The basement membrane is physically displaced by the UNC-40–generated invasive protrusion. (A) Lateral view images show two regions of laminin::Dendra (one beneath the AC and an adjacent control) that were photoconverted by brief exposure to 405-nm light (left, fluorescence overlay; right, grayscale of red fluorescence). Only time points after photoconversion are shown. Cytoplasmic GFP expression (cdh-3 > GFP) was used to precisely determine the boundaries of the AC’s footprint. The same animal is shown before invasion (top) and 2 h later, after AC invasion (bottom). The region of photoconverted laminin:Dendra beneath the AC was displaced laterally during invasion (red bar) compared with the control region that remained unchanged (blue bar; quantification reported in C). (B) Ventral view images show grayscale (top) and corresponding spectral representation of fluorescence intensity (middle) of wild-type (left) and unc-40(e271) (right) animals in which the entire region shown was photoconverted before invasion. Only time points after invasion are shown. Yellow arrows point to accumulation of photoconverted laminin:Dendra at the boundary of the expanding breach. The schematic diagram (bottom) depicts the quantitative method used to estimate basement membrane displacement. (C) Graph displays the fold change in optically highlighted regions before and after invasion (left, see A [right] for corresponding measurements). Measurements of the percentage of basement membrane displaced (middle) and the circularity of basement membrane breaches (right and see Materials and methods) in wild-type and unc-40(e271) animals are reported. The asterisks denote statistically significant differences (P < 0.001, Student’s t test; n ≥ 14 animals for each genotype). Error bars represent SEM. Bars, 5 µm.