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 recent work has begun to unveil the importance of N-cadherin regulation of and interaction with cytoskeletal proteins, including microtubules. Microtubules play an important role in cell elongation and directional migration, and thus may impact the elongation process of lens fiber cells. Here we investigated the possible roles of microtubules and N-cadherin in lens morphogenesis and the necessity of their interaction for proper fiber cell elongation.
Methods:
Co-immunoprecipitation analysis was performed on E10 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 and in eyes from a lens-specific N-cadherin conditional knockout mouse (mlr10 N-cadherin cKO). Analysis was performed on cryosections from the above lenses labeled for alpha-tubulin, acetylated tubulin, and/or F-actin and imaged by confocal microscopy.
Results:
Tubulin and its acetylated form characteristic of stable microtubules are linked to N-cadherin primarily in the cortical fiber zone, where lens fiber cells elongate. Disassembly of microtubules with nocodazole impaired length and directionality of fiber cell elongation. By E13.5, mlr10 N-cadherin cKO lenses demonstrated loss of fiber cell directionality similar to effects of depolymerizing stable microtubules. By E16.5 severe morphogenetic defects and failure of elongation were observed. mlr10 N-cadherin cKO lenses also demonstrated loss of acetylated tubulin, especially in elongating fiber cells. These results provide demonstration of a coordinated role for microtubules with N-cadherin in lens fiber cell elongation and lens morphogenesis.
Conclusions:
Lens fiber cell elongation and morphogenesis depends on N-cadherin/microtubule interactions.