Roles of Ca(2+) activity in injury-induced migration of microglia in zebrafish in vivo

Microglia are the resident immune cells in the brain. It is well known that brain injury can activate the microglia and induce its directional migration towards the injury sites for exerting immune functions. While extracellular ATP released from the injury site mediates the directionality of activated microglia's migration, what endows activated microglia with migration capability remains largely unexplored. In the present study, we used the larval zebrafish as an in vivo model to visualize the dynamics of both morphology and Ca(2+) activity of microglia during its migration evoked by local brain injury. We found that, in response to local injury, activated microglia exhibited an immediate Ca(2+) transient and later sustained Ca(2+) bursts during its migration towards the local injury site. Furthermore, suppression of Ca(2+) activities significantly retarded microglial cell migration. Thus, our study suggests that intracellular Ca(2+) activity is required for activated microglia's migration.