Figure 4.

Epithelial rotation. (A) A cross-section showing the internal rotating movement of the follicular epithelium (blue cells) on the ECM–basement membrane (orange layer). The internal germline cells (large green cells) follow the follicle cells. The epithelium is continuous with no free edge in the intact structure. (B) Side-view of a small group of epithelial or endothelial cells plated on an island of substrate. The cells will rotate together on the substrate for prolonged periods. (C) A small cluster of epithelial cells in a three-dimensional matrix. An apical lumen might have formed internally; the basal sides of the cells are facing outwards. Such clusters will rotate coherently in one direction. ECM, extracellular matrix.