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. 2015 Dec 7;112(52):15940–15945. doi: 10.1073/pnas.1521818112

Fig. 5.

Fig. 5.

Gli3 expression inversion and the mechanism of skate fin development. (A–C) Gli3 expression at stage 30 in the pectoral (A), pelvic (B), and dorsal fin (C) of skate. Gli3 is expressed in the posterior side of the pectoral and dorsal fin while it is expressed in the anterior pelvic fin. The expression in the posterior tip of pelvic fin is likely in the clasper. (D and E) Gli3 expression at stage 30 in the pectoral (D) or pelvic fin (E) of shark. Gli3 is expressed in the posterior pectoral fin and in the anterior pelvic fin, as seen in skate. (F) Summary of molecular mechanisms controlling skate unique fin development. Although the posterior genetic module is similar to that of tetrapods, the anterior genetic module is distinct. Fgf7 and 3′Hox genes are expressed in the anterior mesenchyme and induce Wnt3 expression, resulting in an extra AER-like tissue in the anterior fin. The posterior AER and anterior AER-like tissue extend the fin in posterior and anterior directions. Note that Gli3 is coexpressed with Shh and 5′Hox in the posterior fin.