Chromosome 9p21 primary open-angle glaucoma susceptibility locus: a review

Modeling complex age-related eye disease

Modeling complex eye diseases like age-related macular degeneration (AMD) and glaucoma poses significant challenges, since these conditions depend highly on age-related changes that occur over several decades, with many contributing factors remaining unknown. Although both diseases exhibit a relatively high heritability of >50%, a large proportion of individuals carrying AMD- or glaucoma-associated genetic risk variants will never develop these diseases. Furthermore, several environmental and lifestyle factors contribute to and modulate the pathogenesis and progression of AMD and glaucoma. Several strategies replicate the impact of genetic risk variants, pathobiological pathways and environmental and lifestyle factors in AMD and glaucoma in mice and other species. In this review we will primarily discuss the most commonly available mouse models, which have and will likely continue to improve our understanding of the pathobiology of age-related eye diseases. Uncertainties persist whether small animal models can truly recapitulate disease progression and vision loss in patients, raising doubts regarding their usefulness when testing novel gene or drug therapies. We will elaborate on concerns that relate to shorter lifespan, body size and allometries, lack of macula and a true lamina cribrosa, as well as absence and sequence disparities of certain genes and differences in their chromosomal location in mice. Since biological, rather than chronological, age likely predisposes an organism for both glaucoma and AMD, more rapidly aging organisms like small rodents may open up possibilities that will make research of these diseases more timely and financially feasible. On the other hand, due to the above-mentioned anatomical and physiological features, as well as pharmacokinetic and -dynamic differences small animal models are not ideal to study the natural progression of vision loss or the efficacy and safety of novel therapies. In this context, we will also discuss the advantages and pitfalls of alternative models that include larger species, such as non-human primates and rabbits, patient-derived retinal organoids, and human organ donor eyes.

Genetic association between CDKN2B-AS1 polymorphisms and the susceptibility of primary open-angle glaucoma (POAG): a meta-analysis from 21,775 subjects

Background

Primary open-angle glaucoma (POAG) is affected by both genetics and environmental factors. CDKN2B-AS1 polymorphisms have been reported to be involved in the pathogenesis of POAG. However, the results of the genetic associations between the CDKN2B-AS1 polymorphisms and POAG risk were inconclusive.

Aims

This study aimed to evaluate the correlation of CDKN2B-AS1 polymorphisms and POAG susceptibility using a meta-analysis.

Methods

Meta-analysis was performed by searching PubMed, Web of science, the Cochrane database of system reviews, CNKI, and Embase databases. The relationship of CDKN2B-AS1 rs4977756, rs10120688, rs2157719, and rs7049105 polymorphisms and POAG risk was evaluated by the odds ratios (ORs) and 95% confidence intervals (CIs).

Results

Eleven studies with 8290 cases and 13,485 controls were included in the present meta-analysis. The alleles of rs4977756 and rs10120688 significantly increased the risk of POAG (rs4977756: OR = 1.20, 95%CI = 1.03–1.39, p = 0.02; rs10120688: OR = 1.36, 95%CI = 1.29–1.44, p < 0.00001). As for ethnicity, rs4977756 polymorphism significantly increased POAG risk in Caucasians (OR = 1.33, 95%CI = 1.12–1.57, p = 0.0009), but not in Asians. In addition, the rs2157719 allele was significantly associated with POAG risk in Asians (OR = 0.66, 95%CI = 0.55–0.80, p < 0.0001), but not in Caucasians (p > 0.05).

Conclusions

The CDKN2B-AS1 rs4977756 might increase the POAG risk in Caucasian population, and rs2157719 might decrease the POAG risk in Asian population, while rs10120688 might increase the risk of POAG.

