Dynamic actin waves in primary rat cortical astrocytes sense environmental cues*

Recent work has highlighted the importance of the brain's non-neuronal cells in cognitive function. Astrocytes, one type of these non-neuronal glial cells, have physiological roles ranging from maintaining brain homeostasis to modulating neuronal communication. Astrocytes perform these functions by regulating the flux of ions and water molecules across their membranes and by communicating with other astrocytes within the brain’s networks. These functions require dynamic reorganization of the cytoskeleton in response to changes in the brain’s microenvironments, but these dynamics have not been well studied in astrocytes, especially on shorter time scales of seconds to minutes. To this end, we use live confocal microscopy to capture actin dynamics in live astrocytes under control and “triggering” conditions after astrocytes have been transduced with actin-GFP. We then employ optical flow to analyze these actin dynamics by tracking changes in fluorescence. We also study the persistence of these dynamics and identify small regions of especially high activity, which we call functional microdomains. We propose that actin dynamics are a local manifestation of astrocytes’ global homeostatic response to changes in the extracellular microenvironment.