Investigating the role of fatty acid metabolism in melanocyte differentiation: Insights into the metabolic requirements of development

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PROJECT SUMMARY Melanocytes are a key cell lineage in the skin and are required for skin pigmentation. Defects in melanocyte development and function can lead to pigmentation disorders causing hypo or hyperpigmentation as well as one of the most deadly forms of skin cancer, melanoma. Many of the transcriptional and signaling events which cause these diseases have been explored, however, there has been little investigation into the role of the metabolic environment and intracellular metabolic state of the melanocyte during development. Recent work from our lab has demonstrated that during melanoma progression, adipocytes in the tumor microenvironment can transfer fatty acids to the melanoma cells, promoting invasion. This raises the question of whether fatty acid uptake plays a role in normal melanocytes. Our preliminary data suggests that melanocytes require extrinsic uptake of fatty acids through Fatty Acid Transport Proteins (FATPs) for proper differentiation. In Aim 1, we will investigate the relative importance of fatty acid uptake and de novo fatty acid synthesis in the melanocyte. We will compare multiple mechanisms of fatty acid uptake as well as fatty acid synthesis to determine which play the most important role in melanocyte development and pattern formation. We will also dissect in a stage specific manner when these pathways are required by the melanocyte during differentiation using genetic perturbations. We hypothesize that the importance of fatty acids in the melanocyte reflects certain lineage specific needs, including high levels of fatty acids to support phospholipid synthesis and dendrite formation. In Aim 2 we will examine the importance of fatty acids as building blocks for phospholipid synthesis relative to a requirement for fatty acid breakdown through b-oxidation. There is evidence for the importance of phospholipid synthesis in other dendritic cell types. Because melanocytes also form extensive dendrites which are critical for proper pigmentation we will dissect the importance major phospholipid synthesis pathways to the melanocyte in a stage specific manner. Conversely, melanocytes might break down fatty acids as a source of ATP to support cell proliferation and migration. We will also determine the role b-oxidation in melanocyte development by targeting key proteins in this pathway in a stage specific manner. We will assess the effects of these genetic perturbations on energy production and melanocyte development. To perform these studies we will primarily rely on zebrafish as an in vivo model of melanocyte development. We will use stage specific promoters for the neural crest, melanoblast, and melanocyte to generate stable germline transgenics. Using a combination of genetic methods and image analysis we will investigate the role of fatty acid and lipid metabolism in melanocyte development. When appropriate, we will also apply an in vitro model of melanocyte development, based on the differentiation of melanocytes from human pluripotent stem cells These combined experiments will lead to novel discoveries regarding the role of metabolism in melanocyte development, which could increase our understanding and treatment of pigmentation diseases.