The association between lumican gene polymorphisms and high myopia

Proteomic signatures of retinal pigment epithelium-derived exosomes in myopic and non-myopic tree shrew eyes

Purpose

The retinal pigment epithelium (RPE) transmits growth signals from the neural retina to the choroid in the emmetropization pathway, but the underlying molecular mechanisms remain poorly understood. Here, we compared the proteomic profiles of RPE-derived exosomes between myopic and non-myopic eyes of tree shrews, dichromatic mammals closely related to primates.

Methods

Four myopic (159-210 days of visual experience, DVE) and seven non-myopic eyes (156-210 DVE) of tree shrews were included. Non-cycloplegic refractive error was measured with Nidek autorefractor, and axial ocular component dimensions were recorded with LenStar. Tissue was collected, yielding RPE-lined eyecups, which were subsequently incubated in L-15 culture media for 2 h. The RPE-derived exosomes were then enriched and purified from the incubation media by double ultracentrifugation and characterized by imaging and molecular methods. Exosomal proteins were identified and quantified with mass spectrometry, examined using GO and KEGG analyses, and compared between myopic and non-myopic samples.

Results

Out of 506 RPE exosomal proteins identified, 48 and 41 were unique to the myopic and non-myopic samples, respectively. There were 286 differentially expressed proteins in the myopic samples, including 79 upregulated and 70 downregulated. The top three upregulated proteins were Histone H4 (Fold Change, FC = 3.04, p = 0.09), PTB 1 (FC = 2.59, p = 0.08) and Histone H3.1 (FC = 2.59, p = 0.13), while the top three downregulated proteins were RPS5 (FC = -2.41, p=0.004), ACOT7 (FC=-2.15, p = 0.04) and CRYBB2 (FC = -2.14, p = 0.05). Other differentially expressed proteins included LUM, VCL, SEPTIN11, GPX3, SPTBN1, SEPTIN7, RPL10A, KCTD12, FGG, and FMOD. Proteomic analysis revealed a low abundance of ATP6V1B2 and crystallin beta B2, and a significant depletion of the crystallin protein family (crystallin A2, A3, and B3 subunits) in the myopic samples. The enrichment analyses showed extracellular matrix, cytoskeletal dynamic, and cell-matrix adhesion as the primary components associated with the RPE exosomal proteins in myopic eyes.

Conclusion

Using standard molecular and imaging techniques, this study provides the first demonstration of the ex-vivo RPE exosome biogenesis from tree shrew eyes. The results showed distinct differential expressions of the RPE exosomal proteins between the myopic and non-myopic eyes, with several proteins unique to each group. Future targeted proteomic studies of identified candidate exosomal protein signatures could elucidate the molecular mechanism of RPE exosome-mediated growth signal transmission in the emmetropization pathway.

The versatile roles of lumican in eye diseases: A review

Lumican is a keratan sulfate proteoglycan that belongs to the small leucine-rich proteoglycan family. Research has lifted the veil on the versatile roles of lumican in the pathogenesis of eye diseases. Lumican has pivotal roles in the maintenance of physiological tissue homogenesis and is often upregulated in pathological conditions, e.g., fibrosis, scar tissue formation in injured tissues, persistent inflammatory responses and immune anomaly, etc. Herein, we will review literature regarding the role of lumican in pathogenesis of inherited congenital and acquired eye diseases, e.g., cornea dystrophy, cataract, glaucoma and chorioretinal diseases, etc.

Lumican inhibits immune escape and carcinogenic pathways in colorectal adenocarcinoma

Lumican (LUM), a small leucine-rich proteoglycan, is a component of the extracellular matrix. Abnormal LUM expression is potentially associated with cancer progression. In the present study, we confirmed high LUM mRNA expression in colorectal adenocarcinoma (COAD) through the UALCAN database. The Kaplan-Meier method, univariate, and multivariate COX analysis showed that high LUM expression is an independent determinant of poor prognosis in COAD. A COX regression model was constructed based on clinical information and LUM expression. The receiver operating characteristic (ROC) curve indicated that this model was highly accurate in monitoring COAD prognosis. The co-expression network of LUM was determined by LinkedOmics, which showed that LUM expression was closely related to immune escape and the miR200 family. Furthermore, we studied the co-expression network of LUM and found that LUM could promote tumor metastasis and invasion. The Tumor Immune Estimation Resource website showed that LUM was closely related to immune infiltration and correlated with regulatory T cells, tumour-associated macrophages, and dendritic cells. We found that LUM cultivated cancer progression by targeting the miR200 family to promote epithelial-to-mesenchymal transition. These findings suggest that LUM is a potential target for inhibiting immune escape and carcinogenic pathways.

