Article

The structure and evolution of the melanocortin and MCH receptors in fish and mammals

MRC Human Genetics Unit, Western General Hospital, Edinburgh, EH4 2XU, UK.
Genomics (Impact Factor: 2.28). 03/2003; 81(2):184-91. DOI: 10.1016/S0888-7543(02)00037-X
Source: PubMed

ABSTRACT

Zebrafish are an excellent genetic model system for studying developmental and physiological processes. Pigment patterns in zebrafish are affected by mutations in three types of chromatophores. The behavior of these cells is influenced by alpha-melanocyte-stimulating hormone (alphaMSH) and melanin-concentrating hormone (MCH). Mammals have five alphaMSH receptors (melanocortin receptors) and one or two MCH receptors. We have identified the full complement of melanocortin and MCH receptors in both zebrafish and the pufferfish, Fugu. Zebrafish have six melanocortin receptors, including two MC5R orthologues, while Fugu, lacking MC3R, has only four. We also demonstrate that Fugu and zebrafish have two and three MCHR genes, respectively. MC2R and MC5R are physically linked in all species examined. Unlike other species, we find the Fugu genes contain introns, one of which is in a conserved location and is probably ancestral. We also detail the differential expression of the zebrafish genes throughout development.

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    • "The agouti gene expresses a secreted neuropeptide that acts as an endogenous antagonist of melanocortin receptors (Lu et al., 1994; Logan et al., 2003) and is involved in the suppression of melanin deposition during the hair cycle to produce the characteristic striped brown color of mouse and rat fur (Bultman et al., 1992; Millar et al., 1995). Mutations that result in the ubiquitous overexpression of agouti lead to the widespread blockade of melanocortin receptor signaling (Furumura et al., 1996) demonstrating that agouti is a non-specific antagonist of melanocortin receptors. "
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    • "The other intriguing aspect of the MCR family evolution is the absence of MC3R in most teleost fishes but this receptor is present in the genome of cartilaginous, amphibian, avian and mammalian species (Schiöth et al., 2005; Västermark and Schiöth, 2011). Some fishes also exhibit MC3R including spotted gar and coelacanth (Västermark and Schiöth, 2011) but the only known teleost fish exhibiting MC3R is the zebrafish (Logan et al., 2003) and goldfish. Kumar et al. (2011) reported that zebrafish MC3R does not share synteny relationship with the tetrapod MC3R. "
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