Regulated transport of intracellular cargo by molecular motor proteins is essential for cellular organization, particularly in polarized cells such as neurons, yet the mechanisms controlling motor activity remain poorly understood. This dissertation uses zebrafish melanocytes as a genetic model to study regulation of organelle transport, focusing on melanosome movement controlled by cAMP signaling. A forward genetic screen identified several mutants with transport defects. Characterization of the mlphd120 mutant revealed a novel role for melanophilin in regulating microtubule-based transport, in addition to its known function in actin-based transport. Two additional mutants, smutz and b867, suggest defects in actin-based transport regulation. These findings demonstrate that zebrafish melanocytes are a powerful model for studying coordinated motor protein regulation.
