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M.E. Ireland; Epidermal Growth Factor Receptors (EGFRs) are Up-regulated and Activated in Differentiating Lens Fibers After Birth . Invest. Ophthalmol. Vis. Sci. 2003;44(13):4490.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To determine if functional EGFRs were present in differentiating lens fibers. Methods: Whole lens immunoprecipitates (IPs) were prepared from chicken embryos at various developmental stages with antibodies recognizing the activated human EGFR autophosphorylated on tyrosine residue 1173 (pEGFR). In addition to pEGFR, IPs were also prepared from annular pad and fiber cell masses from newborn, 3-month old or 1-year old chickens with antibodies recognizing total human EGFRs (TEGFR). Western blots of embryonic IP samples were stained with pEGFR while post-hatching IP samples were stained with TEGFR, stripped and re-probed with pEGFR. TEGFR and pEGFR levels were densitometrically quantified. Results: In embryonic IPs equalized for total number of epithelial cells, activated EGFRs were detected by 14 days of development and increased 2-fold in abundance by hatching. At hatching, TEGFR and pEGFR were found nearly exclusively in annular pad cells. At both 3-months and 1-year post-hatching, fiber cell TEGFR levels increased to 10% of the annular pad. However, on a per lens basis, pEGFR levels were equivalent in annular pad and fiber cells. Conclusions: Its increased abundance and activation in epithelial cells during embryonic development indicates an important delayed onset role for the EGFR during pre-natal lens formation or growth. After birth and well into post-natal life, additional functions for the EGFR in directing lens fiber terminal differentiation may also be hypothesized. These additional functions may supplement or replace other previously characterized growth factor receptor activities.
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