Whole-exome sequencing identifies multiple pathogenic variants in a large South Indian family with primary open-angle glaucoma.
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ABSTRACT: Purpose
To identify the pathogenic variants associated with primary open-angle glaucoma (POAG) using whole-exome sequencing (WES) data of a large South Indian family.Methods
We recruited a large five-generation South Indian family (n = 84) with a positive family history of POAG (n = 19). All study participants had a comprehensive ocular evaluation. We performed WES for 16 samples (nine POAG and seven unaffected controls) since Sanger sequencing of the POAG candidate genes (MYOC, OPTN, and TBK1) showed no genetic variation. We used an in-house pipeline for prioritizing the pathogenic variants based on their segregation among the POAG individual.Results
We identified one novel and five low-frequency pathogenic variants with consistent co-segregation in all affected individuals. The variant c.G3719A in RPGR-interacting domain of RPGRIP1 that segregated heterozygously with the six POAG cases is distinct from variants causing photoreceptor dystrophies, reported affecting the RPGR protein complex signaling in primary cilia. The cilia in trabecular meshwork (TM) cells has been reported to mediate the intraocular pressure (IOP) sensation. Furthermore, we identified a novel c.A1295G variant in Rho guanine nucleotide exchange factors Gene 40 (ARHGEF40) and a likely pathogenic variant in the RPGR gene, suggesting that they may alter the RhoA activity essential for IOP regulation.Conclusion
Our study supports that low-frequency pathogenic variants in multiple genes and pathways probably affect Primary Open Angle Glaucoma's pathogenesis in the large South Indian family. Furthermore, it requires larger case-controls to perform family-based association tests and to strengthen our analysis.
SUBMITTER: Shah MH
PROVIDER: S-EPMC8544095 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:PURPOSE: Glaucoma is a heterogeneous group of optic neuropathies with a complex genetic basis. To date, only the following four genes have been identified: viz. myocilin (MYOC), optineurin (OPTN), WD repeat domain 36 (WDR36), and neurotrophin 4 (NTF4). However, there are conflicting reports regarding the involvement of WDR36 in the pathogenesis of primary open-angle glaucoma (POAG). In the Asian population, mutations in WDR36 appear to play a minor role in POAG pathogenesis but polymorphic variants have been found to be associated with POAG, especially in patients with high tension glaucoma (HTG). The purpose of this study is to determine the role of WDR36 in East Indian POAG patients. To date, no other studies have yet examined this role. METHODS: Ten single nucleotide polymorphisms (SNPs; rs1971050, rs1993465, rs13153937, rs10038177, rs11241095, rs10043631, rs10038058, rs10491424, rs17553936, and rs13186912) spanning almost the entire WDR36 gene were selected and their association with eastern Indian POAG patients was evaluated. Our study pool consisted of 323 POAG patients. Of these 116 were patients who had HTG with intraocular perssure (IOP) >21mmHg and 207 were found to be non-HTG patients (presenting IOP<21mmHg). The study also included 303 participants as controls. The polymorphisms were genotyped in both the patients and the controls using the PCR-RFLP method. Moreover, the SNP that showed significant association was validated by DNA sequencing. The haplotypes were obtained using Haploview 4.1 software. The allele and haplotype frequencies were compared between the patient group and the control group using Pearson's ?(2) test. RESULTS: First, we genotyped the selected SNPs in the 323 POAG patients and 119 of the participants in the control group, in which only rs10038177 (c.710+30C>T) was found to be strongly associated with the HTG cases (OR=2.186; 95% CI=1.458-3.277; p=1.4×10(-4)). To increase the significance of the study, the SNP was genotyped in an additional 184 of the participants in the control group and it was observed that the SNP retained the association (OR=1.216; 95% CI=1.064-2.306; p=0.002). However, no haplotype was found to have any sustainable association with POAG. Based on the LD pattern and location of rs10038177, exon 5 of WDR36 was sequenced but no suspected disease-causing variant was detected. CONCLUSIONS: Our study suggests a possible association between WDR36 SNP in a cohort of eastern Indian POAG patients who also have high intraocular pressure (IOP). This study needs to be further validated in a larger patient cohort.
