The protective variant rs7173049 at LOXL1 locus impacts on retinoic acid signaling pathway in pseudoexfoliation syndrome.

LOXL1 (lysyl oxidase-like 1) has been identified as the major effect locus in pseudoexfoliation (PEX) syndrome, a fibrotic disorder of the extracellular matrix and frequent cause of chronic open-angle glaucoma. However, all known PEX-associated common variants show allele effect reversal in populations of different ancestry, casting doubt on their biological significance. Based on extensive LOXL1 deep sequencing, we report here the identification of a common non-coding sequence variant, rs7173049A>G, located downstream of LOXL1, consistently associated with a decrease in PEX risk (odds ratio, OR = 0.63; P = 6.33 × 10-31) in nine different ethnic populations. We provide experimental evidence for a functional enhancer-like regulatory activity of the genomic region surrounding rs7173049 influencing expression levels of ISLR2 (immunoglobulin superfamily containing leucine-rich repeat protein 2) and STRA6 [stimulated by retinoic acid (RA) receptor 6], apparently mediated by allele-specific binding of the transcription factor thyroid hormone receptor beta. We further show that the protective rs7173049-G allele correlates with increased tissue expression levels of ISLR2 and STRA6 and that both genes are significantly downregulated in tissues of PEX patients together with other key components of the STRA6 receptor-driven RA signaling pathway. siRNA-mediated downregulation of RA signaling induces upregulation of LOXL1 and PEX-associated matrix genes in PEX-relevant cell types. These data indicate that dysregulation of STRA6 and impaired retinoid metabolism are involved in the pathophysiology of PEX syndrome and that the variant rs7173049-G, which represents the first common variant at the broad LOXL1 locus without allele effect reversal, mediates a protective effect through upregulation of STRA6 in ocular tissues.

Exfoliation Syndrome: A Disease of Autophagy and LOXL1 Proteopathy.

Exfoliation syndrome (XFS) is an age-related disease involving the deposition of aggregated fibrillar material (exfoliation material) at extracellular matrices in tissues that synthesize elastic fibers. Its main morbidity is in the eye, where exfoliation material accumulations form on the surface of the ciliary body, iris, and lens. Exfoliation glaucoma (XFG) occurs in a high proportion of persons with XFS and can be a rapidly progressing disease. Worldwide, XFG accounts for about 25% of open-angle glaucoma cases. XFS and XFG show a sharp age-dependence, similarly to the many age-related diseases classified as aggregopathies. Progress in understanding the cellular bases for XFS/XFG has been slowed by a lack of experimental models. Working with primary human tenon fibroblasts (TF) derived from trabeculectomies of XFG patients and age-matched primary open-glaucoma controls, we found that TF from XFG cells display many of the functional features observed in cells from other protein aggregate diseases, such as Parkinson, Alzheimer, Huntington, and age-related macular degeneration. We have documented defects in lysosomal positioning, microtubule organization, autophagy processing rate, and mitochondrial health. In regard to failure of lysosomal and autophagosome positioning in XFG cells, we have found that XFG TF are unable to establish the transnuclear microtubule organizing center that is required for efficient centripetal vesicular locomotion along microtubules. In regard to potential sources of the autophagy malfunction, we have directed our attention to a potential role of the lysyl oxidase-like 1 protein (LOXL1), the elastic fiber catalyst that displays variant-dependent association with risk for XFG. Our experiments show that (a) in XFG cells, a substantial fraction of LOXL1 is processed for degradation by the autophagic system; (b) most of the LOXL1 N-terminus domain exists in a highly disordered state, a condition known to greatly increase the frequency of polypeptide misfolding; (c) that maximum misfolding occurs at amino acid position 153, the location of the high risk variant G153D; and (d) that replacement of glycine (G) by aspartate (D) there results in a substantial decrease in disorder within the 20 amino acid surrounding domain. Finally, we show that clusterin, a protein that can be induced by the presence of intracellular, or extracellular aggregates, is uniformly overexpressed in XFG TF. The implications of our results for a theory relating XFG to cellular aggregopathy are discussed.

