A Systematic Investigation on Complement Pathway Activation in Diabetic Retinopathy.

The complement system plays a crucial role in retinal homeostasis. While the proteomic analysis of ocular tissues in diabetic retinopathy (DR) has shown the deposition of complement proteins, their exact role in the pathogenesis of DR is yet unclear. We performed a detailed investigation of the role of the complement system by evaluating the levels of major complement proteins including C3, C1q, C4b, Complement Factor B (CFB), and Complement Factor H (CFH) and their activated fragments from both the classical and alternative pathways in vitreous humor and serum samples from proliferative DR (PDR) patients and controls. Further, the expressions of complements and several other key pro- and anti-angiogenic genes in the serum and vitreous humor were analyzed in the blood samples of PDR and non-PDR (NPDR) patients along with controls without diabetes. We also assessed the pro-inflammatory cytokines and matrix metalloproteinases in the vitreous humor samples. There was a significant increase in C3 and its activated fragment C3bα' (110 kDa) along with a corresponding upregulation of CFH in the vitreous of PDR patients, which confirmed the increased activation of the alternative complement pathway in PDR. Likewise, a significant upregulation of angiogenic genes and downregulation of anti-angiogenic genes was seen in PDR and NPDR cases. Increased MMP9 activity and upregulation of inflammatory markers IL8 and sPECAM with a downregulation of anti-inflammatory marker IL-10 in PDR vitreous indicated the possible involvement of microglia in DR pathogenesis. Further, a significantly high C3 deposition in the capillary wall along with thickening of basement membranes and co-localization of CFH expression with CD11b+ve activated microglial cells in diabetic retina suggested microglia as a source of CFH in diabetic retina. The increased CFH levels could be a feedback mechanism for arresting excessive complement activation in DR eyes. A gradual increase of CFH and CD11b expression in retina with early to late changes in epiretinal membranes of DR patients indicated a major role for the alternative complement pathway in disease progression.

Angiopoietin receptor TEK interacts with CYP1B1 in primary congenital glaucoma.

Primary congenital glaucoma (PCG) is a severe autosomal recessive ocular disorder associated with considerable clinical and genetic heterogeneity. Recently, rare heterozygous alleles in the angiopoietin receptor-encoding gene TEK were implicated in PCG. We undertook this study to ascertain the second mutant allele in a large cohort (n = 337) of autosomal recessive PCG cases that carried heterozygous TEK mutations. Our investigations revealed 12 rare heterozygous missense mutations in TEK by targeted sequencing. Interestingly, four of these TEK mutations (p.E103D, p.I148T, p.Q214P, and p.G743A) co-occurred with three heterozygous mutations in another major PCG gene CYP1B1 (p.A115P, p.E229K, and p.R368H) in five families. The parents of these probands harbored either of the heterozygous TEK or CYP1B1 alleles and were asymptomatic, indicating a potential digenic mode of inheritance. Furthermore, we ascertained the interactions of TEK and CYP1B1 by co-transfection and pull-down assays in HEK293 cells. Ligand responsiveness of the wild-type and mutant TEK proteins was assessed in HUVECs using immunofluorescence analysis. We observed that recombinant TEK and CYP1B1 proteins interact with each other, while the disease-associated allelic combinations of TEK (p.E103D)::CYP1B1 (p.A115P), TEK (p.Q214P)::CYP1B1 (p.E229K), and TEK (p.I148T)::CYP1B1 (p.R368H) exhibit perturbed interaction. The mutations also diminished the ability of TEK to respond to ligand stimulation, indicating perturbed TEK signaling. Overall, our data suggest that interaction of TEK and CYP1B1 contributes to PCG pathogenesis and argue that TEK-CYP1B1 may perform overlapping as well as distinct functions in manifesting the disease etiology.

Mutation spectrum of the FZD-4, TSPAN12 AND ZNF408 genes in Indian FEVR patients.