Characteristics of Visual Field Defects in Korean Advanced Glaucoma

Purpose: We investigated the clinical characteristics of visual field (VF) defects in Korean advanced glaucoma patients.Methods: The present study included 109 eyes of 109 advanced glaucoma patients whose mean deviation (MD) is under -12 dB. The subjects were classified into primary open angle glaucoma (POAG) and normal tension glaucoma (NTG) group. Average numeric decibel in each VF points were visualized with color topographic image and dot graph image using python 3.5. VF was divided into four quadrants or two half fields, and the differences in the degree of VF defects in each locations were assessed with raw decibel data. Additionally, mean sensitivity of central 12 points were compared between the two groups.Results: Generally the features of VF defects were severely depressed VF sensitivity at the superonasal quadrant and relatively preserved central area and inferotemporal quadrant in both of the glaucoma groups. But we found the extent of deflection for VF defect in the NTG eyes was higher than that of the POAG eyes (p < 0.05). The POAG eyes tended to show more diffuse and evenly distributed VF defect, whereas NTG eyes tended to have more severely depressed VF at the superonasal quadrant and relatively preserved VF at the inferotemporal quadrant. There was no significant difference in the degree of central VF defects between the two groups.Conclusions: The characteristics of VF defect in Korean advanced glaucoma revealed different features based on the glaucoma diagnosis. The POAG eyes tended to show diffuse VF defects, whereas NTG eyes tended to have more severely depressed VF sensitivity at the superonasal quadrant and relatively preserved VF at the inferotemporal quadrant.

Polymorphism analysis of miR182 and CDKN2B genes in Greek patients with primary open angle glaucoma

Glaucoma is a progressive optic neuropathy resulting from retinal ganglion cells death; it represents one of the leading causes of irreversible blindness worldwide. Although, primary open angle glaucoma (POAG) is the most common type of the disease, the pathogenesis of POAG and the genetic factors contributing to disease development remain poorly understood. The aim of this study was to investigate whether the polymorphisms rs76481776 in miR182 gene and rs3217992 in cyclin-dependent kinase inhibitor-2B (CDKN2B) gene are risk factors for POAG in a series of patients of Greek origin. A case-control study was conducted including 120 patients with POAG and 113 unaffected healthy controls of Greek origin, surveyed for polymorphisms with potential correlation to POAG. DNA from each individual was tested for the miR182 rs76481776 and CDKN2B rs3217992 polymorphisms. Regarding the miR182 rs76481776 polymorphism, the T allele occurred with significantly higher frequency in POAG patients compared to controls (OR: 2.62, 95% CI: 1.56-4.39; p = 0.0002). The CDKN2B rs3217992 A allele frequency was found significantly increased in POAG patients compared to healthy individuals (OR: 1.72, 95% CI: 1.18-2.49; p = 0.005). Therefore, both rs76481776 polymorphism in miR182 gene and rs3217992 polymorphism in CDKN2B gene seem to be associated with the development of POAG in a Greek population. The carriers of the T allele of rs76481776 in miR182 and the carriers of the A allele of rs3217992 in CDKN2B have an increased risk of developing POAG.

DEVELOPMENT OF PRIMARY OPEN-ANGLE GLAUCOMA AND DELETION POLYMORPHISM OF THE GLUTATHIONE-S-TRANSFERASE GENES

The aim of the research. To investigate the association of the development of primary open-angle glaucoma with deletion polymorphism of glutathione-S-transferase genes. Materials and methods. Under our observation there were 172 patients, residents of Ukraine with primary open-angle glaucoma I–IV stages. Analysis of the deletion polymorphism of GSTM1 and GSTT1 genes was performed by real-time polymerase chain reaction using unified TaqMan Mutation Detection Assays Life-Technology (USA) test systems. Statistical analysis of the obtained data was performed using the MedStat package and the statistical package MedCalc v.15.1 (MedCalc Software bvba). Results and discussion. The detection of null alleles of the GSTM1 gene was observed in 39 % of patients in the control group, in patients with POAG a significant increase in the frequency of deletion polymorphism to 50–56 % was observed with the progression of the disease in stages II-IV. In patients with stage IV disease, the effect of the zero GSTM1- null allele on POAG course was determined (χ2=3.97; p=0.047), and the null allele of GSTM1 doubled the probability of developing the disease (OR=2.01; 95 % CI=1.01–4.01) in patients of group 4 compared with control. The null allele of the GSTT1 gene in the control group was found in 31 %, an increase in the frequency of the GSTT1-null allele was also observed in the second and fourth stages of POAG from 41 % to 54 %. Statistically significant differences of GSTT1 gene allele frequencies were determined between the control group and all patients with POAG (χ2=4.43; p=0.03), between the control and the 4th group (χ2=7.64; p=0.01), and between the 1st and 4th groups (χ2=5.52; p=0.02). An association with the development of POAG (χ2=4.43; p=0.03) was determined for the deletion polymorphism of the GSTT1 gene when comparing the control group with the data of all patients with POAG (1–4 groups). At stratification by stages of POAG (that is, by groups of patients), an association with the development of POAG was determined only in patients of group 4 (χ2=7.64; p=0.01) compared with the control group. Conclusions. The association of the null allele of the GSTT1 gene with POAG was established (p=0.03). The presence of the GSTT1-null allele significantly increased the risk of developing POAG (OR=1.75; BI=1.04–2.96) compared with the control group. The presence of null alleles (GSTM1-null and GSTT1-null) of the GST deletion polymorphism significantly increased the risk of stage IV POAG (OR=2.01; BI=1.01–4.01 and OR=2.66; VI=1.32–5.37, respectively) compared with the control group, which indicated the effect of zero alleles on the rapid progression of the disease.

