Figure 1
From: Distinct predictive performance of Rac1 and Cdc42 in cell migration
Quantification of cell edge displacement and Rho GTPase activity.
(a) Snapshot images showing the spontaneous migration of HT-1080 cells expressing the biosensors Raichu–Cdc42 (left) and Raichu–Rac1 (right). See also Supplementary Movies 1,2. FRET/CFP ratio ranges in intensity modulated display (IMD) mode, which associates color hue with emission ratio value and the intensity of each hue with the source image brightness, are shown at the right of each image. (b) Migrating HT1080 cells are tracked based on the CFP image. Different-colored polygons (connected markers) indicate the time-series of the tracked cellular boundaries (from cyan to red). The vertices (virtual markers) are placed in an equidistant manner along the perimeter at each time. Edge displacement is quantified based on the length of the connected link between the vertices at serial time frames. (c,d) Quantified edge displacement (elongation/retraction) (b) and Cdc42 activity, i.e., the FRET/CFP ratio value (c) at each virtual marker is mapped onto a two-dimensional heat map consisting of time (abscissa) and marker index (ordinate). (e) The spatiotemporal cross-correlation function between the edge displacement and Cdc42 activity of a specific cell (the same one as in (c,d)) is plotted. Abscissa and ordinate indicate the shifts in time and marker indices, respectively. (f) The temporal cross-correlation functions between edge displacement and Cdc42 activity are plotted with the time shift. The blue line was calculated by (c) and (d). In each sample (a single black line), the local shape change precedes the molecular activity change. The red line shows the mean cross-correlation function of all of the cells (N = 11).
