Fig. 5. Laminin and basal actin organization in the follicle cell epithelium is disrupted in a Dystroglycan mutant clone. (A) Drawing of a wild-type egg chamber with a basal surface view of three follicle cells. The basal actin fibers (red lines) in these cells are arrayed at a direction perpendicular to the long (AP) axis of the egg chamber from stage 8 to 12. Laminin stripes in the ECM (blue lines) shows the same orientation. (B) Drawing of a Dg follicle cell clone with misoriented basal actin fibers and Laminin stripes. (C) Phalloidin staining shows the basal actin array in the wild-type FE. Three cells are outlined. (D) In a Dg³²³ mutant egg chamber, the basal actin organization is disrupted. (E,F) The role of DG in basal actin organization is non-cell-autonomous, as cells adjacent to the follicle cell clone (broken outline) also frequently show a disrupted basal actin distribution (arrow in F). In wild-type egg chambers, Laminin is oriented in stripes (surface stripes in G), similar to the basal actin. This Laminin orientation is disrupted in Dg mutant clones (H). The left-hand image in H shows where the mutant follicle cell clone (black area) is located. (I) At stage 10, Laminin is mainly detected at the basal surface (arrowhead) of the wild-type FE (area lacking green). However, overexpression of DG (marked by co-expression of GFP, green) causes accumulation of Laminin ECM to the apical and lateral surfaces (arrow). (J) A model for Dystroglycan function in planar polarity (basal actin organization). In this study, we have shown that the DG function is involved in cell-cell communication, which is essential for basal actin planar polarity. This communication probably involves the cyto-architecture of the Laminin ECM. DG directs the orientation of the Laminin stripes. This information is transmitted into a neighboring cell to coordinate the orientation of the actin fibers. GFP (green) marks the wild-type cells in E and H; Actin is white in C,D,F; Laminin is turquoise in G,H.

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