Consistent with the altered early endosome marker (EEA1) signal observed by immunostaining (Fig. 3), fluid-phase endocytosis was also altered in homozygous CbCln3Δex7/8 cells, as measured by dextran-FITC uptake (Fig. 7). Following a 15-minute incubation in media containing dextran-FITC, wild-type and heterozygote cells displayed brightly stained, large endocytic vesicles that were clustered in the perinuclear region. However, homozygous CbCln3Δex7/8 cells were less brightly stained with most dextran-FITC signal localizing to smaller vesicles scattered throughout the cytoplasm of the cell.