mc1r Pathway regulation of zebrafish melanosome dispersion.

Abstract Zebrafish rapidly alter their pigmentation in response to environmental changes. For black melanocytes, this change is due to aggregation or dispersion of melanin in the cell. Dispersion and aggregation are controlled by intracellular cyclic adenosine monophosphate (cAMP) levels, which increase upon stimulation by α melanocyte–stimulating hormone (α-MSH) or reduce with melanin-concentrating hormone (MCH). In mammals and birds, the melanocortin-1-receptor (MC1R) responds to MSH, and stimulates the synthesis of black eumelanin. While MSH–cAMP signaling stimulates melanogenesis in mammals, and melanosome dispersal in cold-blood vertebrates, the pathway components are highly conserved. However, it has only been assumed that mc1r mediates melanosome dispersal in fish. Here, using morpholino oligonucleotides designed to knockdown mc1r expression, we find that mc1r morphants are unable to disperse melanosomes when grown in dark conditions. We also use chemical modifiers of the cAMP pathway, and find an ...