Lysyl Oxidases: Functions and Disorders.

Lysyl oxidases (LOX) are copper-dependent enzymes that oxidize lysyl and hydroxylysyl residues in collagen and elastin, as a first step in the stabilization of these extracellular matrix proteins through the formation of covalent cross-linkages, an essential process for connective tissue maturation. Five different LOX enzymes have been identified in mammals, LOX and LOX-like (LOXL) 1 to 4, being genetically different protein products with a high degree of homology in the catalytic carboxy terminal end and a more variable amino terminal proregion. Intensive investigation in the last years has delineated the main biological functions of these enzymes and their involvement in several pathologies including fibrosis, cancer, and ocular disorders. This review article summarizes the major findings on the role of LOX isoforms, with particular focus on their contribution to the development and progression of human disorders.

Functional Activity of Matrix Metalloproteinases 2 and 9 in Tears of Patients With Glaucoma.

Purpose: To evaluate the differential expression of tear matrix metalloproteinases (MMP) 2 and 9 in of patients with various forms of glaucoma. Methods: Tear samples were collected with a Schirmer's strip from 148 eyes of 113 patients (medically naïve patients with primary open-angle [POAG] or angle closure glaucoma [PACG] and those with pseudoexfoliation syndrome [PXF] or glaucoma [PXG]). These were compared to patients undergoing cataract surgery (controls) for this cross-sectional study. Functional activities of tear MMP-9 and MMP-2 were analyzed by gelatin zymography. Tenon's capsules (n = 15) were harvested from the inferior quadrant in those undergoing cataract surgery and protein expression of MMP-9 was analyzed by immunohistochemistry (IHC). Hydrogen peroxide (H2O2) stress-induced effects on in vitro activities of MMP-9 in human trabecular meshwork (HTM) cells were analyzed. Results: The MMP-9 activity in tears was increased significantly in POAG, (n = 27), PACG (n = 24), and PXF (n = 40) eyes compared to controls (n = 35), and was increased significantly in eyes with glaucoma compared to moderate/severe glaucoma (P < 0.001). The MMP-9 expression was significantly lower in PXG (n = 22) eyes. Immunohistochemistry of Tenon's capsule revealed increased expression of MMP-9 in primary glaucoma eyes. Increased MMP-9 activity was seen in in vitro by gelatin zymography and was confirmed by Western and immunofluorescent assay on HTM upon 800 and 1000 µM H2O2-induced stress for 2 to 3 hours with approximately 80% cell death. Conclusions: Increased tear MMP-9 activity in early glaucoma and pseudoexfoliation syndrome suggesting activation of extracellular matrix (ECM) degradation can be used as a tear-based predictive biomarker. Decreased expression in advanced stages suggests exhaustion of the degradation response.

Serum prolidase activity and oxidative stress in patients with pseudoexfoliation syndrome.

PURPOSE: We aimed to evaluate the serum prolidase activity (SPA), malondialdehyde (MDA), and catalase levels in patients with pseudoexfoliation (PEX) syndrome. METHOD: Thirty-four patients with PEX syndrome and thirty-eight age- and gender-matched healthy subjects were included in this prospective clinical study. Each participant underwent full ophthalmologic examination. The SPA, serum MDA, and catalase levels were measured and compared between the patients with PEX syndrome and healthy subjects. RESULTS: The SPA was significantly lower in patients with PEX syndrome compared to healthy controls (14.1 ± 7.1 vs. 30.1 ± 4.3 ng/ml; p = 0.001). The mean serum MDA values the of PEX syndrome and control groups were comparable (28.7 ± 5.7 vs. 30.4 ± 5.3 nmol/ml, respectively; p = 0.185). The mean serum catalase level tended to be lower in the PEX group compared to healthy controls (0.12 ± 0.02 vs. 0.21 ± 0.05 k/ml, respectively; p = 0.077). CONCLUSION: Our findings suggest that the SPA was significantly lower in patients with PEX syndrome compared to healthy controls. Thus, prolidase may have a role in the pathogenesis of the PEX syndrome.

