Localization of sperm-associated antigen (Spag)5 by immunoelectron microscopy. Electron micrographs of pre-embedded anti-SPAG5 labeling in (A,B) longitudinal and (C) cross-sections of mouse rod photoreceptor cells. Spag5 was detected (A-B) around the basal body (BB), (A-C) in the collar-like extension (CE) of the apical inner segment; and (A) in some photoreceptors at the region of the rootlet (R). CC = connecting cilium; OS = outer segment; IS = inner segment. Scale bars: 0.5 μm.