The following monoclonal antibodies were used: mouse anti-TYRP1 (TA99) from ATCC; rat anti-LAMP1 (1D4B) and rat anti-LAMP2 (GL2A7) from Developmental Studies Hybridoma Bank; mouse anti-PMEL (HMB-45) from Lab Vision; and mouse anti-HA.11 from Covance. Anti-VAMP7 mAb (158.2) and pAb (TG50) have previously been described and validated using Vamp7−/− mice (Danglot et al., 2012 (link)). Polyclonal rabbit antisera to STX13 (Prekeris et al., 1998 (link)) have been previously described, and rabbit anti-Giantin was purchased from Abcam (ab24586). Species-specific secondary antibodies from donkey conjugated to Alexa Fluor 488, 594, or 647 or Dylite 488, 594, or 647 used in immuno-FM were obtained from Jackson ImmunoResearch Laboratories, Inc.