Association of Gene Polymorphisms with Normal Tension Glaucoma: A Systematic Review and Meta-Analysis.

BACKGROUND: Normal tension glaucoma (NTG) is becoming a more and more serious problem, especially in Asia. But the pathological mechanisms are still not illustrated clearly. We carried out this research to uncover the gene polymorphisms with NTG. METHODS: We searched in Web of Science, Embase, Pubmed and Cochrane databases for qualified case-control studies investigating the association between single nucleotide polymorphisms (SNPs) and NTG risk. Odds ratios (ORs) and 95% confidence intervals (CIs) for each SNP were estimated by fixed- or random-effect models. Sensitivity analysis was also performed to strengthen the reliability of the results. RESULTS: Fifty-six studies involving 33 candidate SNPs in 14 genetic loci were verified to be eligible for our meta-analysis. Significant associations were found between 16 SNPs (rs166850 of OPA1; rs10451941 of OPA1; rs735860 of ELOVL5; rs678350 of HK2; c.603T>A/Met98Lys of OPTN; c.412G>A/Thr34Thr of OPTN; rs10759930 of TLR4; rs1927914 of TLR4; rs1927911 of TLR4; c.*70C>G of EDNRA; rs1042522/-Arg72Pro of P53; rs10483727 of SIX1-SIX6; rs33912345 of SIX1-SIX6; rs2033008 of NCK2; rs3213787 of SRBD1 and c.231G>A of EDNRA) with increased or decreased risk of NTG. CONCLUSIONS: In this study, we confirmed 16 genetic polymorphisms in 10 genes (OPA1, ELOVL5, HK2, OPTN, TLR4, EDNRA, P53, NCK2, SRBD1 and SIX1-SIX6) were associated with NTG.

Exploring the role of apolipoprotein E gene promoter polymorphisms in susceptibility to normal-tension glaucoma in a Korean population.

Glaucoma, particularly primary open-angle glaucoma (POAG), poses a significant global health concern. Distinguished by intraocular pressure (IOP), POAG encompasses high-tension glaucoma (HTG) and normal-tension glaucoma (NTG). Apolipoprotein E (APOE) is a multifaceted protein with roles in lipid metabolism, neurobiology, and neurodegenerative diseases. However, controversies persist regarding the impact of APOE single-nucleotide polymorphisms (SNPs) on open-angle glaucoma and NTG. This study aimed to identify APOE-specific SNPs influencing NTG risk. A cohort of 178 patients with NTG recruited from Uijeongbu St. Mary's Hospital and 32,858 individuals from the Korean Genome and Epidemiology Study (KoGES) cohort were included in the analysis. Genotype and haplotype analyses were performed on three promoter SNPs (rs449647, rs769446, and rs405509) and two exonic SNPs (rs429358 and rs7412) located on chromosome 19. Among the five SNPs, rs769446 genotypes exhibited significant differences between cases and controls. The minor allele C of rs769446 emerged as a protective factor against NTG. Furthermore, haplotype analysis of the five SNPs revealed that the A-T-G-T-T haplotype was a statistically significant risk factor for NTG. This study indicated an association between APOE promoter SNPs and NTG in the Korean population. Further studies are required to understand how APOE promoter SNPs contribute to NTG pathogenesis.

Primary open-angle glaucoma risk prediction with ABCA1 and LOC102723944 variants and their genotype-phenotype correlations in southern Chinese population.

