Mercury ions impact the kinetic and thermal stabilities of human lens γ-crystallins via direct metal-protein interactions.

Loss of metal homeostasis may be involved in several age-related diseases, such as cataracts. Cataracts are caused by the aggregation of lens proteins into light-scattering high molecular weight complexes that impair vision. Environmental exposure to heavy metals, such as mercury, is a risk factor for cataract development. Indeed, mercury ions induce the non-amyloid aggregation of human γC- and γS crystallins, while human γD-crystallin is not sensitive to this metal. Using Differential Scanning Calorimetry (DSC), we evaluate the impact of mercury ions on the kinetic stability of the three most abundant human γ-crystallins. The metal/crystallin interactions were characterized using Isothermal Titration Calorimetry (ITC). Human γD-crystallins exhibited kinetic stabilization due to the presence of mercury ions, despite its thermal stability being decreased. In contrast, human γC- and γS-crystallins are both, thermally and kinetically destabilized by this metal, consistent with their sensitivity to mercury-induced aggregation. The interaction of human γ-crystallins with mercury ions is highly exothermic and complex, since the protein interacts with the metal at more than three sites. The isolated domains of human γ-D and its variant with the H22Q mutation were also studied, revealing the importance of these regions in the mercury-induced stabilization by a direct metal-protein interaction.

Expression of oxysterols in human lenses: Implications of the sterol pathway in age-related cataracts.

Lanosterol, an oxysterol molecule, has been proposed to help maintain lens transparency by inhibiting the formation of protein aggregates. This sterol is produced by the enzyme lanosterol synthase and is part of a metabolic pathway that forms cholesterol as a final step. Abnormalities in lanosterol synthase are responsible for congenital cataracts. The αA-crystallin protein, which acts as a molecular chaperone to lanosterol synthase, has been reported to have anti-protein aggregation, anti-inflammatory and anti-apoptotic properties. In this work, we evaluated the correlation of lanosterol synthase and αA-crystallin in human cataractous lenses with the grade of opacity, as well as the expression of lanosterol synthase, farnesyl DPP, geranyl synthase and squalene epoxidase genes. Lanosterol synthase and αA-crystallin were overexpressed in cataractous lenses as well as farnesyl-DP synthase, squalene epoxidase, lanosterol synthase and geranyl synthase genes in cataratous lenses in comparison with normal lenses. Our data confirm that lanosterol synthase and the sterol pathway are upregulated in cataractous lenses. This argues for a functional role of the oxysterol pathway and its products as an important mediator in the pathogenesis of human cataracts.

Expression of miR-210-3p in the aqueous humor of patients with age-related cataracts and its effect on human lens epithelial cell injury induced by hydrogen peroxide.

PURPOSE: The regulatory effect of microRNA on diseases has been confirmed. This study aimed to evaluate the expression of microRNA-210-3p in age-related cataracts and assess the effect of abnormal miR-210-3p expressions on H2O2-induced SAR01/04 cells. METHODS: Reverse-transcription quantitative polymerase chain reaction method was performed to assess the levels of miR-210-3p in aqueous humor samples. Receiver operating characteristic analysis was employed to assess the discrimination ability of miR-210-3p between patients with age-related cataracts and healthy people, and Pearson correlation analysis was used to identify the correlation between miR-210-3p and oxidative stress indices such as superoxide dismutase, glutathione peroxidase, malonaldehyde. Cell counting kit-8 assay and Transwell assay were used to estimate the biological function of H2O2-induced age-related cataract cell model. The levels of oxidative stress indices such as superoxide dismutase, glutathione peroxidase, and malonaldehyde were measured to evaluate the degree of oxidative stress damage in the age-related cataract cell model. The relationship between miR-210-3p and its target gene was verified by luciferase reporter gene analysis. RESULTS: The miR-210-3p expression was elevated in the aqueous humor of patients with age-related cataracts. A high miR-210-3p expression showed a high diagnostic value for age-related cataracts and was significantly associated with the level of oxidative stress markers in patients with age-related cataracts. The inhibition of miR-210-3p can reverse oxidative stress stimulation and adverse effects on H2O2-induced cell function. CONCLUSIONS: The results suggested that miR-210-3p could promote cell viability, cell migration, and oxidative stress by targeting autophagy-related gene 7 in in vitro age-related cataract cell model.

