Hedgehog family member is expressed throughout regenerating and developing limbs

Members of the hedgehog family have been shown to play a key role in many developmental processes, including limb patterning and chondrogenesis. We have therefore investigated whether members of this family are also expressed during regeneration of the adult urodele limb and are regulated by retinoic acid (RA), since this derivative induces proximodistal duplications in regenerating limbs, and has been shown to regulate sonic hedgehog (shh) in the developing limbs of birds and mammals. We report here that a newt homologue of Xenopus banded hedgehog, called N-bhh, is uniformly expressed by mesenchymal blastemal cells from the initial stages of regeneration and is up-regulated by RA. In addition, we show that N-bhh is uniformly expressed in the early limb bud of the newt embryo. Since bhh has not been detected in developing limbs of higher vertebrates, its expression in developing and regenerating newt limbs may be related to the regenerative capability of urodeles.