Fig. 1. The mont blanc (mob^m610) mutation affects zebrafish craniofacial development. (A,B) Lateral view of wild-type (A) and mob^m610 (B) live embryos at 4 dpf. In mob^m610 embryos the Meckel's cartilage is pointing ventrally and the posterior arches are missing (arrowheads point to the anterior and posterior tips of the Meckel's cartilage). The heart develops an edema. (C,D) Ventral view of Alcian Blue stained heads visualizes the craniofacial skeleton of wild-type (C) and mob^m610 (D) embryos at 4 dpf. Cartilage elements corresponding to second and posterior arches are severely reduced. bh, basihyal; cb, ceratobranchial; ch, ceratohyal; ep, ethmoid plate; h, heart; hs, hyosymplectic; m, Meckel's cartilage; pq, palatoquadrate. (E,G) Wild-type and (F,H) mob^m610 embryos at 4 dpf. (E,F) Ventral view of cranial musculature; muscles of second and posterior arches are disorganized in the mutant. The asterisk marks the area of ceratobranchial muscles. (G,H) At higher magnification, a lateral view of the head reveals that a number of dorsal muscles are missing in mutant embryos (arrow in F,H). ah, adductor hyomandibulae; am, anterior mandibularis; ao, adductor opercule; do, dilator operculi; hh, hyohyoideus; ih, interhyoideus; ima, intermandibularis anterioris; imp, intermandibularis posterioris; lap, levator arcus palatini; sh, sternohyoideus.