Dooley, C.M., Mongera, A., Walderich, B., and Nüsslein-Volhard, C. (2013) On the embryonic origin of adult melanophores: the role of ErbB and Kit signalling in establishing melanophore stem cells in zebrafish. Development (Cambridge, England). 140(5):1003-1013.
Pigment cells in vertebrates are derived from the neural crest (NC), a pluripotent and migratory embryonic cell population.
In fishes, larval melanophores develop during embryogenesis directly from NC cells migrating along dorsolateral and ventromedial
paths. The embryonic origin of the melanophores that emerge during juvenile development in the skin to contribute to the striking
colour patterns of adult fishes remains elusive. We have identified a small set of melanophore progenitor cells (MPs) in the
zebrafish (Danio rerio, Cyprinidae) that is established within the first 2 days of embryonic development in close association with the segmentally
reiterated dorsal root ganglia (DRGs). Lineage analysis and 4D in vivo imaging indicate that progeny of these embryonic MPs spread segmentally, giving rise to the melanophores that create the
adult melanophore stripes. Upon depletion of larval melanophores by morpholino knockdown of Mitfa, the embryonic MPs are prematurely
activated; their progeny migrate along the spinal nerves restoring the larval pattern and giving rise to postembryonic MPs
associated with the spinal nerves. Mutational or chemical inhibition of ErbB receptors blocks all early NC migration along
the ventromedial path, causing a loss of DRGs and embryonic MPs. We show that the sparse like (slk) mutant lacks larval and metamorphic melanophores and identify kit ligand a (kitlga) as the underlying gene. Our data suggest that kitlga is required for the establishment or survival of embryonic MPs. We propose a model in which DRGs provide a niche for the
stem cells of adult melanophores.