Fig. 6. Movement of cells derived from the EGO and the MGO. (A) Serial images taken at 6 hour intervals showing the localization of the EGFP-expressing cells derived from the EGO during 30 hours of in vitro development from the ES to the early neural plate stage. At 0-6 hours, the EGO-derived cells are displaced anteriorly to the site of the MGO, followed by the dispersal of the EGO-derived cells out of the MGO (lateral and posterior view at 12 hours) laterally to the mesodermal layer and along the midline of the embryo (arrowheads at 12 hours). The EGO-derived cells are spreading anteriorly in both the paraxial and axial mesoderm under the head folds (18-30 hours). Embryos are viewed from the left side at 0, 6, 12 and 18 hours, posterior side at 12 hours, and anterior side at 24 and 30 hours. (B) The EGO-derived cells in the mesodermal (yellow fluorescent DiI-labeled cells) and axial (green fluorescent EGFP-expressing cells, arrowhead) position in the MS stage embryo colonize, respectively, the paraxial (orange-red DiI-labeled cells) and axial mesoderm (green fluorescent cells, arrowheads in C) of the early-somite stage host embryo (C,D). (B) Lateral view, anterior towards the left; (C,D) dorsal view, anterior towards the top. (E) Serial images showing the localization of the EGFP-expressing MGO-derived cells during development from the MS to the early neural plate stage. The MGO-derived cells migrate anteriorly in a tight column along the midline at 6-15 hours. After 24 hours of culture, some MGO-derived cells are in the axial mesoderm as well as underneath the anterior of the neural plate. 0-10 hours: lateral view, anterior towards the left; 15-24 hours: anterior view. Broken lines mark the distance of the MGO cells from the anterior end of the body axis. Scale bars: in E, 150 µm in A,B,E; in D, 50 µm in C,D.