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M.E. Ireland, D.M. Richiert; Developmental Expression of Transforming Growth Factor–Alpha (TGF–) Transcripts in the Chicken Lens . Invest. Ophthalmol. Vis. Sci. 2006;47(13):2557.
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Activation of the epidermal growth factor receptor (EGFR) during lens development and growth may be due to exogenous or endogenous sources of TGF–α. These experiments seek to determine the presence of endogenous TGF–α transcripts during embryonic and post–natal development of the chicken lens.
Total RNA was isolated with Trizol from whole lenses of 7–, 14– and 21–day chicken embryos plus annular pad and superficial cortical fiber cells of 3–month post–hatching chickens. First strand cDNA was synthesized with SuperScriptTM III reverse transcriptase. Primer pairs were designed for chicken TGF–α (target) and ß–actin (housekeeping) genes using Primer3 software. Transcript levels were determined with multiplexed PCR. Multiplexed PCR products were visualized on ethidium bromide agarose gels and digitized for quantification. Ratios of target:housekeeping genes were compared between the embryonic age groups plus two post–natal differentiated cell types.
Similar levels of TGF–α transcripts were observed in both post–natal annular pad and superficial cortical fiber cells. Transcript levels of TGF–α in 7–day embryonic lenses were approximately 50% of those observed in post–hatching cells. Transcript levels increased gradually during development until post–hatching levels were attained.
The EGFR is present at constant levels but exhibits increased activation in the chicken lens during embryonic development. The post–natal chicken lens continues to show highly activated levels of the EGFR in both annular pad and superficial cortical fiber cells. Similar observations have been reported for post–natal human lenses. These results indicate that increased activation of the EGFR during embryonic development and sustained activation of the EGFR during post–natal lens growth may be due to the presence of endogenous TGF–α within autocrine or juxtacrine signaling pathways.
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