Abstract
Axolotl digits offer an experimentally versatile model for studying complex tissue regeneration. Here, we provide a comprehensive morphological and molecular characterization of digit regeneration, revealing both conserved features and notable divergences from classical limb regeneration. Digit blastemas progress through similar morphological stages, are nerve-dependent, contain key regenerative cell populations, and express many canonical morphogens and mitogens. However, they exhibit minimal expression of the A–P patterning genes Shh, Fgf8, and Grem1; suggesting distal outgrowth and patterning occur independently of these signals. Joint regenerative fidelity varies significantly across digits and cannot be explained by differences in nerve supply, cell proliferation, or differential expression of any patterning genes assessed in this study. Furthermore, functional experiments reveal Hedgehog signaling is essential for interphalangeal joint regeneration, but activation alone is insufficient to improve fidelity in less robust digits. This system combines experimental accessibility with intrinsic variation in regenerative outcomes, making it an ideal platform to identify critical determinants of successful tissue regeneration and refine models of appendage patterning.
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Data availability
All data generated and analyzed during this study are included in this published article and its supplementary source data files.
Code availability
All custom code generated for the analysis of datasets within this manuscript is available for public access on GitHub via this link: https://github.com/Monaghan-Lab/digitPaper.
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Acknowledgements
The authors thank Guoxin Rong and the Institute for Chemical Imaging of Living Systems (RRID:SCR_022681) at Northeastern University for consultation and instrument support. We also appreciate Alex Lovely and the Harvard Center for Biological Imaging (RRID:SCR_018673) for infrastructure and support. The Ambystoma Genetic Stock Center at the University of Kentucky, supported by the NIH (P40-OD019794), is recognized for providing animals for this study. Funding for this work was provided by NIH grant R01HD099174 and NSF grants 2318594 and DGE-1938052.
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J.R.G. and J.R.M. conceived the project. J.R.M. secured funding and supervised the project. J.R.G. performed all experiments and analyses, with assistance from T.J.D. for qRT-PCR data. A.E.O. assisted in cell cycle phase analysis. M.M. assisted in data analysis and visualization. J.R.G. led the writing of the manuscript with input and approval from all authors.
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Griffiths, J.R., Miller, M., Duerr, T.J. et al. A characterization of axolotl digit regeneration: conserved mechanisms, divergent patterning, and a critical role for hedgehog signaling. npj Regen Med (2026). https://doi.org/10.1038/s41536-026-00461-2
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DOI: https://doi.org/10.1038/s41536-026-00461-2
