fgfr1a, fgfr1b, and fgfr2 function redundantly to regulate viscerocranial development. (A–C) Lateral views of 5 dpf wild-type (WT, A; n = 12), fgfr1a−/−;fgfr1b−/− (n = 3)/fgfr1a−/−;fgfr1b−/−;fgfr2+/− (B; n = 6), fgfr1a−/−;fgfr1b−/−;fgfr2−/− (C; n = 7) mutant larvae. (A′–C′′) Alcian blue cartilage stains of 5 dpf larvae; arrowheads noting corresponding jaw features between the live larvae in (A–C) and lateral view cartilage mounts in (A′–C ′); m, Meckel’s cartilage; pq, palatoquadrate; hs, hyosymplectic; ch, ceratohyal; op, operculum; cb 1–5, ceratobranchials; t, teeth. (D–F) Pharyngeal arch (D and E) and pouch (F) marker analysis of fgfr double and triple mutant embryos at the 18-somite stage (dlx2a in purple/krox20 in brown labeling rhombomeres 3 (R3) and 5 (R5); D) and 24 hpf (dlx2a, E; alcama; F). Whole mount in situ hybridization was performed, embryos were scored for expression, and genotypes were determined post hoc. All embryos had indistinguishable dlx2a expression at the 18-somite stage (D; n = 7, 26, 6, for WT, fgfr1a−/−;fgfr1b−/−, and fgfr1a−/−;fgfr1b−/−;fgfr2−/−, respectively). In (E and F), the percentage of embryos expressing particular levels of each marker gene is represented in a stacked column chart on the left (sample size for each genotype is listed at the top of each bar), and representative images of those expression levels are shown for each marker to the right (dorsolateral views, rostral to the left and dorsal up; pharyngeal arches (E) and pouches (F) are labeled 1–4. Bars: in (C), 100 μm for (A–C); in (C′′), 100 μm for (A′–C′′); in (D), 50 μm; in (E), 100 μm for (E and F). abs., absent; Ant., Anterior arches/pouches; in (F), ov, otic vesicle; Post., Posterior arches/pouches.
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