BACKGROUND: Mutations in candidate genes that encode for a ligand (NDP) and receptor complex (FZD4, LRP5 and TSPAN12) in the Norrin ß-catenin signaling pathway are involved in the pathogenesis of familial exudative vitreoretinopathy (FEVR, MIM # 133780). Recently, a transcription factor (ZNF408) has also been implicated in FEVR. We had earlier characterized the variations in NDP among FEVR patients from India. The present study aimed at understanding the involvement of the remaining genes (FZD4, TSPAN12 and ZNF408) in the same cohort. METHODS: The DNA of 110 unrelated FEVR patients and 115 unaffected controls were screened for variations in the entire coding and untranslated regions of these 3 genes by resequencing. Segregation of the disease-associated variants was assessed in the family members of the probands. The effect of the observed missense changes were further analyzed by SIFT and PolyPhen-2 scores. RESULTS: The screening of FZD4, TSPAN12 and ZNF408 genes identified 11 different mutations in 15/110 FEVR probands. Of the 11 identified mutations, 6 mutations were novel. The detected missense mutations were mainly located in the domains which are functionally crucial for the formation of ligand-receptor complex and as they replaced evolutionarily highly conserved amino acids with a SIFT score < 0.005, they are predicted to be pathogenic. Additionally 2 novel and 16 reported single nucleotide polymorphisms (SNP) were also detected. CONCLUSIONS: Our genetic screening revealed varying mutation frequencies in the FZD4 (8.0 %), TSPAN12 (5.4 %) and ZNF408 (2.7 %) genes among the FEVR patients, indicating their potential role in the disease pathogenesis. The observed mutations segregated with the disease phenotype and exhibited variable expressivity. The mutations in FZD4 and TSPAN12 were involved in autosomal dominant and autosomal recessive families and further validates the involvement of these gene in FEVR development.

Genotype-Phenotype Correlations in CYP1B1-Associated Primary Congenital Glaucoma Patients Representing Two Large Cohorts from India and Brazil.

BACKGROUND: Primary congenital glaucoma (PCG), occurs due to the developmental defects in the trabecular meshwork and anterior chamber angle in children. PCG exhibits genetic heterogeneity and the CYP1B1 gene has been widely implicated worldwide. Despite the diverse mutation spectra, the clinical implications of these mutations are yet unclear. The present study attempted to delineate the clinical profile of PCG in the background of CYP1B1 mutations from a large cohort of 901 subjects from India (n=601) and Brazil (n=300). METHODS: Genotype-phenotype correlations was undertaken on clinically well characterized PCG cases from India (n=301) and Brazil (n=150) to assess the contributions of CYP1B1 mutation on a set of demographic and clinical parameters. The demographic (gender, and history of consanguinity) and quantitative clinical (presenting intraocular pressure [IOP] and corneal diameter [CD]) parameters were considered as binary and continuous variables, respectively, for PCG patients in the background of the overall mutation spectra and also with respect to the prevalent mutations in India (R368H) and Brazil (4340delG). All these variables were fitted in a multivariate logistic regression model using the Akaike Information Criterion (AIC) to estimate the adjusted odds ratio (OR) using the R software (version 2.14.1). RESULTS: The overall mutation spectrum were similar across the Indian and Brazilian PCG cases, despite significantly higher number of homozygous mutations in the former (p=0.024) and compound heterozygous mutations in the later (p=0.012). A wide allelic heterogeneity was observed and only 6 mutations were infrequently shared between these two populations. The adjusted ORs for the binary (demographic) and continuous (clinical) variables did not indicate any susceptibility to the observed mutations (p>0.05). CONCLUSIONS: The present study demonstrated a lack of genotype-phenotype correlation of the demographic and clinical traits to CYP1B1 mutations in PCG at presentation. However, the susceptibility of these mutations to the long-term progression of these traits are yet to be deciphered.

Exome sequencing reveals the likely involvement of SOX10 in uveal melanoma.

