Abstract
Purpose :
Tissue development and regeneration involve high-order 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. Recent work has begun to unveil the importance of N-cadherin in the regulation of developmental migration in addition to its traditional role in cell adhesion. 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 for Aquaporin 0, Connexin 50, Rac1, active-Rac1, myosin-II, phospho-myosin and/or F-actin and imaged by confocal microscopy. Immunoblotting was performed on E16.5 lenses for Rac1, active-Rac1, myosin-II, phospho-myosin and N-cadherin.
Results :
By E13.5, mlr10 N-cadherin cKO lenses demonstrated increased clustering of the apical domains of newly differentiating fiber cells along the lens equator, just past the transition zone. This finding revealed that fiber cell elongation is governed in part by N-cadherin junctional-dependent migration of fiber cell apical tips along the anterior surface of the lens epithelium. This defect worsened over time as new fiber cells are added at the transition zone but fail to create and migrate along an epithelial fiber interface, but without loss of cell-cell adherence. In the absence of along the lateral interfaces of fiber cells Aquaporin 0 was greatly increased and Connexin 50 reorganized at cell-cell borders, potentially playing a primary in maintaining lateral fiber cell adhesion. This migration defect was accompanied by loss of Rac1 activation and over-activation of myosin-II, with changes in these migration-promoting proteins suggesting the mechanism behind the dysmorphogenesis seen in knockout lenses. These results demonstrate the necessity of N-cadherin in lens fiber cell elongation, lens morphogenesis, and the maintenance of lens cytoarchitecture.
Conclusions :
Lens fiber cell migration, elongation, and morphogenesis depends on N-cadherin.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.