Expression of five homeobox genes in the adult newt appendages and regeneration blastemas.

Many animals are able to replace large sections of their body by the process of epimorphic regeneration, although this ability is distinctly circumscribed in higher vertebrates for reasons that are not understood. However, urodele amphibians (such as newt) is one class of vertebrate that keeps the capacity to regenerate their limbs and tail in adulthood. We investigated whether the molecular mechanisms controlling newt limb regeneration were having similarities to those involved in the initial formation of the structure during development. We found that the expression of many homeobox genes is sustained in the tissue of the adult newt. Moreover, some of these genes showed a marked increase of their expression during limb regeneration and a graded level of expression along the limb. Here we review the cloning, the molecular analysis and the expression pattern of the NvHBox-2.7, -3, -4, -5 and -6 genes in the adult newt. The results are discussed in relation to the putative function of these genes in regeneration.