Abstract
Purpose: :
The ERM (ezrin, radixin, moesin) proteins which regulate crosslinking of the transmembrane proteins to the cytoskeleton and the activities of signaling pathways are abundantly expressed in lens fiber cells. However, the role of the ERM proteins in lens differentiation and function are not very clear. In this study, we determined distribution pattern of ezrin in the differentiating mouse lens fibers, to explore the role of this protein in lens differentiation.
Methods: :
Paraffin embedded sagittal sections derived from the embryonic mouse eyes at day 16.5, 18.5, neonatal day 1, postnatal day 3, 7, 10, 21 and 30, were immunostained using anti-ezrin, monoclonal and anti-phospho ezrin polyclonal antibodies and imaged by confocal microscopy. Enriched nuclear and membrane fractions were isolated from the different regions of the mouse and porcine lens to examine the distribution profile of ezrin and phospho-ezrin by immunoblot analyses.
Results: :
Immunofluorescence analysis of ezrin in the differentiating and mature lenses revealed an interesting and unique subcellular distribution pattern. While in the embryonic lenses, ezrin distribution was localized predominantly to the plasma membrane of both epithelium and differentiating fibers, this protein was found to stain intensely and discretely in the nuclei of the late stage differentiating fibers in addition to its distribution to the plasma membrane of epithelium and fiber cells in postnatal and adult lenses. Ezrin was not found in epithelial nuclei or in early differentiating lens fibers. Ezrin localization to the nuclei of the fiber cells undergoing terminal differentiation was additionally confirmed by immunoblot analysis using nuclei enriched fractions of the mouse and porcine lens fibers derived from the cortical and nuclear regions. Both total and phospho-ezrin were found to be localized to the nuclei of late and terminal differentiating fibers.
Conclusions: :
The initial results from this ongoing project reveal that ezrin exhibits a differentiation dependent redistribution, translocating discretely to the nuclei of the late stage differentiating fiber cells suggesting a potential role for ezrin in denucleation of differentiated lens fibers.
Keywords: differentiation • cytoskeleton • signal transduction