XB-IMG-159298
Xenbase Image ID: 159298
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Figure 6. Heterogeneity of filopodia responses to VASP accumulation within their tips. (A) A filopodium from Xenopus RGC growth cone expressing mNeonGreen-VASP, showing a positive response to VASP accumulation within its tip (surge of forward movement from 96 s, retraction concomitant with the loss of tip fluorescence from 184 s). (B) Concurrent measurements of VASP fluorescence and tip movement for the example filopodium shown in A. (Interruption at t = 160 s represents loss of focus during those time points.) (C) Positive correlation between VASP tip fluorescence and tip movement across the time-lapse for the example filopodium shown in A (at time offset 0). (D) An example filopodium expressing mNeonGreen-VASP showing stalling at elevated levels of VASP (0–80 s) and forward tip extension during a period of reduced VASP fluorescence (112–136 s). (E) Concurrent VASP fluorescence and tip movement measurements across the time-lapse for the filopodium shown in D. (F) Absence of positive correlation between VASP fluorescence and tip movement across the time-lapse for the filopodium shown in D, at time offset 0. (G) Cross-correlation between VASP fluorescence and tip movement for each filopodium (rows) as a function of time offset (columns). n = 76 filopodia. Red shows a negative correlation and blue a positive correlation. Negative offset, fluorescence leads before movement; positive offset, fluorescence lags behind movement. Blue shaded block over the dendrogram represents most strongly positively correlating (VASP-responding) filopodia, and red indicates all other filopodia. (H) The VASP-responding and other filopodia from A and D occupy adjacent positions in the same growth cone. Dashed rectangles indicate crop regions used for the kymographs in A and D. (A still image from Video 10.) (I and J) Filopodia from the VASP-responsive subcluster have a higher rate of tip extension (I) and spend more time retracting (J) than other filopodia. Tukey box plots (box: first and third quartile; upper and lower whiskers: within 1.5 interquartile range of the upper and lower quartile, respectively); p-values are provided for Mann–Whitney test after Holm correction for multiple comparisons. Full information on subcluster properties is in Table S1. Bars: (A and D) 1 µm; (H) 2 µm. Image published in: Urbančič V et al. (2017) © 2017 Urbančič et al. This image is reproduced with permission of the journal and the copyright holder. This is an open-access article distributed under the terms of the Creative Commons Attribution license Larger Image Printer Friendly View |