Fig. 4. snail1b expression is excluded from the hgg1 expression domain within the axial mesendoderm. (A). Dual fluorescent in situ hybridisation demonstrates that snail1b expression is excluded from the hgg1-positive prechordal plate cells. The domains occupied by the two populations have ill-defined borders (B). (C) Sagittal sections of the embryo shown in A (dotted line) reveal the intermingling of the adjacent cell populations. Inset: border region at higher magnification. (D) At the tailbud stage, the cells have sorted out and a sharp boundary is defined. (E-G) The hgg1-positive prechordal plate cells also express cdh1 transcripts.