Figure 4
Spreading of photolysis-induced nuclear calcium signals. A, schematic illustration of the position of the 5 μm2 area (pink circle) inside the nucleus that was illuminated with UV light for photolysis of NP-EGTA; arrows indicate possible directions of calcium signal spreading within the nucleus and across the NE to the cytoplasm. B, the positioning of the uncaging spot was guided by MitoTracker staining shown in red. C, time series of raw Fluo-4 fluorescence images of the calcium measurements shown in D, E and F; the indicated times correspond to the time scale of the graphs (D and E). The 5 μm2 areas in the nucleus that were illuminated with UV light for photolysis of NP-EGTA are indicated with white circles. D and E, time courses of calcium transients were averaged in areas of 6 × 6 pixels (filled white squares) in the nucleus (continuous line) and the cytoplasm (dotted line) at 2 μm and 5 μm distances from the uncaging spot as indicated by arrows. UV exposure (t exp = 10.2 msec) occurred as indicated by the dashed line. Images were taken every 401 msec. F, the spatial profile of calcium signals at different time points (t1 = basal level, t2 = peak value, t3 = decay) is shown. Signals were measured as depicted in the mitochondria-stained image (filled white squares). The corresponding time points are indicated by arrows in the graphs (D and E). Scale bar is 5 μm.