Time-lapse imaging of elongation of a fGFP tagged astrocyte-like cell process. fGFP infected neurospheres were added to myelinating cultures prepared from wild type embryos, on 12 DIV. Frames were captured from a 17 hours time-lapse sequence after 19 DIV. A-D) Times shown in upper right corner, represent time elapsed after the start of imaging. The culture was visualised every 3 min. A fGFP-positive cell was detected making contact with a bundle of neurites with continual movement along these neurite bundles as followed over time. The yellow arrow indicates the process extension which was variable, ranging from <1 μm to >15 μm. The process length changed during the first 160-min of the imaging sequence. E) Immunostaining of a sister myelinating culture for MBP (red) and for neurites (SMI-31, blue) showed the presence of myelin-like membrane in association with a GFP-positive astrocyte-like cell (green). F) Immunostaining of a sister myelinating culture for O4 (red) and for GFAP (blue) showed the presence of typical oligodendrocytes and flat astrocytes in association with a GFP-positive staining (green). Representative images from at least 4 separate experiments.