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

Glaucoma, the world's leading cause of irreversible blindness, is a complex disease, with differential presentation as well as ethnic and geographic disparities. The multifactorial nature of glaucoma complicates the study of genetics and genetic involvement in the disease process. This review synthesizes the current literature on glaucoma and genetics, as stratified by glaucoma subtype and ethnicity. Primary open-angle glaucoma (POAG) is the most common cause of glaucoma worldwide, with the only treatable risk factor (RF) being the reduction of intraocular pressure (IOP). Genes associated with elevated IOP or POAG risk include: ABCA1, AFAP1, ARHGEF12, ATXN2, CAV1, CDKN2B-AS1, FOXC1, GAS7, GMDS, SIX1/SIX6, TMCO1, and TXNRD2. However, there are variations in RF and genetic factors based on ethnic and geographic differences; it is clear that unified molecular pathways accounting for POAG pathogenesis remain uncertain, although inflammation and senescence likely play an important role. There are similar ethnic and geographic complexities in primary angle closure glaucoma (PACG), but several genes have been associated with this disorder, including MMP9, HGF, HSP70, MFRP, and eNOS. In exfoliation glaucoma (XFG), genes implicated include LOXL1, CACNA1A, POMP, TMEM136, AGPAT1, RBMS3, and SEMA6A. Despite tremendous progress, major gaps remain in resolving the genetic architecture for the various glaucoma subtypes across ancestries. Large scale carefully designed studies are required to advance understanding of genetic loci as RF in glaucoma pathophysiology and to improve diagnosis and treatment options.

https://www.mdpi.com/2073-4425/12/1/55/pdf

Molecular Genetics of Glaucoma: Subtype and Ethnicity Considerations

OBJECTIVE: We present the genetic evaluation of a male with Wildervanck Syndrome (WS) and his family. BACKGROUND: Wildervanck Syndrome (cervico-oculo-acoustic syndrome) consists of the Klippel-Feil anomaly, Duane retraction syndrome, and congenital deafness. It is much more common in females than males and could be due to an X-linked mutation that is lethal to hemizygous males. DESIGN/METHODS: Clinical evaluation; sequencing of candidate genes; and array comparative genomic hybridization. RESULTS: The patient had fusion of almost the entire cervical spine, bilateral type 1 DRS, and bilateral severe sensorineural hearing loss due to bilateral cochlear dysplasia. He also had congenital heart disease requiring surgery. His parents were unrelated, and he had eight unaffected siblings. The patient had no mutation found by Sanger sequencing of HOXA1, KIF21A, SALL4, and CHN1. He had a 3kB deletion in the X-chromosome at Xq26.3 that was not found in his mother, one unaffected sibling, or 56 healthy controls of matching ethnicity. This deletion encompassed only one gene, Fibroblast Growth Factor Homologous Factor 2 (FGF13), which encodes a 216-amino acid protein that acts intracellularly in neurons throughout brain development. CONCLUSIONS: Analysis of this patient9s phenotype and genotype open the possibility that X-chromosome deletions may be a cause of WS with larger deletions being lethal to males and that FGF13 mutations may be a cause of WS. Disclosure: Dr. Bosley has nothing to disclose. Dr. Kondkar has nothing to disclose. Dr. Alorainy has nothing to disclose. Dr. Khan has nothing to disclose. Dr. Oystreck has nothing to disclose. Dr. Abu-Amero has nothing to disclose.

Xq26.3 Microdeletion in a Male with Wildervanck Syndrome (P02.255)

