Molecular Cloning of Mast Cell Growth Factor, a Hematopoietin That is Active in Both Membrane Bound and Soluble Forms

We have previously reported the identification of a novel mast cell growth factor (MGF) that was shown to be a ligand for c-kit and is encoded by a gene that maps near the steel locus on mouse chromosome 10. We now report the cloning of cDNAs encoding the MGF protein. The MGF protein encoded by this cDNA can be expressed in a biologically active form as either a membrane bound protein or as a soluble factor. The soluble protein promotes the proliferation of MGF-responsive cell lines and, in the presence of erythropoietin, stimulates the formation of macroscopic [corrected] erythroid and multilineage hematopoietic colonies.