Ptpn11^D61Y erythroid progenitors show enhanced BFU-E and reduced CFU-E activity. MEPs from control and Ptpn11^D61Y (A,B) or ER-Cre;Ptpn11^D61Y mice (C,D) were cultured for 2 days in EPO-containing methylcellulose media for CFU-E colonies (A,C) or for 8 days in medium containing SCF, IL-3, IL-6, and EPO for BFU-E colonies (B,D). (E) EPs from control and Ptpn11^D61Y mice were plated on methylcellulose media in the presence of 0.5 U/mL EPO for 2 days before they were numerated.