Fig. 6. Impaired development of the prechordal plate in the MZ hdf (fgfr1) medaka mutant. (A-D) Sagittal sections of the bud-stage (st. 18) embryos hybridized with a gooescoid (gsc) probe that stains the prechordal plate. Anterior head region (anterior to the left) is shown. Arrows indicate the expression domain of gsc (i.e. the prechordal plate) underlying the neural epithelium. Note that in the MZ embryo (D), the expression domain of gsc does not cover the entire anterior head region but is prematurely terminated. (E,F) Early migration of the prechordal plate at 50% epiboly (st 15). Dorsal views of maternal (E) and MZ (F) embryos stained with a gsc probe. (E',F') Sagittal sections through the dorsal midline of the embryos shown in E and F. Dashed lines in E',F' represent the border between the epiblast (EP, the future neural epithelium) and the migrating axial mesoderm (arrows). Scale bars: 100 µm in A-D; 50 µm in E',F'. M; maternal; MZ; maternal zygotic fgfr1 mutants; NE, neural epithelium; WT; wild type; Z, zygotic.