PURPOSE: To identify the spectrum of somatic mutations in an Asian Indian patient with uveal melanoma (UM) without metastasis using exome sequencing. CASE REPORT: A 49-year-old man from India was diagnosed as having cilio-choroidal (uveal) melanoma (UM), without metastasis, in his right eye with the help of magnetic resonance imaging. This was later confirmed by histopathological evaluation. Two individuals from India with non-neoplastic blind eyes were recruited as controls. The affected eyes from the UM patient and the two control individuals were enucleated, and uveal tissues were collected. DNA was extracted from uveal tissue, and the matched blood sample from each of the three individuals was followed by exome sequencing. Statistical and bioinformatic analyses were done to identify somatic mutations and their putative associations with UM. Thirty-one somatic mutations (25 amino acid altering) in protein-coding (exonic) regions were detected in the UM patient. Of the amino acid-altering somatic mutations, 16 mutations were predicted to be candidate mutations relevant to UM. Somatic mutations, putatively causal for UM, were identified in GNAQ, SF3B1, and SOX10. CONCLUSIONS: Somatic mutations in GNAQ and SF3B1 genes were probable drivers of UM in the Indian patient; these were also reported earlier in some White patients. In addition, a frameshift deletion of 20 base pairs has been identified in SOX10 in the UM patient. Somatic mutations in SOX10, a transcription factor, which acts upstream of microphthalmia-associated transcription factor and synergizes with microphthalmia-associated transcription factor, was identified in some melanoma cell lines. The transcription factor SOX10 was found to have an essential role in melanocyte development and pigmentation. Our finding of the frameshift deletion (p.H387fs) in exon 4 of SOX10 in UM provides an important insight and complements earlier findings of mutations in GNAQ and SF3B1 on the genomic basis of UM.

TNF-α (g.-308 G > A) and ADIPOQ (g. + 45 T > G) gene polymorphisms in type 2 diabetes and microvascular complications in the region of Punjab (North-West India).

AIMS: The present study aims to examine the association of tumor necrosis factor-α (TNF-α) g.-308 G > A and adiponectin (ADIPOQ) g. + 45 T > G gene polymorphisms in type 2 diabetes (T2D) and its microvascular complications diabetic retinopathy (DR) and diabetic nephropathy (DN). MATERIALS AND METHODS: A total of 672 individuals were analysed from the North-West population of Punjab. Genotyping was accomplished by a combination of allele specific amplification refractory mutation system and restriction digestion for TNF-α g. - 308 G > A and ADIPOQ g. + 45 T > G polymorphisms, respectively. Further, in silico modeling was done to predict secondary structure of mRNA for g. + 45 T > G polymorphism in the ADIPOQ gene by RNA fold. RESULTS: The minor allele frequency observed in the controls for the TNF-α G > A and ADIPOQ T > G polymorphisms were 0.07 and 0.10, respectively. The results show no significant association with TNF-α g. - 308 G > A polymorphism in T2D as well as in any of the microvascular complication. However, the ADIPOQ g. + 45 T > G polymorphism shows significant association in T2D (p = 0.048) and DR (p = 0.001) but in DN patients, no association was observed. Interactive analysis revealed that the two polymorphisms jointly conferred a 1.45-fold risk towards the occurrence of T2D [p = 0.031; OR = 1.45 (1.03-2.05)]. In the secondary structure of mRNA, slight free energy change was observed between the wild ( - 1370.28 kcal/mol) and variant allele (-1369.08 kcal/mol). CONCLUSIONS: Our results indicated a higher risk of T2D and DR in the background of ADIPOQ TT genotype. Further, the ADIPOQ g. + 45 T > G and TNF-α g. - 308 G > A polymorphisms jointly give 1.45-fold risk towards T2D.

Cataract, visual impairment and long-term mortality in a rural cohort in India: the Andhra Pradesh Eye Disease Study.

BACKGROUND: A large-scale prevalence survey of blindness and visual impairment (The Andhra Pradesh Eye Diseases Study [APEDS1]) was conducted between 1996-2000 on 10,293 individuals of all ages in three rural and one urban clusters in Andhra Pradesh, Southern India. More than a decade later (June 2009-March 2010), APEDS1 participants in rural clusters were traced (termed APEDS2) to determine ocular risk factors for mortality in this longitudinal cohort. METHODS AND FINDINGS: Mortality hazard ratio (HR) analysis was performed for those aged >30 years at APEDS1, using Cox proportional hazard regression models to identify associations between ocular exposures and risk of mortality. Blindness and visual impairment (VI) were defined using Indian definitions. 799/4,188 (19.1%) participants had died and 308 (7.3%) had migrated. Mortality was higher in males than females (p<0.001). In multivariable analysis, after adjusting for age, gender, diabetes, hypertension, body mass index, smoking and education status the mortality HR was 1.9 (95% CI: 1.5-2.5) for blindness; 1.4 (95% CI: 1.2-1.7) for VI; 1.8 (95% CI: 1.4-2.3) for pure nuclear cataract, 1.5 (95% CI: 1.1-2.1) for pure cortical cataract; 1.96 (95% CI: 1.6-2.4) for mixed cataract, 2.0 (95% CI: 1.4-2.9) for history of cataract surgery, and 1.58 (95% CI: 1.3-1.9) for any cataract. When all these factors were included in the model, the HRs were attenuated, being 1.5 (95% CI: 1.1-2.0) for blindness and 1.2 (95% CI: 0.9-1.5) for VI. For lens type, the HRs were as follows: pure nuclear cataract, 1.6 (95% CI: 1.3-2.1); pure cortical cataract, 1.5 (95% CI: 1.1-2.1); mixed cataract, 1.8 (95% CI: 1.4-2.2), and history of previous cataract surgery, 1.8 (95% CI: 1.3-2.6). CONCLUSIONS: All types of cataract, history of cataract surgery and VI had an increased risk of mortality that further suggests that these could be potential markers of ageing.