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.

Cross-ancestry genome-wide association analysis of corneal thickness strengthens link between complex and Mendelian eye diseases

Central corneal thickness (CCT) is a highly heritable trait associated with complex eye diseases such as keratoconus and glaucoma. We perform a genome-wide association meta-analysis of CCT and identify 19 novel regions. In addition to adding support for known connective tissue-related pathways, pathway analyses uncover previously unreported gene sets. Remarkably, >20% of the CCT-loci are near or within Mendelian disorder genes. These included FBN1, ADAMTS2 and TGFB2 which associate with connective tissue disorders (Marfan, Ehlers-Danlos and Loeys-Dietz syndromes), and the LUM-DCN-KERA gene complex involved in myopia, corneal dystrophies and cornea plana. Using index CCT-increasing variants, we find a significant inverse correlation in effect sizes between CCT and keratoconus (r = -0.62, P = 5.30 × 10-5) but not between CCT and primary open-angle glaucoma (r = -0.17, P = 0.2). Our findings provide evidence for shared genetic influences between CCT and keratoconus, and implicate candidate genes acting in collagen and extracellular matrix regulation.

Analysis of the association between the LUM rs3759223 variant and high myopia in a Japanese population

Purpose

Many studies have investigated the relationship of the lumican gene (LUM) rs3759223 variant with the risk of high myopia, but the results have been inconsistent and inconclusive. In this study, we investigated whether LUM rs3759223 is associated with high myopia in a Japanese population.

Methods

We recruited 1,585 Japanese patients with high myopia (spherical equivalent [SE] <−9.00 diopters [D]) and 1,011 Japanese healthy controls (SE ≥−1.00 D). The rs3759223 variant was genotyped using the TaqMan assay, and the allelic and genotypic diversity among cases and controls was analyzed according to the SE level.

Results

In the allelic tests, the odds ratio (OR) for the T allele of rs3759223 tended to increase with the progression of SE, and the highest OR (1.56) was found in patients with SE <−15 D in both eyes. The OR of the T allele tended to increase with the progression of SE in the additive, dominant, and recessive inheritance models. However, we found no significant associations for any of the alleles or genotype models.

Conclusion

These data support the possibility that the LUM rs3759223 T allele accelerates the progression of SE in the Japanese population, although no significant associations were observed in this study. Additional genetic studies with larger samples that take into account the degree of SE are needed to clarify the contribution of rs3759223 to the risk of high myopia.

Enlargement of the Axial Length and Altered Ultrastructural Features of the Sclera in a Mutant Lumican Transgenic Mouse Model

Lumican (LUM) is a candidate gene for myopia in the MYP3 locus. In this study, a mutant lumican (L199P) transgenic mouse model was established to investigate the axial length changes and ultrastructural features of the sclera. The mouse model was established by pronuclear microinjection. Transgenic mice and wild-type B6 mice were killed at eight weeks of age. Gene expression levels of LUM and collagen type I (COL1) in the sclera were analyzed by quantitative real-time polymerase chain reaction (qPCR), and the protein levels were assessed by Western blot analysis. Ocular axial lengths were measured on the enucleated whole eye under a dissecting microscope. Ultrastructural features of collagen fibrils in the sclera were examined with transmission electron microscopy (TEM). Lumican and collagen type I were both elevated at the transcriptional and protein levels. The mean axial length of eyes in the transgenic mice was significantly longer than that in the wild-type mice (3,231.0 ± 11.2 μm (transgenic group) vs 3,199.7 ± 11.1 μm (controls), p<0.05 =). Some ultrastructural changes were observed in the sclera of the transgenic mice under TEM, such as evident lamellar disorganizations and abnormal inter-fibril spacing. The average collagen fibril diameter was smaller than that in their wild-type counterparts. These results indicate that the ectopic mutant lumican (L199P) may induce enlargement of axial lengths and abnormal structures and distributions of collagen fibrils in mouse sclera. This transgenic mouse model can be used for the mechanistic study of myopia.

