Plasticity of MEP cells transformed by E26 leukemia virus.

(A) Differentiation potential of MEP cells, as demonstrated by the use of ts mutants of E26 virus with point mutations in eitherv-ets or v-myb. (B) Differentiation of MEP cells into eosinophils and myeloblasts (granulocyte/macrophage precursors) by activation of the Ras or PKC pathways. Different phorbolester concentrations preferentially lead to the differentiation of either eosinophils or myeloblasts (high and low PKC levels). (C) Arrows indicate induction of eosinophil, myeloblast, and MEP cell differentiation by enforced expression of transcription factors shown. GATA-1 low indicates that lower levels of the factor are required for eosinophil differentiation than for MEP cell differentiation.