Glaucoma is a leading cause of irreversible visual impairment and blindness worldwide. Previous genome-wide association studies have identified caveolin-1 (CAV1), ATP-binding cassette A1 (ABCA1), and forkhead box C1 (FOXC1) loci associated with primary open angle glaucoma (POAG), a major subtype of glaucoma. This study aimed to fine map the association pattern of FOXC1 locus with POAG and determine the correlations of FOXC1, ABCA1, and CAV1 variants with ocular and lipidemic parameters in southern Chinese population. In total, 1291 unrelated Han Chinese subjects were recruited, including 301 high-tension glaucoma (HTG), 126 normal-tension glaucoma (NTG), and 864 control subjects. Twelve variants in FOXC1 locus, and two variants in ABCA1 and CAV1 genes, were genotyped by TaqMan assays. Genetic risk score and genotype-phenotype correlation analyses were conducted. In the FOXC1 locus, LOC102723944 rs6596830, rather than previously reported rs2745572, showed significant association with POAG (P = 8.61 × 10-4, odds ratio (OR) = 0.75) and HTG (P = 3.68 × 10-3, OR = 0.75). ABCA1 rs2487032 was also significantly associated with POAG (P = 3.00 × 10-5, OR = 0.70) and HTG (P = 2.08 × 10-4, OR = 0.70). Joint analysis showed that carriers of homozygous non-protective alleles of ABCA1 rs2487032 and LOC102723944 rs6596830 had 2.99-fold higher risk of POAG (P = 1.27 × 10-3) when compared to those carrying homozygous non-risk alleles. Patients with POAG carrying ABCA1 rs2487032 G allele had higher HDL cholesterol, and those with LOC102723944 rs6596830 A allele had lower LDL. This study revealed individual and joint association of ABCA1 and LOC102723944 variants with POAG in southern Chinese population. Subjects carrying non-protective alleles had increased risk to POAG, and corresponding genotypes would affect the lipid profiles.

Familial normal tension glaucoma genetics.

Glaucoma is defined by characteristic optic nerve damage and corresponding visual field defects and is the leading cause of irreversible blindness in the world. Elevated intraocular pressure (IOP) is a strong risk factor for developing glaucoma. However, glaucoma can occur at any IOP. Normal tension glaucoma (NTG) arises with IOPs that are within what has been defined as a normal range, i.e., 21 mm Hg or less, which may present challenges in its diagnosis and management. Identifying inheritance patterns and genetic mutations in families with NTG has helped elucidate mechanisms of NTG, however the pathophysiology is complex and not fully understood. Approximately 2% of NTG cases are caused primarily by mutations in single genes, optineurin (OPTN), TANK binding kinase 1 (TKB1), or myocilin (MYOC). Herein, we review pedigree studies of NTG and autosomal dominant NTG caused by OPTN, TBK1, and MYOC mutations. We review identified mutations and resulting clinical features of OPTN-associated and TBK1-associated NTG, including long-term follow up of these patients with NTG. In addition, we report a new four-generation pedigree of NTG caused by a Glu50Lys OPTN mutation, including six family members with a mean follow up of 17 years. Common features of OPTN -associated NTG due to Glu50Lys mutation included early onset of disease with an IOP <21 mm Hg, marked optic disc cupping, and progressive visual field loss which appeared to stabilize once an IOP of less than 10 mm Hg was achieved. Lastly, we review risk factor genes which have been identified to contribute to the complex inheritance of NTG.

Low mitochondrial DNA copy number in buffy coat DNA of primary open-angle glaucoma patients.

Primary open-angle glaucoma (POAG) is characterized by optic nerve degeneration and irreversible loss of retinal ganglion cells (RGCs). The pathophysiology is not fully understood. Since RGCs have a high energy demand, suboptimal mitochondrial function may put the survival of these neurons at risk. In the present study, we explored whether mtDNA copy number or mtDNA deletions could reveal a mitochondrial component in POAG pathophysiology. Buffy coat DNA was isolated from EDTA blood of age- and sex-matched study groups, namely POAG patients with high intraocular pressure (IOP) at diagnosis (high tension glaucoma: HTG; n = 97), normal tension glaucoma patients (NTG, n = 37), ocular hypertensive controls (n = 9), and cataract controls (without glaucoma; n = 32), all without remarkable comorbidities. The number of mtDNA copies was assessed through qPCR quantification of the mitochondrial D-loop and nuclear B2M gene. Presence of the common 4977 base pair mtDNA deletion was assessed by a highly sensitive breakpoint PCR. Analysis showed that HTG patients had a lower number of mtDNA copies per nuclear DNA than NTG patients (p-value <0.01, Dunn test) and controls (p-value <0.001, Dunn test). The common 4977 base pair mtDNA deletion was not detected in any of the participants. A lower mtDNA copy number in blood of HTG patients suggests a role for a genetically defined, deficient mtDNA replication in the pathology of HTG. This may cause a low number of mtDNA copies in RGCs, which together with aging and high IOP, may lead to mitochondrial dysfunction, and contribute to glaucoma pathology.

