To assess the localization of OA1-mCherry and GFP-Rab27a, we expressed them independently in mouse B16-F1 melanoma cells and used fluorescence microscopy to analyze their colocalization with established antibodies against melanosomal-specific proteins tyrosinase-related protein 1 (TRP-1) and Pmel-17. The gene discussed is TYRP1; the disease is melanoma.