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.

Caspase-9 activation in hypoxic human corneal epithelial cells.

The purpose of this study was to determine the effect of hypoxia on caspase-8 and -9 gene and protein expression and activity in corneal epithelium. Non-transformed human corneal epithelial cells (HCEC) were cultured in 2% oxygen. A cDNA expression array coupled with densitometric analysis was used to compare relative mRNA expression levels of 96 apoptosis-related genes in hypoxic and normoxic HCEC.

Thymosin beta 4 stimulates laminin-5 production independent of TGF-beta.

Thymosin beta 4 (Tbeta(4)) stimulates epithelial cell migration and promotes laminin-5 (LM-5) expression. Using gene expression analysis with human corneal epithelial cells treated with Tbeta(4), we find that both LM-5 gamma2 chain and transforming growth factor beta 1 (TGFbeta-1) are increased by more than 2-fold over untreated cells. These findings were confirmed by RT-PCR and at the protein level.

A role for endogenous TGFalpha and associated signaling pathways in the differentiation of lens fiber cells.

TGFalpha is hypothesized to be an endogenous regulator of lens fiber terminal differentiation. With immunofluorescence, TGFalpha was localized to differentiating cells in the lens epithelium and superficial fiber cell mass of the adult chicken. A similar pattern of localization was also noted when differentiating epithelial cells were cultured.

Differentiation of chick lens epithelial cells: involvement of the epidermal growth factor receptor and endogenous ligand.

Purpose: To characterize the constitutively activated epidermal growth factor receptor in a lens epithelial cell population experiencing initial stages of lens fiber formation, the chick lens annular pad.

Methods: Phosphotyrosine levels of the receptor were examined with western blot analysis and immunoprecipitation after ligand stimulation. Endogenous receptor ligands were immunologically identified in whole cell lysates of freshly isolated cells.