Novel mutations in theZEB1 gene identified in Czech and British patients with posterior polymorphous corneal dystrophy

Abstract

We describe the search for mutations in six unrelated Czech and four unrelated British families with posterior polymorphous corneal dystrophy (PPCD); a relatively rare eye disorder. Coding exons and intron/exon boundaries of all three genes (VSX1, COL8A2, and ZEB1/TCF8) previously reported to be implicated in the pathogenesis of this disorder were screened by DNA sequencing. Four novel pathogenic mutations were identified in four families; two deletions, one nonsense, and one duplication within exon 7 in the ZEB1 gene located at 10p11.2. We also genotyped the Czech patients to test for a founder haplotype and lack of disease segregation with the 20p11.2 locus we previously described. Although a systematic clinical examination was not performed, our investigation does not support an association between ZEB1 changes and self reported non-ocular anomalies. In the remaining six families no disease causing mutations were identified thereby indicating that as yet unidentified gene(s) are likely to be responsible for PPCD.

Heterozygous deletions at the ZEB1 locus verify haploinsufficiency as the mechanism of disease for posterior polymorphous corneal dystrophy type 3

“…1,16 For inclusion in this analysis, the presence of ZEB1 coding and/or splice-site mutations by direct sequencing had previously been excluded. 11,16,17 All probands identified to be positive for ZEB1 locus deletions in the current study were also negative for mutations in COL8A2, either by Sanger sequencing or by whole-exome sequencing (WES) (unpublished data). 11 …”

“…11,16,17 All probands identified to be positive for ZEB1 locus deletions in the current study were also negative for mutations in COL8A2, either by Sanger sequencing or by whole-exome sequencing (WES) (unpublished data). 11 …”

“…Analysis of the WES data for affected individuals (II:2, III:1, and IV:1) confirmed that there were no mutations in the coding region or splice sites of the PPCD-associated genes ZEB1 and COL8A2. 11 Furthermore, no shared rare (minor allele frequency ≤ 1% in NHLBI ESP Release Version: v.0.0.25 (http://evs.gs. washington.edu/EVS/) and 1000 Genomes dataset release version 14 Heterozygous deletions at the PPCD3 locus P Liskova et al (http://www.1000genomes.org/)) variants were identified in any other corneal dystrophy-associated genes.…”

“…20,24 PPCD often presents in small nuclear families or as an isolated case such that linkage to a specific genomic region is not conclusive, or is confounded by incomplete penetrance in some cases, so a substantial proportion of patients currently lack a molecular diagnosis. [9][10][11][12][14][15][16][17] In this study we demonstrate that, in some of these cases, PPCD can be attributed to heterozygous deletions at the ZEB1 locus, providing insights into the molecular diagnosis of previously unexplained PPCD cases and verifying haploinsufficiency as the mechanism of disease for PPCD3.…”

“…[9][10][11][12][13][14][15][16][17] There are regional variations in the contribution of these PPCD subtypes, and the proportion attributed to ZEB1 mutations (PPCD3) has been reported to be 9% in New Zealand, 20% in the Czech Republic, 30% in the United Kingdom and Canada, and 34% in the United States. [9][10][11][12][13][14][15][16][17] In contrast to other PPCD subtypes, PPCD3 is often associated with corneal steepening. 16,18 Systemic features such as inguinal hernias have also been described.…”