Collective cell migration in a topologically closed epithelium

The follicle cell epithelium has its apical surface toward the germ cells and its basal surface facing out. Consequently, the basement membrane ECM forms the egg chamber's outermost layer. During egg chamber elongation, the follicle cells undergo a directed migration across the inner surface of the basement membrane that causes the entire egg chamber to rotate within this stationary matrix. Although migration has been intensively studied in single cells, the mechanisms by which cells migrate collectively are less well understood. Moreover, follicle cell migration occurs in a topologically closed epithelium with no leading edge, suggesting that novel mechanisms may polarize this epithelium for forward movement.
Some of our favorite questions about epithelial migration include
  • How is symmetry broken within the epithelium to initiate collective movement?
  • How is the migratory behavior reinforced by cell-cell and cell-matrix interactions?
  • How does follicle cell motility drive elongation morphogenesis?