Fig. 8. Epiblast cells require hab to maintain superficial positions in the epiblast. Progeny of a single superficial cell labeled near the animal pole at the 4000-cell stage visualized at 80% epiboly in live homozygous mutants, ZMD mutants and wild-type siblings. (A) Clone in a wild-type embryo, in which all epiblast cells are located in the exterior layer. Note epithelial cell morphology of unlabeled cells. (B) Clone in a ZMD mutant, in which all epiblast cells are located in the exterior layer. (C) Rare clone in a homozygous hab mutant, in which the majority of epiblast cells are located in the exterior layer. Note the loose cell morphology of unlabeled cells. (D) Typical clone in a homozygous hab mutant, in which the majority of epiblast cells are located in the interior layer. (E) Distribution of clonal progeny in the epiblast layers of homozygous mutants, ZMD mutants and wild-type embryos. Arrows indicate examples of the large nuclei of EVL cells; diffuse staining (in D) is from thin cells of the EVL portion of the clone.