v-Myb can transform and regulate the differentiation of melanocyte precursors

The activity of the c-Myb transcription factor is essential for the develop ment of definitive multi- and uni-lineage progenitors of the haemopoietic s ystem. Reflecting this requirement, c-Myb has been oncogenically activated by transduction in the E26 avian retrovirus which elicits an acute leukaemi a by transforming haemopoietic progenitors, Here, we report the novel findi ng that Myb in cooperation with EGF receptor signalling can be used to gene rate clonally expanded populations of transformed cells which have the phen otype of melanocyte precursors. Through the use of a conditional temperatur e sensitive mutant of Myb, we show that in the transformed cells Myb regula tes commitment to melanocyte differentiation and possibly proliferation. Th ese results add to our understanding of the roles of c-Myb beyond the haemo poietic system and to our knowledge and means of investigating the importan ce of transcription factors in the melanocyte linage.