Figure 3

Ectopic Wnt3a alters the movement behaviour of posterior primitive streak cells in vivo. (A) Injection of DiI (red) and DiO (green) into the anterior and posterior primitive streak followed by long-term time-lapse video microscopy shows the normal cell movement patterns of paraxial and lateral plate mesoderm progenitors. (B) A pellet of cells expressing Wnt3a adjacent to the anterior primitive streak had no effect on cell movement behaviour. (C) Implanting Wnt3a cells into the posterior streak blocked cell migration and production of lateral plate mesoderm in HH7-9 embryos. (D) Wnt3a cells implanted into the posterior streak at HH6 did not affect cell migration. (E) Graphical illustration of the effects of Wnt cell pellets on primitive streak cell behavior; grey shading indicates normal behavior, black shading indicates altered behavior. Only posterior grafts of Wnt3a altered normal movements in HH7-9 embryos. Asterisks indicate the position of the cell pellet at 0 h (B, C, D). White arrows indicate the most recently formed somite and arrowheads indicate the most anterior DiI and DiO labelled cells that have left the primitive streak.