Evaluation of 10 AMD Associated Polymorphisms as a Cause of Choroidal Neovascularization in Highly Myopic Eyes

Choroidal neovascularization (CNV) commonly occurs in age related macular degeneration and pathological myopia patients. In this study we conducted a case-control prospective study including 431 participants. The aim of this study was to determine the potential association between 10 single nucleotide polymorphisms (SNPs) located in 4 different genetic regions (CFI, COL8A1, LIPC, and APOE), and choroidal neovascularization in age-related macular degeneration and the development of choroidal neovascularization in highly myopic eyes of a Caucasian population. Univariate and multivariate logistic regression analysis adjusted for age, sex and hypertension was performed for each allele, genotype and haplotype frequency analysis. We found that in the univariate analysis that both single-nucleotide polymorphisms in COL8A1 gene (rs13095226 and rs669676) together with age, sex and hypertension were significantly associated with myopic CNV development in Spanish patients (p<0.05). After correcting for multiple testing none of the polymorphisms studied remained significantly associated with myopic CNV (p>0.05); however, analysis of the axial length between genotypes of rs13095226 revealed an important influence of COL8A1 in the development of CNV in high myopia. Furthermore we conducted a meta-analysis of COL8A1, CFI and LIPC genes SNPs (rs669676, rs10033900 and rs10468017) and found that only rs669676 of these SNPs were associated with high myopia neovascularization.

Construction of adenovirus vectors encoding the lumican gene by gateway recombinant cloning technology

AIM

To construct adenovirus vectors of lumican gene by gateway recombinant cloning technology to further understand the role of lumican gene in myopia.

METHODS

Gateway recombinant cloning technology was used to construct adenovirus vectors. The wild-type (wt) and mutant (mut) forms of the lumican gene were synthesized and amplified by polymerase chain reaction (PCR). The lumican cDNA fragments were purified and ligated into the adenovirus shuttle vector pDown-multiple cloning site (MCS)-/internal ribozyme entry site (IRES)/enhanced green fluorescent protein (EGFP). Then the desired DNA fragments were integrated into the destination vector pAV.Des1d yielding the final expression constructs pAV.Ex1d-cytomegalovirus (CMV)>wt-lumican/IRES/EGFP and pAV.Ex1d-CMV>mut-lumican/IRES /EGFP, respectively.

RESULTS

The adenovirus plasmids pAV.Ex1d-CMV>wt-lumican/IRES/EGFP and pAV.Ex1d-CMV>mut-lumican/IRES/EGFP were successfully constructed by gateway recombinant cloning technology. Positive clones identified by PCR and sequencing were selected and packaged into recombinant adenovirus in HEK293 cells.

CONCLUSION

We construct adenovirus vectors containing the lumican gene by gateway recombinant cloning technology, which provides a basis for investigating the role of lumican gene in the pathogenesis of high myopia.

Lack of association between LUM rs3759223 polymorphism and high myopia

PURPOSE

Previous evidence has indicated that the lumican (LUM) gene is a candidate susceptibility gene of high myopia; however, the association between LUM promoter regions rs3759223 polymorphism and high myopia remains controversial and ambiguous. This study performed a meta-analysis to clarify the association between the rs3759223 polymorphism and high myopia risk.

METHODS

Eligible studies were identified by comprehensive search of PubMed, EMBASE, Web of Science, and Chinese Biomedical Literature database. The crude odds ratios (ORs) and their corresponding 95% confidence intervals (CIs) were used to estimate the association between the rs3759223 polymorphism and high myopia susceptibility. Meta-regression and subgroup analyses were performed to identify the source of heterogeneity.

RESULTS

Finally, six studies including 1238 cases and 1059 healthy controls were included. Meta-analyses showed no association between rs3759223 polymorphism and high myopia susceptibility in all genetic models (CC vs. TT, OR = 1.089; 95% CI, 0.690 to 1.718; CT vs. TT, OR = 0.865; 95% CI, 0.646 to 1.157; CC + CT vs. TT, OR = 1.202; 95% CI, 0.730 to 1.980; CC vs. CT + TT, OR = 0.914; 95% CI, 0.771 to 1.083) and no significance in subgroup analyses according to the definition of high myopia (based on more myopic than -6.00 diopters vs. not based on more myopic than -6.00 diopters). Publication bias was not evident in this study.