Comparison of the clinical and genetic features of autosomal dominant optic atrophy and normal tension glaucoma in young Chinese adults.

BACKGROUND/OBJECTIVES: To compare the clinical and optical coherence tomography (OCT) characteristics of autosomal dominant optic atrophy (ADOA) and normal tension glaucoma (NTG) in Chinese patients. SUBJECTS/METHODS: Twenty-four unrelated patients with ADOA and 21 unrelated patients with NTG, younger than 30 years, were enrolled in this study. Data regarding the demographic and clinical characteristics of the patients were collected, and their peripapillary retinal nerve fibre layer (RNFL) and macular ganglion cell complex (GCC) thicknesses were evaluated using OCT. Sequencing of genes associated with neuro-ophthalmic disorders was performed for all patients. RESULTS: The average age at onset of the ADOA group (13.92 ± 10.73 years) was significantly younger than that of the NTG group (23.67 ± 4.98 years, P = 0.002). Best-corrected visual acuity was significantly poorer in the ADOA group (0.75 ± 0.32) than in the NTG group (0.16 ± 0.19, P < 0.001). The average peripapillary RNFL thickness and the RNFL thicknesses in the temporal upper, temporal lower, and nasal lower sectors were significantly thinner in the ADOA group than in the NTG group (all P < 0.05). Moreover, the macular GCC thickness of the ADOA group was significantly thinner than that of the NTG group (P < 0.001). Twenty-three OPA1 variants (11 novel OPA1 variants) and one OPA3 variant were detected in 24 patients with ADOA. CONCLUSIONS: Our study revealed a distinct difference between the patterns of RNFL and GCC loss in ADOA and NTG, which will help to differentiate ADOA from NTG in young patients. Additionally, this study expanded the genetic spectrum of ADOA.

Association of Polymorphisms at the SIX1/SIX6 Locus With Normal Tension Glaucoma in a Korean Population.

PRCIS: We demonstrated that SIX1/SIX6 locus polymorphism (rs10483727 and rs33912345) was significantly associated with a genetic susceptibility to NTG in a Korean population. More studies are needed to investigate whether the SIX1/SIX6 locus is associated with NTG among various ethnic populations. PURPOSE: Several previous studies have reported that the relevance of the SIX1/SIX6 locus to open angle glaucoma (OAG) in various ethnic populations. However, definitions of OAG patients were different among those studies. The relevance of the SIX1/SIX6 locus to normal tension glaucoma (NTG) in a Korean population remains uncertain. Therefore, the purpose of this study was to investigate the relationship of the SIX1/SIX6 locus with NTG in a Korean cohort. METHOD: Patients with NTG and ethnically matched healthy controls were recruited from eye clinics in Korea (210 cases and 117 controls). Four polymorphisms (rs33912345, rs12436579, rs2179970, and rs10483727) of the SIX1/SIX6 locus were genotyped for 327 subjects using a TaqMan single nucleotide polymorphism genotyping assay. RESULTS: The rs33912345 polymorphism was significantly correlated with NTG in the recessive model [odds ratio (OR): 0.265; 95% confidence interval (CI): 0.078-0.898, P =0.033], but not in the allelic and dominant models (both P >0.05). The SNP rs10483727 was significantly associated with NTG in the allelic model (OR: 0.674; 95% CI: 0.464-0.979, P =0.038) and the recessive model (OR: 0.187; 95% CI: 0.058-0.602, P =0.005). Genetic association analysis of SNP rs12436579 and rs2179970 revealed no significant difference in genotype distribution between NTG cases and controls in the allelic, dominant, or recessive models (all P >0.05). CONCLUSION: The current study found that SIX1-SIX6 locus rs10483727 and rs33912345 polymorphisms were significantly associated with NTG risk in the Korean population.

Association between HSPA5 Promoter Polymorphisms and a Reduced Risk of Normal Tension Glaucoma.

