Genetik Reseptor Melanokortin 1 (Mcir) pada Kuskus Papua (Genus Spilocuscus) dan Hubungannya dengan Pigmentasi Kulit.

Abstract

Coat color in mammals is determined by the pigment melanin, produced by melanocyte cells and regulated by the melanocortin-1 receptor (MC1R). While the association between coat color and MC1R has been extensively studied in eutherian (placental) mammals, data on the MC1R gene and its cellular function in marsupials are limited. We investigated coat color variation and MC1R function in two Papuan marsupial species of the genus Spilocuscus: the widely distributed S. maculatus (n = 12) and the range-restricted S. wilsoni (n = 4). Phenotypic observations revealed that S. maculatus displays diverse coat color patterns, including solid white, yellow, orange, and spotted combinations. In contrast, S. wilsoni shows more uniform cream coloration with light and dark brown markings. The analysis of the MC1R coding sequences identified three nucleotide haplotypes in each species. S. maculatus carried a conserved amino acid haplotype, while S. wilsoni possessed three distinct amino acid haplotypes, with variations at positions 25, 173, 280, and 305. Haplotype network analysis showed that the two species do not share MC1R haplotypes and may reflect species-specific divergence. Our functional assays showed species-specific differences in MC1R signaling. S. maculatus MC1R showed consistently high basal and maximum cAMP production, indicating strong constitutive activation of the receptor and response to a-MSH ligand. In contrast, S. wilsoni MC1R variants exhibited reduced basal and maximum cAMP production compared to S. maculatus and variation in basal activity among haplotypes of S. wilsoni. Overall, these results suggest that although the MC1R function has changed at the molecular level, its role in determining pigmentation may be less central in these species. Our findings highlight the complexity of pigmentation regulation in marsupials, suggesting that additional genetic and regulatory factors likely contribute to the diversity of coat colors in these species.