Rtn4a is excluded from FP-17–positive ER cisternae. Cells were microinjected with cDNAs coding for EGFP-17 or -22 (both lacking the myc epitope in the linker region) and myc-tagged Rtn4a, as indicated in the top. Cells were fixed after 75 min at 37°C, and Rtn4a was revealed with an anti-myc monoclonal followed by secondary Alexa 568–conjugated antibodies. The bottom 3 rows show single-channel and merged images, with the indicated pseudocolors, of enlargements of the boxed areas in the top panels. Bars: (top) 20 μm; (enlargements) 4 μm.