Early removal of senescent cells protects retinal ganglion cells loss in experimental ocular hypertension

Experimental ocular hypertension induces senescence of retinal ganglion cells (RGCs) that mimics events occurring in human glaucoma. Senescence-related chromatin remodeling leads to profound transcriptional changes including the upregulation of a subset of genes that encode multiple proteins collectively referred to as the senescence-associated secretory phenotype (SASP). Emerging evidence suggests that the presence of these proinflammatory and matrix-degrading molecules has deleterious effects in a variety of tissues. In the current study, we demonstrated in a transgenic mouse model that early removal of senescent cells induced upon elevated intraocular pressure (IOP) protects unaffected RGCs from senescence and apoptosis. Visual evoked potential (VEP) analysis demonstrated that remaining RGCs are functional and that the treatment protected visual functions. Finally, removal of endogenous senescent retinal cells after IOP elevation by a treatment with senolytic drug dasatinib prevented loss of retinal functions and cellular structure. Senolytic drugs may have the potential to mitigate the deleterious impact of elevated IOP on RGC survival in glaucoma and other optic neuropathies.

Long non-coding RNA 00607 as a tumor suppressor by modulating NF-κB p65/p53 signaling axis in hepatocellular carcinoma

Accumulating evidence suggests that long non-coding RNA (lncRNA) plays important roles in some malignant tumors. However, the mechanism underlying how lncRNA regulates hepatocellular carcinoma (HCC) process remains largely unknown. In this study, we explored the potential role of lncRNA 00607 as a novel tumor suppressor in HCC. In this study, we examined the regulation of lncRNA 00607 by the important inflammatory cytokine tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6). We also determined the expression of LINC000607 in 159 HCC tumors and paired adjacent tissues. Effects of LINC000607 in HCC proliferation and apoptosis were examined in vitro in HCC cell lines and in vivo tumor xenografts. Furthermore, we also examine underlying mechanism by which lncRNA 00607 regulates NF-κB p65 and how LIN00607 exerts its tumor suppressor role in HCC. We found that lncRNA 00607 expression level is lower in HCC tumors compared with matched normal liver tissue, and its low expression predicts worse prognosis in HCC. Functionally, lncRNA 00607 overexpression leads to decreased HCC cell proliferation in vitro and in vivo, enhanced apoptosis and chemotherapeutic drug sensitivity. Mechanistically, lncRNA 00607 inhibits the p65 transcription by binding to the p65 promoter region, therefore contributing to increased p53 levels in HCC. Taken together, the findings of this study show that the TNF-α/IL-6-lncRNA 00607-NF-κB p65/p53 signaling axis represents a novel therapeutic avenue in cancer chemotherapy.

Genetic Architecture of Primary Open-Angle Glaucoma in Individuals of African Descent: The African Descent and Glaucoma Evaluation Study III

PURPOSE

To find genetic contributions to glaucoma in African Americans.

DESIGN

Cross-sectional, case-control study.

PARTICIPANTS

One thousand eight hundred seventy-five primary open-angle glaucoma (POAG) patients and 1709 controls, self-identified as being of African descent (AD), from the African Descent and Glaucoma Evaluation Study (ADAGES) III and Wake Forest School of Medicine.

METHODS

MegaChip genotypes were imputed to Thousand Genomes data. Association of single nucleotide polymorphisms (SNPs) with POAG and advanced POAG was tested by linear mixed model correcting for relatedness and population stratification. Genetic risk scores were tested by receiver operator characteristic curves (ROC-AUCs).

MAIN OUTCOME MEASURES

Primary open-angle glaucoma defined by visual field loss without other nonocular conditions (n = 1875). Advanced POAG was defined by age-based mean deviation of visual field (n = 946).

