Fig. 1

Effects of RA on shh/vhh-1 expression and pectoral fin bud development. Embryos were treated with 1 x 10^-6M RA (B, D, E, G, and H) in 0.5% DMSO for a period of 2 hr at 24 hr postfertilization. Controls (A, C, and F) were incubated in 0.5% DMSO for the same period of time. RA-treated and control embryos and larvae were fixed at 48 hr (A and B), 56 hr (C and D), and 72 hr (E, F, G, and H). The normal pattern of shh/vhh-1 expression in the posterior part of the pectoral fin bud is indicated by an arrow. Ectopic shh/vhh-1 expression is indicated by an arrowhead. The rotation of the pectoral fin bud that normally occurs during the third day of development (compare A and C) does not occur in RA-treated embryos (B, D, and E). RA-treated embryos show a swelling of the pharyngeal arch region (open triangles in B, D, and E). (A-D) Dorsal views; (E) lateral view with anterior to the left. (F-H) Dissected pectoral fin buds. (H) Caudal view of a fin comparable to that shown in (G) and which shows the thickening of the fin at the base (dotted line). Scale bars (A-E), 100 μm; (F-H), 50 μm.