The genetic architecture of corneal endothelial dystrophies remains unknown in a substantial number of affected individuals. The proband investigated in the current study was diagnosed in the neonatal period with bilateral corneal opacification due to primary endothelial cell dysfunction. Neither his parents nor his sister had signs of corneal disease. Conventional karyotyping revealed a de novo translocation involving chromosomes 3 and 20, t(3;20)(q25;p11-12). Following genome and targeted Sanger sequencing analysis, the breakpoints were mapped at the nucleotide level. Notably, the breakpoint on chromosome 20 was identified to lie within the same topologically associated domain (TAD) as corneal endothelial dystrophy-associated gene OVOL2, and it is predicted to disrupt distal enhancers. The breakpoint at chromosome 3 is located within intron 2 of PFN2, which is currently not associated with any human disease. Further interrogation of the proband's genome failed to identify any additional potentially pathogenic variants in corneal endothelial dystrophy-associated genes. Disruption of a candidate cis-regulatory element and/or positional effects induced by translocation of OVOL2 to a novel genomic context may lead to an aberrant OVOL2 expression, a previously characterized disease mechanism of corneal endothelial dystrophy. Further research is necessary to explore how disruption of regulatory elements may elucidate genetically unsolved corneal endothelial dystrophies.

• MeSH
• dědičné dystrofie rohovky * genetika   diagnóza   MeSH
• genetická predispozice k nemoci MeSH
• lidé MeSH
• lidské chromozomy, pár 3 genetika   MeSH
• novorozenec MeSH
• regulační oblasti nukleových kyselin * MeSH
• rodokmen MeSH
• transkripční faktory * genetika   MeSH
• translokace genetická MeSH
• Check Tag
• lidé MeSH
• mužské pohlaví MeSH
• novorozenec MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• Ovol2 protein, human MeSH Prohlížeč
• transkripční faktory * MeSH

The aim of this study was to describe the ocular phenotype in a case with Kearns-Sayre syndrome (KSS) spectrum and to determine if corneal endothelial cell dysfunction could be attributed to other known distinct genetic causes. Herein, genomic DNA was extracted from blood and exome sequencing was performed. Non-coding gene regions implicated in corneal endothelial dystrophies were screened by Sanger sequencing. In addition, a repeat expansion situated within an intron of TCF4 (termed CTG18.1) was genotyped using the short tandem repeat assay. The diagnosis of KSS spectrum was based on the presence of ptosis, chronic progressive external ophthalmoplegia, pigmentary retinopathy, hearing loss, and muscle weakness, which were further supported by the detection of ~6.5 kb mtDNA deletion. At the age of 33 years, the proband's best corrected visual acuity was reduced to 0.04 in the right eye and 0.2 in the left eye. Rare ocular findings included marked corneal oedema with central corneal thickness of 824 and 844 µm in the right and left eye, respectively. No pathogenic variants in the genes, which are associated with corneal endothelial dystrophies, were identified. Furthermore, the CTG18.1 genotype was 12/33, which exceeds a previously determined critical threshold for toxic RNA foci appearance in corneal endothelial cells.

• Klíčová slova
• CTG18.1, Kearns-Sayre syndrome, TCF4, corneal dystrophy, corneal endothelium, endothelial failure, exome sequencing,
• MeSH
• dospělí MeSH
• fenotyp MeSH
• Fuchsova endoteliální dystrofie patologie   MeSH
• genotyp MeSH
• katarakta genetika   MeSH
• Kearnsův-Sayreův syndrom genetika   MeSH
• lidé MeSH
• mitochondriální DNA MeSH
• rohovkový endotel patologie   patofyziologie   MeSH
• sekvenční delece MeSH
• sekvenování exomu MeSH
• transkripční faktor 4 genetika   MeSH
• trinukleotidové repetice * MeSH
• Check Tag
• dospělí MeSH
• lidé MeSH
• mužské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• kazuistiky MeSH
• práce podpořená grantem MeSH
• Názvy látek
• mitochondriální DNA MeSH
• TCF4 protein, human MeSH Prohlížeč
• transkripční faktor 4 MeSH

ZEB1 loss-of-function (LoF) alleles are known to cause a rare autosomal dominant disorder-posterior polymorphous corneal dystrophy type 3 (PPCD3). To date, 50 pathogenic LoF variants have been identified as disease-causing and familial studies have indicated that the PPCD3 phenotype is penetrant in approximately 95% of carriers. In this study, we interrogated in-house exomes (n = 3616) and genomes (n = 88) for the presence of putative heterozygous LoF variants in ZEB1. Next, we performed detailed phenotyping in a father and his son who carried a novel LoF c.1279C>T; p.(Glu427*) variant in ZEB1 (NM_030751.6) absent from the gnomAD v.2.1.1 dataset. Ocular examination of the two subjects did not show any abnormalities characteristic of PPCD3. GnomAD (n = 141,456 subjects) was also interrogated for LoF ZEB1 variants, notably 8 distinct heterozygous changes presumed to lead to ZEB1 haploinsufficiency, not reported to be associated with PPCD3, have been identified. The NM_030751.6 transcript has a pLI score ≥ 0.99, indicating extreme intolerance to haploinsufficiency. In conclusion, ZEB1 LoF variants are present in a general population at an extremely low frequency. As PPCD3 can be asymptomatic, the true penetrance of ZEB1 LoF variants remains currently unknown but is likely to be lower than estimated by the familial led approaches adopted to date.

• Klíčová slova
• ZEB1, cornea, loss-of-function, penetrance,
• MeSH
• dědičné dystrofie rohovky genetika   patologie   MeSH
• haploinsuficience MeSH
• heterozygot MeSH
• kultivované buňky MeSH
• lidé středního věku MeSH
• lidé MeSH
• mutace ztráty funkce * MeSH
• penetrance * MeSH
• rodokmen MeSH
• transkripční faktor Zeb1 genetika   metabolismus   MeSH
• Check Tag
• lidé středního věku MeSH
• lidé MeSH
• mužské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• kazuistiky MeSH
• práce podpořená grantem MeSH
• Názvy látek
• transkripční faktor Zeb1 MeSH
• ZEB1 protein, human MeSH Prohlížeč

Name of the disease (synonyms) CUGC for posterior polymorphous corneal dystrophy (PPCD).OMIM# of the disease 122000; 609141; 618031.Name of the analysed genes or DNA/chromosome segments OVOL2 (PPCD1); ZEB1 (PPCD3); GRHL2 (PPCD4).OMIM# of the gene(s) 616441; 189909; 608576. Review of the analytical and clinical validity as well as of the clinical utility of DNA-based testing for variants in theOVOL2, ZEB1andGRHL2gene(s) in a diagnostic setting, predictive and parental settings and for risk assesment in relatives.

• MeSH
• dědičné dystrofie rohovky diagnóza   genetika   MeSH
• DNA vazebné proteiny genetika   MeSH
• genetické testování metody   normy   MeSH
• lidé MeSH
• senzitivita a specificita MeSH
• směrnice pro lékařskou praxi jako téma MeSH
• transkripční faktor Zeb1 genetika   MeSH
• transkripční faktory genetika   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• DNA vazebné proteiny MeSH
• GRHL2 protein, human MeSH Prohlížeč
• Ovol2 protein, human MeSH Prohlížeč
• transkripční faktor Zeb1 MeSH
• transkripční faktory MeSH
• ZEB1 protein, human MeSH Prohlížeč