Melanosome Motility in Fish Retinal Pigment Epithelial (RPE) Cells.

Several model systems have been developed to investigate mechanism and regulation of intracellular organelle motility. The fish retinal pigment epithelial (RPE) cell represents a novel yet simple system for the study of organelle motility. Primary cultures of dissociated RPE cells are easily prepared and amenable to motility studies. In vivo, melanin-containing pigment granules (melanosomes) within fish RPE migrate distances up to 100 μm in response to light flux. When dissociated from the epithelial layer and cultured in vitro, RPE cells attach to the substrate with the apical projections extending radially from the central cell body. Melanosomes can be chemically triggered to aggregate or disperse throughout the projections, and are easily observed using phase contrast microscopy. Melanosome migration in RPE apical projections is dependent on actin filaments, and thus renders this model system useful for investigations of actin-dependent organelle motility.