Brazilian family with hyperferritinemia-cataract syndrome: case report.

Hereditary hyperferritinemia-cataract syndrome is a rare autosomal dominant disease caused by a genetic mutation in the iron responsive element in the 5' untranslated region of the ferritin light chain gene. Hereditary hyperferritinemia-cataract syndrome is characterized by elevated serum ferritin levels and bilateral cataract development early in life and may be misdiagnosed as hemochromatosis. This case report describes a Brazilian family with a clinical diagnosis of hereditary hyperferritinemia-cataract syndrome, which was submitted to ferritin light chain gene sequencing. The genetic mutation c.-164C>G was identified in the 5' untranslated region. In conclusion, genetic testing can be used for accurate diagnosis of hereditary hyperferritinemia-cataract syndrome to avoid misdiagnosis of hemochromatosis, other diseases associated with iron overload or ophthalmic diseases.

Novel Mutation in CRYBB3 Causing Pediatric Cataract and Microphthalmia.

Up to 25% of pediatric cataract cases are inherited, with half of the known mutant genes belonging to the crystallin family. Within these, crystallin beta B3 (CRYBB3) has the smallest number of reported variants. Clinical ophthalmological and genetic-dysmorphological evaluation were performed in three autosomal dominant family members with pediatric cataract and microphthalmia, as well as one unaffected family member. Peripheral blood was collected from all participating family members and next-generation sequencing was performed. Bioinformatics analysis revealed a novel missense variant c.467G>A/p.Gly156Glu in CRYBB3 in all family members with childhood cataract. This variant is classified as likely pathogenic by ACMG, and no previous descriptions of it were found in ClinVar, HGMD or Cat-Map. The only other mutation previously described in the fifth exon of CRYBB3 is a missense variant that causes a change in amino acid from the same 156th amino acid to arginine and has been associated with pediatric cataract and microphthalmia. To the best of our knowledge, this is the first time the c.467G>A/p.Gly156Glu variant is reported and the second time a mutation in CRYBB3 has been associated with microphthalmia.

Pseudoexfoliation and Cataract Syndrome Associated with Genetic and Epidemiological Factors in a Mayan Cohort of Guatemala.

The Mayan population of Guatemala is understudied within eye and vision research. Studying an observational homogenous, geographically isolated population of individuals seeking eye care may identify unique clinical, demographic, environmental and genetic risk factors for blinding eye disease that can inform targeted and effective screening strategies to achieve better and improved health care distribution. This study served to: (a) identify the ocular health needs within this population; and (b) identify any possible modifiable risk factors contributing to disease pathophysiology within this population. We conducted a cross-sectional study with 126 participants. Each participant completed a comprehensive eye examination, provided a blood sample for genetic analysis, and received a structured core baseline interview for a standardized epidemiological questionnaire at the Salama Lions Club Eye Hospital in Salama, Guatemala. Interpreters were available for translation to the patients' native dialect, to assist participants during their visit. We performed a genome-wide association study for ocular disease association on the blood samples using Illumina's HumanOmni2.5-8 chip to examine single nucleotide polymorphism SNPs in this population. After implementing quality control measures, we performed adjusted logistic regression analysis to determine which genetic and epidemiological factors were associated with eye disease. We found that the most prevalent eye conditions were cataracts (54.8%) followed by pseudoexfoliation syndrome (PXF) (24.6%). The population with both conditions was 22.2%. In our epidemiological analysis, we found that eye disease was significantly associated with advanced age. Cataracts were significantly more common among those living in the 10 districts with the least resources. Furthermore, having cataracts was associated with a greater likelihood of PXF after adjusting for both age and sex. In our genetic analysis, the SNP most nominally significantly associated with PXF lay within the gene KSR2 (p < 1 × 10-5). Several SNPs were associated with cataracts at genome-wide significance after adjusting for covariates (p < 5 × 10-8). About seventy five percent of the 33 cataract-associated SNPs lie within 13 genes, with the majority of genes having only one significant SNP (5 × 10-8). Using bioinformatic tools including PhenGenI, the Ensembl genome browser and literature review, these SNPs and genes have not previously been associated with PXF or cataracts, separately or in combination. This study can aid in understanding the prevalence of eye conditions in this population to better help inform public health planning and the delivery of quality, accessible, and relevant health and preventative care within Salama, Guatemala.

