eye enucleation, the sclerae were harvested for DNA methylation assay and qPCR. The DNA methylation pattern in the promoter and exon regions of IGF-1 and MMP-2, along with the mRNA expression level of them, were determined by base-specific cleavage and mass spectrometry and qPCR, respectively.

RESULTS

After four weeks of form-deprivation, DNA methylation at 4/8 cytosine-guanine sites in the IGF-1 promoter was significantly lower in the MDT eyes than in the MCC or CG eyes. In addition, the level of IGF-1 mRNA was moderately higher in MDT eyes compared to the MCC eyes and CG eyes. DNA methylation at 4/14 cytosine-guanine sites in the MMP-2 gene was very low, and no significant change was observed between the MDT eyes and the MCC or CG ones. However, the level of MMP-2 mRNA in MDT eyes was significant higher compared with MCC eyes and CG eyes, with an increase of 217% and 222%, respectively.

CONCLUSIONS

In our guinea pig model of form-deprivation myopia, the methylation of four cytosine-guanine sites in the IGF-1 gene promoter was significantly lower in the sclera after four weeks of MDT, and the transcription level of scleral IGF-1 was moderately higher. Hence, the IGF-1 gene methylation might play a role in the pathogenesis of form-deprivation myopia in guinea pigs. The level of MMP-2 mRNA in the sclera of MDT eyes was significantly higher, but not regulated by the methylation pathway, as the methylation status of MMP-2 was unchanged.

Association of IGF1 single-nucleotide polymorphisms with myopia in Chinese children

Purpose

To investigate the association between insulin-like growth factor 1 (IGF1) single-nucleotide polymorphisms (SNPs) and myopia in a young Chinese population.

Methods

A total of 654 Chinese children aged 6–13 years from one primary school participated in our study and underwent a series of comprehensive ocular examinations, including cycloplegic refraction and measurements of axial length. Myopia was defined as a spherical equivalence (SE) ≤ −0.5 D in the worse eye. In total, six tagging SNPs of IGF1 were genotyped using the PCR-LDR (Polymerase Chain Reaction-Ligation Detection Reaction) method. We tested four different genetic modes (the allele, dominant, recessive, and additive models) of these SNPs and used multivariate logistic regression to calculate the effect of SNPs on myopia. In addition, we conducted a haplotype analysis with a variable-sized slide-window strategy.

Results

Overall, 281 myopic children and 373 non-myopic controls were included in the analysis. The SNP rs2162679 showed a statistical difference between the two groups in both the allele (p = 0.0474) and additive (p = 0.0497) models. After adjusting for age and gender, children with the genotype AA in the SNP rs2162679 had a higher risk of myopia than those with the genotype GG (OR = 2.219, 95% CI [1.218–4.039], p = 0.009). All haplotypes that varied significantly between the two groups contained the SNP rs2162679, and the four-SNP window rs5742653–rs2162679 had the lowest p value (Chi square = 5.768, p = 0.0163). However, after permutation tests, none of the associations remained statistically significant.

Conclusion

The SNP rs2162679 in IGF1 was associated with myopia in a young Chinese population. The G allele in the SNP rs2162679 may protect against myopia.

IMI - Myopia Genetics Report

The knowledge on the genetic background of refractive error and myopia has expanded dramatically in the past few years. This white paper aims to provide a concise summary of current genetic findings and defines the direction where development is needed. We performed an extensive literature search and conducted informal discussions with key stakeholders. Specific topics reviewed included common refractive error, any and high myopia, and myopia related to syndromes. To date, almost 200 genetic loci have been identified for refractive error and myopia, and risk variants mostly carry low risk but are highly prevalent in the general population. Several genes for secondary syndromic myopia overlap with those for common myopia. Polygenic risk scores show overrepresentation of high myopia in the higher deciles of risk. Annotated genes have a wide variety of functions, and all retinal layers appear to be sites of expression. The current genetic findings offer a world of new molecules involved in myopiagenesis. As the missing heritability is still large, further genetic advances are needed. This Committee recommends expanding large-scale, in-depth genetic studies using complementary big data analytics, consideration of gene-environment effects by thorough measurement of environmental exposures, and focus on subgroups with extreme phenotypes and high familial occurrence. Functional characterization of associated variants is simultaneously needed to bridge the knowledge gap between sequence variance and consequence for eye growth.

HOXA9 is a novel myopia risk gene

Purpose

A recent meta-analysis revealed PAX6 as a risk gene for myopia. There is a link between PAX6 and HOXA9. Furthermore, HOXA9 has been reported to activate TGF-β that is a risk factor for myopia. We speculate HOXA9 may participate in myopia development.

