PRIMARY OPEN-ANGLE GLAUCOMA DUE TO MUTATIONS IN THE MYOC GENE.

AIM: Mutations in the myocilin gene (MYOC) cause trabecular dysfunction and thus are involved in the pathogenesis of primary open-angle glaucoma (POAG). The aim of this study was to characterize and describe the clinical findings in two Czech families with POAG due to pathogenic variants in the MYOC gene. MATERIAL AND METHODS: Members of the two families affected by POAG underwent complete ophthalmological examination. In the proband from the first family, a direct sequencing of the three most frequent mutations in the MYOC gene was performed, and in the proband from the second family, an exome sequencing was performed. Other family members underwent targeted tests using direct sequencing. RESULTS: In total, 10 individuals diagnosed with POAG aged 20-70 years (mean 32.2 years, SD ±10,9 years) were examined. Eight of them showed advanced glaucomatous neuropathy with severe changes in the retinal nerve fiber layer. Clinical signs of POAG were present in six individuals in the third decade of life already; another four developed POAG during the fourth decade of life. Eight out of 10 patients had to undergo filtration surgery. Surgery was performed within 1 to 7 years of diagnosis, but mostly was performed within 2 years of glaucoma diagnosis. In the first family, MYOC variant c.1099G>A p.(Gly367Arg) was shown in the affected family members; in the second family MYOC variant c.1440C>A p.(Asn480Lys), both in heterozygous state. The changes were assessed as pathogenic. CONCLUSION: Our study is the first to describe mutations in the MYOC gene causing POAG in Czech patients. Genetic testing may be recommended for this diagnosis, especially in individuals with early presentation and a positive family history. Carriers of pathogenic variants of the MYOC gene have a lifetime risk of developing POAG of more than 50% and the course of their disease is often more aggressive, requiring surgical intervention to permanently control the intraocular pressure.

Phenotype Variability in Czech Patients Carrying PAX6 Disease-Causing Variants.

The aim of this study was to report PAX6 disease-causing variants in six Czech families, to describe the associated phenotypes, and to perform functional assessment of the splice site variants. Detailed ophthalmic examination was performed. The PAX6 coding region was directly sequenced in three probands. Two probands were analysed by exome sequencing and one by genome sequencing. The effect of two variants on pre-mRNA splicing was evaluated using an exon trapping assay. Six different heterozygous PAX6 variants were identified, with c.111_120del and c.1183+1G˃T being novel. Both c.1183+1G˃T and c.1032+1G>A were proved to cause aberrant splicing with exon skipping and subsequent frameshift. The phenotypic features were variable between and within families. One individual, aged 31 years, presented with mild unilateral ptosis accompanied by aniridia in the right eye, partial aniridia in the left eye, and bilateral congenital cataracts, without marked foveal hypoplasia. Bilateral microcornea, partial aniridia, congenital cataracts, and a large posterior segment coloboma were found in another proband, aged 32 years. One child, aged 8 years, had bilateral high myopia, optic nerve colobomas, anterior polar cataracts, but no iris defects. Another individual, aged 46 years, had bilateral congenital ptosis, iris hypoplasia, keratopathy with marked fibrovascular pannus, anterior polar cataract, and foveal hypoplasia combined with impaired glucose tolerance. However, his daughter, aged 11 years, showed classical features of aniridia. Our study extends the genetic spectrum of PAX6 disease-causing variants and confirms that the associated phenotypic features may be very broad and different to the 'classical' aniridia.

Molecular genetic cause of achromatopsia in two patients of Czech origin.

