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  3. Ectopic GRHL2 Expression Due to Non-coding Mutations Promotes Cell State Transition and Causes Posterior Polymorphous Corneal Dystrophy 4

Ectopic GRHL2 Expression Due to Non-coding Mutations Promotes Cell State Transition and Causes Posterior Polymorphous Corneal Dystrophy 4

  • Am J Hum Genet. 2018 Mar 1;102(3):447-459. doi: 10.1016/j.ajhg.2018.02.002.
Petra Liskova 1,  Lubica Dudakova 2,  Cerys J Evans 3,  Karla E Rojas Lopez 3,  Nikolas Pontikos 3,  Dimitra Athanasiou 3,  Hodan Jama 3,  Josef Sach 4,  Pavlina Skalicka 5,  Viktor Stranecky 2,  Stanislav Kmoch 2,  Caroline Thaung 6,  Martin Filipec 7,  Michael E Cheetham 3,  Alice E Davidson 3,  Stephen J Tuft 8,  Alison J Hardcastle 9
Affiliations

Affiliations

  • 1 Research Unit for Rare Diseases, Department of Paediatrics and Adolescent Medicine, First Faculty of Medicine, Charles University and General University Hospital in Prague, Ke Karlovu 2, Prague 128 08, Czech Republic; Department of Ophthalmology, First Faculty of Medicine, Charles University and General University Hospital in Prague, U Nemocnice 2, Prague 128 08, Czech Republic; UCL Institute of Ophthalmology, University College London, London EC1V 9EL, UK. Electronic address: petra.liskova@lf1.cuni.cz.
  • 2 Research Unit for Rare Diseases, Department of Paediatrics and Adolescent Medicine, First Faculty of Medicine, Charles University and General University Hospital in Prague, Ke Karlovu 2, Prague 128 08, Czech Republic.
  • 3 UCL Institute of Ophthalmology, University College London, London EC1V 9EL, UK.
  • 4 Institute of Pathology, Third Faculty of Medicine, Charles University, Faculty Hospital Kralovske Vinohrady, Srobarova 50, Prague 100 34, Czech Republic.
  • 5 Research Unit for Rare Diseases, Department of Paediatrics and Adolescent Medicine, First Faculty of Medicine, Charles University and General University Hospital in Prague, Ke Karlovu 2, Prague 128 08, Czech Republic; Department of Ophthalmology, First Faculty of Medicine, Charles University and General University Hospital in Prague, U Nemocnice 2, Prague 128 08, Czech Republic.
  • 6 UCL Institute of Ophthalmology, University College London, London EC1V 9EL, UK; Moorfields Eye Hospital, London EC1V 2PD, UK.
  • 7 Department of Ophthalmology, First Faculty of Medicine, Charles University and General University Hospital in Prague, U Nemocnice 2, Prague 128 08, Czech Republic.
  • 8 Moorfields Eye Hospital, London EC1V 2PD, UK.
  • 9 UCL Institute of Ophthalmology, University College London, London EC1V 9EL, UK; Moorfields Eye Hospital, London EC1V 2PD, UK. Electronic address: a.hardcastle@ucl.ac.uk.
PMID: 29499165 DOI: 10.1016/j.ajhg.2018.02.002
Abstract

In a large family of Czech origin, we mapped a locus for an autosomal-dominant corneal endothelial dystrophy, posterior polymorphous corneal dystrophy 4 (PPCD4), to 8q22.3-q24.12. Whole-genome Sequencing identified a unique variant (c.20+544G>T) in this locus, within an intronic regulatory region of GRHL2. Targeted Sequencing identified the same variant in three additional previously unsolved PPCD-affected families, including a de novo occurrence that suggests this is a recurrent mutation. Two further unique variants were identified in intron 1 of GRHL2 (c.20+257delT and c.20+133delA) in unrelated PPCD-affected families. GRHL2 is a transcription factor that suppresses epithelial-to-mesenchymal transition (EMT) and is a direct transcriptional repressor of ZEB1. ZEB1 mutations leading to haploinsufficiency cause PPCD3. We previously identified promoter mutations in OVOL2, a gene not normally expressed in the corneal endothelium, as the cause of PPCD1. OVOL2 drives mesenchymal-to-epithelial transition (MET) by directly inhibiting EMT-inducing transcription factors, such as ZEB1. Here, we demonstrate that the GRHL2 regulatory variants identified in PPCD4-affected individuals induce increased transcriptional activity in vitro. Furthermore, although GRHL2 is not expressed in corneal endothelial cells in control tissue, we detected GRHL2 in the corneal "endothelium" in PPCD4 tissue. These cells were also positive for epithelial markers E-Cadherin and Cytokeratin 7, indicating they have transitioned to an epithelial-like cell type. We suggest that mutations inducing MET within the corneal endothelium are a convergent pathogenic mechanism leading to dysfunction of the endothelial barrier and disease.

Keywords

GRHL2; PPCD; corneal dystrophy; corneal edema; corneal endothelium; ectopic expression; epithelial-to-mesenchymal transition; mesenchymal-to-epithelial transition; non-coding mutation; regulatory region.

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