CONCLUSIONS

This meta-analysis has suggested that there is a lack of association of the rs3759223 polymorphism with high myopia risk. However, further large and well-designed studies with the consideration of LUM gene locus interactions and gene-gene and gene-environment interactions are still required to further evaluate high myopia risk.

Meta-analysis of the association between lumican gene polymorphisms and susceptibility to high Myopia

Backgrounds

Many studies have evaluated the association between lumican (LUM) gene polymorphisms and high myopia. However, the results remain controversial. This meta-analysis aims to comprehensively evaluate the relationship between two common LUM polymorphisms (rs3759223 and rs3759222) and the risk of high myopia.

Methods

A comprehensive literature search for studies published up until September of 2013 was performed. Data were extracted independently by two investigators, and the weighted Odds Ratios (ORs) and 95% Confidence Intervals (CIs) for the associations were obtained by using a random-effects model.

Results

Eight studies (1425cases and 1271 controls) were identified for the analysis of the association between rs3759223 polymorphism and high myopia. The results indicated that rs3759223 polymorphism was associated with high myopia under a recessive model (OR = 1.71, 95%CI 1.04–2.81). Further subgroup analysis indicated that this polymorphism was associated with high myopia among Chinese people in the additive model (OR = 1.17, 95%CI 1.06–1.29) and a recessive model (OR = 1.75, 95%CI 1.00–3.06) with control group coming from hospital based population. Four studies (1024 cases and 1163 controls) were identified for the analysis of the association between rs3759222 polymorphism and high myopia. The results indicated that rs3759222 polymorphism was not associated with high myopia in all genetic models, even the subgroup analysis couldn't provide relative proof to assure the outcome.

Conclusion

This meta-analysis suggests that LUM polymorphisms are associated with the risk of high myopia. However, well-designed studies with larger sample sizes and more ethnic groups are required to further validate this association.

Association of Lumican gene polymorphism with high myopia: a meta-analysis

PURPOSE

Numerous studies have evaluated the association between the single-nucleotide polymorphism (SNP) (rs3759223, C→T) in Lumican gene and high myopia risk in the Chinese population. However, the results have been inconsistent. We therefore here examined whether the rs3759223 polymorphism confers high myopia risk by conducting a meta-analysis.

METHODS

PubMed, EMBASE, Science Citation Index, and Chinese National Knowledge Infrastructure (up to November 30, 2012) were searched by two investigators independently. Pooled relative ratios (RRs) and 95% confidence interval (CI) were used to assess the strength of the associations between SNP rs3759223 and myopia. Statistical analysis was undertaken using the program STATA 11.0 software (Stata Corporation, College Station, TX).

RESULTS

Five case-control studies involving 923 patients with high myopia and 622 controls were included in this meta-analysis. A significant relationship between SNP rs3759223 and high myopia in the Chinese population was found under the homozygote (RR = 1.47, 95% CI 1.01-2.12, p = 0.04) and recessive (RR = 1.69, 95% CI 1.09-2.62, p = 0.02) genetic models. However, no significant association was found under the heterozygote (RR = 1.01, 95% CI 0.76-1.35, p = 0.93) and dominant (RR = 1.06, 95%CI 0.90-1.26, p = 0.48) genetic models.

CONCLUSIONS

This meta-analysis showed the evidence that SNP rs3759223 may affect individual susceptibility to high myopia in the Chinese population. Given the limited sample size, further investigations are needed to validate the association.

Association between a lumican promoter polymorphism and high myopia in the Chinese population: a meta-analysis of case-control studies

PURPOSE

To evaluate the relationship between lumican polymorphisms and high myopia in Chinese populations.

METHODS

An electronic search was conducted in Pubmed, Embase, Cochrane Library and the China Biological Medicine Database for articles published prior to September 30, 2012. A meta-analysis was performed to assess heterogeneity, combine results and determine publication bias.

RESULTS

This meta-analysis, including 1,545 subjects from 5 studies, indicated that Chinese lumican rs3759223 C allele carriers had a decreased risk of high myopia in comparison to T allele carriers (odds ratio: 0.531; 95% confidence interval, CI: 0.304-0.925; p = 0.025). There was some heterogeneity between studies. A metaregression showed that the mean axial length of controls weakens the effect of rs3759223 on high myopia (slope: -0.914; 95% CI: -1.490 to 0.337; p = 0.002). Sensitivity analysis confirmed the reliability and stability of this meta-analysis.