Objectives To investigate the three single nucleotide polymorphisms (SNPs) (rs3825942, rs1048661, and rs2165241) of the LOXL1 gene in pseudoexfoliation syndrome (XFS) and pseudoexfoliation glucoma (XFG) in the Turkish population. Materials and methods DNA was obtained from blood samples of 48 XFS, 58 XFG, and 171 control subjects. Three LOXL1 SNPs (rs3825942, rs1048661, rs2165241) were investigated with real time PCR, a probe-based genotyping method, and melting curve analysis. Results All three SNPs of LOXL1 were significantly associated with XFS (rs3825942 p=3.54x10-6, odds ratio [OR]=∞; rs1048661 p=0.008, OR=2.18; rs2165241 p=8.69x10-9, OR=4.30) and XFG (rs3825942 p=3.41x10-7, OR=∞; rs1048661 p=1.75x10-5, OR=3.78; rs2165241 p=3.85x10-11 OR=4.90). No significant differences were observed between the XFS and XFG groups for any of the SNPs. The GG genotype of rs3825942 was more valuable for distinguishing pseudoexfoliative cases from healthy individuals. The homozygous TT genotype of rs2165241 was associated with 6-fold increased XFS risk (p=8.15x10-8, OR=6.32) and 7-fold increased XFG risk (p=1.45x10-10 OR=7.95). The GGT haplotype consisting of all three risk alleles was associated with a 7.45-fold higher risk of XFS/XFG (p=8.65x10-14, OR=7.45). Presence of T allele of rs2165241 conferred 3 times higher risk for men than women (p=6.78x10-5, OR=3.202). Conclusion LOXL1 SNPs are associated with increased risk for pseudoexfoliation in the Turkish population. T allele of rs2165241 was found to be the most important characterized risk factor for our cohort. All SNP distributions were similar to other European and American populations.

Three Single Nucleotide Polymorphisms of LOXL1' in a Turkish Population with Pseudoexfoliation Syndrome and Pseudoexfoliation Glaucoma.

Background Single nucleotide polymorphisms (SNPs) in the gene encoding LOXL1 are risk factors for exfoliation syndrome and exfoliation glaucoma. This meta-analysis comprehensively investigated the association between LOXL1 gene polymorphisms (rs1048661, rs3825942, and rs2165241) and the risk of exfoliation syndrome/exfoliation glaucoma (XFS)/(XFG). Methods All eligible case-control studies, published before August 17, 2020, were searched on Medline (Ovid), PubMed, CNKI, EMBASE, and Wanfang databases. Results In total, 5022 cases and 8962 controls were included in this meta-analysis. Significant associations between LOXL1 gene polymorphisms and XFS/XFG risk was observed in the disease types-based subgroups. In addition, in the subgroup analysis of ethnicity, positive associations between LOXL1 gene polymorphisms (rs1048661, rs3825942, and rs2165241) and XFS/XFG risk were found in Caucasians. Furthermore, rs1048661 and rs3825942 polymorphisms were related to XFS/ XFG risk in Asians; however, no significant association was observed between the LOXL1 gene rs2165241 polymorphism and XFS/XFG risk in Asians. In addition, rs1048661 and rs3825942 correlated with XFS/XFG susceptibility in Africans. Conclusions Our results implicate LOXL1 gene polymorphisms as XFS/XFG risk factors, especially in Caucasians.

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LOXL1 gene polymorphisms are associated with exfoliation syndrome/exfoliation glaucoma risk: An updated meta-analysis.

The purpose of this study is to evaluate whole lysyl oxidase like 1 (LOXL1) gene by sequence analysis in Turkish patients with exfoliation glaucoma (XFG). A total of 48 (35 male, 13 female) patients with XFG were enrolled. Besides routine ophthalmological examination, peripapillary retinal nerve fibre layer (RNFL) analysis with optic coherence tomography was performed. Blood samples of 2 ml with EDTA were obtained and sent to Medical Genetics Department, Molecular Genetics Laboratory for LOXL1 polymorphism (PCR and agarose gel imaging) analysis. The role of the detected changes on disease severity was evaluated. No LOXL1 gene mutations in any of the patients were detected. Three types of single-nucleotide polymorphisms (SNPs) including R141L(rs1048661), A320A(rs41435250), and F184F were detected in 17 (35.3 %) patients. When compared, SNP-positive patients had thinner RNFL than SNP-negative patients (64.5 ± 17.6 and 66.1 ± 20.4 µ, respectively), and SNP-positive patients had higher cupping/disc ratio than SNP-negative patients (0.76 ± 0.2 and 0.70 ± 0.3, respectively). However, both values were not statistically significant (p = 0.966 and p = 0.539, respectively). When compared, R141L-positive patients had significantly thinner cornea thickness (516.11 ± 30.3 µ) than R141L-negative patients (556.69 ± 27.2 µ) (p = 0.004). There was not any statistical significant difference in the means of age, gender, BCVA, MD, PSD, IOP, number of hypotensive agents, and percent of glaucoma surgery (p > 0.05). In this study group of Turkish population, no LOXL1 mutations were found. No associations between the defined SNPs (A320A, R141L and F184F) and the severity of the disease were detected.

