A new study by researchers at the University of Virginia (UVA) and other institutions has revealed the existence of a type of pigment cell in zebrafish that can transform after development into another cell type. The work was reported online on May 28, 2019 in PNAS in an open-access article titled “Fate Plasticity and Reprogramming in Genetically Distinct Populations of Danio leucophores.” David Parichy, PhD, the Pratt-Ivy Foundation Distinguished Professor of Morphogenesis in UVA's Department of Biology, said that researchers in his lab noticed that some black pigment cells on zebrafish became gray and then eventually white. When they looked more closely, they found dramatic changes in gene expression and pigment chemistry. "We realized that the cells have a secret history hiding in plain sight," he said. "Zebrafish have been studied closely for more than 30 years - we know a lot about them - but this is the first time this transformation has been noticed. It's a very surprising discovery." The unique cell population sheds the pigment melanin, changing in color from black to white during the life cycle of an individual fish. These special cells are found at the edges of the fins, where they seem to act as a signal to other zebrafish. The ability of a developed cell to differentiate directly into another type of cell is exceptionally rare. Normally such a change requires experimental intervention, returning the cell to a stem-cell state in a dish, before it can differentiate, or transform, as something else. The new finding suggests that some developed cells might be more amenable to change than generally believed.
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