EGF-R as a hemopoietic growth factor receptor: The c- erbB product is present in chicken erythrocytic progenitors and controls their self-renewal

c- erbB, encoding the EGF receptor (EGF-R), was originally identified as the cellular homolog of a chicken leukemia oncogene. In humans, EGF-R is distributed widely except in hemopoietic tissues, and its amplification is associated with epidermal and glial malignancies. Here we show that c- erbB is present in normal chicken erythrocytic progenitors and transmits the mitogenic signal induced by TGFα. Cells that contain high affinity EGF-R are at approximately the BFU-E stage, and their long-term renewal can be Induced by TGFa. Upon addition of insulin and erythropoletin, they can be induced to terminally differentiate into red cells. We previously demonstrated that v- erbA blocks differentiation of chicken erythrocytic progenitors but does not abrogate their growth factor dependence for proliferation. These data indicate that proliferation and differentiation are not necessarily coupled in these cells. They also demonstrate a direct role of c- erbB in the control of self-renewal of normal chicken erythrocytic progenitors and could account for the predominant leukemogenic potential of the chicken erbB gene.