Methods

The Singapore GUSTO birth cohort provides data on children’s cycloplegic refraction measured at age of 3 years and their methylation profile based on the umbilical cord DNA. The HOXA9 expression levels were measured in the eyes of mono-ocular form deprivation myopia in mice. The plasmid with the mouse HOXA9 cDNA was constructed and then transfected to mouse primary retinal pigment epithelial (RPE) cells. The expression levels of myopia-related genes and cell proliferation were measured in the HOXA9-overexpressed RPE cells.

Results

A total of 519 children had data on methylation profile and cycloplegic refraction. The mean spherical equivalent refraction (SE) was 0.90D. Among 8 SE outliers (worse than -2D), 7 children had HOXA9 hypomethylation. The HOXA9 levels in the retina of myopic eyes was 2.65-fold (p = 0.029; paired t-test) higher than the uncovered fellow eyes. When HOXA9 was over-expressed in the RPE cells, TGF-β, MMP2, FGF2 and IGF1R expression levels were dose-dependently increased by HOXA9. However, over-expression of HOXA9 had no significant influence on IGF1 or HGF expression. In addition, HOXA9 also increased RPE proliferation.

Conclusion

Based on the human, animal and cellular data, the transcription factor HOXA9 may promote the expression of pro-myopia genes and RPE proliferation, which eventually contribute to myopia development.

Genes and genetics in eye diseases: a genomic medicine approach for investigating hereditary and inflammatory ocular disorders

Past 25y have witnessed an exponential increase in knowledge and understanding of ocular diseases and their respective genetic underpinnings. As a result, scientists have mapped many genes and their variants that can influence vision and health of our eyes. Based on these findings, it is becoming clear that an early diagnosis employing genetic testing can help evaluate patients' conditions for instituting treatment plan(s) and follow-up care to avoid vision complications later. For example, knowing family history becomes crucial for inherited eye diseases as it can benefit members in family who may have similar eye diseases or predispositions. Therefore, gathering information from an elaborate examination along with complete assessment of past medical illness by ophthalmologists followed by consultation with geneticists can help create a roadmap for making diagnosis and treatment precise and beneficial. In this review, we present an update on ocular genomic medicine that we believe has tremendous potential towards unraveling genetic implications in ocular diseases and patients' susceptibilities. We also discuss translational aspects of genetic ophthalmology and genome engineering that may help advance molecular diagnostics and therapeutics.

Insight into the molecular genetics of myopia

Myopia is the most common cause of visual impairment worldwide. Genetic and environmental factors contribute to the development of myopia. Studies on the molecular genetics of myopia are well established and have implicated the important role of genetic factors. With linkage analysis, association studies, sequencing analysis, and experimental myopia studies, many of the loci and genes associated with myopia have been identified. Thus far, there has been no systemic review of the loci and genes related to non-syndromic and syndromic myopia based on the different approaches. Such a systemic review of the molecular genetics of myopia will provide clues to identify additional plausible genes for myopia and help us to understand the molecular mechanisms underlying myopia. This paper reviews recent genetic studies on myopia, summarizes all possible reported genes and loci related to myopia, and suggests implications for future studies on the molecular genetics of myopia.

Association of IGF1 polymorphism rs6214 with high myopia: A systematic review and meta-analysis

PURPOSE

To conduct a comprehensive evaluation of the association of Insulin-like growth factor 1 (IGF1) polymorphism rs6214 with high myopia through a systematic review and meta-analysis of candidate genetic association study.

METHODS

All case-control association studies on IGF1 and high myopia reported up to 15 June 2016 in PubMed, Embase, Web of Science, and the Chinese Biomedical Database were retrieved. Odds ratios (ORs) and 95% confidence intervals (95% CIs) were calculated for single-nucleotide polymorphism (SNP) using fixed and random effects models according to between study heterogeneity. Publication bias analyses were conducted using Begg's test.

RESULTS

A total of eight studies from published articles were included in our analysis. The meta-analyses for IGF1 rs6214, composed of 4242 high myopia patients and 4430 controls, showed low heterogeneity for the included populations in all the genetic models, except that of the allelic genetic model in the pooled populations. The analyses of all the genetic models in Chinese, Japanese, and overall pooled populations did not identify any significant association between high myopia and IGF1 rs6214.

CONCLUSIONS

This meta-analysis showed there was no association detected between IGF1 rs6214 and high myopia. Given the limited sample size, further investigations including more ethnic groups are required to validate the association.