LOXL1 gene analysis in Turkish patients with exfoliation glaucoma

Purpose To investigate CHN1 (chimerin 1) gene mutations in patients with isolated nonsyndromic Duane syndrome and accompanying positive familial history, bilaterality, or various systemic disorders. Methods Patients with Duane retraction syndrome (DRS) and a positive family history of congenital ocular motility disturbance or bilateral involvement or accompanying any congenital disorder(s) seen consecutively at a single center from 2013 to 2016 were enrolled. All subjects underwent full ophthalmologic examination, including refraction, best-corrected visual acuity, ocular alignment and motility, globe retraction, and biomicroscopic or fundus evaluation. DNA samples were investigated by direct sequencing of the coding regions of the CHN1 gene. Results A total of 30 patients (15 males) were included (mean age, 11.8 ± 10.4 years; range, 2-45 years): 8 cases presented with bilateral DRS; 22, with unilateral DRS. Family history of ocular motility abnormality was positive in 16 patients. Eleven cases had an additional congenital disorder. In 2 patients, 2 different mutations were detected in the CHN1 gene: p.E313K (c.937G>A) and p.N224S (c.671A>G). Conclusions CHN1 mutations were identified in 2 bilateral cases and in 1 parent of 1 affected case. One mutation is novel and occurred with additional vertical gaze abnormalities. Additional genetic studies evaluating chimerin 1 (CHN1) and its role in the development of the ocular motor axis are needed to provide new data about these mutations and phenotypic variations.

CHN1 gene mutation analysis in patients with Duane retraction syndrome.

Objective To investigate TGFB1 and LAMA1 gene polymorphisms in children with high myopia in order to determine the genetic basis of large myopic shifts causing severe visual impairment and complications. Methods Seventy-four children with high myopia (≥6 diopters [D]; study group) and 77 emmetropic children (±0.5D; control group) were included. Genetic and polymorphism analyses were performed in the Medical Genetics Laboratory using DNA purified from the patients' blood samples. Results Mean ages of the patients were 7.1±3 (3-13) and 9.6±1.8 (6-13) years in the study and control groups, respectively. Mean refraction in the high myopia group were -10.1±4.3D in the right and -8.9±3.6D in the left eye. LAMA1 gene analysis of the study group revealed heterozygous mutations in 34 patients (45.9%), homozygous mutations in 25 patients (33.8%), and no mutations in the remaining 15 patients (20.3%). In the control group, there were 31 subjects (40.3%) with heterozygous, 27 (35.1%) with homozygous LAMA1 mutations, and no mutations in 19 (24.7%) (p=0.73). TGFB1 gene analysis showed heterozygous mutations in 32 (43.2%) and homozygous mutations in 10 patients (13.5%) in the study group, while 32 patients (43.2%) had no mutations. In the control group, 35 subjects (45.5%) had heterozygous, 8 (10.4%) had homozygous, and 34 (44.1%) had no TGFB1 mutations (p=0.36). Conclusion This is the first study to simultaneously examine two genes in high myopia in a Turkish population. However, we observed no significant differences in TGFB1 and LAMA1 gene polymorphisms in patients with high myopia compared to healthy subjects.

Orhan Ilim

Papers

LOXL1 gene analysis in Turkish patients with exfoliation glaucoma

CHN1 gene mutation analysis in patients with Duane retraction syndrome.

TGFB1 and LAMA1 gene polymorphisms in children with high myopia.

Association of Lysyl Oxidase-like 1 Gene Polymorphism in Turkish Patients With Pseudoexfoliation Syndrome and Pseudoexfoliation Glaucoma.