Serum and aqueous xanthine oxidase levels, and mRNA expression in anterior lens epithelial cells in pseudoexfoliation.

PURPOSE: The aim of this study was to determine serum and aqueous xanthine oxidase (XO) levels, and mRNA expression in anterior lens epithelial cells in pseudoexfoliation (PEX). METHODS: In this prospective study, serum, aqueous and anterior lens capsules were taken from 21 patients with PEX and 23 normal subjects who had undergone routine cataract surgery. Serum and aqueous XO levels were analyzed using the colorimetric method. mRNA expression of XO in anterior lens epithelial cells was evaluated using reverse transcription polymerase chain reaction analysis. RESULTS: Serum XO levels (means ± standard deviations) were 207.0 ± 86.1 IU/mL and 240.6 ± 114.1 IU/mL in the normal and PEX groups, respectively (p = 0.310). Aqueous XO levels (means ± standard deviations) were 65.5 ± 54.3 IU/mL in the normal group and 130.5 ± 117.4 IU/mL in the PEX group (p = 0.028). There was a 2.9 fold decrease in mRNA expression in anterior lens epithelial cells of PEX, which is significantly lower than the normal group (p = 0.01). CONCLUSIONS: Higher aqueous XO levels lacking associated different serum XO suggests higher oxidative stress in the aqueous. Higher aqueous XO levels in PEX with decreased mRNA expression in anterior lens epithelial cells indicate possible overexpression of XO in other structures related to the aqueous.

Exfoliation syndrome: a disease with an environmental component.

PURPOSE OF REVIEW: Exfoliation syndrome (XFS), the most common cause of secondary open angle glaucoma, is associated with significant ocular morbidity. Recent studies have pointed toward environmental components that may alter the risk of XFS development. This review focuses on the recent studies elucidating the role of environmental factors that play a role in the development of exfoliation syndrome. RECENT FINDINGS: In XFS, aberrant microfibril formation emanating from the cell-extracellular matrix interface admixes with other macromolecules and is cross-linked by lysyl oxidase like 1 (LOXL1) activity. A common gene variant in the LOXL1 enzyme, an enzyme critical for enhancing the tensile strength of collagen and elastin in extracellular matrices, has been found in approximately 90% of XFS cases. However, approximately 80% of controls also have disease-associated LOXL1 gene variants. These findings point toward other nongenetic factors influencing the development of XFS. Increasing latitude, solar radiation, climatic variables and dietary factors such as high coffee consumption and low dietary folate intake are among the nongenetic factors associated with increased risk of XFS. SUMMARY: A greater understanding of the environmental components associated with XFS may lead to lifestyle preventive strategies to ameliorate disease burden.

Update on pseudoexfoliation syndrome pathogenesis and associations with intraocular pressure, glaucoma and systemic diseases.

PURPOSE OF REVIEW: Pseudoexfoliation (PEX) syndrome is a common age-related disorder affecting intraocular and extraocular tissues. This review focuses on recent publications related with the pathogenesis and associations of PEX syndrome with intraocular pressure (IOP), glaucoma and systemic diseases. RECENT FINDINGS: In PEX tissues, expression of lysyl oxidase-like 1 (LOXL1) was found to be markedly dysregulated. This may adversely affect elastin metabolism and lead to elastotic alteration in tissues such as lamina cribrosa. There is increasing evidence that cellular stress conditions and low-grade chronic inflammatory processes are involved in the pathogenesis of PEX. Although there is an increased risk for glaucoma development in patients with PEX and ocular hypertension as compared with non-PEX patients with ocular hypertension, LOXL1 single nucleotide polymorphisms were not associated with intraocular pressure (IOP) differences. Lack of association of PEX with all-cause mortality or dementia has been reported recently. The association with vascular diseases is not consistent among different studies. SUMMARY: Despite the high prevalence of the LOXL1 variants in the general population, a much lower proportion of the population develops PEX, suggesting that in addition to LOXL1, other genetic, epigenetic and environmental factors may contribute to the development of PEX. Also, LOXL1 cannot help to identify those with PEX at increased risk for glaucoma development. Increased risk for glaucoma development in PEX patients who present with increased IOP may be related to other factors beyond IOP, contributing to increased vulnerability of the optic nerve to glaucoma development in the presence of PEX.

