Fig. 7.

Rhombomere patterning is established but not maintained in mind bomb mutants. All panels show dorsal views with anterior to the left. Asterisks identify the otocyst. A–D: At 16.5 hours postfertilization (hpf; A,B) and 20 hpf (C,D), krox20 is expressed normally in rhombomeres 3 and 5 (r3 and r5) in wild-type (WT) and mutant embryos, even though huC-expressing cells are greatly increased in the mutant hindbrains (B,D). By 20 hpf, the ventricular surface (arrow) and lumen (arrowhead) are well developed in the wild-type embryo (C) but are poorly developed in the mutant (D). E,F: In a mib mutant (F), krox20 expression in r3 and r5 is absent, while hoxb1a expression in r4 is maintained but greatly reduced, compared with a wild-type sibling (E). In addition, the ventricle (arrowhead) seen in the wild-type embryo is missing in the mutant. tg, trigeminal ganglion.