Association of Insulin-Like Growth Factor-1 Gene Polymorphisms with Different Types of Myopia in Egyptian Patients

AIMS

To investigate the effect of the insulin-like growth factor-1 (IGF-1) gene's rs6214 and rs5742632 polymorphisms on IGF-1 expression levels and their association with different types of myopia in Egyptian patients.

METHODS

A case-control format was used that included 272 patients with myopia and 136 controls. The IGF-1 gene rs6214 and rs5742632 polymorphisms were genotyped using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analyses. IGF-1 levels were measured by an enzyme-linked immunosorbent assay.

RESULTS

In patients with high-grade myopia, the frequencies of the IGF-1 rs6214 GA and AA genotypes, and the A allele were significantly increased compared to the control group: 41.9% vs. 33.8%, 17.7% vs. 8.9%, and 38.9% vs. 25.7%, respectively. Subjects with the GA and AA genotypes and carriers of A allele were significantly more likely to have high-grade myopia: odds ratios (OR) = 1.75, 95% confidence interval (CI) = 1.03-2.9, and p = 0.03; OR = 2.8, 95% CI = 1.3-6.0, and p = 0.003; and OR = 1.8, 95% CI = 1.25-2.61, and p = 0.001, respectively. A nonsignificant association of the IGF-1 gene rs5742632 polymorphism with the two myopia groups was also observed. The IGF-1 levels were significantly increased in patients with high-grade myopia and simple myopia compared to the control group (p < 0.05). In addition, our results showed a nonsignificant association of the IGF-1 (rs6214-rs5742632) haplotype with either simple myopia or high-grade myopia.

CONCLUSIONS

We found a significant association of the IGF-1 gene rs6214 polymorphism in Egyptian patients with simple myopia and high-grade myopia. IGF-1 levels were significantly increased in relation to the IGF-1 rs6214 genotypes, while a nonsignificant association was found between IGF-1 level and the IGF-1 (rs5742632) genotypes.

Association of IGF1 and IGF1R gene polymorphisms with high myopia in a Han Chinese population

OBJECTIVES

Insulin-like growth factor 1 (IGF1) and insulin-like growth factor 1 receptor (IGF1R) have been shown to influence the development of form-deprivation myopia. However, genetic association between these two genes and high myopia remains inconsistent in different studies. This study was conducted to investigate the association between IGF1and IGF1R and high myopia in a Han Chinese population.

METHODS

Fourteen single nucleotide polymorphisms (SNPs) in the IGF1 and IGF1R genes were genotyped by SNaPshot method in a Han Chinese subject group composed of 1244 high myopia patients and 1380 controls. The genotyping data was analyzed by χ² test and the linkage disequilibrium block structure was examined by Haploview software.

RESULTS

There were no statistically significant differences in the allele frequencies of IGF1 and IGF1R SNPs and genotypes between patients and controls after Bonferroni multiple-correction (p > 0.05). However, the G allele of rs35766 in the IGF1 gene showed a protective effect for high myopia (p = 0.015, corrected p = 0.21, odds ratio [OR] = 0.77, 95% CI = 0.70-0.97). The carriers of rs35766GG and rs35766GG+AG genotypes displayed a decreased risk of high myopia compared with rs35766AA carriers (p = 0.012, OR = 0.65, 95% CI = 0.47-0.91; p = 0.019, OR = 0.68, 95% CI = 0.50-0.94, respectively).

CONCLUSIONS

Genetic variants in the IGF1 and IGF1R genes might not be associated with high myopia in Han Chinese. Further studies are needed to verify the possible function of IGF1 and IGF1R in the development of myopia.

Association between Insulin-Like Growth Factor 1 Gene rs12423791 or rs6214 Polymorphisms and High Myopia: A Meta-Analysis

Objective

To evaluate the association of insulin-like growth factor 1 gene rs12423791 and rs6214 polymorphisms with high myopia.

Methods

An electronic search was conducted on PubMed, Embase, the Cochrane Library and the Chinese Biological Abstract Database for articles published prior to May 6, 2014. A meta-analysis was performed using Revman 5.1 and Stata 12.0, and the odds ratios with 95% confidence intervals were calculated in fixed or random effects models based on the results of the Q test. The subgroup analysis was conducted on the basis of the various regions, the sensitivity analysis was also performed to evaluate the stability of the results, and the publication bias was evaluated by a funnel plot and Egger’s linear regression analysis.