INTRODUCTION: Achromatopsia is an autosomal recessive retinal disorder with an estimated prevalence ranging from 1 in 30.000 to 50.000. The disease is caused by mutations in six different genes. The aim of the study was to perform molecular genetic analysis in 11 unrelated probands with a clinical diagnosis of achromatopsia and to describe clinical findings in those that were found to carry biallelic pathogenic mutations. METHODS: All probands and their parents underwent ophthalmic examination. Mutation detection was performed using Sanger sequencing of CNGB3 exons 6, 7, 9-13, which have been found to harbour most disease-causing mutations in patients with achromatopsia of European origin. RESULTS: Three known pathogenic variants in CNGB3 were identified in 2 probands. Proband 1 was a compound heterozygote for the c.819_826del; p.(Arg274Valfs*13) and c.1006G>T; p.(Glu336*). Proband 2 carried the c.1148del; p.(Thr383Ilefs*13) in a homozygous state. The best corrected visual acuity in proband 1 (aged 19 years) was 0.1 in both eyes, in proband 2 (aged 8 years) 0.05 in the right eye and 0.1 in the left eye. Both individuals had nystagmus, photophobia, and absence of colour discrimination. Fundus examination appeared normal however spectral-domain optical coherence tomography revealed subtle bilaterally symmetrical structural changes in the fovea. CONCLUSION: Molecular genetic analysis of Czech patients with achromatopsia was performed for the first time. Identification of disease-causing mutations in achromatopsia is important for establishing an early diagnosis, participation in clinical trials assessing gene therapies and may be also used for preimplantation genetic diagnosis.

[Gene Therapy for Inherited RETINAL AND OPTIC NERVE Disorders: Current Knowledge]. / Genová terapie dedicných onemocnení SÍTNICE A ZRAKOVÉHO NERVU: soucasný stav poznání.

The aim of this review is to provide a comprehensive summary of current gene therapy clinical trials for monogenic and optic nerve disorders.The number of genes for which gene-based therapies are being developed is growing. At the time of writing this review gene-based clinical trials have been registered for Leber congenital amaurosis 2 (LCA2), retinitis pigmentosa 38, Usher syndrome 1B, Stargardt disease, choroideremia, achromatopsia, Leber hereditary optic neuropathy (LHON) and X-linked retinoschisis. Apart from RPE65 gene therapy for LCA2 and MT-ND4 for LHON which has reached phase III, all other trials are in investigation phase I and II, i.e. testing the efficacy and safety.Because of the relatively easy accessibility of the retina and its ease of visualization which allows monitoring of efficacy, gene-based therapies for inherited retinal disorders represent a very promising treatment option. With the development of novel therapeutic approaches, the importance of establishing not only clinical but also molecular genetic diagnosis is obvious.Key words: gene therapy, monogenic retinal diseases, optic nerve atrophy, mitochondrial disease.

[Clinical Tests Testing New Therapies for Stargardt Disease]. / Klinické zkousky testující nové terapie pro Stargardtovu chorobu.

PURPOSE: To provide information on currently ongoing clinical trials for Stargardt disease. METHODS: We have searched the clinical trial register (www.clinicaltrials.gov) for the keyword "Stargardt" and list active ongoing studies. RESULTS: There are currently eight registered clinical trials enrolling patients with Stargardt disease; all in phase I or II aiming at four mechanisms of action: inhibition of the production of vitamin A toxic dimers, gene therapy restoring wild type transcription of the ABCA4 gene, neuroprotection preventing retinal cells from oxidative damage, and replacement of the damaged retinal pigment epithelium using stem cell therapy. The basic prerequisite for enrolment in the vast majority of clinical trials is confirmation of the clinical diagnosis by mutational analysis. CONCLUSION: The wide variety of therapies that are registered as clinical trials for Stargardt disease significantly raises the possibility that effective treatments will be available in the near future for this currently incurable condition and that molecular genetic testing should be increasingly considered. KEY WORDS: Stargardt disease, clinical trial, ABCA4, mutation.

[Preimplantation genetic diagnosis and monogenic inherited eye diseases]. / Preimplantacní genetická diagnostika a dedicná onemocnení oka.