RESULTS

Eighteen million two hundred eighty-one thousand nine hundred twenty SNPs met imputation quality of r2 > 0.7 and minor allele frequency > 0.005. Association of a novel locus, EN04, was observed for advanced POAG (rs185815146 β, 0.36; standard error, 0.065; P < 3×10-8). For POAG, an AD signal was observed at the 9p21 European descent (ED) POAG signal (rs79721419; P < 6.5×10-5) independent of the previously observed 9p21 ED signal (rs2383204; P < 2.3×10-5) by conditional analyses. An association with POAG in FNDC3B (rs111698934; P < 3.9×10-5) was observed, not in linkage disequilibrium (LD) with the previously reported ED SNP. Additional previously identified loci associated with POAG in persons of AD were: 8q22, AFAP1, and TMC01. An AUC of 0.62 was observed with an unweighted genetic risk score comprising 11 SNPs in candidate genes. Two additional risk scores were studied by using a penalized matrix decomposition with cross-validation; risk scores of 50 and 400 SNPs were identified with ROC of AUC = 0.74 and AUC = 0.94, respectively.

CONCLUSIONS

A novel association with advanced POAG in the EN04 locus was identified putatively in persons of AD. In addition to this finding, this genome-wide association study in POAG patients of AD contributes to POAG genetics by identification of novel signals in prior loci (9p21), as well as advancing the fine mapping of regions because of shorter average LD (FNDC3B). Although not useful without confirmation and clinical trials, the use of genetic risk scores demonstrated that considerable AD-specific genetic information remains in these data.

Auxiliary diagnostic value of p16 amplification combined with the detection of heterozygous and homozygous loss for urothelial carcinoma

The present study aimed to investigate the significance of detecting cyclin dependent kinase inhibitor 2A (p16) gene aberrations in the diagnosis of urothelial carcinoma (UC) using fluorescence in situ hybridization (FISH). A total of 77 voided urine specimens from 65 patients with UC and 12 patients with benign urinary disease were recruited into the current study. Under a fluorescence microscope, cells with large and irregular nuclei were assessed for chromosomal aberrations. The positive rate of p16 amplification in UC samples was 32.3% (21/65), which was significantly higher than that in benign urinary disease samples (16.7%, 2/12; P<0.05). Heterozygous and homozygous loss of p16 was identified in 12 (18.5%) and 23 (35.4%) patients with UC, respectively; p16 expression in the remainder of patients was normal. In addition, as tumor stage or grade advanced, the positive rate of p16 aberrations also increased significantly (P<0.05). In conclusion, p16 gene aberrations may serve important roles in the auxiliary diagnosis of UC by FISH and could be utilized to monitor UC progression.

LncRNAs in genetic basis of glaucoma

Glaucoma is an umbrella term used to designate a heterogeneous group of ocular disorders characterised by progressive excavation of the optic disc, optic atrophy and gradual loss of the visual field caused by the slow death of retinal ganglion cells and their axons. Glaucoma can potentially lead to blindness if left untreated. It usually starts from the periphery and progresses gradually toward the centre of the visual field. Vision loss caused by glaucoma is irreversible and causes a heavy burden on affected families and society, therefore the importance of early diagnosis and prevention should be emphasised. Genetic factors appear to play a role in glaucoma pathogenesis; it has been shown that individuals with a positive family history are at a greater risk because they are more likely predisposed be affected. Notable advances have been recorded in the past decade concerning the genetic and environmental factors likely to contribute or cause glaucoma with the discovery of multiple glaucoma-associated genes and genetic loci. Thorough investigations by a handful of studies on the function of long non-coding RNAs discovered that, although lacking protein-coding potential, lncRNAs can still participate in the regulation of gene expression at various levels, thus their possible implication in different disease aetiologies. In this review, we focus on the lncRNAs characteristics and its regulation, and summarise these results from separate, independent, glaucoma-related studies in addition to discussing possible pathways by which lncRNAs might contribute to glaucoma.