INTRODUCTION: In normal tension glaucoma (NTG), factors other than elevated intraocular pressure (IOP) are likely to play a role in the pathogenesis of optic neuropathy. The potential similarities between Alzheimer's disease (AD) and NTG in cellular apoptosis leading to neurodegeneration have been shown in recent studies. Heat Shock Protein family A member 5 (HSPA5) promoter polymorphisms have been reported to be associated with a risk of AD. The purpose of our study was to investigate the role of HSPA5 promoter polymorphisms in NTG patients. METHODS: A total of 222 patients with NTG, along with 236 normal controls were enrolled in this study. Genomic DNA was amplified through a polymerase chain reaction (PCR) and identified for the polymorphic HSPA5 (-415 and -370) by Xmn1 and BstY1 restriction digestion, respectively. PCR fragments with potential polymorphic HSPA5 (-180) were subjected to sequence-analyses by a Hex-labeled primer. Genotypes for both NTG patients and control groups were compared for statistically significant differences. RESULTS: Polymorphisms (-415) G/A and (-180) del/G were completely linked in our population. The genotype and allele frequency distribution at the -415 G/A and -180 del/G sites showed a significant difference between the NTG cases and controls. The genotype frequency of HSPA5 (-415) AA/(-180) GG and the allele frequency of HSPA5 (-415) A/(-180) G were significantly lower (p = 0.04 and p = 0.01, respectively) in the NTG patients when compared with those in the control group. There was no significant difference in genotype or allele frequency distribution of the HSPA5 (-370) C/T between the NTG and control groups. There was a reduced risk of NTG associated with the carriers for the HSPA5 (-415) A/(-180) G allele compared with that in the control population (p = 0.01). CONCLUSION: HSPA5 (-415) A and (-180) G allele polymorphisms may be protective factors in the development of NTG.

MicroRNA profiles in aqueous humor between pseudoexfoliation glaucoma and normal tension glaucoma patients in a Korean population.

We aimed to obtain microRNA (miRNA) profiles of patients with pseudoexfoliation (PEX) glaucoma or normal-tension glaucoma (NTG) compared to normal controls using individual aqueous humor (AH) samples and investigate the role of miRNAs in the pathogenesis of PEX glaucoma compared to NTG in Korean. AH (80-120 µl) was collected before cataract surgery or trabeculectomy from 26 Korean subjects (eleven with PEX glaucoma, age-matched eight NTG, and seven controls). RNA sequencing was conducted for RNA samples extracted from 26 AH samples. Bioinformatics analysis was performed for targets and related pathways. A total of 334 and 291 discrete miRNAs were detected in AH samples of PEX glaucoma and NTG patients, respectively. Two significantly upregulated miRNAs (hsa-miR-30d-5p and hsa-miR-320a) and ten significantly downregulated miRNAs (hsa-miR-3156-5p, hsa-miR-4458, hsa-miR-6717-5p, hsa-miR-6728-5p, hsa-miR-6834-5p, hsa-miR-6864-5p, hsa-miR-6879-5p, hsa-miR-877-3p, hsa-miR-548e-3p, and hsa-miR-6777-5p) in PEX glaucoma patients compared to control (fold-change > 2, p < 0.05) were found. In NTG patients, ten significantly upregulated and two downregulated miRNAs compared to control were found. Only hsa-miR-6777-5p was commonly downregulated in both PEX glaucoma and NTG patients. Related pathways were proteoglycans in cancer, glioma, and TGF-beta signaling pathway in PEX glaucoma. These differentially expressed miRNAs between PEX glaucoma and NTG samples suggest the possible role of miRNA in the pathogenesis of glaucoma, further implying that pathogenic mechanisms may differ between different types of glaucoma.

Associations between OPA1, MFN1, and MFN2 polymorphisms and primary open angle glaucoma in Polish participants of European ancestry.

