Homozygous mutations in PXDN cause congenital cataract, corneal opacity, and developmental glaucoma.

Anterior segment dysgenesis describes a group of heterogeneous developmental disorders that affect the anterior chamber of the eye and are associated with an increased risk of glaucoma. Here, we report homozygous mutations in peroxidasin (PXDN) in two consanguineous Pakistani families with congenital cataract-microcornea with mild to moderate corneal opacity and in a consanguineous Cambodian family with developmental glaucoma and severe corneal opacification. These results highlight the diverse ocular phenotypes caused by PXDN mutations, which are likely due to differences in genetic background and environmental factors. Peroxidasin is an extracellular matrix-associated protein with peroxidase catalytic activity, and we confirmed localization of the protein to the cornea and lens epithelial layers. Our findings imply that peroxidasin is essential for normal development of the anterior chamber of the eye, where it may have a structural role in supporting cornea and lens architecture as well as an enzymatic role as an antioxidant enzyme in protecting the lens, trabecular meshwork, and cornea against oxidative damage.

Identification of a novel oligomerization disrupting mutation in CRYΑA associated with congenital cataract in a South Australian family.

Congenital cataract is a heterogeneous disorder causing severe visual impairment in affected children. We screened four South Australian families with autosomal dominant congenital cataract for mutations in 10 crystallin genes known to cause congenital cataract. We identified a novel segregating heterozygous mutation, c.62G>A (p.R21Q), in the CRYΑA gene in one family. Western blotting of proteins freshly extracted from cataractous lens material of the proband demonstrated a marked reduction in the amount of the high-molecular-weight oligomers seen in the lens material of an unaffected individual. We conclude that the p.R21Q mutation, which is located in the highly conserved and structurally significant N-terminal region of the protein, is responsible for the cataract phenotype observed in the family as this mutation likely reduces the formation of the functional oligomeric alpha-crystallin.

A novel syndrome of paediatric cataract, dysmorphism, ectodermal features, and developmental delay in Australian Aboriginal family maps to 1p35.3-p36.32.

BACKGROUND: A novel phenotype consisting of cataract, mental retardation, erythematous skin rash and facial dysmorphism was recently described in an extended pedigree of Australian Aboriginal descent. Large scale chromosomal re-arrangements had previously been ruled out. We have conducted a genome-wide scan to map the linkage region in this family. METHODS: Genome-wide linkage analysis using Single Nucleotide Polymorphism (SNP) markers on the Affymetrix 10K SNP array was conducted and analysed using MERLIN. Three positional candidate genes (ZBTB17, EPHA2 and EPHB2) were sequenced to screen for segregating mutations. RESULTS: Under a fully penetrant, dominant model, the locus for this unique phenotype was mapped to chromosome 1p35.3-p36.32 with a maximum LOD score of 2.41. The critical region spans 48.7 cM between markers rs966321 and rs1441834 and encompasses 527 transcripts from 364 annotated genes. No coding mutations were identified in three positional candidate genes EPHA2, EPHB2 or ZBTB17. The region overlaps with a previously reported region for Volkmann cataract and the phenotype has similarity to that reported for 1p36 monosomy. CONCLUSIONS: The gene for this syndrome is located in a 25.6 Mb region on 1p35.3-p36.32. The known cataract gene in this region (EPHA2) does not harbour mutations in this family, suggesting that at least one additional gene for cataract is present in this region.

Apparent autosomal dominant keratoconus in a large Australian pedigree accounted for by digenic inheritance of two novel loci.

Keratoconus is a debilitating ocular disease characterised by progressive asymmetrical thinning of the cornea, the clear covering at the front of the eye. The resulting protrusion of the cornea results in severe refractive error, in the most severe cases requiring corneal grafting. It is a complex disease with a genetic component. Despite several reports of linked loci, major gene identification has been elusive. A genome-wide linkage scan in a large Australian pedigree with apparent autosomal dominant keratoconus was conducted using the Affymetrix 10K SNP chip and two regions of linkage identified. Functional candidate genes from within both linkage peaks were assessed for corneal expression and screened for mutations in affected family members. Equal evidence of linkage was detected to both 1p36.23-36.21 and 8q13.1-q21.11 with LOD scores of 1.9. Analysis of both loci concurrently suggests digenic linkage with two-locus LOD score of 3.4. All affected individuals carry identical haplotypes at both loci. Carriers of either linked haplotype without the other do not have keratoconus. No mutations were identified in the following candidate genes expressed in the cornea: ENO1, CTNNBIP1, PLOD1, UBIAD1, SPSB1 or TCEB1. Although the pedigree appears to demonstrate simple autosomal dominant inheritance, the disorder is actually genetically complex. This pedigree may provide a link between inherited forms of keratoconus and sporadic cases.

Investigation of eight candidate genes on chromosome 1p36 for autosomal dominant total congenital cataract.

