The Gene Expression Patterns of the Canonical Wnt/β-catenin Signaling Pathway Related Genes during Anterior Regeneration in Aeolosoma viride

Aeolosoma viride, a fresh water annelid, has been used as an animal model for regeneration study. After decapitation, in which the anteriormost 4 segments including the brain were removed, A. viride can regenerate its lost parts within five days. Among many physiological pathways, the canonical Wnt signaling pathway is known to play roles not only in development and stem cell fate determination but also in regeneration. In this study, genes encoding four different components of Wnt signaling pathway, Avi-wnt4, Avi-wnt8, Avi-β-catenin and Avi-notum, have been cloned. All of them were expressed in the newly regenerating cell mass, the blastema. In addition, this pathway exerts its effect by nuclear import of β-catenin, functioning as a transcription co-activator, it was demonstrated that β-catenin indeed localizes into the nucleus in cells of blastema during regeneration. This result indicates that the pathway is in an on state during A. viride regeneration. Furthermore, after treated with XAV939, a Wnt pathway inhibitor, the anterior regeneration of A. viride was obviously inhibited. This result supports that Wnt pathway is indispensable for proper head regeneration in A. viride. However, after treated with azakenpaulone, a Wnt pathway activator, the anterior regeneration of A. viride was also obviously inhibited. However, the inhibitory effects of XAV939 and azakenpaulone took place at different time points. Therefore, it can be inferred that the canonical Wnt signaling pathway is regulated differently in the regeneration process of A. viride. That is, this pathway should be inactivated at the beginning, and then be activated at late during the anterior regeneration.