EXPRESSION OF AN ACTIVATED ERYTHROPOIETIN OR A COLONY-STIMULATING FACTOR-1 RECEPTOR BY PLURIPOTENT PROGENITORS ENHANCES COLONY FORMATION BUT DOES NOT INDUCE DIFFERENTIATION

Whether the presence of specific receptors on the surface of developin g cells is the cause of consequence of lineage restriction is not know n. If activation of specific receptors is the driving event in differe ntiation, the premature expression of specific receptors would promote differentiation along that pathway. In this study pluripotent progeni tors, obtained from blast cell colonies (pooled or individual) of 5-fl urouracil-treated mice, were infected with retroviral vectors containi ng either an activated receptor for erythropoietin (EPO), an erythroid progenitor growth factor, or the receptor for colony-stimulating fact or 1 (CSF-1), a macrophage growth factor. These receptors exhibit expr ession patterns restricted to committed progenitors. The developmental potential of infected pluripotent progenitors was not changed, althou gh they expressed the exogenous genes, suggesting that in these cells activation of lineage-specific receptors does not induce differentiati on. Acquisition of a constitutively activated EPO receptor allowed ery throid development in mixed colonies in the absence of EPO, as expecte d. Infection of progenitors with a virus containing the CSF-1 receptor promoted the development of granulocyte/macrophage (GM) colonies but did not alter the differentiation potential of either colony-forming u nit (CFU)-GM or CFU-mix.