PURPOSE: To identify the causative gene for autosomal dominant total congenital cataract in a six-generation Australian family displaying linkage to chromosome 1p36. METHODS: Eight candidate genes (HSPB7, FBXO42, EFHD2, ZBTB17, CAPZB, FBLIM1, ALDH4A1, and MFAP2) from within the previously defined linkage interval were selected based on expression in lens and their known or putative function. The coding exons were sequenced in multiple affected family members and compared to the reference sequence. RESULTS: No segregating mutations were identified in any of the eight genes. Thirty-one polymorphisms were detected, 20 of which were in the exons and 11 in the flanking introns. CONCLUSIONS: Coding mutations in HSPB7, FBXO42, EFHD2, ZBTB17, CAPZB, FBLIM1, ALDH4A1, and MFAP2 do not account for congenital cataract in this family.

Association of Polymorphisms in MACRO Domain Containing 2 With Thyroid-Associated Orbitopathy.

PURPOSE: Thyroid-associated orbitopathy (TO) is an autoimmune-mediated orbital inflammation that can lead to disfigurement and blindness. Multiple genetic loci have been associated with Graves' disease, but the genetic basis for TO is largely unknown. This study aimed to identify loci associated with TO in individuals with Graves' disease, using a genome-wide association scan (GWAS) for the first time to our knowledge in TO. METHODS: Genome-wide association scan was performed on pooled DNA from an Australian Caucasian discovery cohort of 265 participants with Graves' disease and TO (cases) and 147 patients with Graves' disease without TO (controls). Top-ranked single nucleotide polymorphisms (SNPs) then were genotyped in individual DNA samples from the discovery cohort, and two replication cohorts totaling 584 cases and 367 controls. RESULTS: In the GWAS of pooled DNA samples, several SNPs showed suggestive association with TO at genome-wide P ≤ 10-6; rs953128 located on chr10q21.1, rs2867161 on chr7q11.22, rs13360861 on chr5q12.3, rs7636326 on chr3q26.2, rs10266576 on chr 7q11.22, rs60457622 on chr3q23, and rs6110809 on chr20p12.1. However, the only SNP consistently associated with TO on individual genotyping in the discovery and replication cohorts was rs6110809, located within MACROD2 on chromosome 20p12.1. On combined analysis of discovery and replication cohorts, the minor A allele of rs6110809 was more frequent in TO than in Graves' disease controls without TO (P = 4.35 × 10-5; odds ratio [OR] = 1.77; 95% confidence interval [CI], 1.35-2.32) after adjusting for age, sex, duration of Graves' disease, and smoking. CONCLUSIONS: In patients with Graves' disease, a common genetic variant in MACROD2 may increase susceptibility for thyroid-associated orbitopathy. This association now requires confirmation in additional independent cohorts.

Association of polymorphisms in the hepatocyte growth factor gene promoter with keratoconus.

PURPOSE: Keratoconus is a progressive disorder of the cornea that can lead to severe visual impairment or blindness. Although several genomic regions have been linked to rare familial forms of keratoconus, no genes have yet been definitively identified for common forms of the disease. METHODS: Two genome-wide association scans were undertaken in parallel. The first used pooled DNA from an Australian cohort, followed by typing of top-ranked single-nucleotide polymorphisms (SNPs) in individual DNA samples. The second was conducted in individually genotyped patients, and controls from the USA. Tag SNPs around the hepatocyte growth factor (HGF) gene were typed in three additional replication cohorts. Serum levels of HGF protein in normal individuals were assessed with ELISA and correlated with genotype. RESULTS: The only SNP observed to be associated in both the pooled discovery and primary replication cohort was rs1014091, located upstream of the HGF gene. The nearby SNP rs3735520 was found to be associated in the individually typed discovery cohort (P = 6.1 × 10(-7)). Genotyping of tag SNPs around HGF revealed association at rs3735520 and rs17501108/rs1014091 in four of the five cohorts. Meta-analysis of all five datasets together yielded suggestive P values for rs3735520 (P = 9.9 × 10(-7)) and rs17501108 (P = 9.9 × 10(-5)). In addition, SNP rs3735520 was found to be associated with serum HGF level in normal individuals (P = 0.036). CONCLUSIONS: Taken together, these results implicate genetic variation at the HGF locus with keratoconus susceptibility.

Aldose reductase gene polymorphisms and diabetic retinopathy susceptibility.

OBJECTIVE: Aldose reductase (ALR) is involved in diabetic microvascular damage via the polyol pathway. A recent meta-analysis found genetic variation in the ALR gene (AKR1B1) to be significantly associated with diabetic retinopathy (DR). We investigated the genetic association of AKR1B1 with DR. RESEARCH DESIGN AND METHODS: The study enrolled 909 individuals with diabetes. Participants were genotyped for an AKR1B1 (CA)n microsatellite and 14 tag single nucleotide polymorphisms, and ophthalmological assessment was performed. RESULTS: A total of 514 individuals were found to have DR. rs9640883 was significantly associated with DR (P = 0.0005). However, AKR1B1 variation was not independently associated with DR development after adjusting for relevant clinical parameters. rs9640883 was associated with duration of diabetes (P = 0.002). CONCLUSION: Many previous reports have failed to account for known risk factors for DR. The commonly reported association of AKR1B1 with DR may be due to an association of the gene with younger age at onset of diabetes.