A Multi-Locus Genetic Risk Score for Primary Open-Angle Glaucoma (POAG) Variants Is Associated with POAG Risk in a Mediterranean Population: Inverse Correlations with Plasma Vitamin C and E Concentrations

Primary open-angle glaucoma (POAG) is a leading cause of blindness worldwide. The genetics of POAG are complex, and population-specific effects have been reported. Although many polymorphisms associated with POAG risk have been reported, few studies have analyzed their additive effects. We investigated, in a southern European Mediterranean population, the association between relevant POAG polymorphisms, identified by initial genome-wide association studies (GWASs) and POAG risk, both separately and as an aggregated multi-locus genetic risk score (GRS). Also, bearing in mind that oxidative stress is a factor increasingly recognized in the pathogenesis of POAG, we analyzed the potential association of the GRS with plasma concentrations of antioxidant vitamins (C and E). We carried out a case–control study including 391 POAG cases and 383 healthy controls, and analyzed four genetic polymorphisms (rs4656461-TMCO1, rs4236601-CAV1/CAV2, rs2157719-CDKN2B-AS1 and rs3088440-CDKN2A). An unweighted GRS including the four non-linked polymorphisms was constructed. A strong association between the GRS and POAG risk was found. When three categories of the GRS were considered, subjects in the top category of the GRS were 2.92 (95% confidence interval (CI): 1.79–4.77) times more likely to have POAG compared with participants in the bottom category (p < 0.001). Moreover, the GRS was inversely correlated with plasma vitamin C (p = 0.002) and vitamin E (p = 0.001) concentrations, even after additional adjustment for POAG status. In conclusion, we have found a strong association between the GRS and POAG risk in this Mediterranean population. While the additional correlation found between GRS and low levels of vitamins C and E does not indicated a causal relationship, it does suggest the need for new and deeper research into the effects of oxidative stress as a potential mechanism for those associations.

Modeling Glaucoma: Retinal Ganglion Cells Generated from Induced Pluripotent Stem Cells of Patients with SIX6 Risk Allele Show Developmental Abnormalities

Glaucoma represents a group of multifactorial diseases with a unifying pathology of progressive retinal ganglion cell (RGC) degeneration, causing irreversible vision loss. To test the hypothesis that RGCs are intrinsically vulnerable in glaucoma, we have developed an in vitro model using the SIX6 risk allele carrying glaucoma patient-specific induced pluripotent stem cells (iPSCs) for generating functional RGCs. Here, we demonstrate that the efficiency of RGC generation by SIX6 risk allele iPSCs is significantly lower than iPSCs-derived from healthy, age- and sex-matched controls. The decrease in the number of RGC generation is accompanied by repressed developmental expression of RGC regulatory genes. The SIX6 risk allele RGCs display short and simple neurites, reduced expression of guidance molecules, and immature electrophysiological signature. In addition, these cells have higher expression of glaucoma-associated genes, CDKN2A and CDKN2B, suggesting an early onset of the disease phenotype. Consistent with the developmental abnormalities, the SIX6 risk allele RGCs display global dysregulation of genes which map on developmentally relevant biological processes for RGC differentiation and signaling pathways such as mammalian target of rapamycin that integrate diverse functions for differentiation, metabolism, and survival. The results suggest that SIX6 influences different stages of RGC differentiation and their survival; therefore, alteration in SIX6 function due to the risk allele may lead to cellular and molecular abnormalities. These abnormalities, if carried into adulthood, may make RGCs vulnerable in glaucoma. Stem Cells 2017;35:2239-2252.

Characterizing the "POAGome": A bioinformatics-driven approach to primary open-angle glaucoma

Primary open-angle glaucoma (POAG) is a genetically, physiologically, and phenotypically complex neurodegenerative disorder. This study addressed the expanding collection of genes associated with POAG, referred to as the "POAGome." We used bioinformatics tools to perform an extensive, systematic literature search and compiled 542 genes with confirmed associations with POAG and its related phenotypes (normal tension glaucoma, ocular hypertension, juvenile open-angle glaucoma, and primary congenital glaucoma). The genes were classified according to their associated ocular tissues and phenotypes, and functional annotation and pathway analyses were subsequently performed. Our study reveals that no single molecular pathway can encompass the pathophysiology of POAG. The analyses suggested that inflammation and senescence may play pivotal roles in both the development and perpetuation of the retinal ganglion cell degeneration seen in POAG. The TGF-β signaling pathway was repeatedly implicated in our analyses, suggesting that it may be an important contributor to the manifestation of POAG in the anterior and posterior segments of the globe. We propose a molecular model of POAG revolving around TGF-β signaling, which incorporates the roles of inflammation and senescence in this disease. Finally, we highlight emerging molecular therapies that show promise for treating POAG.

