Fig. 4. Vesicle trafficking defects in sec6^Ex15 larvae at 72 hours AEL. (A) From quantitative fluorescent microscopy of the transport assay in neuronal cell bodies, surface-expressed CD8 immunofluorescence, total GFP fluorescence and cell surface area (measured by HRP immunoreactivity) were expressed as fluorescent units after background subtraction. n=10 for wild-type larvae fed RU486 (white); n=8 for wild-type larvae uninduced (blue); n=13 for sec6^Ex15 larvae fed RU486 (grey); and n=9 for uninduced sec6^Ex15 larvae (black). (B) Representative lateral bd sensory neurons as used in the assay in A. In particular, a wild-type larva that had been fed RU486 at 24 hours AEL and dissected and stained in the absence of Triton X-100 at 36 hours AEL is compared with a sec6^Ex15 mutant fed RU486 at 72 hours AEL similarly stained at 84 hours AEL. Anti-HRP immunostaining (gray) was used to find bd sensory neurons in each animal. The sec6^Ex15 larvae show less cell surface CD8 than the control, but also showa large decrease in GFP fluorescence. (C) When normalized to the anti-HRP signal, there was a significant induction of the mCD8-GFP transgene in the sec6^Ex15 mutant after feeding RU486 (P=0.01), but the amount of mCD8 at the soma surface was not significantly increased. (D) To measure the amount of transgene induction in the cell body by feeding RU486, the uninduced averages (blue and black bars in A) were subtracted from the RU486 averages (white and gray bars in A). To control for differences in cell size, GFP and surface CD8 were also normalized to the anti-HRP signal, as in C. The amount of induced mCD8 trafficked to the cell surface, when normalized to the corrected GFP signal, is decreased in the mutant compared with control.