Fig. 4. Mesoderm induction in the MZ hdf (fgfr1) medaka mutant. (A-P) Expression of the early mesoderm markers, no tail (ntl) (A-D) and fgf8 (E-H), dorsal mesoderm marker, chordin (I-L), and the Fgf-downstream target, sprouty4 (M-P), in each of the indicated types of hdf (fgfr1) mutant at the early gastrula stage (50% epiboly, st. 15). Dorsal (upper) and lateral (lower) views of the same embryo are shown in A-D, E-H and M-P. Arrows indicate the organizer region; arrowheads in N indicate weak expression of sprouty4. The embryos of each genotype express ntl (A-D), fgf8 (E-H) and chordin (I-L) in the blastoderm margin. (Q-V) ntl and sprouty4 expression in SU5402-treated embryos at the early gastrula stage (50% epiboly, st. 15). Embryos were treated with SU5402 at concentrations of 0 (2% DMSO) (Q,T), 0.05 (R,U), and 0.1 mg/ml (S,V) from morula to 50% epiboly. The level of ntl expression persisted at the 0.1 mg/ml concentration, whereas sprouty4 expression was undetectable. M; maternal; MZ; maternal zygotic fgfr1 mutants; WT, wild type; Z, zygotic.