WNT Planar Polarity Signaling is Required for Inward Migration of the Centripetal Follicle Cells During Drosophila Oogenesis. D.M. Ruden , L. Xiao. Enviromental Hlth Sci, Univ Alabama Birmingham, Birmingham, AL.

   The centripetal follicle cells, using a mechanism that resembles purse-string contraction of an extra-cytoplasmic actin network in wound healing, migrate between the nurse cells and the oocyte to form a cap over the anterior of the oocyte. StarKojak, a dominant loss-of-function allele of a pro-TGFa chaperone protein that moves pro-Spitz from the endoplasmic reticulum to the Golgi, prevents centripetal follicle cell metastasis-like movement in a cell-nonautonomous manner. In experiments designed to determine what cell-autonomous signaling events are required in the centripetal follicle cells for the metastasis-like movement, we show that WNT planar polarity signaling is required. We propose a model for crosstalk between EGF Receptor signaling and WNT signaling in which an EGF Receptor inhibitory ligand Argos diffuses a large distance from the posterior follicle cells to the centripetal follicle cells. In this model, WNT signaling is derepressed in the centripetal follicle cells by the inhibition of EGF Receptor signaling in a novel process called "Remote Derepression".