Expression and activation of the epidermal growth factor receptor in differentiating cells of the developing and post-hatching chicken lens.

The epidermal growth factor receptor is hypothesized to play an important role in the post-natal growth and differentiation of the ocular lens. Immunohistochemistry and western blotting were utilized to examine the distribution and activation of the epidermal growth factor receptor in embryonic and post-hatching chicken lenses. Although present at constant levels within epithelial cells throughout embryonic development, the receptor becomes increasingly activated on a highly conserved tyrosine residue necessary for intracellular signal transduction as hatching approaches. After hatching, activated receptors are found in epithelial cells committed to fiber cell formation and in fiber cells undergoing initial stages of terminal differentiation. Activated receptors could not be identified in central epithelial cells or nuclear fiber cells. This pattern persists until at least one year post-hatching. These data indicate that the epidermal growth factor receptor is positioned to influence not only post-natal patterns of lenticular gene expression but also the greatest amount of lens growth and development.