Conjunctival matrix metalloproteinases and their inhibitors in glaucoma patients.

PURPOSE: Chronic conjunctival inflammation, caused by various reasons, for example long-term use of topical drugs and/or their preservatives, affects the outcome of glaucoma surgery by interfering with wound healing. Matrix metalloproteinases (MMPs) remodel extracellular matrix (ECM) and are involved in the wound healing process. This study was designed to evaluate the conjunctival expression of MMPs and their tissue inhibitors (TIMPs) in the normal eye, primary open-angle glaucoma (POAG) and exfoliation glaucoma (ExG) and whether there is an association between staining intensities and deep sclerectomy outcome. METHODS: Immunohistochemical procedures were performed on conjunctival samples which were obtained from POAG (n=11) and ExG (n=14) patients as well as normal (n=7) subjects. Antibodies against MMPs (MMP-1, -2, -3 and -9) and TIMPs (TIMP-1, -2 and -3) were used. RESULTS: In conjunctival stroma, expression levels of MMP-2 (p=0.047), MMP-3 (p=0.009), MMP-9 (p<0.001), TIMP-1 (p=0.003), TIMP-2 (p<0.001) and TIMP-3 (p<0.001) in ExG and MMP-9 (p=0.008), TIMP-2 (p=0.02) and TIMP-3 (p=0.002) in POAG were significantly increased compared to control. We further found correlations between expression of MMP-1 and MMP-3 and the length of pilocarpine treatment. CONCLUSION: The expression of MMPs and TIMPs is increased in the conjunctiva of POAG and ExG patients having a long history of topical antiglaucoma drops. Antiglaucoma agents and/or their preservatives alter the remodelling balance of ECM in conjunctiva of POAG and ExG eyes. The balance between MMPs and TIMPs may play a crucial role in the conjunctival wound healing process and the outcome of glaucoma surgery.

Lysyl oxidases in the trabecular meshwork.

The mechanical properties of the extracellular matrix (ECM) play an important role in maintaining cellular function and overall tissue homeostasis. Emerging evidence suggests that biomechanical modifications of the ECM may be initiators and/or drivers of disease, exemplified by increased tissue stiffness. Specific ECM cross-linking enzymes (tissue transglutaminase, lysyl oxidase, and lysyl oxidase-like 1) are expressed in the trabecular meshwork and are regulated by transforming growth factor beta (TGF-ß) isoforms. As TGF-ß isoforms are elevated in the aqueous humor of glaucoma patients, trabecular meshwork stiffness mediated by ECM cross-linking may be responsible for increased aqueous humor outflow resistance and elevated intraocular pressure.

Evaluation of oxidative stress and paraoxonase phenotypes in pseudoexfoliation syndrome and pseudoexfoliation glaucoma.