Transcriptome analysis of adult and fetal trabecular meshwork, cornea, and ciliary body tissues by RNA sequencing

PURPOSE

To characterize the transcriptional landscape of human adult and fetal trabecular meshwork (TM), cornea, and ciliary body (CB) tissues, and to evaluate the expression level of candidate genes selected from genetic association studies of primary-open angle glaucoma, central corneal thickness, intraocular pressure, vertical cup to disc ratio, and optic nerve parameters.

METHODS

Deep RNA sequencing was performed on the selected human tissues. Transcriptome analyses were performed to 1) characterize the total number of expressed genes, 2) identify the most highly expressed genes, 3) estimate the number of novel transcripts, and 4) evaluate the expression of candidate genes in each tissue. Finally, a differential gene expression analysis was conducted to compare the adult and fetal ocular tissues.

RESULTS

There was an average of 12,362 protein coding genes and 3725 novel transcripts expressed in each tissue. The top most expressed genes in each tissue included SPARC (fetal cornea and TM), APOD (adult TM), CLU (adult cornea), and PTGDS (adult and fetal CB). Twenty-nine candidate genes selected from genetic association studies primarily showed high expression levels in the trabecular meshwork and cornea. Comparison of adult and fetal samples identified 2012 and 1261 differentially expressed protein-coding genes within the cornea and trabecular meshwork, respectively.

CONCLUSIONS

This study has provided an unbiased glimpse into the transcriptome of three essential anterior ocular tissues, resulting in the development of several novel hypotheses. These data can be used in the future to better guide ocular research questions.

Analysis of Cyclin-Dependent Kinase Inhibitor-2B rs1063192 Polymorphism in Saudi Patients with Primary Open-Angle Glaucoma

AIMS

To investigate whether the polymorphism rs1063192 (A>G) in the cyclin-dependent kinase Inhibitor-2B (CDKN2B) gene is a risk factor for primary open-angle glaucoma (POAG).

METHOD

A case-control study was conducted wherein we genotyped 87 unrelated POAG cases and 94 control subjects from Saudi Arabia using the Taq-Man^® assay.

RESULTS

The minor allele frequency was 0.20 in POAG cases and 0.21 in controls. Both the genotype and allele frequencies were not significantly different between cases and controls. No significant association was found between genotypes and glaucoma clinical indices, except that the mutant homozygous genotype (G/G) was associated with the family history of glaucoma (p = 0.024).

CONCLUSION

Polymorphism rs1063192 in CDKN2B is not a risk factor for POAG in Saudi cohort.

Risk factors for open-angle glaucoma in Nigeria: results from the Nigeria National Blindness and Visual Impairment Survey

BACKGROUND

The glaucoma-specific blindness prevalence in Nigeria (0.7 %, 95 % CI 0.6-0.9 %) among those aged ≥40 years is one of the highest ever reported. This study determined the risk factors for open-angle glaucoma (OAG) in adults examined in the Nigeria National Blindness and Visual Impairment Survey.

METHODS

A nationally representative sample of 13,591 people aged ≥40 years in 305 clusters in Nigeria were examined (response rate 90.4 %) between January 2005 to June 2007. Everyone had logMAR visual acuity measurement, Frequency Doubling Technology (FDT) visual field testing, autorefraction, A-scan biometry and optic disc assessment. Full ocular examination (n = 6397), included Goldmann applanation tonometry. Values for defining glaucoma using International Society of Geographical and Epidemiological Ophthalmology criteria were derived from the study population. Disc images were graded by Moorfields Eye Hospital Reading Centre. Socio-demographic factors (age, gender, ethnicity, literacy and place of residence), ocular parameters (intraocular pressure [IOP], axial length and mean ocular perfusion pressure [MOPP]) and systemic parameters (blood pressure, blood glucose and body mass index [BMI]) were assessed for association with OAG.

RESULTS

Thirteen thousand eighty-one (96 %) of 13,591 participants had vertical cup:disc ratio measured in at least one eye. 682 eyes of 462 participants were classified as OAG, with 12,738 controls. In univariate analyses the following were associated with OAG: increasing age, male gender, Igbo and Yoruba ethnic groups, illiteracy, longer axial length, higher IOP, lower MOPP, greater severity of hypertension and low BMI (underweight). In multivariate analysis, increasing age (odds ratio [OR] 1.04, 95 % CI 1.03-1.05), higher IOP (OR 1.22, 95 % CI 1.18-1.25) and Igbo ethnicity (OR 1.73, 95 % CI 1.18-2.56) were independent risk factors for OAG.