LV Prasad Eye Institute Glaucoma Epidemiology and Molecular Genetic Study (LVPEI- GLEAMS). Report 1: study design and research methodology.

PURPOSE: In the developing world, more than 90% of glaucoma is undetected due to the lack of appropriate screening methods. The LV Prasad Eye Institute Glaucoma Epidemiology and Molecular Genetic Study (LVPEI-GLEAMS) is a population-based study which aims to estimate the prevalence of, along with clinical, systemic and genetic risk factors for glaucoma in a rural population sampled from the state of Andhra Pradesh, India. The study aims to develop community screening strategies to diagnose glaucoma. This article describes the methodology adopted in LVPEI-GLEAMS. METHODS: A sample of 3833 participants aged 40 years and older has been estimated to be enrolled using a compact segment sampling method with probability proportionate to size. Each participant will undergo a complete medical history and comprehensive eye examination including slit lamp photography, imaging of anterior and posterior segment, frequency doubling technology and standard automated perimetry. Additionally, glycosylated hemoglobin will be measured and a genetic profile based on candidate gene analysis will be undertaken. Clinical, biochemical and genetic data will be stored in a computerized database and analyzed. The novelty of this study lies in the fact that it is conducted at a vision center (primary eye care center serving a population of 50,000) by a vision technician (high school educated rural youth trained in basic ophthalmic techniques for a year). CONCLUSION: Information from the diagnostic techniques of the study will be used to develop effective community-level screening strategies, and insights from risk factors associated with glaucoma will help develop appropriate detection and management strategies.

Changing trends in the prevalence of blindness and visual impairment in a rural district of India: systematic observations over a decade.

Context : Globally, limited data are available on changing trends of blindness from a single region. Aims : To report the changing trends in the prevalence of blindness, visual impairment (VI), and visual outcomes of cataract surgery in a rural district of Andhra Pradesh, India, over period of one decade. Settings and Design : Rural setting; cross-sectional study. Materials and Methods : Using a validated Rapid Assessment of Cataract Surgical Services (RACSS) method, population-based, cross-sectional survey was done in a rural district in the state of Andhra Pradesh, India. Two-stage sampling procedure was used to select participants ≥50 years of age. Further, a comparative analysis was done with participants ≥50 years from the previously concluded Andhra Pradesh Eye Disease Study (APEDS) study, who belonged to the same district. Statistical Analysis : Done using 11 th version of Stata. Results : Using RACSS, 2160/2300 (93.9%) participants were examined as compared with the APEDS dataset (n=521). Age and sex adjusted prevalence of blindness in RACSS and APEDS was 8% (95% CI, 6.9-9.1%) and 11% (95% CI, 8.3-13.7%), while that of VI was 13.6% (95% CI, 12.2-15.1%) and 40.3% (95% CI, 36.1-44.5%), respectively. Cataract was the major cause of blindness in both the studies. There was a significant reduction in blindness following cataract surgery as observed through RACSS (17.3%; 95% CI, 13.5-21.8%) compared with APEDS (34%; 95% CI, 20.9-49.3%). Conclusion : There was a significant reduction in prevalence of blindness and VI in this rural district of India over a decade.

Population based outcomes of cataract surgery in three tribal areas of Andhra Pradesh, India: risk factors for poor outcomes.