BACKGROUND: Our purpose was to determine whether total oxidant and antioxidant status, total thiol levels and activities of serum paraoxonase 1, an HDL-associated antioxidant enzyme, are related with pseudoexfoliation syndrome (PEX) and pseudoexfoliation glaucoma (PG). METHODS: Serum samples from 32 PEX, 30 PG, and 32 control subjects were collected at the Gülhane Military Medical Academy, Ankara. Basal paraoxonase (PON1), salt stimulated paraoxonase (stPON1), arylesterase (ARE), and total thiol levels were measured spectrophotometrically. Total antioxidant status (TAS) and total oxidant status (TOS) were determined on an autoanalyzer. Oxidative stress index (OSI) was calculated using the TAS and TOS values. PON1 phenotypes were calculated from the ratio of stPON1 to ARE. Continuous variables were compared by independent samples t-test and one-way ANOVA, except for age which was compared using Mann-Whitney U test. Categorical variables were compared using Fisher's exact test (PON1 phenotypes) or chi-square test (gender). RESULTS: TAS levels were significantly lower in PEX and PG patients compared to controls. TOS, OSI and total thiol levels did not differ significantly among the study groups, although there was a trend towards lower TOS and total thiol levels in patients compared to controls. PON1 activities were significantly higher in PEX patients (131.37 +/- 81.20 U/L) compared to controls (95.53 +/- 55.65 U/L; p = 0.046). The PON1 phenotype which is known to have high activity towards the substrate paraoxon, but low antioxidant activity (BB phenotype) was observed significantly more in PEX patients compared to controls. CONCLUSIONS: PON1 phenotypes and lack of antioxidants might play an important role in the development of PEX/ PG.

Disruption of the blood-aqueous barrier and lens abnormalities in mice lacking lysyl oxidase-like 1 (LOXL1).

PURPOSE: Exfoliation syndrome (ES) is commonly associated with glaucoma, premature cataracts, and other ocular and systemic pathologies. LOXL1 gene variants are significantly associated with ES; however, the role of the protein in ES development remains unclear. The purpose of this study was to characterize the ocular phenotype in Loxl1(-/-) (null) mice. METHODS: Loxl1 null mice and strain-matched controls (C57BL) were evaluated by clinical and histologic analyses. RESULTS: Anterior segment histology showed a pronounced vesiculation of the anterior lens in the null mice. The lesions were subcapsular and in direct apposition with the posterior iris surface. Fluorescein angiography showed increased diffusion of fluorescein into the anterior chamber of the null mice compared with age-matched controls (P = 0.003, two-tailed, unequal variance t-test), suggesting compromise of the blood-aqueous barrier. Intraocular pressure measurements were within the normal range (16.5 ± 2.0 mm Hg) in null mice up to 1 year of age. Immunohistochemistry showed decreased elastin in the iris and ciliary body in the null mouse compared with controls. CONCLUSIONS: Elimination of LOXL1 in mice impairs the blood-aqueous humor barrier in the ocular anterior segment and causes lens abnormalities consistent with cataract formation, but does not result in deposition of macromolecular material or glaucoma. These results show that mice lacking LOXL1 have some ES features but that complete disease manifestation requires other factors that could be genetic and/or environmental.

The T allele of lysyl oxidase-like 1 rs41435250 is a novel risk factor for pseudoexfoliation syndrome and pseudoexfoliation glaucoma independently and through intragenic epistatic interaction.

PURPOSE: Two coding single nucleotide polymorphisms (SNPs) in lysyl oxidase-like 1 (LOXL1) are major genetic risk factors for pseudoexfoliation syndrome (XFS) and pseudoexfoliation glaucoma (XFG) in diverse populations. However, recent conflicting results suggest that the currently known disease-associated missense variants R141L and G153D are not causal and that they may be proxies for other unknown functional LOXL1 variants. The purpose of this study was to investigate the possible association of XFS/XFG with a novel LOXL1 exonic variant. METHODS: Genotypes of the synonymous coding LOXL1 SNP rs41435250 (p.A310A) were identified with direct sequencing. A case-control study was conducted with 115 unrelated Mexican patients with XFS/XFG (43 XFS/72 XFG) as well as 130 control subjects. Allele frequencies, genotype frequencies, and Hardy-Weinberg equilibrium were assessed with the HaploView software. A probable intragenic epistasis effect was assessed by comparing the frequencies of the rs41435250 alleles among a subset of 51 patients with XFS/XFG without the high-risk TT genotype at LOXL1 intronic rs2165241 and the control group. RESULTS: The T allele of the exonic SNP rs41435250 was more frequent in patients with XFS/XFG than in controls (odds ratios [95% confidence intervals] = 2.0 [1.1-3.6]; p = 0.01). Interestingly, the strength of association with the rs41435250 T allele was strongly increased (odds ratio [95% confidence intervals] = 4.9 [2.7-9.1]; p = 0.00000005) in the subgroup of subjects without the risk genotype at rs2165241. CONCLUSIONS: Our results indicate that allele T of rs41435250 is a novel risk genetic factor for XFS/XFG development in our population and points toward the possibility of a LOXL1 intragenic epistatic effect between rs41435250 and rs2165241. Functional studies are needed to investigate if the synonymous p.A310A mutation could affect messenger ribonucleic acid stability and thus LOXL1 enzymatic activity.

