Robust nature of the filopodial length and distance separation lognormal distribution. Perturbation analysis of Rat2 cells after genetic, chemical and physical induction of filopodia. (A) PПI4KIIIβ expression induces filopodia and increases both length and separation distance relative to the empty vector control. Rat2 cells stably expressing PI4KIIIβ and controls have been previously described . (B) Bradykinin, a chemical inducer of filopodia, increased the length but had no effect on the interfilopodial distances compared to the DMSO control. Rat2 cells were treated with 100 ng/mL bradykinin. (C) Poly-D-lysine, a physical inducer of filopodia, increased the length of filopodia modestly but had no effect on distances.