Fig. 4

Fig. 4 Morphological characterization of the ventralized boz mutant phenotype. (a) Animal pole view of wild-type embryo at the onset of gastrulation (6 hpf). A condensation of cells (arrowhead) denotes the forming shield on the dorsal side of the embryo. (b) Severely affected homozygous boz^m168 mutant embryos fail to form a shield. (c and d) Dorsal views of wild-type and homozygous boz^m168 mutant embryos, respectively, at 12 hpf. Anterior is toward the top. In wild-type embryos the notochord (arrowhead) is present in the midline separating the lateral blocks of somites (arrow) (c). In homozygous boz^m168 mutant embryos (d), the notochord is absent, and the somites are fused across the dorsal midline. (e and f) Optical section of the embryos in (c) and (d), respectively, at the level of the first somite. View is from the anterior. The notochord (arrowhead) is present in wild-type embryos (e) and absent in homozygous boz^m168 mutant embryos (f). (g and h) Profiles of wild-type and homozygous boz^m168 mutant embryos, respectively, at 26 hpf. Anterior is to the left. Dorsal midline structures such as notochord and floorplate (arrow) are present in wild-type embryos (g), but lacking in homozygous boz^m168 mutant embryos (h). (i and j) Profile view of the head region of wild-type and homozygous boz^m168 mutant embryos, respectively, at 26 hpf. (j) Homozygous boz^m168 mutant embryos often lack differentiated eyes (arrowhead) and display a loss of rostral forebrain neural fates and aberrant patterning of the midbrain region (arrow).