High-Throughput Genetic Screening of 51 Pediatric Cataract Genes Identifies Causative Mutations in Inherited Pediatric Cataract in South Eastern Australia.

Pediatric cataract is a leading cause of childhood blindness. This study aimed to determine the genetic cause of pediatric cataract in Australian families by screening known disease-associated genes using massively parallel sequencing technology. We sequenced 51 previously reported pediatric cataract genes in 33 affected individuals with a family history (cases with previously known or published mutations were excluded) using the Ion Torrent Personal Genome Machine. Variants were prioritized for validation if they were predicted to alter the protein sequence and were absent or rare with minor allele frequency <1% in public databases. Confirmed mutations were assessed for segregation with the phenotype in all available family members. All identified novel or previously reported cataract-causing mutations were screened in 326 unrelated Australian controls. We detected 11 novel mutations in GJA3, GJA8, CRYAA, CRYBB2, CRYGS, CRYGA, GCNT2, CRYGA, and MIP; and three previously reported cataract-causing mutations in GJA8, CRYAA, and CRYBB2 The most commonly mutated genes were those coding for gap junctions and crystallin proteins. Including previous reports of pediatric cataract-associated mutations in our Australian cohort, known genes account for >60% of familial pediatric cataract in Australia, indicating that still more causative genes remain to be identified.

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.

Elevation of serum asymmetrical and symmetrical dimethylarginine in patients with advanced glaucoma.

PURPOSE: Asymmetric dimethylarginine (ADMA) and symmetric dimethylarginine (SDMA) are the dimethylated isomeric derivatives of the amino acid L-arginine. ADMA is an endogenous inhibitor of nitric oxide synthase (NOS), while SDMA is a competitive inhibitor of cellular uptake of L-arginine, the substrate for NOS. As such, these metabolites are associated with endothelial dysfunction. As the nitric oxide pathway and endothelial dysfunction have been implicated in glaucoma, the aim of this study was to investigate serum ADMA, SDMA, and L-arginine levels in individuals with advanced glaucoma compared with normal controls. In addition, we have investigated genetic variation in the DDAH1 and DDAH2 genes, encoding the enzymes responsible for degradation of ADMA, for association with ADMA level in glaucoma patients and controls. METHODS: Two hundred eleven patients with advanced glaucoma and 295 normal controls were recruited. Liquid chromatography-tandem mass spectrometry was used to measure the serum ADMA, SDMA, and L-arginine levels of participants. Single nucleotide polymorphisms in the DDAH1 and DDAH2 genes reportedly associated with ADMA level were genotyped in all individuals. RESULTS: A significant increase in both serum ADMA and SDMA concentration was detected in advanced glaucoma cases compared with controls (P ≤ 0.0001). No significant change was detected in serum L-arginine concentration. No association of polymorphisms in DDAH1 and DDAH2 with either ADMA level or glaucoma was detected. CONCLUSIONS: The serum levels of two dimethylarginines, ADMA and SDMA, are associated with advanced glaucoma. These data further implicate the nitric-oxide pathway in glaucoma pathogenesis.

Australian and New Zealand Registry of Advanced Glaucoma: methodology and recruitment.

BACKGROUND: Glaucoma is a sight-threatening disease affecting 3% of the population over the age of 50. Glaucoma is treatable, and severe vision loss can usually be prevented if diagnosis is made at an early stage. Genetic factors play a major role in the pathogenesis of the condition, and therefore, genetic testing to identify asymptomatic at-risk individuals is a promising strategy to reduce the prevalence of glaucoma blindness. Furthermore, unravelling genetic risk factors for glaucoma would also allow a better understanding of the pathogenesis of the condition and the development of new treatments. DESIGN: The Australian and New Zealand Registry of Advanced Glaucoma is a prospective study that aims to develop a large cohort of glaucoma cases with severe visual field loss to identify novel genetic risk factors for glaucoma blindness. METHODS: Clinical information and blood are collected from participants after referral by eye practitioners. Samples are collected across Australia and New Zealand using postage kits. PARTICIPANTS: Our registry has recruited just over 2000 participants with advanced glaucoma, as well as secondary and developmental glaucomas. RESULTS: A positive family history of glaucoma is present in more than half of the advanced glaucoma cases and the age at diagnosis is significantly younger for participants with affected relatives, which reinforces the involvement of genetic factors in glaucoma. CONCLUSIONS: With the collection of glaucoma cases recruited so far, our registry aims to identify novel glaucoma genetic risk factors to establish risk profiling of the population and protocols for genetic testing.

