Expression of aldh1a2 in wild-type pectoral fins. Whole-mount in situ hybridizations. Anterior is towards the left: dorsal (A) and lateral views (B-F). Pectoral fin buds at 28 hpf (A,B), 32 hpf (C), and 2, 3 and 5 dpf (D-F). (A,B) aldh1a2 is expressed in the posterior part of developing pectoral fins and adjoining lateral plate mesoderm; bracket demarcates the fin proper. (C,D) aldh1a2 expression is restricted to the fin mesenchyme. (E,F) From 3 dpf onwards, expression is restricted to the proximal, anterior and distal margins of the mesenchyme, and is downregulated in the distal margin by 5 dpf. Scale bars: 100 µm.