Fig. 4. [C93A]Wingless accumulates in the ER of wing disc cells and is absent from MVBs. (A,B) Portion of the apical surface of a disc cell. Empty space is the peripodial lumen (PL). HA-[C93A]Wingless and HA-Wingless (WT) expressed with dpp-Gal4 are visualized with anti-HA and a secondary antibody labelled with 15-nm gold particles. Arrowheads indicate examples of HA-positive ER areas. These are particularly abundant in the [C93A]Wingless sample. (C,D) Basolateral region of disc cells. Note again the relatively abundant labelling in the perinuclear and other ER areas of cells expressing [C93A]Wingless (C). See for comparison an equivalent area in wild-type-Wingless-producing cells (D). Arrowheads indicate examples of ER areas positive for Wingless labelling. (E,F) MVBs (^*) in cells expressing high levels of [C93A]Wingless. Note the absence of label in these areas. (G,H) By contrast, anti-HA labelling is seen in the MVBs of cells expressing wild-type Wingless. G, Golgi unit; M, mitochondrion; N, nucleus; PL, peripodial lumen. ER is recognised by its characteristic morphology, as indicated from an independent preparation stained with anti-KDEL (see supplementary material, Fig. S1). Scale bars: 200 nm.