CONCLUSION

Case detection strategies for OAG should be improved for those aged ≥40 years and for ethnic groups most at risk as a public health intervention.

Functional and Structural Analyses of CYP1B1 Variants Linked to Congenital and Adult-Onset Glaucoma to Investigate the Molecular Basis of These Diseases

Glaucoma, the leading cause of irreversible blindness, appears in various forms. Mutations in CYP1B1 result in primary congenital glaucoma (PCG) by an autosomal recessive mode of inheritance while it acts as a modifier locus for primary open angle glaucoma (POAG). We investigated the molecular basis of the variable phenotypes resulting from the defects in CYP1B1 by using subclones of 23 CYP1B1 mutants reported in glaucoma patients, in a cell based system by measuring the dual activity of the enzyme to metabolize both retinol and 17β-estradiol. Most variants linked to POAG showed low steroid metabolism while null or very high retinol metabolism was observed in variants identified in PCG. We examined the translational turnover rates of mutant proteins after the addition of cycloheximide and observed that the levels of enzyme activity mostly corroborated the translational turnover rate. We performed extensive normal mode analysis and molecular-dynamics-simulations-based structural analyses and observed significant variation of fluctuation in certain segmental parts of the mutant proteins, especially at the B-C and F-G loops, which were previously shown to affect the dynamic behavior and ligand entry/exit properties of the cytochrome P450 family of proteins. Our molecular study corroborates the structural analysis, and suggests that the pathologic state of the carrier of CYP1B1 mutations is determined by the allelic state of the gene. To our knowledge, this is the first attempt to dissect biological activities of CYP1B1 for correlation with congenital and adult onset glaucomas.

Novel Insights into the Role of Long Noncoding RNA in Ocular Diseases

Recent advances have suggested that long noncoding RNAs (lncRNAs) are differentially expressed in ocular tissues and play a critical role in the pathogenesis of different types of eye diseases. Here, we summarize the functions and mechanisms of known aberrantly-expressed lncRNAs and present a brief overview of relevant reports about lncRNAs in such ocular diseases as glaucoma, proliferative vitreoretinopathy (PVR), diabeticretinopathy (DR), and ocular tumors. We intend to highlight comprehensive studies that provide detailed data about the mechanisms of lncRNAs, their applications as diagnostic or prognostic biomarkers, and their potential therapeutic targets. Although our understanding of lncRNAs is still in its infancy, these examples may provide helpful insights into the methods by which lncRNAs interfere with ocular diseases.

Mice Homozygous for a Deletion in the Glaucoma Susceptibility Locus INK4 Show Increased Vulnerability of Retinal Ganglion Cells to Elevated Intraocular Pressure

A genomic region located on chromosome 9p21 is associated with primary open-angle glaucoma and normal tension glaucoma in genome-wide association studies. The genomic region contains the gene for a long noncoding RNA called CDKN2B-AS, two genes that code for cyclin-dependent kinase inhibitors 2A and 2B (CDKN2A/p16(INK4A) and CDKN2B/p15(INK4B)) and an additional protein (p14(ARF)). We used a transgenic mouse model in which 70 kb of murine chromosome 4, syntenic to human chromosome 9p21, are deleted to study whether this deletion leads to a discernible phenotype in ocular structures implicated in glaucoma. Homozygous mice of this strain were previously reported to show persistent hyperplastic primary vitreous. Fundus photography and optical coherence tomography confirmed that finding but showed no abnormalities for heterozygous mice. Optokinetic response, eletroretinogram, and histology indicated that the heterozygous and mutant retinas were normal functionally and morphologically, whereas glial cells were activated in the retina and optic nerve head of mutant eyes. In quantitative PCR, CDKN2B expression was reduced by approximately 50% in the heterozygous mice and by 90% in the homozygous mice, which suggested that the CDKN2B knock down had no deleterious consequences for the retina under normal conditions. However, compared with wild-type and heterozygous animals, the homozygous mice are more vulnerable to retinal ganglion cell loss in response to elevated intraocular pressure.

Role of the nucleolus in neurodegenerative diseases with particular reference to the retina: a review

The nucleolus has emerged as a key regulator of cellular growth and the response to stress, in addition to its traditionally understood function in ribosome biogenesis. The association between nucleolar function and neurodegenerative disease is increasingly being explored. There is also recent evidence indicating that the nucleolus may well be crucial in the development of the eye. In this present review, the role of the nucleolus in retinal development as well as in neurodegeneration with an emphasis on the retina is discussed.