Association of lysyl oxidase-like 1 gene common sequence variants in Greek patients with pseudoexfoliation syndrome and pseudoexfoliation glaucoma.

PURPOSE: Three common sequence variants in the lysyl oxidase-like 1 (LOXL1) gene were recently associated with pseudoexfoliation (PEX) and pseudoexfoliation glaucoma (PEXG) in populations from various parts of the world. In this study, the genetic association of these variants was investigated in Greek patients with PEX and PEXG. METHODS: The three LOXL1 single nucleotide polymorphisms (SNPs), one intronic (rs2165241) and two nonsynonymous coding SNPs (rs1048661: R141L and rs3825942: G153D), were genotyped in a total of 48 unrelated patients with PEX, 35 patients with PEXG, and 52 healthy subjects who had normal findings in repeated ophthalmic examinations. A genetic association study was performed. RESULTS: Between the two coding SNPs, R141L did not show an association with PEX (p=0.297 for allele G, p=0.339 for genotype GG), whereas allele G of G153D showed a significant association (odds ratio [OR]=3.52, 95% confidence interval [CI]=1.735-7.166, p=3.24×10(-4) for allele G, p=0.004 for genotype GG). Likewise, for the intronic SNP of rs2165241, genotype TT (p=0.005) and its corresponding allele T (OR=2.99, 95% CI=1.625-5.527, p=3.53×10(-4)) showed a significant association with PEX. The allele G of G153D showed a significant association with PEXG (OR=3.74, 95% CI=1.670-8.387, p=0.001). The combined haplotype GGT, consisting of all three risk alleles, was associated with PEX (p=0.037), conferring a 1.8-fold of increased risk to the disease (OR=1.799, 95% CI=1.04-3.13). Furthermore, the haplotype GGT presented in 39.8% of the patients with PEX and 26.9% of the controls. CONCLUSIONS: Certain genetic variants in LOXL1 confer risk for PEX in Greek populations, confirming in part findings in patients from Northern Europe.

Quantitative analysis of SOD2, ALDH1A1 and MGST1 messenger ribonucleic acid in anterior lens epithelium of patients with pseudoexfoliation syndrome.

PURPOSE: The aim of the study was to investigate the expression of selected genes encoding enzymes involved in the antioxidant defense system (superoxide dismutase 2, SOD2; aldehyde dehydrogenase 1, ALDH1A1; microsomal glutathione S-transferase 1, MGST1) in fragments of anterior lens capsules of patients with pseudoexfoliation syndrome (PEX). The specificity and sensitivity of these molecular markers for PEX development were also assessed. METHODS: The study group consisted of 20 patients (9 women and 11 men) with diagnosed PEX and cataract. The control group included 23 patients (8 women and 15 men) who needed cataract surgery but did not have PEX. Quantification of SOD2, ALDH1A1, and MGST1 messenger ribonucleic acid (mRNA) was performed with quantitative real-time PCR. RESULTS: SOD2, ALDH1A1, and MGST1 mRNAs were detected in all studied samples. The examined genes had statistically significant higher expression in the group of patients with PEX than in the control group (SOD2, p=0.0015; ALDH1A1, p=0.0001; MGST1, p=0.0001, Mann-Whitney U test). The areas under the curve (AUC) of SOD2, MGST1, and ALDH1A1 were 0.766, 0.818, and 0.957, respectively. CONCLUSIONS: Differential expression of SOD2, ALDH1A1, and MGST1 genes in the anterior lens capsules of patients with PEX suggest that diseased tissue appears to respond to the previously reported oxidative stress. A possible role of ALDH1A1 mRNA level as a risk factor or marker for PEX needs further confirmation.