Spondyloepimetaphyseal dysplasia with elevated plasma lysosomal enzymes caused by homozygous variant in MBTPS1.

Variants in MBTPS1 (membrane-bound transcription factor peptidase, site 1) encoding the protein convertase site-1 protease (S1P) were recently reported in a single individual with skeletal dysplasia and elevated plasma lysosomal enzymes. Here, we report the second individual with this newly described autosomal recessive spondyloepiphyseal dysplasia (OMIM #618392), presenting severe growth retardation, cataract and dysmorphic features, mainly retromicrognathia. Epilepsy and craniosynostosis were novel findings in our proband. She was found to be homozygous for a novel nonsense variant p.Trp983Ter in MBTPS1. In addition, she had normal levels of lysosomal enzyme activity in leukocytes but elevated levels in plasma. Our description confirms the existence of this new skeletal dysplasia and expands the phenotype and genotype of the disease.

WAGRO syndrome: a rare genetic condition associated with aniridia and additional ophthalmologic abnormalities / Síndrome WAGRO: uma condição genética rara associada à aniridia e a anormalidades oftalmológicas adicionais

ABSTRACT Aniridia is a congenital eye disorder with a variable degree of hypoplasia or absence of iris tissue. It is caused by loss of function of the PAX6 gene and may be an isolated ocular abnormality or part of a syndrome. WAGRO refers to a rare genetic condition leading to Wilms tumor, aniridia, genitourinary anomalies, mental retardation, and obesity and is caused by a deletion of the short arm of chromosome 11 (11p), where the PAX6 gene is located. Here, we report on an 8-year-old boy with aniridia, polar cataract, and lens subluxation along with neuropsychomotor and speech delays. Karyotype evaluation showed an interstitial deletion including region 11p13-p14, confirming the diagnosis of WAGRO syndrome. In cases of aniridia, a diagnosis of WAGRO syndrome should be considered.

RESUMO A aniridia é uma doença ocular congênita com grau variável de hipoplasia ou ausência do tecido da íris. É causada pela perda de função do gene PAX6 e pode ser uma anormalidade ocular isolada ou parte de uma síndrome. WAGRO refere-se a uma condição genética rara que leva ao tumor de Wilms, aniridia, anomalias geniturinárias, déficit intelectual e obesidade e é causada por uma deleção do braço curto do cromossomo 11 (11p), onde o gene PAX6 está localizado. Aqui, nós relatamos um menino de 8 anos de idade com aniridia, catarata polar e subluxação do cristalino, além de retardo neuropsicomotor e de fala. A avaliação cariotípica revelou uma deleção intersticial envolvendo a região 11p13-p14, confirmando o diagnóstico da síndrome WAGRO. Em casos de aniridia, um diagnóstico de síndrome de WAGRO deve ser considerado.

WAGRO syndrome: a rare genetic condition associated with aniridia and additional ophthalmologic abnormalities.

