suc/et-1 is required for later mesodermal and endodermal patterning in the pharyngeal arches. (A-D) myoD expression at 54 hours in wild types (A,C) and suc/et-1 mutants (B,D). In mutants, the mouth is displaced ventrally, and the ventral myoD-expressing premyogenic condensations in arches 1 and 2 are absent. (E-H) Larval muscles at 5 days detected with the 1025 antibody to muscle myosins in wild types (E,G) and suc/et-1 mutants (F,H). In mutant larvae, ventral muscles are severely mispatterned. The first arch ventral muscles, intermandibularis anterior and posterior (ima and imp), are missing in suc/et-1 mutants, other than a few occasional fibers spanning the midline. The ventral arch two muscles, interhyoideus and hyohyoideus (ih and hh), are dramatically shorter and do not meet in the midline as they do in wild-types (E-F). Dorsal muscles (am, lap, do, ao) appear normal in suc/et-1 mutants. (I-L) shh expression in wild types (I,K) and suc/et-1 mutants (J,L) at 54 hours. (I,J) Anterior views, focused deep to the mouth at the level of the first pharyngeal pouch, (K,L) lateral views. In mutants, expression in the first pharyngeal pouch does not extend as laterally as in wild types (arrows in I and J) and a midline diverticulum has not formed (arrows in K and L). am, adductor mandibulae; ao, adductor operculi; do, dilator operculi; h, heart; ih, interhyoideus; ima, intermandibularis anterior; imp, intermandibularis posterior; hh, hyohyoideus; lap, levator arcus palantini; p, pharynx; sh, sternohyoideus; tv1-4, branchial muscles transversus ventralis 1-4 (see Schilling and Kimmel, 1997 for wild-type muscle description). Scale bars: 50 μm.
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