Axial differences in cellular regeneration responses in the annelid Capitella teleta

Regeneration abilities vary among species, but they also vary within and across individuals of a single species. Many annelids (segmented worms) have variable regenerative ability along their anterior-posterior (AP) body axis. However, satisfactory explanations for the diverse regenerative outcomes at different amputation positions remain elusive. The annelid Capitella teleta demonstrates robust posterior regenerative ability but lacks anterior regenerative ability, although anterior regenerative ability has not been rigorously assessed at multiple amputation sites. In this study, we characterize regenerative ability along the AP axis of C. teleta by comparing the post-amputation response of tail fragments cut between segments 1 and 2, 4 and 5, 10 and 11, and 15 and 16. Cell proliferation, gene expression, and protein expression assays demonstrate that the anterior-most amputation site progresses to later stages of regeneration than more posterior amputation sites, but regeneration does not reach completion. The distribution of neoblast-like cells after amputation suggests that these cells do not substantially contribute to formation of the anterior-facing blastema. Additionally, regeneration outcome is not improved following activation of Wnt/β-catenin signaling in tail fragments amputated between segments 1 and 2. Conversely, inhibition of Wnt/β-catenin signaling at the same amputation position leads to increased regenerative ability with distinct phenotypes consistent with anterior regeneration. Although not all differentiated anterior structures form, this result hints at partial anteriorization. Taken together, our data show the value of comparing regenerative abilities of tissues within an individual organism and demonstrate potential of increasing regenerative ability in regeneration-deficient tissues.