Schematic illustration of the second dynamic assay: tubulin is added to measure centrosome nucleation capacity and washed out. Then actin is added followed by actin and tubulin. Representative images showing microtubules (top line) and the merged images of actin and microtubule (bottom line) during the three steps of the assay; in the presence of tubulin only (left column), in the absence of tubulin and presence of actin (middle column) and in the presence of tubulin and actin (right column). Scale bar:10 µm. Arrowheads indicate microtubules unable to re-grow after assembly of actin filaments. Quantification of the differences in the number of microtubules per centrosome between the first and last steps of the experiment described above (panels D and E) on centrosomes capable (first condition), or not (second condition), to grow actin filaments. Data were pooled from 2 independent experiments; asters without actin filaments: n= 24; asters with actin filaments: n= 13. ****:P<0.001 Student t-test. 