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. Microtubules have many roles in the cell, among them as determinants of directional migration and as the highways for vesicle transport. Here we investigated the possible role of microtubules and their interactions with N-cadherin in providing directionality to fiber cell elongation.
Methods:
Co-immunoprecipitation analysis was performed on chick embryo lenses microdissected into four distinct zones of differentiation to analyze association of tubulin/acetylated tubulin with N-cadherin. The role of tubulin in fiber cell elongation was examined by treating E10 lenses in organ culture with the microtubule depolymerizing drug nocodazole. Treated lenses were microdissected as above and immunoblotted for tubulin expression/acetylation. Lens cryosections were labeled for α-tubulin, acetylated tubulin, N-cadherin, and/or F-actin.
Results:
N-Cadherin interacts with tubulin primarily in the cortical fiber zone, where lens fiber cells elongate. No association was detected between N-cadherin and the acetylated form of tubulin. Disassembly of microtubules with nocodazole affected fiber cell elongation and directionality. High doses of nocodazole also affected interactions between fiber cells and epithelial cells along the epithelial-fiber interface (EFI). These effects were accompanied by changes in levels of F-actin and increased localization of N-cadherin along the EFI. These results provide the first demonstration of a role for microtubules in lens fiber cell elongation, in lens morphogenesis and in the maintenance of lens tissue integrity.
Conclusions:
Microtubules have an important role in the determination of proper lens morphogenesis.
Keywords: 493 cytoskeleton •
497 development •
446 cell adhesions/cell junctions