Results

This comprehensive meta-analysis included 2808 high myopia patients and 2778 controls from five unrelated studies. The results demonstrated that the significant association was not present in any genetic models between IGF-1 rs12423791 or rs6214 and high myopia. However, subgroup analysis indicated that rs12423791 polymorphism was associated with high myopia in the Chinese populations in the allelic contrast model (C vs. G: OR=1.24, 95% CI=1.04-1.48 in the fixed-effects model), the dominant model (CC+CG vs. GG: OR=1.40, 95% CI=1.16-1.69 in the fixed-effects model), and the codominant model (CG vs. GG: OR=1.37, 95% CI= 1.12-1.68 in the fixed-effects model). Additionally, none of the individual studies significantly affected the association between IGF-1 rs12423791 and high myopia, according to sensitivity analysis.

Conclusion

This meta-analysis shows that IGF-1 rs12423791 or rs6214 gene polymorphism is not associated with high myopia.

Genetic association study between INSULIN pathway related genes and high myopia in a Han Chinese population

To investigate the association between insulin (INS) pathway related genes, including INS, insulin receptor (INSR), insulin receptor substrate 1 (IRS1), insulin-like growth factor 2 (IGF2), IGF2 receptor (IGF2R) and IGF binding protein 1 (IGFBP1), and high myopia (HM) in a Han Chinese population, we have genotyped 24 single nucleotide polymorphisms (SNPs) of these genes in this cohort by Sequenom MassARRAY method. The genotyping data was analyzed by χ(2) test and the linkage disequilibrium block structure was examined by Haploview software. SNPs in the INS-IGF2 region (rs2070762 and rs1003483), and the INSR gene (rs3745551 and rs2229429) showed significant association with HM (allelic P = 0.0085, 0.0494, 0.0171 and 0.0238, respectively). Under the model of risk genotype combination of INSR and IRS1, carrying the variant allele (A) of the IRS1 Gly972Arg SNP (rs1801278) further increased the risk among the rs2229429T allele carriers (odds ratio 6.865, 95 % confidence interval 1.533-30.745). None of the SNPs in the IGF2R and IGFBP1 genes were found to be significantly associated with HM. Genetic variants in the insulin signaling pathway genes may increase the susceptibility of high myopia in Han Chinese.

Association study of IGF1 polymorphisms with susceptibility to high myopia in a Japanese population

PURPOSE

Polymorphisms in the insulin-like growth factor 1 (IGF1) gene were previously associated with high or extreme myopia in Caucasian and Chinese populations. In the present study, we investigated whether IGF1 polymorphisms are associated with high myopia in a Japanese population.

METHODS

A total of 446 Japanese patients with high myopia (≤-9.00 diopters) and 481 Japanese healthy controls (+1.50 diopters to -1.50 diopters) were recruited. We genotyped seven tagging single-nucleotide polymorphisms (SNPs) in IGF1 and assessed allelic and haplotypic diversity in cases and controls.

RESULTS

There were no statistically significant differences in the allele frequencies of IGF1 SNPs and genotypes between cases and controls (P>0.05). However, the A allele of rs5742629 and the G allele of rs12423791 were associated with a moderately increased risk of high myopia (odds ratio [OR] =1.20 and OR =1.21, respectively) with borderline statistical significance (P=0.0502, corrected P (Pc) =0.21 and P=0.064, Pc=0.29, respectively). The haplotype consisting of the A allele of rs5742629 and the G allele of rs12423791 was marginally associated with the risk of high myopia (P=0.041; OR =1.21); this association was not significant after correction (Pc=0.19).

CONCLUSION

We found that the IGF1 SNPs are not significantly associated with high myopia in our Japanese population. Our results are in contrast to a previous study in which extreme myopia cases had significantly higher frequencies of the G allele of rs5742629 and the C allele of rs12423791 than controls. Therefore, the IGF1 SNPs may not be important factors for susceptibility to high myopia in all populations. Further genetic studies are needed to elucidate the possible contributions of the IGF1 region to the development of high myopia.

Genetic susceptibility and mechanisms for refractive error

Refractive errors, myopia and hyperopia, are the most common causes of visual impairment worldwide. Recent advances in genetics have been utilized to identify a wealth of genetic loci believed to contain susceptibility genes for refractive error (RE). The current genetic evidence confirms that RE is influenced by both common and rare variants with a significant environmental component. These studies argue that only by combining genetic and environmental knowledge with in vivo measurements of biological states will it be possible to understand the underlying biology of RE that will lead to novel therapeutic targets and accurate genetic predictions.

Insulin-like growth factor 1 is not associated with high myopia in a large Japanese cohort

PURPOSE

To investigate whether genetic variations in the insulin-like growth factor 1 (IGF-1) gene are associated with high myopia in Japanese.

