Association between polymorphisms in lysyl oxidase-like 1 and susceptibility to pseudoexfoliation syndrome and pseudoexfoliation glaucoma

Red cell distribution width levels in patients with pseudoexfoliation syndrome and pseudoexfoliation glaucoma

Purpose

The purpose of this study was to assess the levels of red cell distribution width (RDW) in patients with pseudoexfoliation syndrome (PEX) and pseudoexfoliation glaucoma (PEXG), and to compare their RDW values with healthy controls.

Methods

40 patients with PEX, 40 with PEXG, and 80 control subjects were enrolled in this study. Complete ophthalmologic examination and complete blood count measurements were performed of all subjects. Complete blood counts were performed within one hour of blood collection.

Results

RDW levels were significantly higher in patients with PEX and PEXG than in controls (P = 0.027 and P < 0.001, respectively). Furthermore, a significant difference was found in RDW values between PEXG and PEX groups (P = 0.016). RDW levels were gradually increased from control group to PEXG group (P < 0.001). Multivariate logistic regression analysis revealed that RDW was independently associated with the presence of PEX/PEXG (odds ratio 1.765, 95% confidence interval (CI) 1.095-2.867, P = 0.013).

Conclusion

We conclude that RDW may be a useful marker for predicting the presence of PEX and progression to PEXG.

DNA Polymorphism of the LOXL1 Promoter Region in Exfoliation Syndrome in Uygur Individuals in XinJiang, China

Purpose

On the basis of our previously reported work, the association of lysyl oxidase-like 1 (LOXL1) promoter region gene polymorphism with exfoliation syndrome (XFS) and exfoliation glaucoma (XFG) in Uygur individuals was examined.

Methods

This was a case-control association trial. A total of 242 unrelated XFS/G and 310 control cases were assessed. The genotypes of 6 single nucleotide polymorphisms (SNPs) of the LOXL1 promoter (rs4886761, rs4886467, rs4558370, rs4461027, rs16958477, and rs12914489) were examined via direct sequencing.

Results

Each of the above SNPs had significant associations with XFS and XFG. The T allele of rs4886761 (OR (95% CI): 2.204 (1.711–2.838)), G of rs4886467 (OR (95% CI): 1.946 (1.513–2.503)), T of rs4461027 (OR (95% CI): 2.26 (1.773–2.881)), A of rs16958477 (OR (95% CI): 1.792 (1.399–2.297)), and G of rs12914489 (OR (95% CI): 1.103 (0.631–1.929)) independently predicted XFS/G. The genotypes TT and CC of rs4886761 (OR (95% CI): 5.655 (3.000–10.660) and 2.241 (1.473–3.408), respectively), TT and GG of rs4886467 (OR (95% CI): 4.026 (2.162–7.497) and 1.631 (1.08–2.463), respectively), CC and TT of rs4461027 (OR (95% CI): 5.245 (3.037–9.058) and 2.210 (1.37–3.564), respectively), CC and AA of rs16958477 (OR (95% CI): 3.530 (1.968–6.334) and 1.740 (1.145–2.646), respectively) also independently predicted XFS/G. The GGT and GTG haplotypes of rs12914489, rs4886467, and rs4558370 and TC and CT of rs4461027 and rs4886761 showed significant associations with XFS/G.

Conclusions

These results confirmed LOXL1 as a susceptibility gene in XFS/XFG among Uygur individuals. The new SNPs of rs4886761, rs4886467, rs4461027, and rs16958477 polymorphisms are involved in the pathogenetic mechanism of XFS/G.

Proteomics of pseudoexfoliation materials in the anterior eye segment

Pseudoexfoliation syndrome (PEX) is characterized by the production of white extracellular fluffy clumps of microfibrillar material that aggregates in various organs throughout the body but is known to cause disease in the eye. The accumulation of PEX material (PEXM) in the anterior segment ocular structures is believed to cause an increase in intraocular pressure (IOP) resulting in pseudoexfoliation glaucoma (PEXG). The onset of PEXG is often bilateral but asymmetric-one eye often presents with glaucoma prior to the other eye. Proteomics has been used to identify key proteins involved in PEXM formation with the end goal of developing effective treatments for PEX and PEXG which may act through inhibiting the formation of the PEX aggregates. To date, a variety of proteins with various molecular functions have been identified from extracted anterior segment structures and fluids, such as aqueous humor (AH) and blood serum of patients affected by PEX. From past studies, some proteins identified in AH, lens capsule epithelium, iris tissue, and blood serum samples include vitamin D binding protein (GC), apolipoprotein A4 (APOA4), lysyl oxidase like-1 (LOXL1), complement C3, beta-crystalline B1, and B2, and antithrombin-III (SERPINC1). Each of these proteins have been observed in eyes with PEX at varying levels within the different eye structures. In this review, we further examine the anterior segment ocular proteomics of PEXM from past studies to better understand the mechanism of PEX and PEXG development. Both genetic and environmental risk factors have been implicated to be involved in the development of PEX and PEXG. This field is at an early stage of investigation identifying how these factors modify proteins both at the expression and functional level to cause changes leading to the pathophysiology of PEX glaucoma.

Association of LOXL1 gene common sequence variants in Jordanian patients with exfoliation syndrome and exfoliative glaucoma

AIM

To investigate the association between single nucleotide polymorphisms (SNPs) in the LOXL1 gene with exfoliation syndrome/glaucoma (XFS/XFG) among Jordanians.

