Abstract
Purpose :
Tissue development and regeneration involve high-ordered morphogenetic processes that are governed by elements of the cytoskeleton in conjunction with cell adhesion molecules. Such processes are particularly important in the lens whose structure dictates its function. Previous work from our lab has demonstrated a role for N-cadherin junctions in lens fiber cell elongation and actin organization within the lens, and recent work has begun to unveil the importance of N-cadherin in the regulation of developmental migration. Here we investigated the role of N-cadherin in lens morphogenesis.
Methods :
A lens-specific N-cadherin conditional knockout mouse (mlr10 N-cadherin cKO) was generated so as to examine effects of loss of N-cadherin on lens morphogenesis. Analysis was performed on cryosections from the above lenses labeled at different stages of development for F-actin, ZO-1 and/or RhoGTPases and imaged by confocal microscopy.
Results :
By E13.5, mlr10 N-cadherin cKO lenses exhibited defects in fiber cell morphogenesis including the clustering of the apical tips of the youngest elongating fiber cells at the lens equator with an enhanced labeling for F-actin where these fiber cells interface with the adjacent epithelium. This morphogenetic defect was even more evident at E14.5 as the apical tips of secondary fiber cells accumulate at the fulcrum, and fail to move anteriorly along the Epithelial Fiber Interface (EFI). By E16.5, secondary fiber cells have elongated partially, and are linked apically by ZO-1 junctions, but their failure to migrate along the EFI results in significant dysmorphogenesis of the lens. These results suggest that N-cadherin junctions that are normally prominent along the EFI play a crucial role in directing the migration of fiber cells along this interface. This phenomenon is evocative of Contact Inhibition of Locomotion, where N-cadherin-dependent regulation of actin organization through RhoGTPases promotes movement following contact. In support of this mechanism we find significant dysregulation of the RhoGTPase Rac in the region of the EFI. These results demonstrate the necessity of N-cadherin in lens fiber cell elongation, lens morphogenesis, and the maintenance of lens cytoarchitecture.
Conclusions :
Fiber cell elongation and migration is dependent on N-cadherin and required for lens morphogenesis.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.