Evidence of requirement for homologous‐mediated DNA repair during Ambystoma mexicanum limb regeneration

Background Limb regeneration in the axolotl is achieved by epimorphosis, thus depending on the blastema formation, a mass of progenitor cells capable of proliferating and differentiating to recover all lost structures functionally. During regeneration, the blastema cells accelerate the cell cycle and duplicate its genome, which is inherently difficult to replicate because of its length and composition, thus being prone to suffer double‐strand breaks. Results We identified and characterized two remarkable components of the homologous recombination repair pathway (Amex.RAD51 and Amex.MRE11), which were heterologously expressed, biochemically characterized, and inhibited by specific chemicals. These same inhibitors were applied at different time points after amputation to study their effects during limb regeneration. We observed an increase in cellular senescent accompanied by a slight delay in regeneration at 28 days postamputation regenerated tissues; moreover, inhibitors caused a rise in the double‐strand break signaling as a response to the inhibition of the repair mechanisms. Conclusions We confirmed the participation and importance of homologous recombination during limb regeneration. The chemical inhibition induces double‐strand breaks that lead to DNA damage associated senescence, or in an alternatively way, this damage could be possibly repaired by a different DNA repair pathway, permitting proper regeneration and avoiding senescence. Key Findings A. mexicanum possesses true homologs for Rad51 and Mre11. B02 and Mirin chemicals inhibit Amex.RAD51 and Amex.MRE11 respectively. B02 and Mirin provoke an increase in DNA damage during regeneration. B02 produces an increase in the number of senescent cells during regeneration.