KLEIP Deficiency in Mice causes Progressive Corneal Neovascular Dystrophy

Abstract

Purpose: : Animal models are very limited to study development and progression of corneal dystrophies in mice. The BTB-kelch protein KLEIP (Kelch-like ECT2-interacting protein) is an actin binding protein that regulates cell-cell contacts via E-cadherin localization and RhoA-dependent cell migration. The purpose of this study was to characterize KLEIP’s function in mouse development.

Methods: : KLEIP^-/- mice were generated using the gene trap technology. Eyes form KLEIP^-/- and KLEIP^+/+ embryos and postnatal mice were histologically examined and functionality of the meibomian glands, lacrimal glands and goblet cells was assessed. Likewise, corneas were stained for keratin 1, loricrin, keratin 14, CD31, LYVE-1, F4/80, E-cadherin and Ki67. Corneal abrasions were performed after eyelid opening.

Results: : KLEIP deficiency in mice led to a partial postnatal lethal phenotype until day P28 due to an unknown reason. KLEIP^-/- mice which survived beyond P28, however, are mostly normal and fertile. Corneas of KLEIP^+/+ and KLEIP^-/- animals could not be distinguished at birth. Yet, after eyelid opening corneal epithelial hypertrophy manifested in all KLEIP^-/- mice between three weeks and four month after birth. All KLEIP^-/- mice developed a diffuse progressive epithelial metaplasia leading to total corneal opacity after 6 month. In KLEIP^-/- mice the initial stratified squamous corneal epithelium was altered to an epidermal histo-architecture with epithelial hyperplasia indentations into the corneal stroma, disorganized E-cadherin expression, stromal infiltrations and superficial keratinized cells. Skin markers keratin 1 and loricrin were positive in KLEIP^-/- corneaes. Surface disease was accompanied by deep stromal vascularisation reaching the center after a mean of 12 weeks. Histological analysis of the meibomian glands, lacrimal glands and goblet cells indicated a similar appearance in KLEIP^+/+ and KLEIP^-/- mice. Removal of the virgin epithelium resulted after 7 days in an accelerated dystrophic development during the healing process in all KLEIP^-/- mice.

Conclusions: : The data identify KLEIP as an important molecule regulating corneal integrity and highlight KLEIP deficient mice as a new and important tool to study corneal dystrophy formation. Further analysis of the phenotype may provide a model for similar human corneal disease as seen in posttraumatic or inflammatory scars.

Keywords: cornea: basic science • genetics • cell adhesions/cell junctions