A, C, E, G, I, K wild-type embryos, B, D, F, H, J, L hdac1b382 mutants. A, B Dorsal view of embryos at 25 hpf with dlx2 expression labeling the mandibular, hyoid and branchial arch precursor populations. C, D Lateral views of the head region at 25 hpf of crestin expression in the head region, black arrowheads indicate branchial arch populations. E, F, Lateral views of the head region at 25 hpf of hoxb3a expression in the hind-brain and branchial arch precursors. G, H, Lateral views of the head region at 96 hpf of col2a1 expression in mandibular, hyoid and branchial arches. I, J, Lateral views of the head region at 56 hpf of TUNEL-positive staining in the head and jaw regions. K, L, Side views of the head region at 32 hpf with tbx1 expression highlighting the endodermal pouches. M, mandibular; H, hyoid; BA, branchial arches.