BACKGROUND: Glaucomatous optic nerve damage is caused by selective death of retinal ganglion cells (RGCs). Another condition with underlying loss of RGCs is autosomal dominant optic atrophy (ADOA). Majority of ADOA patients have mutations in OPA1, gene responsible for mitochondrial fusion final steps. Clinical resemblance between the two diseases make genes involved in mitochondrial fusion good candidates as glaucoma genes. In this study, we investigated if selected polymorphisms of OPA1, MFN1, and MFN2 were associated with glaucoma in Polish population. METHODS: Four OPA1 (rs166850, rs10451941, rs7624750, rs9851685), one MFN1 (rs2111534), and two MFN2 (rs873458, rs2295281) single nucleotide polymorphisms were investigated in 304 primary open angle glaucoma patients (204 with normal tension glaucoma, 100 with high-tension glaucoma) and 258 control subjects using RT-PCR method. RESULTS: There was a significant difference in genotype frequencies of rs9851685 and rs2111534 polymorphisms between glaucoma patients and control subjects. Several genotype combinations comprising SNPs at OPA1 and MFN1 were significantly differently distributed in a three-way comparison between controls, patients with NTG and patients with HTG. None of the studied MFN2 polymorphisms was significantly associated with HTG or NTG. CONCLUSIONS: In studied population, genotype CC and allele C of rs9851685 OPA1 polymorphism are NTG risk factors, whereas TT genotype and T allele of this polymorphism are protective factors against NTG. Genotype GA of rs2111534 MFN1 polymorphism is an HTG risk factor and AA genotype of this polymorphism is a protective factor against HTG. Several OPA1 and MFN2 genotype combinations are significantly associated with either increased or decreased risk of glaucoma in this population.

WDR36-Associated Neurodegeneration: A Case Report Highlights Possible Mechanisms of Normal Tension Glaucoma.

WDR36 is one of a number of genes implicated in the pathogenesis of adult-onset primary open angle glaucoma (POAG). Here we describe in detail the phenotype of a patient with pathogenic variation in WDR36 who presented with a protracted history of central vision loss. On exam visual acuities were at 20/100 level, had a tritan color defect and showed central arcuate visual field defects on visual field testing. Enlarged cup-to-disk ratios with normal intraocular pressures were associated with severe thinning of the ganglion cell layer (GCL) and retinal nerve fiber layer consistent with a clinical diagnosis of normal tension glaucoma. Full-field electroretinograms revealed a severe inner retinal dysfunction with reduced amplitudes and remarkably delayed timings of the b-wave, but preserved photoreceptor (a-wave) function. The pattern described herein recapitulates some of the findings of an animal model of WDR36-associated POAG and suggests a mechanism of disease that involves a retina-wide inner retinal dysfunction and neurodegeneration beyond the GCL. Further detailed structural and functional characterizations of patients with a pathogenic variant in the WDR36 gene are required to confirm these findings.

Profiles of microRNA in aqueous humor of normal tension glaucoma patients using RNA sequencing.

We aimed to identify and compare microRNAs (miRNAs) from individual aqueous humor samples between normal-tension glaucoma (NTG) patients and normal controls. Aqueous humor (80 to 120 µl) was collected before cataract surgery. Six stable NTG patients and seven age-matched controls were included in the final analysis. RNA sequencing was conducted for RNA samples extracted from the 13 aqueous humor samples, and bioinformatics analysis was employed for the miRNA targets and related pathways. Two hundred and twenty-eight discrete miRNAs were detected in the aqueous humor and consistently expressed in all samples. Eight significantly upregulated miRNAs were found in the NTG patients compared to the controls (fold-change > 2, p < 0.05). They were hsa-let-7a-5p, hsa-let-7c-5p, hsa-let-7f-5p, hsa-miR-192-5p, hsa-miR-10a-5p, hsa-miR-10b-5p, hsa-miR-375, and hsa-miR-143-3p. These miRNAs were predicted to be associated with the biological processes of apoptosis, autophagy, neurogenesis, and aging in the gene ontology categories. The related Kyoto encyclopedia of genes and genomes pathways were extracellular matrix-receptor interaction, mucin-type O-glycan biosynthesis, biotin metabolism, and signaling pathways regulating the pluripotency of stem cells. The differentially expressed miRNA in the NTG samples compared to the controls suggest the possible roles of miRNA in the pathogenesis of NTG. The underlying miRNA-associated pathways further imply novel targets for the pathogenesis of NTG.

Neuroprotective effects of bone marrow Sca-1+ cells against age-related retinal degeneration in OPTN E50K mice.

