To regenerate or not to regenerate: Vertebrate model organisms of regeneration‐competency and ‐incompetency

Funder: École Polytechnique Fédérale de Lausanne; Id: http://dx.doi.org/10.13039/501100001703
Funder: Medical Research Council; Id: http://dx.doi.org/10.13039/501100007155
Funder: Wellcome Trust; Id: http://dx.doi.org/10.13039/100010269
Funder: Wellcome; Id: http://dx.doi.org/10.13039/100010269
Funder: EPFL; Id: http://dx.doi.org/10.13039/501100001703
Why only certain species can regenerate their appendages (e.g. tails and limbs) remains one of the biggest mysteries of nature. Unlike anuran tadpoles and salamanders, humans and other mammals cannot regenerate their limbs, but can only regrow lost digit tips under specific circumstances. Numerous hypotheses have been postulated to explain regeneration‐incompetency in mammals. By studying model organisms that show varying regenerative abilities, we now have more opportunities to uncover what contributes to regeneration‐incompetency and functionally test which perturbations restore appendage regrowth. Particularly, Xenopus laevis tail and limb, and mouse digit tip model systems exhibit naturally occurring variations in regenerative capacities. Here, we discuss major hypotheses that are suggested to contribute to regeneration‐incompetency, and how species with varying regenerative abilities reflect on these hypotheses.