The <i>Shh</i> / <i>Gli3</i> gene regulatory network precedes the origin of paired fins and reveals the deep homology between distal fins and digits
Joaquín Letelier, Silvia Naranjo, Ismael Sospedra, Juan Ramón Martínez‐Morales, Javier López-Rı́os, Neil H. Shubin, José Luis Gómez-Skármeta
Abstract
Significance In this study, we show that the inactivation of the gli3 gene in medaka fish results in the formation of larger dorsal and paired fins. These mutant fins display multiple radial bones and fin rays which resemble polydactyly in Gli3 -deficient mice. Our molecular and genetic analyses indicate that the size of fish fins is controlled by an ancient mechanism mediated by SHH-GLI signaling that appeared prior to the evolutionary appearance of paired fins. We also show that the key regulatory networks that mediate the expansion of digit progenitor cells in tetrapods were already in place in the fins of the last common ancestor between ray and lobe-finned fishes, suggesting an ancient similarity between distal fins and digits.