Fig. 7. Contribution of node-derived cells to the notochord. (A) EGFP-expressing cells transplanted to the node of the early-bud stage embryo (t=0 hour). (B) Posterior displacement of the grafted cells and the formation of a trail of notochordal as the node is drawn posteriorly as the primitive streak regresses (t=12 hours after grafting). (C) lacZ-expressing graft-derived cells in the notochord of the early-somite stage host embryo (24 hours after grafting). (D) A histological section of the embryo at the plane indicated by the broken line in C showing the colonization of the notochord (nc) and the ventral neural tube (nt) by the graft-derived cells. (A,B) Lateral view, anterior towards the left; (C) dorsal view, anteriorwards to the top. Scale bar in A, 150 µm in A,B and 50 µm in C,D.