Intracellular Ca2(+) dynamics are required for microglial process motility during surveillance and in response to injury

Microglia, the resident immune cells of the central nervous system, play pivotal roles in brain surveillance and injury responses through highly dynamic process motility. Here, we investigated the role of Ca2(+) signaling in mediating microglial process motility under both physiological and pathological conditions in vivo. Using dual-laser two-photon microscopy in a transgenic mouse model expressing red fluorescent protein (mCherry) and the Ca2(+) indicator (GCaMP6m) specifically in microglia, we observed autonomous Ca2(+) microdomains that operate asynchronously within individual processes, exhibiting significantly more frequent and localized Ca2(+) transients compared to non-motile structures. Upon focal laser-induced cortical injury, we observed rapid Ca2(+) waves in microglia, with processes extending toward the lesion site displaying correlated Ca2(+) activity. Attenuation of Ca2(+) transients by BAPTA-AM, a Ca2(+) chelator, impaired both homeostatic and laser-induced motility. Importantly, microglia-specific genetic overexpression of plasma membrane Ca2(+) ATPase 2 in vivo markedly reduced both homeostatic surveillance and injury-induced motility. Together, our findings provide evidence that microglial intracellular Ca2(+) signaling is required for process motility in vivo, supporting a model in which local Ca2(+) dynamics enable surveillance and injury-directed remodeling.