PURPOSE: To report visual outcomes and risk factors for poor outcomes of cataract surgery in three Integrated Tribal Development Agency (ITDA) areas of Andhra Pradesh, India. METHODS AND RESULTS: Using validated Rapid Assessment of Avoidable Blindness (RAAB) methodology, a population based cross-sectional study, was conducted in three ITDA areas. A two-stage sampling procedure was used to select 7281 participants aged 50 years and above. Vision assessment using a tumbling E chart and standard ocular examinations were completed. Visual outcomes and risk factors for poor outcomes were assessed among subjects undergoing cataract surgery (1548 eyes of 1124 subjects). Mean age at surgery was 67±8 years; Among the operated eyes, presenting visual acuity (PVA) and best corrected visual acuity (BCVA) worse than 6/18 was seen in 492 (31.8%; 95% CI, 29.5-34.2%) and 298 eyes (19.3%; 95% CI, 17.3-21.3%), respectively. Similarly, PVA and BCVA worse than 6/60 was seen in 219 (14.1%; 95% CI, 12.4-16%) and 147 eyes (9.5%; 95% CI, 8.1-11.1%), respectively. When either eye was taken into consideration, the PVA and BCVA worse than 6/18 was seen in 323 (20.1%; 95% CI, 18.9-23%) and 144 subjects (9.3%; 95% CI, 7.9-10.9%), respectively. PVA and BCVA worse than 6/60 was seen in 74 (4.8%; 95% CI, 3.8-6%) and 49 subjects (3.2%; 95% CI, 2.4-4.2%), respectively. Posterior capsular opacification was seen in 51 of 1316 pseudophakic eyes (3.9%; 95% CI, 2.9-5.1%). In multivariable analysis among pseudophakic subjects with PVA worse than 6/18, increasing age (p = 0.002) and undergoing free surgery (p = 0.05) were independent risk factors. Undergoing surgery before 2005 (p = 0.05) and being illiterate (p = 0.05) were independent risk factors for BCVA worse than 6/18. CONCLUSIONS: There are changing trends with improved outcomes in cataract surgery among these tribal populations of India. However, post-operative refractive error correction remains an issue, especially for those undergoing free surgeries.

Association of single nucleotide polymorphisms of interleukins-1ß, -6, and -12B with contact lens keratitis susceptibility and severity.

PURPOSE: To investigate whether single nucleotide polymorphisms (SNPs) in interleukin (IL)-1ß, IL-6, and IL-12ß are associated with the susceptibility and severity of contact lens-related keratitis. DESIGN: Retrospective, case control study. PARTICIPANTS: One hundred twelve cases of keratitis and 225 controls were recruited from studies conducted at Moorfields Eye Hospital and in Australia during 2003 through 2005. METHODS: Buccal swab samples were collected on Whatman FTA cards and were mailed by post for analysis. IL-1ß (-31), IL-6 (-174, -572, -597), and IL-12B (3'+1158) genotypes were analyzed with pyrosequencing and analyzed using a regression model for susceptibility (sterile, microbial keratitis, controls) and severity. Statistical significance was set at 0.05. MAIN OUTCOME MEASURES: The relative risk of developing contact lens-related keratitis and more severe forms of the disease based on allele, genotype, and haplotype associations. RESULTS: Carriers of IL-6 SNPs were more likely to experience moderate and severe events compared with those with nonmutated genotypes (-174 heterozygous: odds ratio [OR], 3.1; 95% confidence interval [CI], 1.1-8.3; homozygous: OR, 6.4; 95% CI, 1.4-28.4; -174/-597: OR, 4.1; 95% CI, 1.6-11.0). More severe keratitis and microbial keratitis were less likely to occur in wearers with the nonmutated IL-6 haplotype (severity OR, 0.4 [95% CI, 0.2-0.7]; microbial OR, 0.6 [95% CI, 0.4-0.9]). Wearers carrying an IL-12B SNP had an increased risk of sterile keratitis (OR, 9.7; 95% CI, 1.2-76.9) compared with controls. CONCLUSIONS: The IL-6 SNPs are known to reduce protein expression of this cytokine and thus ocular immune defense, and carriers of these SNPs were more likely to experience more severe and microbial keratitis, suggesting that IL-6 decreases the severity and susceptibility of contact lens-related keratitis. Carriers of a functional SNP of IL-12B that is known to increase IL-12 expression and stability are more likely to experience sterile keratitis, suggesting that this is associated with the intense inflammatory reaction that occurs in this condition.

Complex genetic mechanisms in glaucoma: an overview.

