Expression of Wnt Genes in Echinaster Sepositus Arm Regeneration

Reparative regeneration is defined as the replacement of lost adult body parts and is a phenomenon widespread yet highly variable among animals, and thus thought to have evolved several times. This raises the question of which key molecular mechanisms have to be implemented in order to efficiently and correctly replace entire body parts. Although arm regeneration in Asteroids is a quite-well studied phenomenon, numerous important aspects have still to be defined in terms of molecular mechanisms. The present work is focused on the expression of Wnt genes in the red starfish Echinaster sepositus (Asteroidea, Echinodermata) arm regeneration. A major reason for undertaking this study is that most of these genes have been previously associated with wound healing, development and regeneration in other animal species. Here, two new Wnt genes were characterized; EsWnt1 and EsWnt4. The expression profiles of these two genes using RT-PCR showed a temporal correlation with the known cellular events. An early expression of the EsWnt1 and EsWnt4 genes was noted after 24 hours of amputation. The number of transcripts of the EsWnt4 gene decreased considerably after 72 hours and disappeared completely by the first week. Later on we observed high levels after 7 weeks of amputation. A late expression of the EsWnt1 gene was seen, at the 4th week, and remaining at low levels until the 7th week. In comparison with other organisms, the early expression of both genes suggests and involvement in wound healing and cell migration and, probably, also in the myogenesis and the establishment of antero-posterior polarity. These expression profiles support the hypothesis of the key regulatory functions of Wnt signalling pathways during embryogenesis and cellular renewal in adult regeneration.