Fig. 6. VG1+TSK can bypass the inhibition by the primitive streak. (A) Grafting a pellet expressing VG1 into the lateral margin of pre-streak stage embryos. Six hours later: (top) a second pellet expressing VG1, TSKA, TSKB, chordin, Nodal or FGF8B; (middle) a combination; (bottom) VG1+chordin + TSKA or TSKB were implanted into the opposite side. (B-D) A pellet of VG1 (B, purple), TSKA (C, pink) or TSKB (D, orange) was implanted into the opposite site. (E-H) A second pellet of VG1 (E-H, purple) and a pellet of TSKA (E, pink), TSKB (F, orange), Nodal (G, blue) or chordin (H, green) were implanted together into the opposite side. (I,J) When VG1 (purple) is implanted laterally, followed 6 hours later by a pellet of cells expressing VG1 (I,J; purple), chordin (I,J, green) and TSKA (I, pink) or TSKB (J, orange) on the opposite side, the combination of VG1+chordin and TSKA or TSKB can induce an ectopic primitive streak. VG1 was used as a probe for in situ hybridization to indicate the cell aggregates expressing VG1 (arrows) in I,J.