Border cells (Drosophila)
The border cells are a cluster of 6–8 cells that migrate in the ovariole of the fruit-fly Drosophila melanogaster, during the process of oogenesis. A fly ovary consists of a string of ovarioles or egg chambers arranged in an increasing order of maturity. Each egg chamber contains 16 central germline, nurse cells surrounded by a monolayer epithelium of nearly 1000 follicle cells. At stage 8 of oogenesis, these cells initiate invading the neighbouring nurse cells, and reach the oocyte boundary by Stage 10.
Mechanism of action
The border cells are specified by the activation of the
VEGF (PVF1) aids in the directional migration of border cells towards the oocyte.[3] The timing of the border cell migration along with egg chamber development is coordinated by ecdysone, a steroid hormone, which functions through Taiman, ecdysone receptor and ultraspiracle receptors.[4] These cells migrate as a free group by means of transient cell-cell adhesions, further initiating signaling cascades that regulate expression of cytoskeletal components and triggers cellular extensions enabling forward movement. The invasive movement of the cluster towards the posteriorly located oocyte is followed by the off-centred movement towards the dorsal side of the egg chamber. The second kind of movement is mediated by the binding of Gurken, Spitz and Keren ligands to the EGFR on the border cells.[5][6]
Significance
The directional and collective migration of border cells aids in the formation of
tumors into metastatic ones.[8]