Abstract
Purpose::
The Beaded Filament is a cytoskeletal structure found only in lens fiber cells, and includes filensin and phakinin, two unusal fiber cell-specific members of the Intermediate Filament family. Immunocytochemical analysis of embryonic mouse lenses established that both proteins are initially expressed in a polarized manner. This work explores the mechansim by which some proteins are spatially segregated in the developing fiber cell.
Methods::
Immunocytochemistry was used to localize proteins; In Situ hybridization was used to localize mRNAs; Light and Electron Microscopy was used to examine the structure of the developing lens fiber cell.
Results::
At about embryonic day 15, both beaded filament proteins were localized to the anterior end of the developing lens fiber cell. In situ hybridization established that the mRNAs for both proteins was also confined to the anterior end of the developing fiber cell. Examination of the localization of both proteins in embryonic vimentin knockout mice, show that spatial constraint of these proteins is lost, implicating vimentin in regulating the spatial distriubution of beaded filament protein/mRNAs.
Conclusions::
The anterior/posterior polarization of the fiber cell begins early in development, and is, in part, mediated by the vimentin cytoskeleton. This documents a new role for vimentin in the lens fiber cell.
Keywords: cytoskeleton • development • ribosomal RNA