Sonic Hedgehog Signalling in the Developing and Regenerating Fins of Zebrafish

Abstract

Zebrafish is now a well established model for the study of developmental and regenerative processes. Indeed, the genetic cascades that control the early development of the structure that will form the paired fins (the fin bud) present similarities with the early formation of the tetrapod fore and hindlimb buds. One of these conserved molecular pathways involves secreted factors of the Hedgehog family [sonic hedgehog (shh) and tiggywinkle hedgehog (twhh)]. As in the tetrapod limbs, hedgehog proteins are initially expressed in the posterior region of the early fin bud where they contribute to the patterning of the antero-posterior axis, then are involved in cell proliferation and the formation of various skeletal elements. The hedgehog pathway is reactivated in adult fish following fin amputation, an event that triggers the regeneration program. During this process, the hedgehog signal is involved in various processes such as the growth and maintenance of the blastema and patterning of the fin ray.