Glaucoma is characterized by retinal ganglion cell (RGC) death, the underlying mechanisms of which are still largely unknown. An E50K mutation in the Optineurin (OPTN) gene is a leading cause of normal-tension glaucoma (NTG), which directly affects RGCs in the absence of high intraocular pressure and causes severe glaucomatous symptoms in patients. Bone marrow (BM) stem cells have been demonstrated to play a key role in regenerating damaged tissue during ageing and disease through their trophic effects and homing capability. Here, we separated BM stem cells into Sca-1+ and Sca-1- cells and transplanted them into lethally irradiated aged OPTN E50K mice to generate Sca-1+ and Sca-1- chimaeras, respectively. After 3 months of BM repopulation, we investigated whether Sca-1+ cells maximized the regenerative effects in the retinas of NTG model mice with the OPTN E50K mutation. We found that the OPTN E50K mutation aggravated age-related deficiency of neurotrophic factors in both retinas and BM during NTG development, leading to retinal degeneration and BM dysfunction. Sca-1+ cells from young healthy mice had greater paracrine trophic effects than Sca-1- cells and Sca-1+ cells from young OPTN E50K mice. In addition, Sca-1+ chimaeras demonstrated better visual functions than Sca-1- chimaeras and untreated OPTN E50K mice. More Sca-1+ cells than Sca-1- cells were recruited to repair damaged retinas and reverse visual impairment in NTG resulting from high expression levels of neurotrophic factors. These findings indicated that the Sca-1+ cells from young, healthy mice may have exhibited an enhanced ability to repair retinal degeneration in NTG because of their excellent neurotrophic capability.

Proteomic analysis of aged and OPTN E50K retina in the development of normal tension glaucoma.

Progressive degeneration of retinal ganglion cells (RGCs) is a major characteristic of glaucoma, whose underlying mechanisms are still largely unknown. An E50K mutation in the Optineurin (OPTN) gene is a leading cause of normal tension glaucoma (NTG), directly affecting RGCs without high intraocular pressure and causing severe glaucomatous symptoms in clinical settings. A systematic analysis of the NTG mouse model is crucial for better understanding of the underlying pathological mechanisms for glaucoma. To elucidate proteomic and biochemical pathway alterations during NTG development, we established an OPTN E50K mutant mouse model through CRISPR/Cas9. Retinal proteins from resulting mice exhibiting glaucomatous phenotypes were subject to tandem mass tag-labeled quantitative proteomics and then analyzed through bioinformatics methods to characterize the molecular and functional signatures of NTG. We identified 6364 quantitative proteins in our proteomic analysis. Bioinformatics analysis revealed that OPTN E50K mice experienced protein synthesis dysregulation, age-dependent energy defects and autophagy-lysosome pathway dysfunction. Certain biological features, including amyloid deposition, RNA splicing, microglia activation and reduction of crystallin production, were similar to Alzheimer's disease. Our study is the first to describe proteomic and biochemical pathway alterations in NTG pathogenesis during disease advancement. Several proteomic signatures overlapped with retinal changes found in the ad mice model, suggesting the presence of common mechanisms between age-related degenerative disorders, as well as prospective new targets for diagnostic and therapeutic strategies.

FOXC1 variant in a family with anterior segment dysgenesis and normal-tension glaucoma.

Our study describes the glaucoma phenotype in a family with Axenfeld-Rieger syndrome (ARS) and a FOXC1 variant. Included were 20 subjects from a large three generation family of Jewish Indian ancestry. Subjects underwent a comprehensive ophthalmic examination including automated perimetry and optical coherence tomography. Eight subjects were available for molecular analysis which included whole genome sequencing on selected patients and Sanger sequencing for variant screening. Eleven patients demonstrated a wide spectrum of Axenfeld-Rieger anomaly signs and symptoms. These ranged from subtle angle abnormalities to remarkable anterior segment abnormalities such as corectopia, iris adhesions and strands. Among them, six had glaucoma and two were glaucoma suspects. Of the six subjects with glaucoma three had high-tension glaucoma and two had normal-tension glaucoma. Molecular analysis revealed a previously described pathogenic variant in the FOXC1 gene (c.378C > G p.I126M; rs104893958), in six affected patients which was not identified in two healthy siblings. Molecular analysis also revealed a PITX2 missense variant (c.28T > A p.L10M; rs755864040) which did not segregate with clinical findings and was considered likely benign. In conclusion, patients with ARS due to FOXC1 variants may present with glaucomatous optic nerve damage without apparent elevation in IOP. Normal-tension glaucoma is less commonly reported in individuals with ARS and a comprehensive glaucoma assessment may be warranted in these individuals even with normal IOP. These findings raise the possibility that glaucomatous damage associated with FOXC1 is not only due to high IOP.