An Updated Review on the Genetics of Primary Open Angle Glaucoma

Epidemiological studies suggest that by 2020 the prevalence of primary open angle glaucoma (POAG) is estimated to increase to 76.0 million, and to 111.8 million by 2040 globally due to the population aging. The prevalence of POAG is the highest among those of African descent, followed by Asians, and the lowest in Europeans. POAG is a genetically complex trait with a substantial fraction exhibiting a significant heritability. Less than 10% of POAG cases in the general population are caused by specific gene mutations and the remaining cases are polygenic. Quantitative traits related to POAG pathogenesis such as intra-ocular pressure (IOP), vertical cup/disc ratio (VCDR), optic disc area, and central corneal thickness (CCT) are highly heritable, and likely to be influenced at least in part by genes and show substantial variation in human populations. Recent genome-wide association studies (GWAS) have identified several single nucleotide polymorphisms (SNPs) at different loci including CAV1/CAV2, TMCO1, CDKN2B-AS1, CDC7-TGFBR3, SIX1/SIX6, GAS7 and ATOH7 to be associated with POAG and its related quantitative traits (endophenotypes). The chapter provides a brief overview on the different GWAS and SNP association studies and their correlation with various clinical parameters important for POAG in the population worldwide, including the Middle East.

Glaucoma Genes and Mechanisms

Genetic studies have yielded important genes contributing to both early-onset and adult-onset forms of glaucoma. The proteins encoded by the current collection of glaucoma genes participate in a broad range of cellular processes and biological systems. Approximately half the glaucoma-related genes function in the extracellular matrix, however proteins involved in cytokine signaling, lipid metabolism, membrane biology, regulation of cell division, autophagy, and ocular development also contribute to the disease pathogenesis. While the function of these proteins in health and disease are not completely understood, recent studies are providing insight into underlying disease mechanisms, a critical step toward the development of gene-based therapies. In this review, genes known to cause early-onset glaucoma or contribute to adult-onset glaucoma are organized according to the cell processes or biological systems that are impacted by the function of the disease-related protein product.

Using genetic mouse models to gain insight into glaucoma: Past results and future possibilities

While all forms of glaucoma are characterized by a specific pattern of retinal ganglion cell death, they are clinically divided into several distinct subclasses, including normal tension glaucoma, primary open angle glaucoma, congenital glaucoma, and secondary glaucoma. For each type of glaucoma there are likely numerous molecular pathways that control susceptibility to the disease. Given this complexity, a single animal model will never precisely model all aspects of all the different types of human glaucoma. Therefore, multiple animal models have been utilized to study glaucoma but more are needed. Because of the powerful genetic tools available to use in the laboratory mouse, it has proven to be a highly useful mammalian system for studying the pathophysiology of human disease. The similarity between human and mouse eyes coupled with the ability to use a combination of advanced cell biological and genetic tools in mice have led to a large increase in the number of studies using mice to model specific glaucoma phenotypes. Over the last decade, numerous new mouse models and genetic tools have emerged, providing important insight into the cell biology and genetics of glaucoma. In this review, we describe available mouse genetic models that can be used to study glaucoma-relevant disease/pathobiology. Furthermore, we discuss how these models have been used to gain insights into ocular hypertension (a major risk factor for glaucoma) and glaucomatous retinal ganglion cell death. Finally, the potential for developing new mouse models and using advanced genetic tools and resources for studying glaucoma are discussed.

Cellular senescence: from physiology to pathology

Recent discoveries are redefining our view of cellular senescence as a trigger of tissue remodelling that acts during normal embryonic development and upon tissue damage. To achieve this, senescent cells arrest their own proliferation, recruit phagocytic immune cells and promote tissue renewal. This sequence of events - senescence, followed by clearance and then regeneration - may not be efficiently completed in aged tissues or in pathological contexts, thereby resulting in the accumulation of senescent cells. Increasing evidence indicates that both pro-senescent therapies and antisenescent therapies can be beneficial. In cancer and during active tissue repair, pro-senescent therapies contribute to minimize the damage by limiting proliferation and fibrosis, respectively. Conversely, antisenescent therapies may help to eliminate accumulated senescent cells and to recover tissue function.