METHODS

A total of 1,339 unrelated Japanese patients with high myopia (axial length ≥26 mm in both eyes) and two independent control groups were evaluated (334 cataract patients without high myopia and 1,194 healthy Japanese individuals). The mean axial length (mm±SD) in the case group was 29.18±1.85 mm, and the mean spherical equivalent (D±SD) of the phakic eyes was -12.69±4.54 D. We genotyped five tagging single nucleotide polymorphisms (SNPs) in IGF-1: rs6214, rs978458, rs5742632, rs12423791, and rs2162679. Chi-square tests for trend, multivariable logistic regression, and haplotype regression analysis were conducted.

RESULTS

We found no significant association between the IGF-1 SNPs and high or extreme myopia (axial length ≥28 mm in both eyes, 837 subjects) in the additive model, even when compared with the cataract and general population controls, with or without adjustments for age and sex. The evaluation using dominant and recessive models also did not reveal any significant associations. The haplotype analysis with a variable-sized sliding-window strategy also showed a lack of association of IGF-1 SNPs with high or extreme myopia.

CONCLUSIONS

The results of the present study using a Japanese subset do not support the proposal that the IGF-1 gene determines susceptibility to high or extreme myopia in Caucasians and Chinese. Further studies are needed to confirm our reports in other populations and to identify the underlying genetic determinants of these ocular pathological conditions.

The combination of IGF1 and FGF2 and the induction of excessive ocular growth and extreme myopia

Different growth factors have been shown to influence the development of form-deprivation myopia and lens-induced ametropias. However, growth factors have relatively little effect on the growth of eyes with unrestricted vision. We investigate whether the combination of insulin-like growth factor 1 (IGF1) and fibroblast growth factor 2 (FGF2) influence ocular growth in eyes with unrestricted vision. Different doses of IGF1 and FGF2 were injected into the vitreous chamber of postnatal chicks. Measurements of ocular dimensions and intraocular pressure (IOP) were made during and at the completion of different treatment paradigms. Histological and immunocytochemical analyses were performed to assess cell death, cellular proliferation and integrity of ocular tissues. Treated eyes had significant increases in equatorial diameter and vitreous chamber depth. With significant variability between individuals, IGF1/FGF2-treatment caused hypertrophy of lens and ciliary epithelia, lens thickness was increased, and anterior chamber depth was decreased. Treated eyes developed myopia, in excess of 15 diopters of refractive error. Shortly after treatment, eyes had increased intraocular pressure (IOP), which was increased in a dose-dependent manner. Seven days after treatment with IGF1 and FGF2 changes to anterior chamber depth, lens thickness and elevated IOP were reduced, whereas increases in the vitreous chamber were persistent. Some damage to ganglion cells was detected in peripheral regions of the retina at 7 days after treatment. We conclude that the extreme myopia in IGF1/FGF2-treated eyes results from increased vitreous chamber depth, decreased anterior chamber depth, and changes in the lens. We propose that factor-induced ocular enlargement and myopia result from changes to the sclera, lens and anterior chamber depth.

Genetic factors for choroidal neovascularization associated with high myopia

PURPOSE

Nonsyndromic high myopia, defined by a refractive error greater than -6 diopters (D), is associated with an increased risk of macular choroidal neovascularization (CNV), a vision-threatening complication. The aim of this study was to investigate whether genetic factors associated with age-related macular degeneration (AMD) are related to myopic CNV.

METHODS

We conducted a case-control study, including 71 cases with myopic CNV and 196 myopic controls without CNV, from Creteil and Toulouse, France, and Boston, MA. Single nucleotide polymorphisms (SNPs) from 15 genes reported to be related to AMD were selected for association testing in this study.

RESULTS

In univariate analysis, the rs10033900 SNP located in CFI was associated with myopic CNV (P = 0.0011), and a SNP in APOE was also related (P = 0.041). After adjustment for age, sex, and degree of myopia, SNPs in three genes were significantly associated, including CFI (odds ratio [OR] 2.1, 95% confidence interval [CI] 1.3-3.37, P = 0.0023), COL8A1 (OR 1.88, 95% CI 1.18-2.98, P = 0.0076), and CFH (OR 1.65, 95% CI 1.02-2.66, P = 0.04). After correction for multiple testing, only CFI remained significantly related to high myopic CNV (P = 0.045).

CONCLUSIONS

We report the first genetic associations with choroidal neovascularization (CNV) in a high myopic Caucasian population. One SNP (rs10033900) in the CFI gene, which encodes a protein involved in the inflammatory pathway, was significantly associated with myopic CNV in multivariate analysis after correction for multiple testing. This SNP is a plausible biological marker associated with CNV outgrowth among high myopic patients. Results generate hypotheses about potential loci related to CNV in high myopia, and larger studies are needed to expand on these findings.

