Citrullination regulates wound responses and tissue regeneration in zebrafish

Calcium signaling is an important early step in wound healing, yet how these early signals promote regeneration remains unclear. Peptidylarginine deiminases (PADs), a family of calcium-dependent enzymes, catalyze citrullination, a post-translational modification that alters protein function and has been implicated in autoimmune diseases. We generated a mutation in the single zebrafish ancestral pad gene, padi2, resulting in a loss of detectable calcium-dependent citrullination. The padi2 mutants exhibit impaired resolution of inflammation and regeneration after caudal fin transection. Further, we identified a new subpopulation of cells displaying citrullinated histones within the notochord bead following tissue injury. Citrullination of histones in this region was absent and wound-induced proliferation was perturbed in Padi2-deficient larvae. Taken together, our results show that Padi2 is required for the citrullination of histones within a group of cells in the notochord bead, and for promoting wound-induced proliferation required for efficient regeneration. These findings identify Padi2 as a potential intermediary between early calcium signaling and subsequent tissue regeneration. Summary Golenberg et al. developed a citrullination-deficient zebrafish and demonstrated a role for Padi2 in fin wound responses and regeneration. This work identified a distinct population of cells within the regenerative notochord bead that exhibited wound-induced histone citrullination.