Fig. 6. Reduced lamella protrusion persistence and increased ruffle frequency in N17Rac1 transgenic keratinocytes. (a,b) Phase-contrast images of individual (a) N17Rac1 transgenic (tg) and (b)wild type (wt) keratinocytes (top) and time-space plots of membrane segments indicated by white lines in the corresponding cells (bottom). Lamella protrusions appear as ascending bright contours, whereas ruffles appear as descending, darker contours. Note that within 5 minutes three ruffle profiles (thick lines) appeared in tg cells, whereas only one ruffle profile became visible in wt cells. By contrast, persistence of lamella protrusion (thin lines) was short in tg cells but prolonged in wt cells. Bar, 10 µm. (c,d) Results of statistical analysis of (c) persistence of lamella protrusion and (d) ruffle frequency expressed as the mean ± s.d. Results are representative for three N17Rac1 tg and three wt cell lines in passages 3-5; at least 80 individual cells per cell line were analysed. Cells were plated on collagen-I-coated glas coverslips. Statistical significance between data groups was determined using the Whitney U-test. Differences between tg and wt keratinocytes were highly significant for persistence of lamella protrusion and for ruffle frequency (P<0.01). (e,f) Micrographs showing focal contacts in primary murine keratinocytes isolated from (e) wt and (f) N17Rac1 tg mice by immunostaining against vinculin. Note reduced number of focal contacts in the transgenic population. Bar, 20 µm.