CONCLUSION

Chinese lumican rs3759223 C allele carriers may be at reduced risk of high myopia.

Association between lumican gene -1554 T/C polymorphism and high myopia in Asian population: a meta-analysis

AIM

To investigate the association between lumican gene -1554 T/C polymorphism and high myopia susceptibility.

METHODS

We searched the published literature in the Medline, Embase, and CBM databases from inception to July 2013. A meta-analysis was performed by the programs RevMan 5.1 and Stata 12.0, and the odds ratio (OR) with 95% confidence interval (CI) was calculated in fixed or random effect model based on heterogeneity test among studies.

RESLUTS

Seven case-control studies with a total of 1 233 cases and 936 controls were included. A statistical significant association with high myopia was observed in the recessive model (TT vs CT+CC: OR=1.92; 95%CI=1.14-3.23) and codominant model (TT vs CT: OR=1.81, 95%CI=1.19-2.75).

CONCLUSION

The present meta-analysis suggested that lumican -1554 T/C polymorphism might be moderately associated with high myopia susceptibility. This conclusion warrants confirmation by further studies.

Genetic contributions to myopic refractive error: Insights from human studies and supporting evidence from animal models

Genetic studies of both population-based and recruited affected patient cohorts have identified a number of genomic regions and candidate genes that may contribute to myopic development. Scientists have developed animal models of myopia, as collection of affected tissues from patents is impractical. Recent advances in whole exome sequencing technology show promise for further elucidation of disease causing variants as in the recent identification of rare variants within ZNF644 segregating with pathological myopia. We present a review of the current research trends and findings on genetic contributions to myopic refraction including candidate loci for myopic development and their genomic convergence with expression studies of animal models inducing myopic development.

Absence of an association between lumican promoter variants and high myopia in the Korean population

PURPOSE

To determine the association of single nucleotide polymorphisms (SNPs) in the promoter region of the lumican (LUM) gene with high myopic Korean patients.

METHODS

Genomic DNA samples were obtained from 128 unrelated Korean patients with high myopia who had refractive errors ≤ -9.25 and axial lengths ≥ 26.5 mm in both eyes, and 235 control subjects. We investigated two promoter SNPs of the LUM gene.

RESULTS

For the rs3759222, the C/C genotype was less prevalent in the high myopia group compared to the control group (46.1% vs. 53.2%); however, there was no statistical significance (p = 0.068, OR = 0.754, 95% CI: 0.491-1.159). The "C" allele frequency in the high myopia group (68.0%) was slightly lower than the control group (72.6%), but this difference was not statistically significant (p = 0.061, OR = 0.810, 95% CI:0.582-1.126). For the rs3759223, the genotype frequencies of T/T, T/C, and C/C were 67.2%, 26.6%, and 6.2%, respectively, in the high myopia group and 64.7%, 30.6%, and 4.7 %, respectively, in the control group. The allele frequency of T was 80.5% in the high myopia group and 80.0% in the control group (p = 0.077, OR = 1.03, 95% CI: 0.703-1.508). There were no significant differences in the distribution of genotype and allele frequencies for the two promoter SNPs tested.

CONCLUSIONS

The current study did not support an association between the promoter SNPs of the LUM gene with high myopia in the Korean population.

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.

Ten SNPs of PAX6, Lumican, and MYOC genes are not associated with high myopia in Han Chinese

PURPOSE

To investigate whether the PAX6, Lumican, and MYOC genes are related to high myopia in Han Chinese since the association between these genes and high myopia is unclear in this patient population.

METHODS

Peripheral venous blood samples were collected for DNA extraction from 220 subjects with high myopia (refractive error ≤-10.00 D) vs. normal controls among the Han Chinese of Northeastern China. Mass spectrometry was applied to detect 10 SNP loci of the PAX6, Lumican, and MYOC genes. The candidate region was analyzed using case-control correlation analysis. The χ(2) test was used to analyze the allele and genotype frequencies in the myopic group vs. the control group. Haploview software was used for haplotype analysis.

RESULTS

The χ(2) test was used to compare the allele and genotype frequencies of SNPs in patients and control subjects and the results showed that ten SNPs of the PAX6, Lumican, and MYOC genes were not significantly associated with high myopia.

CONCLUSIONS

Our results confirm that the PAX6, Lumican, and MYOC genes were not associated with high myopia in the Han Chinese in Northeastern China.

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.

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.