FIGURE 7:

Endoplasmic spreading is a continuous process dependent on coalescence of vimentin filaments at force-bearing adhesions. A cage-like structure surrounds the endoplasm from the beginning of spreading. As microtubules migrate outward, vimentin fragments are transported out to early, maturing adhesions. Vimentin fragments collect at growing adhesions, subsequently forming vimentin filaments that can interact with the central endoplasmic cage. Myosin II contraction in the endoplasmic cage and associated actomyosin structures causes the endoplasm to pull forward on the vIF-strengthened connection to the growing adhesion, resulting in further growth. Vimentin fragments continue to be transported to the periphery on microtubule tracks toward the next layer of growing adhesions. Vimentin filaments collect at the next round of adhesions, connecting with the spreading endoplasmic cage. The process repeats, allowing the endoplasm to spread in any direction that the cell spreads.