Mapping out the pathway taken by newly synthesized α-granule cargo. Differentiated imMKCLs were cotransfected with the RUSH bicistronic plasmid containing PF4-SBP-Cherry as a cargo-reporter and GFP-tagged markers of several compartments. Cells were fixed before and after the addition of biotin at various time points, and numerous cells were imaged for each marker at each time point (n ≥ 5 for each marker at each time point). The line graphs indicate the percent colocalization of the cargo-reporter with the GFP-tagged marker. SiT, sialyltransferase.