Development of a model system to study the regulation of patterning competency in regenerating axolotl limbs

Abstract

Abstract Limb regeneration in the Mexican axolotl requires the dedifferentiation of mature limb cells into progenitor cells known as blastema cells. The blastema cells become competent to the signals that inform the blueprint, or pattern, of the regenerating cells to organize into the complex limb structures. Signaling downstream of the limb nerves plays a role in the induction of patterning competency; however, the underpinnings of this process are poorly understood. Studying patterning competency in amputated axolotl limbs is challenging because the complex network of signals and tissue interactions that occur during regeneration are activated. Here, we address this issue by developing an assay that we call the competency accessory limb model (CALM) assay, which is based on a simplified limb injury model where various signaling inputs can be systemically added and their individual contributions to patterning competency can be evaluated independently. We used the CALM as a platform to generate foundational knowledge by characterizing the specific timing of competency induction and maintenance and identifying nerve-dependent signals sufficient for induction and epigenetic modifications induced in wounded cells by these signals.