Lysosomal abnormalities in REEP1 knockout mice. (A) Primary cortical neurons from REEP1 KO or wild-type littermates were labeled with the neuronal marker βIII-tubulin (red) and LAMP1 (green). The diameter of the largest lysosome was measured, and the mean ± SEM percentage of cells with a largest lysosome >2 µm is shown (n = 3 repeats, at least 50 cells/repeat). (B) EM of primary cortical neurons from REEP1 KO mice or wild-type littermate controls. Middle panels are higher-magnification views of the boxed regions. Bars: (EM) 500 nm; (confocal immunofluorescence microscopy [IF] main panels) 10 µm; (IF magnified insets) 5 µm.