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Project description:Primary open-angle glaucoma (POAG) is a clinically important and genetically heterogeneous cause of progressive vision loss as a result of retinal ganglion cell death. Here we have utilized trio-based, whole-exome sequencing to identify the genetic defect underlying an autosomal dominant form of adult-onset POAG segregating in an African-American family. Exome sequencing identified a novel missense variant (c.418C>T, p.Arg140Trp) in exon-5 of the gene coding for epidermal growth factor (EGF) containing fibulin-like extracellular matrix protein 1 (EFEMP1) that co-segregated with disease in the family. Linkage and haplotype analyses with microsatellite markers indicated that the disease interval overlapped a known POAG locus (GLC1H) on chromosome 2p. The p.Arg140Trp substitution was predicted in silico to have damaging effects on protein function and transient expression studies in cultured cells revealed that the Trp140-mutant protein exhibited increased intracellular accumulation compared with wild-type EFEMP1. In situ hybridization of the mouse eye with oligonucleotide probes detected the highest levels of EFEMP1 transcripts in the ciliary body, cornea, inner nuclear layer of the retina, and the optic nerve head. The recent finding that a common variant near EFEMP1 was associated with optic nerve-head morphology supports the possibility that the EFEMP1 variant identified in this POAG family may be pathogenic.
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Project description:Glaucoma represents a heterogeneous group of optic neuropathies with a complex genetic basis. It is the second-largest cause of blindness in the world that reduces vision without warning and often without symptoms. Among 3 major subtypes of glaucoma, primary open-angle glaucoma (POAG) is the most common form. The focus of this study is to understand the molecular basis of the disease among Indian patients with respect to two genes, Cochlin (COCH) and tumor necrosis factor alpha (TNFA), selected based on reports of possible association with POAG. The genes were screened in patients and controls by PCR and direct sequencing. Although two novel changes (-450?C/T and -79?G/G) were identified in the 5'upstream region of COCH, no causal variant could be identified in either gene. -450?C/T was detected in 3 patients and 2 controls and -79?G/C in a single patient. Further, we did not observe significant association with the promoter SNPs of TNFA that had been previously reported to be associated with POAG pathogenesis. Thus, our study suggests lack of association of both COCH and TNFA with POAG pathogenesis.
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Project description:The total RNA from control and POAG optic nerve lamina cribrosa region was isolated and subjected to analysis on U133A 2.0 affymetrix microarray chip. The results from these two analysis was compared to determine whether PAD II RNA level is altered. Purpose of the study. This study was done to determine which RNA transcripts undergo significant changes in the optic nerve between normal and cadaver primary open-angle glaucoma donors. Using donor tissues from NDRI we have performed proteomic analyses (which will be published shortly), we intend a comparison between the proteomic and RNA changes for select proteins in our study. Sample Collection and Preparation of Labeled Copy RNA; The total RNA from optic nerve was obtained using TRIZOL (Invitrogen Inc., Carlsbad, CA) with modification of recommended protocols. The optic nerve from donor eyes were carefully excised and minced into small pieces first using a scissor and then a scalpel. Prior to use tissue was washed with DEPC water and all solutions were prepared in DEPC water. The minced tissue was placed in a glass homogenizer with 1 ml TRIZOL per 100 mg of tissue and homogenized in a glass homogenizer DUALL 20 (Kimble Kontes Glass Co, Vineland, NJ) with 10 strokes cycles each at room temperature and after freezing with liquid nitrogen for 1 min for 40 cycles. This RNA was extracted with chloroform, isoamylalcohol and precipitated with sodium citrate/sodium chloride and isopropanol. The final air-dried RNA precipitate was suspended in DEPC water and stored in â??80oC prior to use. RNA was prepared for hybridization according to the GeneChip Expression Analysis Technical Manual (Affymetrix, Santa Clara, CA). The hybridization was performed at Gene Expression Array Core Facility at Case Western Reserve University (www.geacf.net). The RNA sample was cleaned using a column from a Qiagen RNeasy kit, (part # 74104 ) in accordance with the manufacturerâ??s instructions. The volume of DEPC water used to elute the RNA from the Qiagen column was dictated by the nominal mass of the loaded RNA sample. Samples were eluted in 100ml of water, precipitated with 0.5 volume of 7.5M Ammonium Acetate and 2.5 volumes of 100% ethanol at -20oC for 1 hr and centrifuged for 10 min at room temperature. The pellet was drained and washed twice in 500µl of 70% ethanol. Supernatant was aspirated. The pellet was dried briefly (less than 1 min) in