Lateral Membrane Waves Constitute a Universal Dynamic Pattern of Motile Cells

We have monitored active movements of the cell circumference on specifically coated substrates for a variety of cells including mouse embryonic fibroblasts and $T$ cells, as well as wing disk cells from fruit flies. Despite having different functions and being from multiple phyla, these cell types share a common spatiotemporal pattern in their normal membrane velocity; we show that protrusion and retraction events are organized in lateral waves along the cell membrane. These wave patterns indicate both spatial and temporal long-range periodic correlations of the actomyosin gel.

Figure 1

Time sequences of cell shapes exhibiting lateral membrane waves for mouse embryonic fibroblasts [(a), $\Delta t=30\mathrm{s}$], fly wing disk cells [(b), $\Delta t=10\mathrm{s}$], and mouse $T$ cells [(c), $\Delta t=84\mathrm{s}$] obtained by total internal reflection fluorescence. Arrows point to isolated but highly correlated (a) or propagating (b) protrusions. Bars denote $3\mu \mathrm{m}$.

Figure 2

Normal velocity maps $v_n(s,t)$ for mouse embryonic fibroblasts (a), fly wing disk cells (b), and mouse $T$ cells (c). The time resolution is 2 s (a), 10 s (b), and 12 s (c), respectively. Cell edge velocities are calculated as discussed in the text [see Eq. (1)] from cells shown in Fig. 1. Note the diagonally striped appearance of the velocity map indicating lateral wave patterns.

Figure 3

Space-time correlation maps $c(\Delta s,\Delta t)$ as defined in the text, see Eq. (2), for mouse embryonic fibroblasts (a), fly wing disk cells (b), and mouse $T$ cells (c). Correlations are calculated from velocity maps shown in Fig. 2. Bands of high correlation corresponding to lateral waves are clearly visible. The slopes correspond to the respective propagation velocity $v_L$, see Table . In panel (b), the time axis has been reversed to allow direct comparison of slopes among panels.

Figure 4

Spatial ($\Delta t=0$) and temporal ($\Delta s=0$) cuts of the correlation maps $c(\Delta s,\Delta t)$ in Fig. 3 for mouse embryonic fibroblasts (a), fly wing disk cells (b), and mouse $T$ cells (c). Numerical characteristics are compiled in Table .

Figure 5

Binary correlation maps of the fly cell depicted in Fig. 1b. Correlation maps were calculated as sign [$c(\Delta s,\Delta t)$] in two different regions of the cell perimeter. Lateral waves are found to move in opposite directions with velocities $v_L=\pm 120\mathrm{nm}/\mathrm{s}$, as indicated by the dashed lines.