Developmental Biology

A Tail of ROS

Science Signaling  12 Feb 2013:
Vol. 6, Issue 262, pp. ec37
DOI: 10.1126/scisignal.2004050

Signaling mediated by the Wnt pathway enables Xenopus tadpoles to regenerate their tails. Various genes involved in the production of reactive oxygen species (ROS) are expressed during regeneration. Love et al. found that H2O2 was required for tail regeneration and induced a signaling cascade that was separate from pathways required for wound healing. Analysis with either a fluorescence reporter for H2O2 or H2O2-sensitive fluorogenic dyes in vivo revealed an increase in intracellular H2O2 concentration that peaked within 1 hour of amputation and remained high during tail regeneration. H2O2 production preceded the recruitment of inflammatory cells to the site of injury. Morphant tadpoles deficient in spib (a lymphoid cell–specific transcription factor) had diminished numbers of inflammatory cells in the regenerative bud tissue but similar intracellular concentrations of H2O2 to controls, indicating that amputation-induced ROS was produced by noninflammatory cells. Treatment with either diphenyleneiodonium (DPI) or apocynin (APO)—chemicals that inhibit the NADPH oxidase (NOX) complex—reduced ROS concentration, impaired tail regeneration, and decreased the number of proliferating cells to a greater extent than did treatment with the antioxidant MCI-186 (MCI). Removal of MCI, but not DPI or APO, restored tail regeneration. Furthermore, amputation-induced Wnt–β-catenin signaling and expression of a downstream transcriptional target fgf20 were reduced after amputation in DPI-, APO-, or MCI-treated tadpoles. Morphant tadpoles deficient in the NOX complex subunit cyba (cytochrome b-245 α polypeptide) showed defects in H2O2 production and tail regeneration similar to those in DPI- or APO-treated tadpoles. Morphant tadpoles deficient in fgf20 could heal the wound at the amputation site but failed to fully regenerate tails and showed specific defects in axial tissue regeneration. Together, the findings indicate that NOX complex–induced ROS signaling is critical to initiate regeneration and facilitates signaling through the Wnt–β-catenin–fgf20 pathway.

N. R. Love, Y. Chen, S. Ishibashi, P. Kritsiligkou, R. Lea, Y. Koh, J. L. Gallop, K. Dorey, E. Amaya, Amputation-induced reactive oxygen species are required for successful Xenopus tadpole tail regeneration. Nat. Cell Biol. 15, 222–228 (2013). [PubMed]