a speeedvac (Savant) and re-suspended in a small volume (~ 12â??15ml) of DEPC water. A small aliquot (2ml) of the sample was used for quantitation. Cleaned RNA samples were annotated as â??clnRNAâ?? and stored at -20oC. cDNA Synthesis; The protocol recommended by Affymetrix Inc. for cDNA synthesis was used at all times. The reaction was primed by annealing an oligo-dT primer coupled to a T7 RNA polymerase promoter to the RNA sample. Whenever possible, 8 mg of clnRNA were reverse transcribed using Superscript II reverse transcriptase in a 20ml reaction at 42oC for 1 hr. Second strand synthesis was carried out immediately in a total reaction volume of 150ml in the presence of E. coli DNA polymerase I, RNAse H and DNA ligase. The reaction mixture incubated for 2 hrs at 16oC and for a further 5 min in the presence of T4 DNA pol.. The reaction was terminated by the addition of EDTA. The sample was cleaned with a Qiagen cDNA clean-up column according to the manufacturers directions. The elution buffer volume was 14ml. The eluted samples were stored overnight at -20oC. In-Vitro Transcription (IVT) reaction; In a 0.5ml microfuge tube, complementary RNA (cRNA) was generated in an IVT reaction using a BioArray High Yield ENZO kit (Affymetrix). The 40ml reaction contained 10ml of cDNA sample and was incubated at 37oC in the heating block for 4-5hrs. Samples were mixed by flicking, pulse-centrifuged and returned to the incubator once every 40 minutes. Upon completion of the reaction, IVT samples were adjusted to a volume of 100ml with DEPC-treated water and cleaned using Qiagen RNA clean-up columns. Samples were eluted in 45ml of DEPC-treated water. A 2ml-aliquot was used for quantitation. Corrected concentrations of cRNA (minus the input clnRNA) were determined. A standard fragmentation reaction volume was 40ml in a 0.5 ml microfuge tube and used 20mg of overall IVT RNA in 1X fragmentation buffer (40mM Tris acetate, pH 8.1, 100mM KOAc, 30mM MgOAc). The reaction was incubated at 94oC for 35min in a heat block. After the 35 min incubation the fragmented samples were placed on ice. The standard hybridization cocktail volume was 300ml. 150ml of 2X hybridization buffer was added (final concentrations : 100mM MES, 1M [Na+], 20mM EDTA, 0.01% Tween 20) Herring sperm and acetylated BSA were added to a final concentration of 0.1 and 0.5mg/ml respectively. The amount of fragmentation reaction containing 15mg of cRNA was added to the cocktail and the remaining volume was made up with molecular biology grade water. A 15ml aliquot of a 20X mixture of in-vitro transcripts of bacterial genes BioB BioC BioD and cre as external controls (spikes) were added to the cocktail to give final concentrations of 1.5, 5, 25 and 100pM respectively. Control oligonucleotide (5ml) was added to a final concentration of 50pM. Array Hybridization; Sample Hyridization cocktails (300ml) were removed from storage at â??20oC and thawed in a 45oC temperature block. The samples were incubated at 45oC for 5 min, incubated at 45oC for 5 min and then centrifuged at 15,000g for 5 min. 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Samples were retrieved from the chips and stored again in a freezer at -20oC. The chips were filled with buffer A and placed in a module of Fluidics 400 wash station. The chips were subjected to the Affymetrix â??EuKws4 ver 2â?? programmed series of stringent post hybridization washes, staining and post-staining washes in accordance with Affy protocols. Upon completion of the wash series (approximately 2 hrs), the chips were removed from the Fluidics station. The chips were inspected. Chips were scanned using an Agilent Gene Array scanner 3000 driven by Affymetrix GCOS software. Generation of Expression Values; Microarray Suite, version 5 (Affymetrix), was used to generate *.cel files, and a computer program (Probe Profiler, ver. 1.3.11; Corimbia Inc., Berkeley, CA) developed specifically for the GeneChip system (Affymetrix) was used to convert intensity data into quantitative estimates of gene expression for each probe set. 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2008-06-12 | E-GEOD-2387 | biostudies-arrayexpress
Project description:In India, mutations in Cytochrome P450 (CYP1B1) are a predominant cause of not only primary congenital glaucoma (PCG) but also involved in primary open angle glaucoma (POAG) and juvenile onset glaucoma (JOAG). After ethical clearance, 100 POAG patients, 30 primary angle closure glaucoma (PACG) patients and 130 ethnically matched controls were recruited in this study. Genomic DNA was isolated from the blood and screened for p.Arg368His mutation in CYP1B1 by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). On PCR-RFLP, 10/100 cases (10%) were found positive for Arg368His mutation. In North Indian POAG cases studied, p.Arg368His mutation was found only in heterozygous state. The frequency of p.Arg368His CYP1B1 mutation in heterozygote state (10.0%) observed in our study in North Indian POAG patients is the highest in comparison to frequency observed in other ethnic groups from Southern and Eastern India.
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