OBJECTIVE: Preimplantation genetic diagnosis (PGD) is an established application of genetic testing in the context of in vitro fertilization. PGD is an alternative method to prenatal diagnosis which aims to prevent the transmission of an inherited disorder to the progeny by implanting only embryos that do not carry genetic predisposition for a particular disease. The aim of this study is to provide an overview of eye disorders for which PGD has been carried out. METHODS: The European literature search focused on best practices, ethical issues, risks and results of PGD for inherited eye disorders. RESULTS: PGD is performed for a number of ocular disorders; a prerequisite for its application is however, the knowledge of a disease-causing mutation(s). The main advantage of this method is that the couple is not exposed to a decision of whether or not to undergo an abortion. Qualified counselling must be provided prior to the PGD in order to completely understand the risk of disability in any child conceived, consequences of disease manifestation, and advantages as well as limitations of this method. In the group of non-syndromic eye diseases and diseases in which ocular findings dominate, PGD has been performed in European countries for aniridia, choroideremia, congenital fibrosis of extraocular muscles, Leber congenital amaurosis, ocular albinism, retinitis pigmentosa, X-linked retinoschisis, Stargardt disease, blepharophimosis-ptosis-inverse epicanthus syndrome and retinoblastoma. Sexing for X-linked or mitochondrial diseases has been carried out for blue cone monochromatism, choroideremia, familial exudative vitreoretinopathy, Leber hereditary optic neuropathy, macular dystrophy (not further specified), Norrie disease, X-linked congenital stationary night blindness, X-linked retinoschisis and nystagmus (not further specified). CONCLUSION: In recent years, there has been an increase in potential to use PGD. The spectrum of diseases for this method has widened to include severe inherited eye diseases.Key words: preimplantation genetic diagnosis; monogenic eye diseases; in vitro fertilization.

[Blepharophimosis-ptosis-epicanthus inversus syndrome]. / Syndrom blefarofimóza-ptóza-inverzní epikantus.

PURPOSE: To report the ocular phenotype of blepharophimosis-ptosis-epicanthus inversus syndrome (BPES). METHODS: Ophthalmological examination of a 36 year-old proband and detailed family history evaluation, including assessment of available facial photographs of affected relatives, was performed. RESULTS: There were four affected males and one female in three generations. The proband underwent two surgical eyelid procedures in childhood. Upon our examination, he had symmetrical ptosis with shorter eye lids, and incomplete medial canthal closure. The skin in the inner canthi was scarred, and the medial lower lids slightly everted, leading to malapposition of lacrimal punctae. There was no epicanthus inversus, however it was impossible to determine the status prior to the eyelid surgeries. The best corrected visual acuity was 0.66 and 0.33, in the right and left eye, respectively. The rest of the ocular examination was normal. There was no strabismus. Based on inspection of photographs taken prior to eyelid surgeries, the typical signs of BPES were also present in a son and a nephew of the proband. Photographs of the affected brother were not available, but family history indicated that he had BPES and underwent in his childhood two eye lid surgeries. Atypical ocular phenotype of the probands mother has been published previously. CONCLUSIONS: Ophthalmologists need to be aware about the phenotype of BPES, with the potential for visual impairment, and the need for personalized management in the affected families.Key words: blepharophimosis-ptosis-epicanthus inversus, phenotype, FOXL2.

Is copper imbalance an environmental factor influencing keratoconus development?

Keratoconus is a bilateral disease characterized by progressive corneal thinning leading to irregular astigmatism that results in significant visual impairment. Despite extensive research, the exact etiopathogenesis of keratoconus remains unknown. Many copper-dependent enzymes such as superoxide dismutases, cytochrome c oxidase and lysyl oxidase have been shown to be altered in keratoconic corneas, and a decrease of copper levels in the diseased tissue has been reported as well. We propose a hypothesis linking all the putative pathways of keratoconus development and suggest that copper imbalance in corneal tissue may be an independent risk factor for the disease. The assessment of copper levels and its distribution in keratoconic corneas warrants further investigation.

Macular corneal dystrophy and associated corneal thinning.

PURPOSE: To identify the molecular genetic cause of macular corneal dystrophy (MCD) in four probands, and characterize phenotypic similarities between MCD and keratoconus. METHODS: We performed ophthalmological examination, Scheimpflug imaging (Pentacam, Oculus Inc.), histopathological examination of excised corneal buttons, and direct sequencing of the CHST6 coding region. RESULTS: Pentacam measurements were taken in six eyes of three probands. All showed diffuse corneal thinning with paracentral steepening of the anterior corneal surface that was graded as keratoconus by the integrated software, but without associated ectasia of the posterior corneal surface or regional thinning. Homozygous or compound heterozygous CHST6 mutations were identified in all cases, including two novel mutations, c.13C>T; p.(Arg5Cys) and c.289C>T; p.(Arg97Cys). DISCUSSION: Localized elevation of the anterior corneal curvature can occur in MCD in the absence of other features of keratoconus. The identification of a further two Czech probands with the compound allele c.[484C>G; 599T>G] supports the enrichment of this allele in the study population.