Time-lapse and cell ablation reveal the role of cell interactions in fly glia migration and proliferation.

Migration and proliferation have been mostly explored in culture systems or fixed preparations. We present a simple genetic model, the chains of glia moving along fly wing nerves, to follow such dynamic processes by time-lapse in the whole animal. We show that glia undergo extensive cytoskeleton and mitotic apparatus rearrangements during division and migration. Single cell labelling identifies different glia: pioneers with high filopodial, exploratory, activity and, less active followers. In combination with time-lapse, altering this cellular environment by genetic means or cell ablation has allowed to us define the role of specific cell-cell interactions. First, neurone-glia interactions are not necessary for glia motility but do affect the direction of migration. Second, repulsive interactions between glia control the extent of movement. Finally, autonomous cues control proliferation.