Aniridia is a congenital eye disorder with a variable degree of hypoplasia or absence of iris tissue. It is caused by loss of function of the PAX6 gene and may be an isolated ocular abnormality or part of a syndrome. WAGRO refers to a rare genetic condition leading to Wilms tumor, aniridia, genitourinary anomalies, mental retardation, and obesity and is caused by a deletion of the short arm of chromosome 11 (11p), where the PAX6 gene is located. Here, we report on an 8-year-old boy with aniridia, polar cataract, and lens subluxation along with neuropsychomotor and speech delays. Karyotype evaluation showed an interstitial deletion including region 11p13-p14, confirming the diagnosis of WAGRO syndrome. In cases of aniridia, a diagnosis of WAGRO syndrome should be considered.

A Rat Eye Lens Model of Cataract Formation.

This chapter describes the use of lenses obtained from rats as a model of cataractogenesis. At the molecular level, this is visualized as reduced activity of oxidative reductive enzymes such as aldose reductase and increased proteolysis of lens structural proteins including vimentin. In this chapter, protocols for assessment of these two pathways are presented. Specifically, this analysis shows a comparison of aldose reductase activity and vimentin cleavage in male and female rat lenses. This is because female rats are more susceptible to cataract formation compared to males.

Next generation sequencing-based molecular diagnosis in familial congenital cataract expands the mutational spectrum in known congenital cataract genes.

Congenital cataract (CC) is a significant cause of childhood blindness worldwide. CC is a genetically heterogeneous disease because mutations in over 40 genes have been demonstrated to cause the disorder and up to 40% of cases arise from single-gene mutations. Hence, next generation sequencing (NGS) of deoxyribonucleic acid is a suitable approach for CC molecular diagnosis. In this study, we used commercially available inherited disease NGS panels including 50 CC genes for the genetic diagnosis of 11 probands with hereditary CC. Causal variants were recognized in six families. A novel CRYGC variant, p.(Phe6Ser), was identified in two apparently unrelated families. Two additional novel variants in the crystallin genes CRYBB2 (p.[Gly149Asp]) and CRYGA (p.[Arg48Cys]) were also identified. One family carried the novel p.[Gly8_Leu11del] variant in GJA8, while another family exhibited the previously reported c.2826-9G>A pathogenic change in EPHA2. Our results illustrate the utility of NGS for diagnosing CC in our population, and our results contribute to expand the mutational spectrum with four novel pathogenic variants in known CC genes.

HPV16-E6 Oncoprotein Activates TGF-ß and Wnt/ß-Catenin Pathways in the Epithelium-Mesenchymal Transition of Cataracts in a Transgenic Mouse Model.

OBJECTIVE: This work aimed to determine if cataractous changes associated with EMT occurring in the K14E6 mice lenses are associated with TGF-ß and Wnt/ß-catenin signaling activation. MATERIALS AND METHODS: Cataracts of K14E6 mice were analysed histologically; and components of TGF-ß and Wnt/ß-catenin signaling were evaluated by Western blot, RT-qPCR, in situ RT-PCR, IHC, or IF technics. Metalloproteinases involved in EMT were also assayed using zymography. The endogenous stabilisation of Smad7 protein was also assessed using an HDAC inhibitor. RESULTS: The K14E6 mice, which displayed binocular cataracts in 100% of the animals, exhibited loss of tissue organisation, cortical liquefaction, and an increase in the number of hyperproliferative-nucleated cells with mesenchymal-like characteristics in the lenses. Changes in lenses' cell morphology were due to actin filaments reorganisation, activation of TGF-ß and Wnt/ß-catenin pathways, and the accumulation of MTA1 protein. Finally, the stabilisation of Smad7 protein diminishes cell proliferation, as well as MTA1 protein levels. CONCLUSION: The HPV16-E6 oncoprotein induces EMT in transgenic mice cataracts. The molecular mechanism may involve TGF-ß and Wnt/ß-catenin pathways, suggesting that the K14E6 transgenic mouse could be a useful model for the study or treatment of EMT-induced cataracts.

Neuromyopathy with congenital cataracts and glaucoma: a distinct syndrome caused by POLG variants.