EAAT1 variants associated with glaucoma.

Glaucoma is one of the leading causes of blindness characterized by progressive loss of retinal ganglion cells (RGCs) and their axons. We reported that glutamate/aspartate transporter (GLAST) knockout mice showed progressive RGC loss and optic nerve degeneration that are similar to glaucoma. To explore the possibility that rare variants in the EAAT1 gene (the human homolog of GLAST) cause susceptibility to glaucoma, we performed targeted sequencing of EAAT1 in 440 patients with glaucoma and 450 control subjects. We identified 8 rare variants in 20 out of 440 patients, including 4 synonymous and 4 missense variants located at protein coding regions. One of these rare variants (rs117295512) showed significant association with the risk of glaucoma (OR = 10.44, P = 0.005). Furthermore, the allele frequency for loss-of-function EAAT1 variants, pAla169Gly and pAla329Thr, was 5.5 folds higher in the glaucoma (1.1%) compared with the control cohort (0.2%). These findings suggest that these rare variants may contribute to the pathogenesis of glaucoma and that loss-of-function variants in EAAT1 are present in a small number of patients with glaucoma.

Lack of correlation between S1 RNA binding domain 1 SNP rs3213787/rs11884064 and normal-tension glaucoma in a population from the Republic of Korea.

Previous studies have reported the association of the S1 RNA binding domain 1 (SRBD1) gene with open-angle glaucoma in various ethnic populations. However, in those studies, the definition of the patients differed, as did the results. Therefore, the relevance of the SRBD1 gene to normal tension glaucoma (NTG) appears uncertain at present. Thus, we investigated the relationship between the SRBD1 gene and NTG in a Korean NTG cohort.In total, 159 unrelated Korean patients with NTG and 103 Korean control subjects were recruited. Thus, a total of 262 participants were analyzed for SRBD1 (rs3213787 and rs11884064) gene polymorphisms.The minor allele frequency of rs3213787 was found to be 0.13 and 0.19 in NTG cases and controls, respectively. The genetic association analysis of SNP rs3213787 revealed no significant difference in genotype distribution between NTG cases and controls in allelic (odds ratio [OR] = 0.634, P = .063), dominant (OR = 0.589, P = .066) or recessive models (OR = 0.639, P = .7716). The minor allele frequency of rs11884064 was found to be 0.24 and 0.25 in NTG cases and controls, respectively. For rs11884064, no significant difference in genotype distribution was observed between NTG cases and controls in allelic (OR = 0.938, P = .755), dominant (OR = 0.927, P = .798) or recessive models (OR = 0.920, P = 1.000).The current study suggested that SRBD1 gene polymorphisms (rs3213787 and rs11884064) may not be associated with genetic susceptibility to NTG in a Korean cohort.

No association between POU4F1, POU4F2, ISL1 polymorphisms and normal-tension glaucoma.

BACKGROUND: Normal-tension glaucoma (NTG) that occurs despite normal intraocular pressure has genetic predisposition. Since retinal ganglion cells (RGCs) are a key node in pathogenesis of glaucoma, neurodegeneration of RGCs is thought to be the main cause increasing the risk of NTG development. Here, we aimed to investigate the association of polymorphisms in RGC development genes with NTG development. MATERIALS AND METHODS: We performed a case-control association study of 435 patients with NTG and 419 normal controls. We genotyped four single nucleotide polymorphisms (SNPs) in genes responsible for RGC development, namely POU4F2 (rs13152799 and rs1504360), POU4F1 (rs9601092), and ISL1 (rs2288468), by either real-time PCR or PCR-RFLP, and evaluated its association with the risk of NTG development. RESULTS: No significant association was observed between the candidate SNPs and NTG development. CONCLUSIONS: To the best of our knowledge, this is the first report exploring the association between genes regulating RGC development and NTG susceptibility. Our data could provide a reference for further researches that focus on finding additional potential SNPs of POU4F2, POU4F1, ISL1 or other RGC development genes for NTG.

Genomic Characterization of TBK1 Duplication in Korean Normal-tension Glaucoma Patients.

