Fig. 2. Dystroglycan function is required for apicobasal polarity in epithelial cells. (A) Schematic drawing of an ovariole and an eye-antennal imaginal disc. The ovariole contains egg chambers at different developmental stages (st). A layer of somatically derived follicle cells (FC), the majority of which have a typical epithelial apicobasal polarity, covers the germline cells (GC). Epithelial cells in the imaginal discs also show apical-basal polarity. (B-D) Mosaic analysis of Dg mutations. GFP in green marks wild-type cells. (E-G') RNAi analysis. (B) In a Dg mutant clone (broken lines in B, Dg²⁴⁸), the apicobasal polarity of the FE is disrupted, as mutant cells form a multi-layer epithelium (white arrow) and also cause discontinuance in the epithelium (yellow arrow) (red, actin; blue, DNA). White arrowheads show the wild-type region. (C,C') In a Dg³²³ follicle cell clone where follicle cells have not lost their columnar shape yet, an apical marker Dlt (red in C and white in C') is detected at both the apical and basal (white arrow in C and green arrow in C') side. C' is an enlarged view of the mutant clone region (broken yellow line) and vicinity shown in C. (D) In a Dg²⁴⁸ clone in an antennal imaginal disc (inset, the white box indicates where the mutant clone is) Dlt (red) is also mislocalized, expanding from the apical (arrowhead) to lateral side (arrow). (E) Multi-layered FE is also detected in tubPGal4/dsDG flies. (F,F',F'') An apical marker ßH-Spec (red; F shows the wild-type pattern, arrow) is mislocalized to the basal side (arrowheads in F' and F'') in dsDG follicle cells. F'' shows a more severe loss-of-polarity phenotype than does F'. (G,G') A basolateral marker, Dlg (red in G shows the wild-type pattern; arrow), is greatly reduced at the basolateral membrane (arrow in G'). DNA is shown in blue at B and E-G'.