We identified three non-related patients manifesting a childhood-onset progressive neuromyopathy with congenital cataracts, delayed walking, distal weakness and wasting, glaucoma and swallowing difficulties. Electrophysiology and nerve biopsies showed a mixed axonal and demyelinating neuropathy, while muscle biopsy disclosed both neurogenic and myopathic changes with ragged red fibers, and muscle MRI showed consistent features across patients, with a peculiar concentric disto-proximal gradient of fatty replacement. We used targeted next generation sequencing and candidate gene approach to study these families. Compound biallelic heterozygous variants, p.[(Pro648Arg)]; [(His932Tyr)] and p.[(Thr251Ile),(Pro587Leu)]; [(Arg943Cys)], were found in the three patients causing this homogeneous phenotype. Our report on a subset of unrelated patients, that showed a distinct autosomal recessive childhood-onset neuromyopathy with congenital cataracts and glaucoma, expands the clinical spectrum of POLG-related disorders. It also confirms the association between cataracts and neuropathy with variants in POLG. Early onset cataract is otherwise rare in POLG-related disorders and so far reported only in a few patients with the clinical pattern of distal myopathy or neuromyopathy.

Nance-Horan syndrome in females due to a balanced X;1 translocation that disrupts the NHS gene: Familial case report and review of the literature.

The Nance-Horan syndrome is an X-linked disorder characterized by congenital cataract, facial features, microcornea, microphthalmia, and dental anomalies; most of the cases are due to NHS gene mutations on Xp22.13. Heterozygous carrier females generally present less severe features, and up to 30% of the affected males have intellectual disability. We describe two patients, mother and daughter, manifesting Nance-Horan syndrome. The cytogenetic and molecular analyses demonstrated a 46,X,t(X;1)(p22.13;q22) karyotype in each of them. No copy-number genomic imbalances were detected by high-density microarray analysis. The mother had a preferential inactivation of the normal X chromosome; expression analysis did not detect any mRNA isoform of NHS. This is the first report of Nance-Horan syndrome due to a skewed X chromosome inactivation resulting from a balanced translocation t(X;1) that disrupts the NHS gene expression, with important implications for clinical presentation and genetic counseling.

Ferritin light chain gene mutations in two Brazilian families with hereditary hyperferritinemia-cataract syndrome / Mutações no gene da cadeia leve da ferritina em duas famílias brasileiras com síndrome hereditária hiperferritinemia-catarata

ABSTRACT Hereditary hyperferritinemia-cataract syndrome is an autosomal dominant genetic disorder associated with mutations in the 5'UTR region of the ferritin light chain gene. These mutations cause the ferritin levels to increase even in the absence of iron overload. Patients also develop bilateral cataract early due to accumulation of ferritin in the lens, and many are misdiagnosed as having hemochromatosis and thus not properly treated. The first cases were described in 1995 and several mutations have already been identified. However, this syndrome is still a poorly understood. We report two cases of unrelated Brazilian families with clinical suspicion of the syndrome, which were treated in our department. For the definitive diagnosis, the affected patients, their parents and siblings were submitted to Sanger sequencing of the 5'UTR region for detection of the ferritin light gene mutation. Single nucleotide polymorphism-like mutations were found in the affected patients, previously described. The test assisted in making the accurate diagnosis of the disease, and its description is important so that the test can be incorporated into clinical practice.

RESUMO A síndrome hereditária hiperferritinemia-catarata é uma doença genética autossômica dominante associada a mutações na região 5'UTR do gene da cadeia leve da ferritina. Estas mutações elevam os níveis de ferritina, mesmo na ausência de sobrecarga de ferro. Os pacientes também desenvolvem catarata bilateral precocemente, devido ao acúmulo de ferritina no cristalino, e muitos são erroneamente diagnosticados como portadores de hemocromatose, sendo tratados de maneira inadequada. Os primeiros casos foram descritos em 1995, e diversas mutações já foram identificadas. Entretanto, essa síndrome ainda é pouco conhecida. Relatamos dois casos de famílias brasileiras, não relacionadas, com suspeita clínica da síndrome, que foram atendidas em nosso serviço. Para o diagnóstico definitivo, os pacientes afetados, seus pais e irmãos foram submetidos à pesquisa de mutação do gene ferritina, por sequenciamento de Sanger da região 5'UTR. Foram encontradas mutações do tipo polimorfismo de nucleotídeo único nos pacientes afetados, já descritas anteriormente. O teste auxiliou no diagnóstico preciso da doença e é importante ser divulgado, para ser incorporado na prática clínica.

