Figure 7. Dual expression of sox5 and pax7a is required for xanthophore development.

(A, B) gch. (C–E, I′) pax7a. (F, G, H′) sox5. (A, F) lf mutant. (B, E, G) lf-2 mutant. (C, H, I) WT. (D) ml-3 mutant. (A–G) Lateral views. (H, I) Dorsal views. (C′, C″, D′, D″, E′, F′, G′) Transverse section. (A, B) gch expression in lf and lf-2 at 34 somite stage (34 s, 74 hpf). gch is normally expressed in lf (A), whereas in lf-2 gch-expressing cells are completely absent (B). (C–E) pax7a expression in WT, ml-3 and lf-2 at 24 somite stage (24 s, 58 hpf). In WT, pax7a is expressed in dorsal neural tube, premigratory NCCs (black arrows) in migratory NCCs between neural tube and somite and on lateral trunk surface (black arrowheads, C–C″). In ml-3, pax7a-expressing cells are lost from lateral trunk surface (D–D″). In lf-2, pax7a expression in premigratory and migratory NCCs was absent (E, E′). (F, G) sox5 expression in lf and lf-2 at 24 s. sox5 expression is normal in lf being detected in dorsal neural tube, premigratory NCCs (black arrows) and migrating NCCs between neural tube and somite and on lateral trunk surface (black arrowheads) as in WT (F, F′). In lf-2, premigratory NCC expression remains detectable, but sox5-expressing cells are lost from lateral trunk surface (G, G′). (E′–G′) The histological section from embryos at the level as indicated by dotted line in E, F and G. (C′, C″, D′, D″) Transverse sections from embryos were selected from the region boxed by dotted line in C and D. (H, I) Expression of sox5 and pax7a on dorsal trunk surface in WT at 90 hpf. (H, I) Pre-fixed WT embryos in bright field. The same embryos were processed for sox5 (H′) and pax7a (I′) ISH. Leucophores are positive for pax7a expression (I′, compare white arrowhead positions with I) but not for sox5 expression (H′). Scale bars: (A, C, E) 200 µm; (C′, E′) 20 µm; (G) 50 µm.