Glaucomas comprise a group of hereditary optic neuropathies characterized by progressive and irreversible visual field loss and damage to the optic nerve head. It is a complex disease with multiple molecular mechanisms underlying its pathogenesis. Genetic heterogeneity is the hallmark of all glaucomas and multiple chromosomal loci have been linked to the disease, but only a few genes have been characterized, viz. myocilin (MYOC), optineurin (OPTN), WDR36 and neurotrophin-4 (NTF4) in primary open angle glaucoma (POAG) and CYP1B1 and LTBP2 in congenital and developmental glaucomas. Case-control-based association studies on candidate genes involved in different stages of glaucoma pathophysiology have indicated a very limited involvement. The complex mechanisms leading to glaucoma pathogenesis indicate that it could be attributed to multiple genes with varying magnitudes of effect. In this review, we provide an appraisal of the various efforts in unraveling the molecular mystery in glaucoma and also some future directions based on the available scientific knowledge and technological developments.

LTBP2 and CYP1B1 mutations and associated ocular phenotypes in the Roma/Gypsy founder population.

Primary congenital glaucoma (PCG) is a genetically heterogeneous autosomal recessive disorder, which is an important cause of blindness in childhood. The first known gene, CYP1B1, accounts for a variable proportion of cases in most populations. A second gene, LTBP2, was recently reported in association with a syndrome, in which glaucoma is secondary to lens dislocation. We report on the molecular and clinical profile of 34 families diagnosed as PCG, all originating from the Roma/Gypsy founder population. Comprehensive sequencing analysis revealed a level of heterogeneity unusual for this population, with five CYP1B1 and one ancestral LTBP2 mutation accounting for ∼70% of patients (25 out of 37) and the remainder still unexplained. Homozygosity for the founder LTBP2 p.R299X mutation resulted in a more severe clinical phenotype and poorer outcome despite a markedly higher number of surgical interventions. The genetically homogeneous group of p.R299X homozygotes showed variable phenotypes (presumably also underlying pathogenetic mechanisms), wherein PCG proper with primary dysgenesis of the trabecular meshwork, and Marfan syndrome-like zonular disease with ectopia lentis and later onset secondary glaucoma are two extremes. The spectrum manifestations may occur in different combinations and have a different evolution even within the same sibship or a single patient. Preliminary observations on compounds with mutations in both CYP1B1-LTBP2 suggest that the observed combinations are of no clinical significance and digenic inheritance is unlikely. We provide a population genetics perspective to explain the allelic heterogeneity, comparing the history and geographic distribution of the two major founder mutations--p.R299X/LTBP2 and p.E387K/CYP1B1.

A polymorphism in the CYP1B1 promoter is functionally associated with primary congenital glaucoma.

Primary congenital glaucoma (PCG) is a childhood autosomal-recessive disorder caused by developmental defects in the trabecular meshwork and anterior chamber angle. These defects cause raised intraocular pressure (IOP) that damages the optic nerve and if left untreated, results in irreversible blindness. Mutations in CYP1B1 gene at the GLC3A locus (2p21) are associated with PCG. However, there has been very limited exploration of its promoter region. We resequenced the CYP1B1 promoter in a large cohort (n = 835) that included patients with PCG (n = 301), other primary glaucomas (primary open-angle glaucoma: n = 115 and primary angle closure glaucoma: n = 100) and unaffected controls (n = 319). We functionally characterized one associated variant by luciferase reporter assay using the trabecular meshwork (TM3) cell line. We found evidence of strong (P = 6.01 × 10(-4)) association of rs2567206 (T2805C) SNP in PCG and not in other primary glaucomas. Luciferase assay indicated a ∼90% reduction in CYP1B1 promoter activity in the risk-allele (C) compared to the other allele (T). The association of the risk allele was stronger in cases harboring homozygous CYP1B1 mutations (P = 3.42 × 10(-12)). The risk haplotype 'C-C-G' in the promoter had a strong non-random association to the previously characterized risk haplotype 'C-G-G-T-A' in the coding region. The independent effect of genotype at the promoter T2805C locus (P = 0.001), and the interaction effect of genotypes at the promoter and coding region mutations loci (P = 0.001) were significant for the presenting IOP of the worst affected eye. This is the first study that unequivocally shows the functional involvement of a CYP1B1 promoter variant in PCG.