Ferritin light chain gene mutations in two Brazilian families with hereditary hyperferritinemia-cataract syndrome.

Hereditary hyperferritinemia-cataract syndrome is an autosomal dominant genetic disorder associated with mutations in the 5'UTR region of the ferritin light chain gene. These mutations cause the ferritin levels to increase even in the absence of iron overload. Patients also develop bilateral cataract early due to accumulation of ferritin in the lens, and many are misdiagnosed as having hemochromatosis and thus not properly treated. The first cases were described in 1995 and several mutations have already been identified. However, this syndrome is still a poorly understood. We report two cases of unrelated Brazilian families with clinical suspicion of the syndrome, which were treated in our department. For the definitive diagnosis, the affected patients, their parents and siblings were submitted to Sanger sequencing of the 5'UTR region for detection of the ferritin light gene mutation. Single nucleotide polymorphism-like mutations were found in the affected patients, previously described. The test assisted in making the accurate diagnosis of the disease, and its description is important so that the test can be incorporated into clinical practice.

Analysis of the prevalence of polymorphisms in the glutathione S transferase gene (GST) in cataract patients from Goiânia.

The aim of this study was to determine the prevalence of polymorphisms in the glutathione S-transferase genes GSTM1 and GSTT1 in patients with lens opacity (cataract). Peripheral blood samples were obtained from male and female patients (N = 23) with cataract. The GSTM1 and GSTT1 polymorphic regions were amplified by polymerase chain reaction, and the amplification products were electrophoresed on a 2% agarose gel. The obtained bands were by staining with ethidium bromide. The results were compared by a chi-square test using the BioEstat software (v.5.0). The frequencies of the GSTM1- and GSTT1-null genotypes were higher than those of the GSTM1- and GSTT1-present genotypes. The frequency of GSTT1-null genotypes was approximately 1.7 times higher than that of GSTM1, which was a statistically significant difference (P = 0.0019). Although a consensus remains to be reached on the correlation between genetic polymorphisms in GSTs and cataract susceptibility, the observations from most scientific studies are similar to those reported in this study. Thus, we conclude that the absence of these genes, particularly GSTT1, is correlated with the development of lens opacity.

Cytogenetic evaluation of cataract patients occupationally exposed to ionizing radiation in northeast China.

Long-term radiation exposure is hazardous to health; late-onset effects of exposure to ionizing radiation (IR) pose risks to the lens, and are associated with other non-cancerous diseases. Individuals occupationally exposed to low-dose IR are prone to developing eye cataracts. Cytogenetic evaluations suggest that IR is associated with chromosomal aberrations in occupationally exposed individuals. However, data regarding the association between chromosomal aberrations in cataract patients and occupational exposure to IR is scarce. Therefore, we aimed to report the characteristics of chromosomal aberrations in cataract patients from a Chinese population, occupationally exposed to IR. We found that the average age and frequency of numerical chromosomal aberrations were significantly lower in the exposed patients as compared with that in the non-exposed patients. In addition, the frequencies of dicentric and acentric chromosomes were significantly higher in the exposed patients as compared with those in the non-exposed patients. Therefore, chronic occupational exposure to IR affects cataract development in the Chinese population. The age of cataract patients exposed to IR was significantly lower than the age of cataract onset in normal individuals. Based on this study, we suggest that there is an urgent need for improved radiation safety and eye protection in individuals exposed to IR in the work place.