Association of LOXL1 gene polymorphisms with exfoliation syndrome/glaucoma and primary open angle glaucoma in a Turkish population.

PURPOSE: To investigate the association of lysyl oxidase like 1 (LOXL1) variants with exfoliation syndrome (XFS), exfoliation glaucoma (XFG), and primary open angle glaucoma (POAG) in a Turkish population. METHODS: Two LOXL1 single nucleotide polymorphisms (SNPs), rs1048661 (R141L) and rs3825942 (G153D), were analyzed in 300 Turkish patients (100 patients with XFS, 100 patients with XFG, 100 patients with POAG) and 100 control subjects. RESULTS: The T allele of rs1048661 was underrepresented in patients with XFS (odds ratio [OR]=0.334, 95% confidence interval [CI]: 0.198-0.564, p=2.54 × 10(-5)) and XFG (OR=0.366, 95% CI: 0.219-0.611, p=8.56 × 10(-5)) compared to the control subjects. None of the patients with XFS or XFG had the A allele of rs3825942, whereas 16% of the control subjects had that variant (OR=0.025, 95% CI: 0.003-0.188, p=3.69×10(-9)). No association was observed between the SNPs studied and POAG. By using logistic regression analysis, the effect of rs1048661 remained significant (p=8.45 × 10(-8)) after controlling for the effect of rs3825942, whereas rs3825942 was not significant with conditioning on rs1048661. Female gender was protective against the disease controlling with the effect of the two SNPs (OR=0.527, 95% CI: 0.358-0.776, p=0.001). CONCLUSIONS: The findings of the current study indicate that in a logistic regression analysis model the T allele of rs1048661 is the most important risk-modifying factor for the development of XFS and XFG. Our results also confirm in a Turkish population the findings of previous reports describing the association between LOXL1 polymorphisms and XFS/XFG but not with POAG. The allele and genotype distribution in this cohort appear to be similar to those of Caucasians.

Evaluation of lysyl oxidase-like 1 gene polymorphisms in pseudoexfoliation syndrome in a Korean population.

PURPOSE: The purpose of this study was to evaluate association profiles of lysyl oxidase-like 1 (LOXL1) gene polymorphisms with pseudoexfoliation syndrome (XFS) in a Korean population. METHODS: A total of 110 Korean patients with XFS and 127 control subjects were included in this study. Genotypes of three single nucleotide polymorphisms (SNPs) of LOXL1 (rs1048661, rs3825942, and rs2165241) were analyzed with direct sequencing, and a case-control association study was performed. Genotype frequencies of each SNP were compared according to the XFS phenotypes. RESULTS: All three SNPs were significantly associated with XFS. The T allele at rs1048661 (odds ratio [OR] = 14.29, 95% confidence interval [CI] = 6.25-33.3) and the C allele at rs2165241 (OR = 7.14, 95% CI = 1.59-33.3) were risk alleles in Korean subjects, which was consistent with findings in other Asian populations. However, our findings were opposite to results from Caucasian populations in which the risk alleles at rs1048661 and rs2165241 were G and T, respectively. At the rs3825942, the G allele (OR = 12.50, 95% CI = 2.94-50.0) was a risk allele for XFS, which was similar to results from most other ethnic groups except black South Africans in whom the A allele increased the risk. In the haplotype analysis, the T-G-C haplotype composed of all three risk alleles was significantly overrepresented in XFS and conferred an 11.36 fold (95% CI = 5.97-23.49) increased likelihood of XFS. There was no significant association between the genotype frequencies of the three SNPs and the XFS phenotypes. CONCLUSIONS: Three SNPs of LOXL1 (rs1048661, rs3825942, and 2,165,241) are highly associated with XFS in a Korean population. The risk alleles of these SNPs were similar to those of other Asian populations, such as Japanese or Chinese, but differed from non-Asian populations, suggesting that still unidentified genetic or environmental factors may contribute to disease expression.

