gms | German Medical Science

Objective: We want to understand how injury-induced signaling molecules activate and guide neural progenitors to initiate the organized posteriorward outgrowth of the spinal cord neuroepithelium

Method: Spinal cord electroporation, laser scanning confocal microscopy

Results: After amputating the tail of an axolotl, those neural progenitors located in the 500µm adjacent to the injury site are called upon to reconstruct the spinal cord. We found that one of the earliest molecular events triggered by injury is the expression of non-canonical Wnts, Wnt5A and Wnt5B, and the planar cell polarity (PCP) component Prickle1 (Pk1), in this particular region. Using confocal microscopy, we analyzed mitotic cells in three dimensions during regeneration and observed preferential alignment of mitotic spindles parallel to the antero-posterior axis of the animal at the Pk1-positive region. To test whether PCP controls this orientation, we generated mosaic clones of Pk1-overexpressing cells in wild-type spinal cords. We found that Pk1-overexpressing cells divide in a randomized manner, suggesting a key role of PCP signaling in polarizing cell divisions. To study the overall effect of PCP in the spinal cord, we overexpressed another core PCP component, Van Gogh-like 2 (Vangl2), which non-autonomously randomizes PCP in overexpressing and neighboring cells. We observed that the the outgrowth of Vangl2-overexpresing spinal cords is signnificantly delayed during regeneration.

Conclusions: Altogether, we have established a link between injury and cell stress to induction of regeneration associated signalling that organizes the Wnt5-dependent posteriorward outgrowth of the regenerating axolotl spinal cord.