Fig. 4. Yan regulates DE-Cad expression levels. (A-C) Egg chambers are stained for actin (with Alexa-568-phalloidin, red), anti-DE-Cad (green) and DAPI (blue). (A'-C') Higher magnification views of A-C; grayscale images of DE-Cad allow the visualization of DE-Cad expression levels. Yellow arrows point towards polar cells, white arrowheads point at outer BCs, white arrows point at the interface between BCs and squamous follicle cells. (A,A') In wild type, high levels of DE-Cad are found at the boundary between polar cells and outer BCs, as well as between outer BCs. DE-Cad is also strongly detectable at the edge of outer BCs. (B,B') DE-Cad surface expression is reduced in outer BCs where UAS-yan^ACT is ectopically expressed using slbo-Gal4. (C,C') Expression of UAS-DE-Cad^5,9 in BCs by slbo-Gal4; arrow in C indicates arrested BCs. (D) Functional interaction between DE-Cad and Yan to regulate BC migration. In wild type, 95% of BCs reach the NC-oocyte boundary. Ectopic expression of UAS-yan^ACT induces strong BC migration defects (60% of BCs migrate less than 25%, 26% migrate 25-50%, 12% migrate 50-75% and 2% complete their migration). Weak expression of UAS-DE-Cad partially suppresses UAS-yan^ACT migration defects (37% migrate less than 25%, 29% migrate 25-50%, 29% migrate 50-75% and 5% reach the nurse cell-oocyte boundary). Forced expression of UAS-DE-Cad^5,9 delays BC migration (20% migrate less than 25%, 30% migrate 25-50%, 32% migrate 50-75% and 18% complete their migration by stage 10 of oogenesis). n>100.