Gene Structure of the Goldfish Agouti-Signaling Protein: A Putative Role in the Dorsal-Ventral Pigment Pattern of Fish

Abstract

One of the most successful chromatic adaptations in vertebrates is the dorsal-ventral pigment pattern in which the dorsal skin is darkly colored, whereas the ventrum is light. In fish, the latter pattern is achieved because a melanization inhibition factor inhibits melanoblast differentiation and supports iridophore proliferation in the ventrum. In rodents, the patterned pigmentation results from regional production of the agouti-signaling protein (ASP). This peptide controls the switch between production of eumelanin and pheomelanin by antagonizing alphaMSH effects on melanocortin receptor (MCR) 1 in the melanocytes. In addition, ASP inhibits the differentiation and proliferation of melanoblast. Thus, the mammalian ASP may be homologous to the poikilotherm melanization inhibition factor. By screening of a genomic library, we deduced the amino acid sequence of goldfish ASP. The ASP gene is a four-exon gene spanning 3097 bp that encodes a 125-amino acid precursor. Northern blot analysis identified two different ASP mRNAs in ventral skin of red- and black-pigmented and albino fish, but no expression levels were observed in the dorsal skin of the same fish. The dorsal-ventral expression polarity was also detected in both black dorsally pigmented fish and albino fish. Pharmacological studies demonstrate that goldfish ASP acts as a melanocortin antagonist at Fugu MC1R and goldfish MC4R. In addition, goldfish ASP inhibited Nle4, D-Phe7-MSH-stimulated pigment dispersion in medaka melanophores. Our studies support agouti signaling protein as the melanization inhibition factor, a key factor in the development of the dorsal-ventral pigment pattern in fish.

Characterization of Japanese Quail yellow as a Genomic Deletion Upstream of the Avian Homolog of the Mammalian ASIP (agouti) Gene

“…The finding of an expressed ASIP gene in birds, involved in dorsoventral pigmentation patterning, is interesting as it suggests a conserved basis for this type of pattern between birds and mammals. This backs up evidence suggesting that ASIP diverged from AGRP early in vertebrate evolution (Klovins and Schiö th 2005) and that ASIP may be involved in regulating dorsoventral pigmentation patterning in fish (Cerdá-Reverter et al 2005). Fish differ from mammals and birds in that they have several different types of pigment cells (chromatophores); only one of these contains melanin (the melanophores) and only eumelanin, not pheomelanin (Ito and Wakamatsu 2003;Kelsh 2004).…”

KERAGAAN WARNA DAN GENOTIPE CALON INDUK (F0) IKAN CLOWN (Amphiprion sp.) STRAIN BLACK PERCULA

“…Pola warna pada ikan terbentuk dari adanya interaksi antara cahaya dengan pola distribusi sel warna (Cerda-Reverter et al, 2009). Terkait pembentukannya, Kelsh et al (2004) menjabarkan tiga model/skenario pembentukan pola warna pada ikan.…”

Spectral Tuning in the Eyes of Deep-Sea Lanternfishes (Myctophidae): A Novel Sexually Dimorphic Intra-Ocular Filter

“…Although pheomelanin has yet to be directly observed in fishes ], the presence of agouti signalling proteins (ASIP), which control the production of pheomelanin, in several fishes, i.e. goldfish [Cerda-Reverter et al, 2005], zebrafish and several species of pufferfishes [Klovins and Schiöth, 2005], indicates that it may be present; it could therefore be one of the components of the yellow pigmentation in lanternfishes.…”