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The mouse ruby-eye 2d (ru2d/Hps5ru2-d) allele inhibits eumelanin but not pheomelanin synthesis


CORRESPONDENCE T. Hirobe, e-mail:


The novel mutation named ru2d/Hps5ru2-d, characterized by light-colored coats and ruby-eyes, prohibits differentiation of melanocytes by inhibiting tyrosinase (Tyr) activity, expression of Tyr, Tyr-related protein 1 (Tyrp1), Tyrp2, and Kit. However, it is not known whether the ru2d allele affects pheomelanin synthesis in recessive yellow (e/Mc1re) or in pheomelanic stage in agouti (A) mice. In this study, effects of the ru2d allele on pheomelanin synthesis were investigated by chemical analysis of melanin present in dorsal hairs of 5-week-old mice from F2 generation between C57BL/10JHir (B10)-co-isogenic ruby-eye 2d and B10-congenic recessive yellow or agouti. Eumelanin content was decreased in ruby-eye 2d and ruby-eye 2d agouti mice, whereas pheomelanin content in ruby-eye 2d recessive yellow and ruby-eye 2d agouti mice did not differ from the corresponding Ru2d/- mice, suggesting that the ru2d allele inhibits eumelanin but not pheomelanin synthesis.