Variations in NTF4, VAV2, and VAV3 genes are not involved with primary open-angle and primary angle-closure glaucomas in an indian population.

PURPOSE: Recently, the neurotrophin-4 (NTF4), VAV2 and VAV3 genes have been implicated in primary open-angle glaucoma (POAG) in the European and Japanese populations, respectively. This study was conducted to determine their involvement in an Indian population with POAG and primary angle-closure glaucoma (PACG). METHODS: The entire NTF4 gene and the POAG-associated SNPs rs2156323 (VAV2) and rs2801219 (VAV3) and their flanking regions were screened by resequencing in a clinically well-characterized cohort of 537 subjects that included cases of POAG (n = 141), PACG (n = 111), and ethnically matched normal controls (n = 285). The data were analyzed by using appropriate statistical software. RESULTS: Resequencing of NTF4 revealed a nonsynonymous (A88V), silent (P151P) and two changes in the 3'UTR region, along with a known polymorphism (rs11669977) in cases of POAG; the PACG cases exhibited only the A88V variation. Of interest, the A88V mutation observed in Europeans was more prevalent in our normal control subjects (4.91%, 95% CI, 2.95-8.07) than in the POAG (2.14%, 95% CI, 0.73-6.11; P = 0.200) and PACG (2.85%, 95% CI, 0.97-8.06; P = 0.577) cases. There were no major differences in the presenting intraocular pressure, cup-to-disc ratio, and visual field defects among patients harboring the A88V variation. The other variations in NTF4 were not associated with the cases. The risk alleles of rs2156323 and rs2801219 in the Japanese were not associated with POAG (P = 0.533 and 0.133, respectively) and PACG (P = 0.223 and 0.394, respectively) in the Indian cohort. CONCLUSIONS: The present data indicate a lack of involvement of variations in NTF4, VAV2, and VAV3 with glaucoma pathogenesis in an Indian population.

Single-nucleotide polymorphisms in peroxisome proliferator-activated receptor gamma and their association with plasma levels of resistin and the metabolic syndrome in a South Indian population.

Studies on the association of the Pro12Ala and C1431T polymorphisms of PPAR? with diabetes and obesity have revealed extensive population-dependent variations. However, association of these polymorphisms with the metabolic syndrome and its individual components has not been well investigated in the Indian population. The Indian population harbours the maximum number of diabetics in the world who are thus more susceptible to metabolic disorders. We screened a South Indian population (N=699) for a possible association of these polymorphisms with the metabolic syndrome (MS) and type 2 diabetes. We also investigated the correlation of these two single-nucleotide polymorphisms (SNPs) with plasma resistin levels. The C1431T SNP was associated with higher levels of plasma resistin (P=0.017). Furthermore, C1431T was associated with resistin in different tertiles. Prevalence of the 'Pro-C' haplotype decreased with increasing tertiles of resistin (84.1% to 75.4%, P=0.037). Plasma resistin levels were not found to be associated with MS and type 2 diabetes. These results point to a likely association of plasma resistin levels with PPAR? polymorphisms in the Indian population.

The molecular genetic basis of age-related macular degeneration: an overview.

Age-related macular degeneration (AMD) is a complex disorder of the eye and the third leading cause of blindness worldwide. With a multifactorial etiology, AMD results in progressive loss of central vision affecting the macular region of the eye in elderly. While the prevalence is relatively higher in the Caucasian populations, it has gradually become a major public health issue among the non-Caucasian populations (including Indians) as well due to senescence, rapidly changing demographics and life-style factors. Recent genome-wide association studies (GWAS) on large case-control cohorts have helped in mapping genes in the complement cascade that are involved in the regulation of innate immunity with AMD susceptibility. Genes involved with mitochondrial oxidative stress and extracellular matrix regulation also play a role in AMD pathogenesis. Majority of the associations observed in complement (CFH, CFB, C2 and C3) and other (ARMS2 and HTRA1) genes have been replicated in diverse populations worldwide. Gene-gene (CFH with ARMS2 and HTRA1) interactions and correlations with environmental traits (smoking and body mass index) have been established as significant covariates in AMD pathology. In this review, we have provided an overview on the underlying molecular genetic mechanisms in AMD worldwide and highlight the AMD-associated-candidate genes and their potential role in disease pathogenesis.

The transcription factor gene FOXC1 exhibits a limited role in primary congenital glaucoma.

