STIM1-dependent SOCE generates filopodial Ca2+entries in Xenopus neuronal growth cones. (A) A pseudocolored Lck-GCaMP3 fluorescent Ca2+ image of growth cone showing rectangular ROIs (region of interest) used to measure fluorescent intensities over time. Pseudocolors indicate Ca2+ levels, with white as the highest and black as the lowest. Scale bar, 10 μm. (B) Representative traces of Lck-GCaMP3 fluorescent Ca2+ signals profile measured in two filopodia (F1, F2) and a growth center (F3) over 7 min period of store-depletion and re-addition of extracellular Ca2+. Images were captured at 200 milliseconds intervals. #, indicates filopodial and global Ca2+ transients that are shown in (C). Right images are kymographs generated from a segmented line along the filopodia from the tip to the base using NIH ImageJ. The arrowheads denote tip and base of filopodia. (C) Representative pseudocolored Lck-GCaMP3 fluorescent Ca2+ images at the time point as indicated by # in B. The arrows show the initiation of filopodial Ca2+ transients. (D-E) The incidence (D) and frequency (E) of filopodial Ca2+ transients were determined in control (n = 21), XSTIM1-DN (n = 12), XTRPC1-MO (n = 10) expressing filopodia. *P < 0.005 and **p < 0.05 compared with control condition using t-test. Values represent mean ± s.e.m.