Functions of Melanogenesis-Related Genes by Chemical and Biochemical Methods

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Mammalian melanins exist in two chemically distinctforms : the brown to black eumelanins and the yellow to reddish pheomelanins. Melanogenesis is influenced by a number of genes, the levels of whose products determine the quantity and quality of the melanins produced. To examine the effects of various coat-color genes on the chemical properties of melanins synthesized in the follicular melanocytes of mice, we have introduced new methods to solubilize differentially pheomelanins and brown -type eumelanins. We applied these and previously developed HPLC and spectrophotometric methods for assaying eu- and pheomelanins to characterize melanins in various mutant mice : black, lethal yellow, viable yellow, agouti, brown, light, albino, dilute, recessive yellow, pink-eyed dilution, slaty, and silver. It was demonstrated that 1) complete solubilization of melanins in Soluene-350 is a convenient method to estimate the total amount of eu- and pheomelanins, 2) lethal yellow, viable yellow, and recessive yellow hairs contain almost pure pheomelanins, and 3) melanins from brown, light, silver, and pink-eyed black hairs share chemical properties in common that are characterized by partial solubility in strong alkali. We suggest that 1) the brown-type eumelanins have lower degrees of polymerization than the black-type eumelanins, and 2) slaty hair melanin contains a greatly reduced ratio of 5,6-dihydroxyindole-2-carboxylic acid-derived units as compared with black and other eumelanic hair melanins. These results indicate that our methodology, HPLC and spectrophotometric methods combined, may be useful in chemically characterizing melanin pigments produced follicular melanocytes.