Time outdoors and physical activity as predictors of incident myopia in childhood: a prospective cohort study

PURPOSE

Time spent in "sports/outdoor activity" has shown a negative association with incident myopia during childhood. We investigated the association of incident myopia with time spent outdoors and physical activity separately.

METHODS

Participants in the Avon Longitudinal Study of Parents and Children (ALSPAC) were assessed by noncycloplegic autorefraction at ages 7, 10, 11, 12, and 15 years, and classified as myopic (≤-1 diopters) or as emmetropic/hyperopic (≥-0.25 diopters) at each visit (N = 4,837-7,747). Physical activity at age 11 years was measured objectively using an accelerometer, worn for 1 week. Time spent outdoors was assessed via a parental questionnaire administered when children were aged 8-9 years. Variables associated with incident myopia were examined using Cox regression.

RESULTS

In analyses using all available data, both time spent outdoors and physical activity were associated with incident myopia, with time outdoors having the larger effect. The results were similar for analyses restricted to children classified as either nonmyopic or emmetropic/hyperopic at age 11 years. Thus, for children nonmyopic at age 11, the hazard ratio (95% confidence interval, CI) for incident myopia was 0.66 (0.47-0.93) for a high versus low amount of time spent outdoors, and 0.87 (0.76-0.99) per unit standard deviation above average increase in moderate/vigorous physical activity.

CONCLUSION

Time spent outdoors was predictive of incident myopia independently of physical activity level. The greater association observed for time outdoors suggests that the previously reported link between "sports/outdoor activity" and incident myopia is due mainly to its capture of information relating to time outdoors rather than physical activity.

Endophenotyping reveals differential phenotype-genotype correlations between myopia-associated polymorphisms and eye biometric parameters

PURPOSE

To investigate the association with ocular biometric parameters in myopia-associated single nucleotide polymorphisms (SNPs) of the gap junction protein delta 2 (GJD2), insulin-like growth factor-1 (IGF1) and hepatocyte growth factor (HGF) genes in two geographically different Chinese cohorts.

METHODS

In 814 unrelated Han Chinese individuals aged above 50 years including 362 inland residents and 432 island dwellers, comprehensive ophthalmic examinations were performed. Three SNPs, including GJD2 rs634990, IGF1 rs6214, and HGF rs3735520, were genotyped. Genetic association with ocular biometric parameters was analyzed in individual cohorts, using linear regression controlled for sex and age. Common associations shared by the two cohorts were revealed by meta-analysis.

RESULTS

Meta-analysis showed that GJD2 rs634990 alone was not associated with any biometric parameters (adjusted p>0.645). The T allele of IGF1 rs6214 was specifically associated with thicker lens (β±SE=0.055±0.022, adjusted p=0.034). The A allele of HGF rs3735520 was associated with longer vitreous chamber depth (β±SE=0.143±0.060, adjusted p=0.050). Significant interaction between HGF rs3735520 and GJD2 rs634990 was found in association with axial length and vitreous chamber depth (adjusted p=0.003 and 0.033, respectively), and possibly with spherical error (adjusted p=0.056).

CONCLUSIONS

Our endophenotyping analysis showed differential association between selected myopia-associated genes and ocular biometric parameters in our Chinese cohorts, which may underline substantial but diversified effects of these genes and their interaction on the development of eye structure and etiology of myopia.

Association of insulin-like growth factor-1 polymorphisms with high myopia in the Chinese population

PURPOSE

The purpose of this study was to determine whether genetic variants in the insulin-like growth factor-1 (IGF-1) gene were associated with high myopia in the Chinese population.

METHODS

A case-control association study of 421 unrelated Chinese patients with high myopia and 401 control subjects matched in ethnicity and gender was undertaken. Genomic DNA was prepared from peripheral blood. All individuals were genotyped for 7 tag single nucleotide polymorphisms (tSNPs) across the IGF-1 gene region. Genotypic distribution was tested for Hardy-Weinberg equilibrium. The genotype and allele frequencies were evaluated using the χ(2) tests. Bonferroni corrections for multiple comparisons were performed.

RESULTS

The polymorphism of rs12423791 showed positive association with extreme myopia (p(allel)=0.006 and p(allel1 recessive model)=0.004, respectively) after Bonferroni correction for multiple testing and the haplotype GC of rs5742629-rs12423791 was also associated with extreme myopia (p=0.033) after 50,000 permutations for multiple comparisons.

