Fig. 7. Loss of frizzled frizzled2 affects intracellular Wingless. (A,A') Distribution of Wingless in frizzled frizzled2 mutant clones (outlined in white, indicated by -/-). This disc has been stained using a protocol that distinguishes extracellular (A) from intracellular (A') Wingless. Extracellular accumulation at the surface of mutant cells can be seen in A. Note in A' the specific depletion of large vesicles within the clone when compared with wild-type tissue (one such vesicle is marked by an arrowhead). Breaks in the stripe of expression are due to occasional loss of wingless transcription in the absence of signalling. (B,B') The same staining protocols were applied to discs containing arrow[2] mutant clones (outlined in white). Extracellular accumulation is seen (B). Intracellularly (B'), large vesicles are still seen in arrow mutant cells, consistent with the suggestion that Wingless continues to be internalized normally.