In one study a couple of years earlier, Yee Han Tee and coworkers plated fibroblasts separately onto circular adhesive islands that required each cell to keep a circular shape, and imaged the motions of 2 sets of actin fibers in each cell: radial fibers, which stretch inward from focal adhesions on the cell membrane, and transverse fibers, which are arranged perpendicularly to the radial fibers and appear to physically connect with them. In the first couple of hours of cytoskeleton advancement, these fibers formed a radially in proportion pattern (left), but after about 3 hours, the radial fibers started to tilt, dragging the transverse fibers sideways and causing a swirling pattern to emerge (middle). At around the 11-hour mark, the swirling broke into a direct pattern of fibers extending across the cell (right).