CONCLUSIONS

The polymorphism of rs12423791 in IGF-1 may be associated with extreme myopia in the Chinese population and should be investigated further.

IGF-1 gene polymorphisms in Polish families with high-grade myopia

PURPOSE

Recent work has suggested that insulin-like growth factor 1 (IGF-1) gene polymorphisms are genetically linked with high-grade myopia (HM), which is a complex-trait eye disorder in which numerous candidate loci and genes are thought to play a role. We investigated whether the IGF-1 single nucleotide polymorphisms (SNPs) rs6214, rs10860860, and rs2946834 are associated with HM (≤-6.0 diopters [D]) and any myopia (≤-0.5 D) phenotype in Polish families.

METHODS

Forty-two multiplex HM Polish families, of whom 127 had HM, participated in the study. All of the family members (n=306) underwent a detailed ophthalmic examination, including axial length measurements. The IGF-1 SNPs rs6214, rs10860860, and rs2946834 were evaluated by PCR-RFLP and direct sequencing methods. Both Family-Based Association Test (FBAT) and family-based Pedigree Disequilibrium Test (PDT) were used to examine the potential association of the IGF-1 SNPs rs6214, rs10860860, and rs2946834 with HM or any myopia. To determine the distribution of the HM-associated SNPs rs6214 and rs10860860, 543 unrelated individuals from the general Polish population were also analyzed.

RESULTS

We found no significant association between the IGF-1 SNPs rs6214, rs10860860, and rs2946834 and HM or any myopia phenotype in Polish HM families. In the general Polish population, the minor allele frequencies of the SNPs rs6214 and rs10860860 did not deviate significantly from the distribution reported for European populations (p=0.629). In the FBAT analysis under the dominant model, the haplotype consisted of T allele of rs10860860, with C allele of rs2946834 of IGF-1 was found less frequently transmitted to HM individuals (p=0.0065), pointing to a nonassociated or protective haplotype.

CONCLUSIONS

Our results do not support recent studies reporting an association of the SNPs rs6214, rs10860860, and rs2946834 in the IGF-1 gene with HM and any myopia phenotypes. Further replication studies involving other populations are needed to investigate the possible role of IGF-1 as a potential myopia candidate gene.

Identification of novel suggestive loci for high-grade myopia in Polish families

PURPOSE

Myopia is the most common human eye disorder with complex genetic and environmental causes. To date, several myopia loci have been identified in families of different geographic origin. However, no causative gene(s) have yet been identified. The aim of this study was the characterization of Polish families with high-grade myopia, including genetic analysis.

METHODS

Forty-two multiplex Polish families with non-syndromic high-grade myopia participated in the study. All family members underwent detailed ophthalmic examination and high-grade myopia was defined as ≤-6.0 diopters (D) based on the spherical refractive error. A genome-wide single nucleotide polymorphism (SNP)-based high-density linkage scan was performed using Affymetrix Human SNP Array 6.0 on a selected family (HM-32) with multiple affected individuals.

RESULTS

Nonparametric linkage analysis identified three novel loci in family HM-32 at chromosome 7p22.1-7p21.1 ([NPL] 8.26; p=0.006), chromosome 7p12.3-7p11.2 ([NPL] 8.23; p=0.006), and chromosome 12p12.3-12p12.1 ([NPL] 8.02; p=0.006), respectively. The effect of linkage disequilibrium on linkage due to dense SNP map was addressed by systematically pruning SNPs from the linkage panel.

CONCLUSIONS

Haplotype analysis with informative crossovers in affected individuals defined a 12.2; 10.9; and 9.5 Mb genomic regions for high-grade myopia spanned between SNP markers rs11977885/rs10950639, rs11770622/rs9719399, and rs4763417/rs10842388 on chromosomes 7p22.1-7p21.1, 7p12.3-7p11.2, and 12p12.3-12p12.1, respectively.

Insulin, insulin-like growth factor-1, insulin receptor, and insulin-like growth factor-1 receptor expression in the chick eye and their regulation with imposed myopic or hyperopic defocus

PURPOSE

Insulin stimulates eye growth in chicks and this effect is greatly enhanced if the retinal image is degraded by the defocus of either sign. However, it is unclear whether the insulin receptor (IR) is expressed at all in the chicken retina in animals 1-2 weeks post-hatching. We have investigated IR expression and whether IR transcript abundance varies in the fundal layers. To elucidate the possible role of insulin and insulin-like growth factor (IGF)-1 signaling in eye growth regulation, mRNA (mRNA) levels were measured for insulin, IGF-1, IR, and IGF-1 receptor (IGF-1R) during imposed negative or positive defocus.

