Stratification of the Corneal Epithelium is Disrupted in the Absence of Vangl2

Abstract

Purpose: Cells of the stratified adult corneal epithelium undergo centripetal migration throughout adult life from the edge of the cornea to the centre. To date nothing is known about the mechanism underpinning the oriented cellular migration. However failure to replenish apoptotic cells lost through desquamation from the superficial layer of the corneal epithelium leads to severe pathological conditions that may result in blindness. In this study we investigated the role of planar cell polarity (PCP) core proteins as the guidance cue for centripetal migration in the cornea.

Methods: Cre-mediated conditional deletion of floxed alleles of the core PCP gene Vangl2 in the corneal epithelium and lens of adult mice was achieved. The effect of this deletion was studied by microscopic and immunohistological observation of the cornea compared to littermate controls. Planar behaviour of the corneal epithelial cells was assayed by breeding the mutant alleles onto an X-linked LacZ reporter transgene (XLacZ) background. In vitro directional migration studies were performed on Vangl2 knock-down human corneal epithelial cells following the application of DC fields compared with non-targeting Vangl2 siRNA controls.

Results: Conditional Le-Cre⁺Vangl2^flox/flox mice showed corneal thickening with disruption in the stratification of the corneal epithelium and decreased levels of mitosis compared with control mice Le-Cre⁺Vangl2^flox/+ controls. Disruption of the radial patterns of LacZ mosacism in Vangl2-mutant eyes indicated that cell mixing occurs between streams of cells migrating to the midline. Silencing of Vangl2 in human corneal epithelial cells results in the reduction of directional migratory response to the DC field.

Conclusions: Loss of the gene encoding the core PCP protein Vangl2 disrupts both the planar polarity and the apical-basal polarity of the corneal epithelium. Polarity is not completely abolished and it is concluded that there is redundancy with other directional and structural cues in the cornea. It is likely that mutations in PCP genes could lead to ocular surface abnormalities in humans.

Keywords: 482 cornea: epithelium