Expression of Tgf-beta in the regenerative process of crinoid echinoderms

For many years, we focused our studies on the remarkable power of regeneration exhibited by crinoid echinoderms. Current investigations are exploring the aspects related to the 'putative' growth factors crucial for the regenerative process in crinoids. Due to its importance in wound healing phenomena of vertebrates and invertebrates, both in the embryo and in adults, the present study concentrates on the possible presence/expression and roles of TGF-β in arm regeneration processe of the crinoid Antedon mediterranea. This problem has been explored by employing 1) a biochemical and immunocytochemical approach, which allowed us to detect the presence of TGF-β1 and its putative changes of pattern distribution during the regeneration process; 2) a molecular approach, thanks to which we cloned a BMP2/4 homologue from crinoids (AnBMP2/4) confirming the possible presence of different genes of the TGF-β superfamily. Expression studies indicate an important role for AnBMP2/4 during the more advanced stages of regeneration at a time when new tissues are being established and the brachial nerve is extending into the regenerate. This expression in an ‘adult’ regenerating system shows remarkable parallels with recent investigations in sea urchin embryos where a BMP2/4 homologue is involved in the regulation of the ectoderm/endoderm boundary and epidermal/non epidermal fate decisions. Our results suggest in particular that AnBMP2/4 plays an important role in crinoid skeletogenesis as well as in neurogenesis and support the idea of an evolutionary developmental programme where essential gene families are conserved throughout phylogeny both in terms of expression and function. The future employment of techniques such as RNA interference or bead implantation, in adult echinoderms, will be of fundamental importance to understand the function of AnBMP2/4 and other related genes.