PVF1, a PDGF/VEGF homolog, is sufficient to guide border cells and interacts genetically with Taiman

The border cells of the Drosophila ovary undergo a well-defined and developmentally regulated cell migration. Two signals have previously been shown to control where and when the cells migrate. The steroid hormone ecdysone, acting through its receptor and a coactivator known as Taiman, contributes to regulating the timing of border cell migration. PVF1, a growth factor related to platelet-derived growth factor and vascular-endothelial growth factor, contributes to guiding the border cells to the oocyte. To probe the mechanisms controlling border cell migration further, we performed a screen for genes that exhibit dominant genetic interactions with taiman. We identified 14 genomic regions that interact with taiman. Within one region, we identified Pvf1 as the gene responsible for the interaction. Signaling by PVF1 has been proposed to guide the border cells to their proper target, but ectopic PVF1 has not been tested for its ability to redirect the border cells. We tested the ability of PVF1, as well as other factors such as Gurken, to guide the border cells to new targets. Our results demonstrate that ectopic expression of PVF1 is sufficient to redirect border cells in some egg chambers but that the other factors tested are not. These data suggest that the guidance of border cell migration is robust and that there are likely to be additional factors that contribute to long-range guidance of these cells. In addition, we find that taiman and Pvf1 regulate the dynamic localization of E-cadherin in the border cells, possibly accounting for the interaction between these two pathways.