Involvement of melanin-concentrating hormone 2 in background color adaptation of barfin flounder Verasper moseri.

In teleosts, melanin-concentrating hormone (MCH) plays a key role in skin color changes. MCH is released into general circulation from the neurohypophysis, which causes pigment aggregation in the skin chromatophores. Recently, a novel MCH (MCH2) precursor gene, which is orthologous to the mammalian MCH precursor gene, has been identified in some teleosts using genomic data mining. The physiological function of MCH2 remains unclear. In the present study, we cloned the cDNA for MCH2 from barfin flounder, Verasper moseri. The putative prepro-MCH2 contains 25 amino acids of MCH2 peptide region. Liquid chromatography-electrospray ionization mass spectrometry with a high resolution mass analyzer were used for confirming the amino acid sequences of MCH1 and MCH2 peptides from the pituitary extract. In vitro synthesized MCH1 and MCH2 induced pigment aggregation in a dose-dependent manner. A mammalian cell-based assay indicated that both MCH1 and MCH2 functionally interacted with both the MCH receptor types 1 and 2. Mch1 and mch2 are exclusively expressed in the brain and pituitary. The levels of brain mch2 transcript were three times higher in the fish that were chronically acclimated to a white background than those acclimated to a black background. These results suggest that in V. moseri, MCH1 and MCH2 are involved in the response to changes in background colors, during the process of chromatophore control.