METHODS

Sixty-one patients with XFS/XFG and 59 healthy control individuals were recruited in the study. Patients were diagnosed with XFS/XFG using standard clinical examination techniques. The exonic rs1048661 SNP and the intronic rs2165241 SNP in LOXL1 gene were genotyped using sequencing technique. Allele and genotype frequencies were compared between cases and controls using Chi-square analysis.

RESULTS

The G allele of the rs1048661 SNP and the T allele of the rs2165241 SNP were common in the sample with frequencies of 86.4% and 81.4%, respectively. In addition, there were no significant differences in the genotypic and allelic distributions between patients and controls for rs1048661 SNP (P=0.770, OR=1.21, 95%CI: 0.56-2.60) and for rs2165241 SNP (P=0.605, OR=1.12, 95%CI: 0.59-2.09). In addition, no significant associations were found between haplotypes of the examined SNPs and XFS/XFG in the sample (P>0.05).

CONCLUSION

Variations in LOXL1 gene may not be associated with XFS/XFG in the Jordanian population. More studies are required to confirm the current findings.

What have we learned about exfoliation syndrome since its discovery by John Lindberg 100 years ago?

Exfoliation syndrome (XFS) is a systemic disease with significant ocular manifestations, including glaucoma and cataract. The disease impacts close to 70 million people globally and is now recognised as the most common identifiable cause of open-angle glaucoma. Since the discovery of XFS 100 years ago by Dr John G. Lindberg, there has been considerable advancement in understanding its pathogenesis and resulting clinical implications. The purpose of this paper is to summarise information regarding the epidemiology, pathophysiology, ocular manifestations and systemic associations of XFS with the objective of sharing clinical pearls to assist in early detection and enhanced management of patients.

Pseudoexfoliation syndrome-associated genetic variants affect transcription factor binding and alternative splicing of LOXL1

Although lysyl oxidase-like 1 (LOXL1) is known as the principal genetic risk factor for pseudoexfoliation (PEX) syndrome, a major cause of glaucoma and cardiovascular complications, no functional variants have been identified to date. Here, we conduct a genome-wide association scan on 771 German PEX patients and 1,350 controls, followed by independent testing of associated variants in Italian and Japanese data sets. We focus on a 3.5-kb four-component polymorphic locus positioned spanning introns 1 and 2 of LOXL1 with enhancer-like chromatin features. We find that the rs11638944:C>G transversion exerts a cis-acting effect on the expression levels of LOXL1, mediated by differential binding of the transcription factor RXRα (retinoid X receptor alpha) and by modulating alternative splicing of LOXL1, eventually leading to reduced levels of LOXL1 mRNA in cells and tissues of risk allele carriers. These findings uncover a functional mechanism by which common noncoding variants influence LOXL1 expression.

LOXL1 is a genetic risk factor for pseudoexfoliation syndrome of the eye but a causal variant has not been identified. Here, Pasutto et al., find intronic LOXL1 risk variants influence transcription factor binding and alternative splicing of LOXL1 in affected tissues reducing levels of LOXL1 mRNA.

Major review: Exfoliation syndrome; advances in disease genetics, molecular biology, and epidemiology

Exfoliation syndrome (XFS) is a common age-related disorder that leads to deposition of extracellular fibrillar material throughout the body. The most recognized disease manifestation is exfoliation glaucoma (XFG), which is a common cause of blindness worldwide. Recent developments in XFS genetics, cell biology and epidemiology have greatly improved our understanding of the etiology of this complex inherited disease. This review summarizes current knowledge of XFS pathogenesis, identifies gaps in knowledge, and discusses areas for future research.

Ethnicity-Based Differences in the Association of LOXL1 Polymorphisms with Pseudoexfoliation/Pseudoexfoliative Glaucoma: A Meta-Analysis

Pseudoexfoliation (PEX) is an age-related disorder of the extracellular matrix; it is strongly associated with glaucoma, the leading cause of irreversible blindness worldwide. We conducted an ethnic-based meta-analysis of the association of LOXL1 polymorphisms with PEX/pseudoexfoliative glaucoma (PEXG). Association studies were retrieved systematically from PubMed, EMBASE, and Web of Knowledge. Allelic and genotype frequencies of rs3825942, rs1048661, and rs2165241 were compared between PEX/PEXG and controls. Odds ratios (OR) and 95% confidence intervals (CI) were calculated using a random effects model. Overall, 39 independent cohorts were included. Rs3825942 (G) was an at risk allele for PEX/PEXG in Caucasians, Japanese, Koreans, Chinese, South Asians, and Middle Easterners, but protective in Black South Africans (OR = 0.10, 95%CI:0.06-0.16). Rs1048661 (G) was an at risk allele for PEX/PEXG in Caucasians, South Asians, Middle Easterners and Black South Africans, but was protective in Japanese (OR = 0.03, 95%CI:0.02-0.06) and Koreans (OR = 0.10, 95%CI:0.05-0.22). These associations we-re confirmed for the genotypic recessive models. Rs2165241 (C) was a protective allele for PEX/PEXG in Caucasians, but was an at risk allele in Japanese (OR = 7.49, 95%CI:3.22-17.41) and Koreans (OR = 6.63, 95%CI:2.60-16.90). This was confirmed for the genotypic dominant model. Other genetic and/or environmental factors may modify the effect of LOXL1 polymorphisms in certain ethnic groups.