Common genetic variants near the Brittle Cornea Syndrome locus ZNF469 influence the blinding disease risk factor central corneal thickness Publication

Copyright: © 2010 Lu et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.Central corneal thickness (CCT), one of the most highly heritable human traits (h2 typically>0.9), is important for the diagnosis of glaucoma and a potential risk factor for glaucoma susceptibility. We conducted genome-wide association studies in five cohorts from Australia and the United Kingdom (total N = 5058). Three cohorts were based on individually genotyped twin collections, with the remaining two cohorts genotyped on pooled samples from singletons with extreme trait values. The pooled sample findings were validated by individual genotyping the pooled samples together with additional samples also within extreme quantiles. We describe methods for efficient combined analysis of the results from these different study designs. We have identified and replicated quantitative trait loci on chromosomes 13 and 16 for association with CCT. The locus on chromosome 13 (nearest gene FOXO1) had an overall meta-analysis p-value for all the individually genotyped samples of 4.6×10−10. The locus on chromosome 16 was associated with CCT with p = 8.95×10−11. The nearest gene to the associated chromosome 16 SNPs was ZNF469, a locus recently implicated in Brittle Cornea Syndrome (BCS), a very rare disorder characterized by abnormal thin corneas. Our findings suggest that in addition to rare variants in ZNF469 underlying CCT variation in BCS patients, more common variants near this gene may contribute to CCT variation in the general population

Ethnic and mouse strain differences in central corneal thickness and association with pigmentation phenotype

The cornea is a transparent structure that permits the refraction of light into the eye. Evidence from a range of studies indicates that central corneal thickness (CCT) is strongly genetically determined. Support for a genetic component comes from data showing significant variation in CCT between different human ethnic groups. Interestingly, these studies also appear to show that skin pigmentation may influence CCT. To validate these observations, we undertook the first analysis of CCT in an oculocutaneous albinism (OCA) and Ugandan cohort, populations with distinct skin pigmentation phenotypes. There was a significant difference in the mean CCT of the OCA, Ugandan and Australian-Caucasian cohorts (Ugandan: 517.3±37 µm; Caucasian: 539.7±32.8 µm, OCA: 563.3±37.2 µm; p<0.001). A meta-analysis of 53 studies investigating the CCT of different ethnic groups was then performed and demonstrated that darker skin pigmentation is associated with a thinner CCT (p<0.001). To further verify these observations, we measured CCT in 13 different inbred mouse strains and found a significant difference between the albino and pigmented strains (p = 0.008). Specific mutations within the melanin synthesis pathway were then investigated in mice for an association with CCT. Significant differences between mutant and wild type strains were seen with the nonagouti (p<0.001), myosin VA (p<0.001), tyrosinase (p = 0.025) and tyrosinase related protein (p = 0.001) genes. These findings provide support for our hypothesis that pigmentation is associated with CCT and identifies pigment-related genes as candidates for developmental determination of a non-pigmented structure.David P. Dimasi, Alex W. Hewitt, Kenneth Kagame, Sam Ruvama, Ludovica Tindyebwa, Bastien Llamas, Kirsty A. Kirk, Paul Mitchell, Kathryn P. Burdon and Jamie E. Crai

The babel of drugs: On the consequences of evidential pluralism in pharmaceutical regulation and regulatory data journeys

This is the final version. Available on open access from Springer via the DOI in this recordThroughout the last century, pharmaceutical regulators all over the world have used various methods to test medical treatments. From 1962 until 2016, the Randomized Clinical Trial (RCT) was the reference test for most regulatory agencies. Today, the standards are about to change, and in this chapter we draw on the idea of the data journey to illuminate the trade-offs involved. The 21st Century Cures Act (21CCA) allows for the use of Electronic Health Records (EHRs) for the assessment of different treatment indications for already approved drugs. This might arguably shorten the testing period, bringing treatments to patients faster. Yet, EHR are not generated for testing purposes and no amount of standardization and curation can fully make up for their potential flaws as evidence of safety and efficacy. The more noise in the data, the more mistakes regulators are likely to make in granting market access to new drugs. In this paper we will discuss the different dimensions of this journey: the different sources and levels of curation involved, the speed at which they can travel, and the level of risk of regulatory error involved as compared with the RCT standard. We are going to defend that what counts as evidence, at the end of the journey, depends on the risk definition and threshold regulators work with.European Research Council (ERC)Engineering and Physical Sciences Research Council (EPSRC

The genetics of central corneal thickness

Evidence in the recent literature has highlighted the importance of central corneal thickness (CCT) in relation to several ocular and non-ocular conditions. Most notably, thinner CCT has been identified as a risk factor for open-angle glaucoma. Despite having an extensive knowledge of the structure and function of the cornea, little is known about the pathways that determine CCT. There are data to suggest however that CCT has a strong genetic component. Heritability studies conducted in twins and family pedigrees indicate that CCT is one of the most highly heritable human traits, whereas data from a diverse range of ethnic groups show clear ethnic-related differences in CCT. Extreme CCT measurements have also been associated with rare genetic diseases. Although there is strong evidence supporting a genetic component to normal CCT variation, to date, no genes have been identified. This review investigates the current literature surrounding this topic and explores the significance of understanding the genetics of CCT and how this might benefit the field of open-angle glaucoma treatment and research

