Fig. 2

Comparative expression pattern of Osr genes and tbx5a during pectoral fin development. All panels show the dorsal view of zebrafish embryos with the anterior towards the left after whole-mount in situ hybridization using riboprobes indicated. (A-C) At 7 somites, osr1 is expressed in the IM (A, arrowhead) adjacent to the LPM domain expressing tbx5a (C, arrow). At this stage, osr2 is observed only in the posterior IM (arrowheads in A and B insets). (D-F) At 12 somites, osr1 and osr2 are found in the kidney anlage (D,E, arrowheads) medial to the fin precursor territories showing tbx5a expression (F, arrow). Asterisk in D shows a lateral displacement of osr1 expression in the posterior IM. (G-I) The same situation is observed at 24 hpf. (J-L) At 48 hpf, osr1 expression is detected very weakly in the fin bud (J), whereas osr2 is found in two patched domains within the tbx5a-expressing territory (K, arrowheads). (M-O) At 72 hpf, osr2 is expressed in a broader domain (N) overlapping with most of the tbx5a-expressing territory (O), whereas osr1 expression occurs only in small patches in the developing limbs (M, arrowheads). hpf, hours postfertilization; s, somites.