Fig. 10 Formation of myosin bundles in the lamellipodia/cell body transition zone of a locomoting keratocyte is associated with forward translocation of myosin features. (a) an overview of a keratocyte at start of observation (top) and after 168 s (bottom). Positions of two images reflect actual displacement of the cell in the horizontal direction. Traces of the cell's leading and rear edges (dashed lines) and selected myosin features (solid lines) are shown in the inset with time indicated in seconds on vertical scale. One of the myosin spots traced is visible on the image at time 0, others have arisen at later time points and ended up, depending on time of their appearance and initial position, in the lamellipodium, in the lamellipodia/cell body transition zone and as part of contracted myosin aggregates in the cell body at 168 s. Traces illustrate that myosin spots are initially stationary but become sequentially involved in forward translocation as the cell advances. (b) details of bundle formation in the cell region indicated with box in (a). Two myosin spots are highlighted with red and yellow. Dotted lines indicate positions fixed with respect to the substratum. Myosin spots are compressed in horizontal direction (direction of locomotion) resulting in bundle formation and displacement to the right (forward). (c) the fate of a small myosin bundle as it forms at the cell body boundary (time 0) and contracts (112 s), fragments (152-232 s) and disappears (272 s) within the cell body. Bars, 2 µm.