A Glaucoma case-control study of the WDR36 gene D658G sequence variant

Purpose: To investigate in Australian patients with glaucoma and normal controls the prevalence and associated phenotype of the WDR36 D658G mutation, which has previously been suggested to be a disease-causing mutation in pedigrees with primary open-angle glaucoma (POAG). Design: Case-control study. Methods: Two hundred forty-nine individuals with POAG and 217 age-matched control subjects were recruited through the Glaucoma Inheritance Study in Tasmania, Australia. Genomic DNA was amplified by polymerase chain reaction by intronic primers. The presence of the D658G variant was detected by BglI restriction enzyme digestion. Results: The D658G variant was identified in four POAG cases (1.6%) and four control subjects (1.8%) (χ2 = 0.04, P = .84). No control subject with the variant had a family history of glaucoma. Conclusions: The WDR36 D658G is a neutral variant in the Australian population. Further populations should be carefully assessed for this variant before concluding that WDR36 is a glaucoma gene.</p

Abnormal iris processes may be a marker of glaucoma gene carrier status in some cases of primary infantile glaucoma

Purpose: To report the presence of dense and abnormal iris processes in the unaffected parents and sibling of a non consanguineous family where 3 children out of 4 suffer from primary infantile glaucoma (PIG). Methods: A descriptive case report. All family members were clinically characterized. Candidate gene screening and chromosome analysis were also performed. Results: The 3 children with PIG displayed a spectrum of anterior chamber angle anomalies with the absence of posterior embryotoxon and iridotrabeculodysgenesis abnormalities. Unaffected family members had dense and abnormal iris processes but no features of glaucoma. Candidate gene screening and chromosome analysis were normal. Conclusion: Iris processes indicate angle maldevelopment and may signify carrier status of an autosomal recessive glaucoma gene. Identification of iris processes in relatives of PIG children is a useful clinical sign that may be of benefit for genetic counseling and risk stratification purposes

Ocular Expression and Distribution of Products of the POAG-Associated Chromosome 9p21 Gene Region

It has recently been shown that there are highly significant associations for common single nucleotide polymorphisms (SNPs) near the CDKN2B-AS1 gene region at the 9p21 locus with primary open angle glaucoma (POAG), a leading cause of irreversible blindness. This gene region houses the CDKN2B/p15(INK4B) , CDKN2A/p16(INK4A) and p14ARF (rat equivalent, p19(ARF) ) tumour suppressor genes and is adjacent to the S-methyl-5'-thioadenosine phosphorylase (MTAP) gene. In order to understand the ocular function of these genes and, therefore, how they may be involved in the pathogenesis of POAG, we studied the distribution patterns of each of their products within human and rat ocular tissues. MTAP mRNA was detected in the rat retina and optic nerve and its protein product was localised to the corneal epithelium, trabecular meshwork and retinal glial cells in both human and rat eyes. There was a very low level of p16(INK4A) mRNA present within the rat retina and slightly more in the optic nerve, although no protein product could be detected in either rat or human eyes with any of the antibodies tested. P19(ARF) mRNA was likewise only present at very low levels in rat retina and slightly higher levels in the optic nerve. However, no unambiguous evidence was found to indicate expression of specific P19(ARF)/p14(ARF) proteins in either rat or human eyes, respectively. In contrast, p15(INK4B) mRNA was detected in much higher amounts in both retina and optic nerve compared with the other genes under analysis. Moreover, p15(INK4B) protein was clearly localised to the retinal inner nuclear and ganglion cell layers and the corneal epithelium and trabecular meshwork in rat and human eyes. The presented data provide the basis for future studies that can explore the roles that these gene products may play in the pathogenesis of glaucoma and other models of optic nerve damage

A myocilin Gln368STOP homozygote does not exhibit a more severe glaucoma phenotype than heterozygous cases

Purpose: To describe the phenotype of an individual homozygous for the common Gln368STOP myocilin mutation and to discuss the other family members. Design: Cascade screening was performed for Australian families that had been identified as having the myocilin Gln368STOP mutation. Methods: Recruited subjects underwent comprehensive clinical examination and mutation analysis for the Gln368STOP myocilin mutation by direct sequencing. Results: One 49-year-old woman was found to be homozygous for the mutation. Her maximal recorded intraocular pressure was 17 mm Hg. Bilateral optic disk examination revealed small, healthy optic discs. Automated perimetry testing was normal. Conclusions: Neither the individual homozygous for the Gln368STOP myocilin mutation nor her younger heterozygous siblings displayed any signs suggestive of glaucoma. One of the two heterozygous parents did manifest glaucoma. Although there is the possibility of the homozygous individual developing glaucoma in the future, she does not manifest a phenotype that is more severe than usual.</p

Lack of association of p53 polymorphisms and haplotypes in high and normal tension open angle glaucoma

Background: The final common pathway for open angle glaucoma (OAG) is retinal ganglion cell apoptosis. Polymorphisms in p53, a major regulator of apoptosis, affect the efficiency of cell death induction. Association studies of p53 haplotypes and OAG have had conflicting results. Objective: To examine the association between p53 haplotypes and OAG in a larger white population than in previous reports, and extend the analysis to normal tension glaucoma. Methods: 345 unrelated people with OAG were recruited (283 subjects with high tension glaucoma and 62 with normal tension glaucoma) and compared with 178 age matched controls. Genomic DNA was analysed for the p53 codon 72 Arg/Pro polymorphism as well as for the presence or absence of a 16 bp intron 3 insertion. Results: In this white cohort no association was found between glaucoma (high or normal tension) and either sequence variant or haplotype. Conclusions: The p53 codon 72 Arg/Pro polymorphism is not associated with age of onset or severity of glaucoma.</p