EGF does not affect microtubule plus-end-dynamics but leads to exploratory microtubule growth into newly-formed cell extensions.
Microtubules were labeled by EB3-CFP in MKN1 cells. (A, B) The images are taken from Video S3. They show DIC images (A’ at time point 42 s, B’ at time point 330 s) and details of fluorescence (inverse presentation in A, B; corresponding regions marked in A’, B’) of a cell that was treated with 30 ng/ml EGF from 192 s onwards. Examples of growing microtubule ends are circled in A, B. The histogram in (C) depicts the mean growth rates ± SEM of individual microtubules before (−EGF) and after addition of EGF (+EGF) in 7 MKN1 cells (number of plus-ends examined was 21 for -EGF and 22 for +EGF (n = 5 for 100 ng/ml and n = 17 for 30 ng/ml). (D–E) Present fluorescence micrographs (inverse presentation) of a MKN1 cell synthesizing EB3-CFP prior to addition of 100 ng/ml EGF. Micrographs in (E) are taken from Video S4 and show a peripheral region of the cell depicted in D (marked by square), where a stable lamellum is formed upon EGF addition (times after EGF supplementation in upper right corner). Stages of microtubule extension into the newly-formed lamellum are depicted. Bars, 5 µm in A’ (same magnification in B’), E; 10 µm in D.