Heritability of central corneal thickness in nuclear families.

PURPOSE: Many ocular parameters show strong heritable tendencies. The significance of central corneal thickness (CCT) in the context of glaucoma has been the subject of much debate recently, but its heritability has not been extensively explored. This study was designed to investigate the parent-child heritability of CCT among groups who have CCT considered to be at the extreme ends of the normal range. METHODS: Index cases were recruited through a tertiary referral center if their CCT was greater than 578 microm (thick) or less than 510 microm (thin), representing +/-1 SD from a previously published meta-analysis mean of 544 microm (34 microm SD). Subsequently, CCT was measured in all available family members of the index cases. Family units were then analyzed to establish the degree of heritability of CCT from parent to child. RESULTS: Thirty-three index cases were included in the analysis (10 >1 SD and 23 <1 SD from the meta-analysis CCT mean). The mean CCT of the children of index cases with a CCT more than 1 SD from the mean (n = 15) and less than 1 SD from the mean (n = 40) was 568 microm (32 microm SD) and 521 microm (22 microm SD), respectively (t = 6.14; P < 0.0001). The parent-child heritability estimate for CCT was h(2) = 0.68 (95% CI, 0.64-0.73). CONCLUSIONS: These results indicate that CCT shows strong parent-child heritability, with offspring likely to demonstrate CCT similar to the parental index case.

A novel genetic syndrome characterized by pediatric cataract, dysmorphism, ectodermal features, and developmental delay in an indigenous Australian family.

A novel syndrome initially presenting with cataract and developmental delay within an Indigenous Australian family is described. We present the extended four generation pedigree and describe in detail the phenotypic appearance of five clearly affected male second cousins in this family. The common features of these children include developmental delay, short stature, cortical cataract, facial dysmorphism, clinodactyly, thin hair and an erythematous skin rash. Initial inspection of the pedigree suggested an inherited disorder with possible X-linked inheritance. However, a thorough scan of the X chromosome failed to reveal linkage. This family represents a new syndrome of familial cataract, dysmorphic features, short stature and developmental delay with probable autosomal inheritance and variable expressivity.

Sensitivity of confocal laser tomography versus optical coherence tomography in detecting advanced glaucoma.

PURPOSE: To determine the sensitivity of manufacturer supported normative algorithms in Heidelberg retinal tomography (HRT) and Stratus optical coherence tomography (OCT) in detecting advanced primary open angle glaucoma. METHODS: A total of 157 subjects with advanced primary open angle glaucoma were recruited. The eye with the more severe glaucoma, as judged by mean deviation on Humphrey visual field, was imaged. The total number of optic disc sectors classified as being outside normal limits on Moorfields Regression Analysis (MRA) from the HRT II and HRT 3 software or from the sector and quadrant averages analysis of the Retinal Nerve Fiber Layer OCT scans was compared using the Wilcoxon signed ranks test. RESULTS: At least one segment in each eye was identified as being outside normal limits by the OCT sector Retinal Nerve Fiber Layer analysis (100% sensitivity). Five eyes were classified as being within normal limits on the OCT quadrant average analysis (96.8% sensitivity). Four eyes were found to be either completely within normal limits or borderline on the HRT II MRA (97.5% sensitivity), of which one was subsequently identified as being outside normal limits by the HRT 3 MRA. The total number of segments classified as being outside normal limits was greater on HRT 3 MRA than HRT II MRA (P < 0.001). CONCLUSION: Automated optic nerve imaging devices rarely produce a totally normal result in the presence of advanced primary open angle glaucoma. The Stratus OCT Retinal Nerve Fiber Layer clock hour normative database performs better than other modalities studied. These findings are important in considering the utility of these algorithms for community screening.