Fig. 2. Microtubule tip dynamics at focal adhesions. (A) Kymograph of a microtubule catastrophe event at a focal adhesion (FA). The microtubule is marked with mCherry-EB3 (red), and the focal adhesion is marked with GFP-paxillin (green). (B) Kymograph of a microtubule tip (mCherry-EB3, red) that does not undergo catastrophe at the adhesion (GFP-paxillin, green). The microtubule tip changes its growth dynamics at the focal adhesion. (C) An example of assigned area zones for microtubule growth paths near focal adhesions (GFP-paxillin, green). Cytoplasmic zones close to the cell center are encoded as zones `–2' and `–1'. The zone adjacent to a focal adhesion is encoded as zone `0'. A focal adhesion contains zones `1-3', according to its length. Cytoplasmic zones towards the cell periphery are encoded as zones `1out' and `2out'. Each zone is 1 µm in size. (D) The distribution between fast (growth rate >0.1 µm/second) and slow (growth rate <0.1 µm/second) microtubules for each zone. In the cytoplasm (yellow background), 70% of microtubules grow at a speed of 0.1 µm/second or faster. At focal adhesions (green background), the percentage of fast microtubules reduces down to 50%. (E) Dependence of the microtubule catastrophe ratio (percentage of approaching microtubules undergoing catastrophe) on the time a microtubule spends in the cytoplasm zone (zone –1, green), at the adhesion base (zone 0, blue) and in the adhesion (zone 1, red). (F) Total microtubule catastrophe ratio for each zone. The percentage of approaching microtubules undergoing catastrophe increases from 2% in the cytoplasm to 25% at focal adhesions. A total of 139 microtubules were quantified in three 3xGFP-EMTB- and mCherry-paxillin-co-transfected cells within 15 minutes. Bar, 1 µm.