Down-regulation of myosin II by compliance mechanosensing promotes fast MT growth globally and short-lived growth excursions in the peripheral cell body. (A) Workflow for categorizing GFP-EB3 comet tracks of MT growth into specific subcellular regions including cell branches and the peripheral cell body. A color code key for the classification of MT growth excursion subpopulations is shown below. Bar, 10 µm. (B) Comparison of percentages (top) of the population of MTs whose growth dynamics were categorized in the four subpopulations described in A, and MT growth speeds and growth excursion lifetimes (bottom) in branch and peripheral cell body regions of cells plated on glass coverslips. (C) Comparison of percentages of the population of MTs whose growth dynamics were categorized in the four subpopulations described in A in branch and peripheral cell body regions. Cells were plated on glass with or without the addition of 20 µM blebbistatin (Glass + Blebb) or on compliant ECMs (0.7 kPa). Percentage values are shown below. (D) Comparison of MT growth speeds (left) and growth excursion lifetimes (right) in branch and peripheral cell body regions of cells plated on glass with or without the addition of 20 µM blebbistatin (Glass + Blebb) or on compliant ECMs (0.7 kPa). **, branches versus cell body; *, between group comparison, P < 0.001. Error bars indicate standard error of the mean.