Fig. 8. Cell-autonomous role of Fgfr1 during anterior migration of axial mesoderm cells in the medaka. (A) Schematic illustration of the shield transplantation experiment. Donor cells were labeled by both rhodamine-dextran and biotin-dextran. The migrating ability of the transplanted cells was then assayed at the bud stage (st. 18) by assessing the position of the anterior limits of the labeled cells (indicated by the arrow). (B-G) Lateral views of the representative transplanted embryos. Anterior is to the left. Rhodamine-labeled cells in the live embryos (B-D) or biotin-labeled cells in the fixed embryos (E-G) contribute to the axial mesoderm in the host embryos. (B,E) Donor, wild type; host, wild type. Transplanted cells reach the most anterior mesoderm region. (C,F) Donor, MZ mutant; host, wild type. The anterior limit of the migrating cells shifts posteriorly compared with the control transplant in B,E. (D,G) Donor, wild type; host, MZ mutant. The anterior limit of the transplanted cells is located at the most anterior region. Arrowheads indicate the positions of the anterior limits of the migratory cells. (H-S) Cross sections of the anterior neural regions. (H-M) Cross sections at the level of the eye vesicle region (indicated by the dashed lines, a, in E-G). (N-S) Cross sections at the level of the hindbrain region (indicated by the dashed lines, b, in E-G). (K-M,Q-S) Higher magnification of the dashed boxes shown in H-J and N-P, respectively. Biotin-labeled cells contribute to the prechordal mesoderm in the host embryos (arrowheads in K-M and Q-S). Scale bars: 100 µm in B,E; 50 µm in H,N; 10 µm in K,Q.