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Fig. 4 sall1a is essential for pectoral fin development. (A,B) sall1a expression during wild type pectoral fin development. (A) Dorsal view of a 26 hpf embryo with red arrows indicating the pectoral fin primordia. (B) Lateral view of a 40 hpf pectoral fin showing sall1a expression in the fin bud. (C) Dorsal view of a 3 dpf embryo injected with 5 ng of sall1a MO. The pectoral fins are truncated as highlighted by red arrows (compare with wild type in Fig. 1F). The percentages of phenotypes observed at 3 dpf following injection of 5 ng and 10 ng of sall1a MO are shown in the table. (D,E) Alcian Blue stained pectoral fins of 5 dpf embryos injected with 2 ng of sall1a MO show that pectoral fin development is disrupted in sall1a morphant embryos (compare with wild-type pectoral fin in Fig. 1L). (F) A lateral view of fgf10 expression at 40 hpf in an embryo injected with 5 ng of sall1a MO. The expression of fgf10 is most profoundly affected in the posterior fin bud (compare with Fig. 3C). (G) sall1a is not expressed in the pectoral fin primordia (red arrows) of embryos injected with 4 ng of tbx5 MO. (H,I) Dorsolateral views show that sall1a (red brackets) continues to be expressed in the pectoral fin primordia of embryos injected 9 ng of fgf24 MO (H), but is in a diffuse pattern when compared with the expression of sall1a in wild-type primordia (I). (J,K) Dorsal views of fgf10 expression at 26 hpf in the fin primordia (as indicated with red arrows) of a wild-type embryo (J) and an embryo injected with 5 ng of sall1a MO (K). (L,M) Expression of the ectodermal fin bud markers sp9 (L) and dlx2 (M) are downregulated in the posterior fin bud ectoderm of embryos injected with 5 ng of sall1a MO (black arrowheads) but continue to be expressed in the anterior fin bud (red arrowheads; compare L with wild-type expression in Fig. 5C, and M with Fig. 3G).