PRéCIS:: One (0.2%) of 418 Korean normal-tension glaucoma (NTG) patients had TBK1 duplication. The putative mechanism of TBK1 duplication in Korean NTG patients is the nonhomologous end-joining. PURPOSE: TBK1 duplication is a genomic cause of familial NTG. NTG accounts for up to 90% of primary open-angle glaucoma in Koreans, with genetic tendency. We aimed to investigate the prevalence of TBK1 duplication in Korean NTG patients and to identify their genomic structure and duplication mechanism. MATERIALS AND METHODS: We obtained DNA samples from 418 NTG patients and 195 healthy controls for evaluating TBK1 copy number variations using a semiquantitative polymerase chain reaction (PCR). The samples with TBK1 gene duplication were further confirmed using droplet digital PCR. The whole-genome sequencing of patient samples with duplications was performed to identify the accurate breakpoints and to elucidate the genomic structure. Ophthalmic evaluation and confirmation of TBK1 duplication using junction PCR were performed in families of positive patients. RESULTS: TBK1 duplication was found in 1 of 418 NTG cases (0.2%). The duplication range was from g.64,803,151 to g.64,927,214 (124,063 bp). It is the smallest region of overlapping duplication in TBK1. Any repetitive sequences were not found near the breakpoints of our case. Inserted sequences were found within the breakpoints. A brother and a niece of the positive case appeared the typical clinical features of NTG and shared the same TBK1 duplications with the index case. CONCLUSIONS: In Korea, the prevalence of TBK1 duplication was 0.2% and the smallest reported TBK1 duplication associated with NTG was found. The mechanism of TBK1 duplication was suggested to be nonhomologous end-joining while a previous report pointed out the mechanism of TBK1 duplications as nonallelic homologous recombination.

Long-Term Follow-Up of Normal Tension Glaucoma Patients With TBK1 Gene Mutations in One Large Pedigree.

PURPOSE: To characterize features of glaucoma associated with a TANK binding kinase 1 (TBK1) gene duplication, which is among the most common molecularly defined causes of normal tension glaucoma (NTG). DESIGN: Retrospective observational case series. METHODS: We conducted a retrospective case series, by reviewing medical records of 7 members of a pedigree with NTG caused by TBK1 gene duplications. Clinical features of these patients at diagnosis, throughout management, and at latest follow-up were identified, including age, intraocular pressure (IOP), central corneal thickness (CCT), optic nerve head appearance, and mean deviation (MD) assessed with Humphrey visual field (HVF) testing protocols. RESULTS: At initial diagnosis, the mean age was 35 ± 7 years, IOP was 16 ± 2.1 mm Hg, cup-to-disc (C/D) ratio was 0.9 ± 0.08, and MD assessed via HVF 30-2 and/or 24-2 testing protocols was -9.0 ± 8.9 (range: -1.8 to -27) dB in the 14 study eyes. At initial diagnosis, 4 of 14 eyes (28%) had no visual field defect, 4 (28%) had early visual field defects, and 6 (43%) had severe visual field defects. Patients had a mean follow-up of 21.5 ± 9.0 years and experienced an average reduction of IOP by 28%. Four of 12 eyes (33%) had stable visual fields throughout follow-up, while 8 eyes (67%) had slow-to-moderate progression. The 30-2 and/or 24-2 HVF tests had an average change in MD of -0.53 ± 0.26 dB/year. No eyes had rapid progression with an MD >1.0 dB/year. At final follow-up, the mean IOP was 11.5 ± 2.9, and C/D ratio was 0.94 ± 0.4. At final follow-up, 3 of 14 eyes (21%) had early visual field defects, 4 (29%) had moderate visual field defects, and 7 (50%) had severe visual field defects. Six of 14 eyes (43%) met criteria for legal blindness. CONCLUSIONS: We provide the first report of the clinical features and long-term clinical course in a family of NTG patients with TBK1 gene duplications. TBK1-associated glaucoma exhibits classic features of NTG. Patients present with severe disease at a relatively early age and most (67%) have slow-to-moderate progression of their visual field defects. The rate of visual field change appears correlated with the magnitude of IOP, suggesting that it may be advantageous to set extremely low IOP targets for some patients with TBK1-associated glaucoma.