SOCS-3 promotes, whereas Klf4 inhibits, ES cell differentiation. (A) Northern blot analysis of LIF stimulation of SOCS3 and KLF4 in WT and Shp-2Δ46-110 ES cells (representative of 2 independent experiments). (B) Schematic diagram of retroviral vectors used to conduct functional studies. IRES indicates internal ribosome entry site; LTR, long terminal repeat. (C) Transduced and sorted ES cells were subjected to in vitro differentiation for hemangioblasts, primitive erythroid (EryP) progenitors, and secondary EBs; data represent 2 independent experiments with cultures plated in triplicate; *P = .02 for pMIEG3-SOCS-3 versus pMIEG3; **P = .03 for pMIEG3-SOCS-3 versus pMIEG3; ***P = .0002 for pMIEG3-Klf4 versus pMIEG3. Error bars represent SEM. Statistics were analyzed using the 2-tailed, unpaired, Student t test.
