Expression of developmentally different β-globin mRNA species in Epo-stimulated EpoR⁺ clones derived from B6SUtA and Ba/F3 cells analyzed by northern hybridization. B6-ER-1 to -4 and Ba-ER-1 to -4 were EpoR⁺ clones derived from B6SUtA and Ba/F3 cells, respectively. Friend MEL cells exposed to 1.5% DMSO for 0 to 4 days served as a control. RNA was probed with β^major-globin, ɛ-globin, and β-actin cDNAs.