A Model of Whole-Body Regeneration in a Larval Echinoderm

Regeneration remains one of science and medicine’s greatest mysteries. It represents an incredible feat that only manifests itself in particular metazoan taxa. Furthermore, some animals are limited to digit and limb regeneration, while others undergo extensive regeneration termed whole-body regeneration. Those animals that can regenerate must be able to detect which tissues are missing, coordinate the

production of lost tissues, and integrate new material with their pre-existing anatomy. On a molecular level, many studies have identified commonalities in the mechanisms

that drive this process in highly regenerative organisms and the gene regulatory machinery that underlie them. However, in order to piece together a complete picture of

regeneration, we must explore these commonalities in species across the phylogenetic tree. Is regeneration an ancestral trait that was lost in certain lineages? Or has it been independently adapted across evolutionary time? This study aims to extend the knowledge of regeneration to an invertebrate deuterostome model of whole-body

regeneration, the larva of the bat star Patiria miniata .

This study has produced three key findings. First, sea star larval regeneration involves rapid epithelial wound healing that utilizes localized cell migration and actin assembly. Wound signaling in this system also strongly activates components of the MAPK signaling pathway, including the phosphorylation of ERK, and a battery of gene expression. Second, sea star larvae use blastemal proliferation in order to reform tissues lost from amputation. The cells of the eventual blastema are specifically activated for regeneration and are distinct from proliferating cells of the uncut larva.

Third, early MAPK signaling functions in regeneration to ensure correct expression of genes during the wound response. This pathway is also implicated in regulating axis

re-specification and blastemal proliferation during regeneration. Together, these results have allowed us to synthesize a model of larval echinoderm whole-body regeneration.