Fig. 7. Tests of the BMP receptor/Smad pathway in EKLF and GATA1 expression. (A) EBs were differentiated for eight days in SR1 + the indicated cytokines, and total RNA was monitored for expression of Smad1, Smad5, Smad8 or HPRT. Expression after differentiation in the presence of serum was included as a positive control, and ‘water’ indicates a no-RNA negative control. (B,C) EBs derived from stable ES cell lines expressing wild-type BMPR-1B (wild-type line 648-3) or a dominant negative BMPR-1B (K231R line 649-6) in (B), or a mock transfected (mock) or Smad6-expressing ES lines (Smad6-4 and Smad6-5) in (C), were differentiated in FBS for 8 days before the harvest of total RNA and expression analysis for hematopoietic markers described in Fig. 2. ‘Water’ indicates a no-RNA negative control.