Developmental activities of the epidermal growth factor receptor.
EGF-Rs are encoded by a single gene which produces two main transcripts that are translated and processed into a single polypeptide chain. The membrane-inserted receptor kinase binds EGF or TGF-alpha at high and low affinities, but how these are related to the pleiotropic activities of the EGF-R is unknown. The widespread distribution of fetal EGF-Rs suggests that they have many functions during mammalian development. The stage- and cell type-specific expression of receptors in tissues such as the placenta, together with the localized production of EGF/TGF-alpha, suggests that fetal EGF-Rs have specific activities and roles. The proliferation of the fetal trophoblast and the maternal deciduum is likely to provide the location for a major and necessary role of TGF-alpha and EGF-Rs, which probably act by autocrine and paracrine means to establish the placenta as rapidly as possible. There is evidence that if placental EGF-Rs malfunction, the fetus is at a disadvantage. This could be partly due to poor placental growth and development, as well as a reduced ability of the placenta to perform a barrier function. The murine fertilized egg at preimplantation stages produces a number of growth factors, including TGF-alpha, but the significance of this is still uncertain. It is likely that several fetal and adult tissues produce low amounts of EGF/TGF-alpha for their self-maintenance. The precise roles for the putative EGF/TGF-alpha produced in the brain, kidney, tooth, and various head tissues are also obscure and will be subjects of close scrutiny in the future.
La Jolla Cancer Research Foundation, California 92037.
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Adamson
D000818:Animals; D066246:ErbB Receptors / Q000235:genetics / Q000378:metabolism*; D005333:Fetus / Q000378:metabolism; D005786:Gene Expression Regulation; D006128:Growth / Q000502:physiology*; D006801:Humans; D015291:Transforming Growth Factors / Q000235:genetics / Q000378:metabolism
D015291:Transforming Growth Factors; D066246:ErbB Receptors