PURPOSE: Primary congenital glaucoma (PCG) is an autosomal recessive disorder that has been linked to CYP1B1 mutations. This study was conducted to explore the role of FOXC1, which is involved in anterior segment dysgenesis, in PCG. METHODS: An earlier screening for CYP1B1 in a clinically well-characterized PCG cohort (n = 301) revealed cases that were either homozygous (n = 73), compound heterozygous (n = 18), or heterozygous (n = 41) for the mutant allele, whereas the remaining (n = 169) did not harbor any mutation. Hence, FOXC1 was screened in 210 PCG cases who were either heterozygous (n = 41) or did not harbor any CYP1B1 mutation (n = 169), along with ethnically matched normal control subjects (n = 157) by resequencing the entire coding region. RESULTS: Two heterozygous missense (H128R and C135Y) and three frame shift mutations (g.1086delC, g.1155del9bp, and g.1947dup25bp) were observed in FOXC1 in 5 (2.38%) of 210 cases. The missense mutations had a de novo origin in two sporadic cases, whereas the FOXC1 deletions were seen in two cases that were also heterozygous for the CYP1B1 allele (R368H). The parents of the proband with g.1086delC were heterozygous for either the FOXC1 or CYP1B1 alleles. The unaffected mother of the proband with the g.1155del9bp was heterozygous for both the FOXC1 and CYP1B1 alleles; the father harbored only the FOXC1 allele. Familial segregation of the g.1947dup25bp could not be performed because of the unavailability of DNA from one parent. Except for the g.1155del9bp (0.95% normal chromosomes), all the other variations were absent in the control subjects. CONCLUSIONS: The present study indicates a limited role of FOXC1 in PCG pathogenesis.

Glaucoma-associated CYP1B1 mutations share similar haplotype backgrounds in POAG and PACG phenotypes.

PURPOSE: To understand the involvement of the CYP1B1 gene in cases of primary open-angle (POAG) and primary angle-closure (PACG) glaucomas and obtain the haplotype background of these mutations. METHODS: The entire coding region of CYP1B1 was screened by resequencing in 224 unrelated cases of POAG (n = 134) and PACG (n = 90) and 200 ethnically matched normal control subjects from Indian populations. Six intragenic single nucleotide polymorphisms (SNPs) in CYP1B1 (-13T>C, R48G, A119S, V432L, D449D, and N453S) were used to generate haplotype data for the cases and controls and linkage disequilibrium (LD) and haplotype analysis were performed with Haploview software, which uses the EM (expectation-maximization) algorithm. RESULTS: The frequency of CYP1B1 mutations was higher among POAG (18.6%; 95% CI, 12.9-26.1) than PACG (11.1%; 95% CI, 6.1-19.3) cases. There was a marked allelic heterogeneity, and the Arg368His was the most prevalent mutation across both the phenotypes. The spectrum of CYP1B1 mutations was largely similar across different POAG populations. Haplotypes generated with intragenic SNPs indicated the C-C-G-G-T-A to be a risk haplotype associated with CYP1B1 mutations in POAG (P = 0.006) and PACG (P = 0.043), similar to that observed in cases of primary congenital glaucoma worldwide. CONCLUSIONS: The results demonstrate an involvement of CYP1B1 in a proportion of POAG and PACG cases that should be explored further. The similar haplotype background of these mutations is indicative of their common origin across multiple glaucoma phenotypes.

Disease-causing mutations in proteins: structural analysis of the CYP1B1 mutations causing primary congenital glaucoma in humans.

In this communication, we report an in-depth structure-based analysis of the human CYP1b1 protein carrying disease-causing mutations that are discovered in patients suffering from primary congenital glaucoma (PCG). The "wild-type" and the PCG mutant structures of the human CYP1b1 protein obtained from comparative modeling were subjected to long molecular dynamics simulations with an intention of studying the possible impact of these mutations on the protein structure and hence its function. Analysis of time evolution as well as time averaged values of various structural properties--especially of those of the functionally important regions: the heme binding region, substrate binding region, and substrate access channel--gave some insights into the possible structural characteristics of the disease mutant and the wild-type forms of the protein. In a nutshell, compared to the wild-type the core regions in the mutant structures are associated with subtle but significant changes, and the functionally important regions seem to adopt such structures that are not conducive for the wild-type-like functionality.