Fig. 2

Expression patterns of some marker genes during development of the median fin fold. Expression patterns of dlx5a (A–E), sp9 (F–J), and fgf24 (K–O): lateral view (B–E, G–J, and L–O) with head toward the left, and tail view (A, F, and K) with dorsal midline toward the top. Insets in panels M–O show higher magnifications focused on the dorsal half of the tail bud corresponding with the region in panels M–O, respectively; lateral view with rostral to the left. Arrowheads indicate the rostral border of the expression domain. Dots indicate the 8th somite level. (A) dlx5a was expressed around the tail bud and in the epidermal cells juxtaposed with the neural keel at 16 hpf. (B) At this stage, dlx5a expression was seen on the dorsal midline at the 8th somite level and caudally. (C–E) The rostral border of the dlx5a expression domain remained around the 8th somite level at 18 hpf (C), 21 hpf (D), and 24 hpf (E). (F, G) At 16 hpf, sp9 expression was observed in neural tissue (indicated by the bracket) and non-neural epidermis around the tail bud. At this stage, sp9 expression was restricted to the tail bud, and the more anterior dorsal midline was sp9-negative. (H–J) The rostral border of the sp9 expression domain expanded toward the head as development proceeded and the tail bud elongated. Compare the position of the arrowhead with the position of the 8th somite indicated by a dot. (K, L) fgf24 expression was seen in the mesenchyme of the tail bud and intermediate mesoderm at 16 hpf. (M–O and insets) fgf24 expression in the epidermal cells was always restricted to the midline of the tail bud, and there was no expansion of the expression domain of fgf24. Scale bars are 250 μm in panels B, C, and E and 125 μm in panel D.