METHODS

Chicks were treated binocularly with positive or negative spectacle lenses for 4 or 24 h, or they remained untreated (n=6, for each treatment group). Northern blot analyses were performed to screen for transcription variants in the different fundal layers of untreated animals. Real-time PCR was used to quantify IR, IGF-1R, IGF-1, and insulin mRNA levels in the different fundal layers of the chick eye in the three treatment groups.

RESULTS

IR mRNA was found in all the studied tissues, although there is evidence of tissue-specific transcript variations. Three major transcripts were detected for IR. The brain, retina, and choroid showed the longest transcript (4.3 kb), which was not present in the liver. Nevertheless, the liver and brain showed a second transcript (2.6 kb) not present in the retina and choroid. A short transcript (1.3 kb) was the predominant form in the liver and choroid, and it seems to be present in the retinal pigment epithelium (RPE) and sclera as well. In the retina, no significant gene expression changes were found when defocus was imposed. Interestingly, in the RPE, both IR and IGF-1R were already downregulated after short periods (4 h) of positive lens wear. In contrast, IR and IGF-1R were upregulated in the choroid and fibrous sclera during treatment with negative, but not positive, lenses.

CONCLUSIONS

Differences observed in the IR transcript length in different tissues suggest possibly different functions. The differential regulation of IR and IGF-1R in the RPE, choroid, and fibrous sclera is consistent with their involvement in a signaling cascade for emmetropization.

Proteome profiling of wild type and lumican-deficient mouse corneas

To elucidate how the deficiency of a major corneal proteoglycan, lumican, affects corneal homeostasis, we used mass spectrometry to derive the proteome profile of the lumican-deficient and the heterozygous mouse corneas and compared these to the wild type corneal proteome. 2108 proteins were quantified in the mouse cornea. Selected proteins and transcripts were investigated by Western blot and quantitative RT-PCR, respectively. We observed major changes in the composition of the stromal extracellular matrix (ECM) proteins in the lumican-deficient mice. Lumican deficiency altered cellular proteins in the stroma and the corneal epithelium. The ECM changes included increases in fibril forming collagen type I, Collagen type VI, fibromodulin, perlecan, laminin β₂, collagen type IV, nidogen/entactin and anchoring collagen type VII in the Lum⁺/⁻ and the Lum⁻/⁻ mouse corneas, while the stromal proteoglycans decorin, biglycan and keratocan were decreased in the Lum⁻/⁻( corneas. Cellular protein changes included increases in alcohol dehydrogenase, superoxide dismutase and decreases in epithelial cytokeratins 8 and 14. We also detected proteins that are novel to the cornea. The proteomes will provide an insight into the lumican-deficient corneal phenotype of stromal thinning and loss of transparency and a better understanding of pathogenic changes in corneal and ocular dystrophies.

Assessment of exonic single nucleotide polymorphisms in the adenosine A2A receptor gene to high myopia susceptibility in Chinese subjects

PURPOSE

The adenosine A(2A) receptor (A(2A)R) modulates collagen synthesis and extracellular matrix production in ocular tissues that contribute to eye growth and the development of myopia. We aimed to determine if single nucleotide polymorphisms (SNPs) in A(2A)R exons associates with high myopia found in Chinese subjects.

METHODS

DNA samples were prepared from venous lymphocytes of 175 Chinese subjects with high myopia of less than -8.00 diopters (D) correction and 101 ethnically similar controls with between -1.00 D and +1.00 D correction. The coding region sequences of A(2A)R were amplified by PCR and analyzed by Sanger sequencing. The detected variations were confirmed by reverse sequencing. Allelic frequencies of all detected common SNPs were assessed for Hardy-Weinberg equilibrium.

RESULTS

Five variations in A(2A)R exons, 5675 A>G, 5765 C>T, 13325 G>A, 13448 C>T, and 14000 T>A, were detected in controls at a low frequency (<1%). However, one SNP, 13772 T>C (rs5751876), showed its polymorphism in 53.3% of the total study population. The rs5751876 is a synonymous substitution located in a tyrosine codon of exon 2. Despite no significant difference in genotype distribution between cases and controls, the frequency of heterozygotes with the rs5751876 genotype was significantly lower in subjects with high myopia.

CONCLUSIONS

The reduced frequency of the heterozygote rs5751876 genotype in subjects suggests a possible association of A(2A)R with high myopia in a Chinese population.

Nature and nurture: the complex genetics of myopia and refractive error

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.