Fig. 6. Nodal signalling can resue the pluripotency defect of Bmpr1a mutant mouse embryos. (A,B) At 4.5 dpc, Nodal is expressed in the epiblast and primitive endoderm in both control and Bmpr1a^-/- mouse embryos (n=5/5). (C,D) At 5.5 dpc, Nodal is expressed in the epiblast and visceral endoderm of controls but is severely downregulated in a proportion of Bmpr1a mutant embryos (n=2/3). (E,F) Cripto is expressed in the epiblast at 5.5 dpc of controls, but is lost in a proportion of Bmpr1a^-/- embryos (n=4/7). (G,H) At 5.5 dpc, Gdf3 expression is observed throughout the epiblast of control and Bmpr1a^-/- embryos (n=5/5). (I,J) Bmpr1a^-/- embryos display self-renewal defects when cultured in serum-free conditions and Bmp4. (K,L) 20 ng/ml activin can rescue the self-renewal defects of Bmpr1a^-/- embryos (n=5/7).