LOXL1 deficiency in the lamina cribrosa as candidate susceptibility factor for a pseudoexfoliation-specific risk of glaucoma.

PURPOSE: To test the hypothesis that a primary disturbance in lysyl oxidase-like 1 (LOXL1) and elastin metabolism in the lamina cribrosa of eyes with pseudoexfoliation syndrome constitutes an independent risk factor for glaucoma development and progression. DESIGN: Observational, consecutive case series. PARTICIPANTS: Posterior segment tissues obtained from 37 donors with early and late stages of pseudoexfoliation syndrome without glaucoma, 37 normal age-matched control subjects, 5 eyes with pseudoexfoliation-associated open-angle glaucoma, and 5 eyes with primary open-angle glaucoma (POAG). METHODS: Protein and mRNA expression of major elastic fiber components (elastin, fibrillin-1, fibulin-4), collagens (types I, III, and IV), and lysyl oxidase crosslinking enzymes (LOX, LOXL1, LOXL2) were assessed in situ by quantitative real-time polymerase chain reaction, (immuno)histochemistry, and light and electron microscopy. Lysyl oxidase-dependent elastin fiber assembly was assessed by primary optic nerve head astrocytes in vitro. MAIN OUTCOME MEASURES: Expression levels of elastic proteins, collagens, and lysyl oxidases in the lamina cribrosa. RESULTS: Lysyl oxidase-like 1 proved to be the major lysyl oxidase isoform in the normal lamina cribrosa in association with a complex elastic fiber network. Compared with normal and POAG specimens, lamina cribrosa tissues obtained from early and late stages of pseudoexfoliation syndrome without and with glaucoma consistently revealed a significant coordinated downregulation of LOXL1 and elastic fiber constituents on mRNA and protein level. In contrast, expression levels of collagens and other lysyl oxidase isoforms were not affected. Dysregulated expression of LOXL1 and elastic proteins was associated with pronounced (ultra)structural alterations of the elastic fiber network in the laminar beams of pseudoexfoliation syndrome eyes. Inhibition of LOXL1 interfered with elastic fiber assembly by optic nerve head astrocytes in vitro. CONCLUSIONS: The findings provide evidence for a pseudoexfoliation-specific elastinopathy of the lamina cribrosa resulting from a primary disturbance in LOXL1 regulation and elastic fiber homeostasis, possibly rendering pseudoexfoliation syndrome eyes more vulnerable to pressure-induced optic nerve damage and glaucoma development and progression.

Lack of association between the C677T single nucleotide polymorphism of the MTHFR gene and glaucoma in Iranian patients.

Glaucoma is a major cause of blindness worldwide. A single nucleotide polymorphism of the MTHFR gene (C677T) has been associated with susceptibility to this disease, although this is controversial in the last decade. In this study, the possible association between the MTHFR C677T polymorphism and the risk of developing primary open angle (POAG) and pseudoexfoliation glaucoma (PEXG) was investigated. For this, a prospective study consisting of 73 POAG, 85 PEXG and 90 matched controls was undertaken in an Iranian population. Genomic DNA was extracted from whole blood. Genotyping of all individuals for the MTHFR C677T polymorphism was conducted using the PCR-RFLP technique. Our findings revealed no significant association between the MTHFR C677T polymorphism in POAG and PEXG compared with controls. Consistent with several other studies, our analysis suggests that the MTHFR C677T polymorphism is unlikely to be a factor contributing to the risk of developing specific forms of glaucoma.