and the response of melanocytes to ultraviolet radiation. Mutat Res. 2005;57:133-52. [ Links ]18. Murisier F, Beermann F. Genetics of pigment cells: lessons from the tyrosinase gene family. Histol Histopathol. 2006;2:567-78. [ Links ]19. Ito S. A chemist's view of melanogenesis. Pigment Cell Res. 2003;16:230-6. [ Links ]20. Thody AJ, Graham A. Does alpha-MSH have a role in regulating skin pigmentation in humans? Pigment Cell Res. 1998;1:265-74. [ Links ]21. Wagner JK, Parra EJ, LNorton H, Jovel C, Shriver MD. Skin responses to ultraviolet radiation: effects of constitutive pigmentation, sex, and ancestry. Pigment Cell Re. 2002;15:385-90. [ Links ]22. Hearing VJ. Biogenesis of pigment granules: a sensitive way to regulate melanocyte function. J Dermatol Sci. 2005;37:3-14. [ Links ]23. Boissy RE. Melanosome transfer to and translocation in the keratinocyte. Exp Dermato. 2003;12 Suppl 2:5-12. [ Links ]24. Szabo G, Hirobe T, Flynn EA, Garcia RI. The biology of the melanocyte. Prog Clin Biol Res.1988;256:463-74. [ Links ]25. Rouzaud F, Hearing VJ. Regulatory elements of the melanocortin 1 receptor. Peptides. 2005;26:1858-70. [ Links ]26. Slominski A, Tobin DJ, Shibahara S, Wortsman J. Melanin pigmentation in mammalian skin and its hormonal regulation. Physiol Rev. 2004;84:1155-228. [ Links ]27. Klaus SN, Snell RS. The response of mammalian epidermal melanocytes in culture to hormones. J Invest Dermatol. 1967;48:352-8. [ Links ]28. Barsh G, Attardi LD. A healthy tan? N Engl J Med. 2007;356:2208-10. [ Links ]29. Wickelgren I. Skin biology. A healthy tan? Science. 2007; 315:1214-6. [ Links ]30. Bastiaens M, ter Huurne J, Gruis N, Bergman W, Westendorp R, Vermeer BJ, et al. The melanocortin-1-receptor gene is the major freckle gene. Hum Mol Genet. 2001;10:1701-8. [ Links ]31. Prusis P, Schioth HB, Muceniece R, Herzyk P, Afshar M, Hubbard RE, et al. Modeling of the three-dimensional structure of the human melanocortin 1 receptor, using an automated method and docking of a rigid cyclic melanocyte-stimulating hormone core peptide. J Mol Graph Model.1997;15:307-17,334. [ Links ]32. Abdel-Malek Z, Scott MC, Suzuki I, Tada A, Im S, Lamoreux L, et al. The melanocortin-1 receptor is a key regulator of human cutaneous pigmentation. Pigment Cell Res. 2000;13 Suppl 8:156-62. [ Links ]33. Thody AJ. alpha-MSH and the regulation of melanocyte function. Ann N Y Acad Sci. 1999;885:217-29. [ Links ]34. Voisey J, Carroll L, van Daal A. Melanocortins and their receptors and antagonists. Curr Drug Targets. 2003;4:586-97. [ Links ]35. Prusis P, Frandberg PA, Muceniece R et al. A three dimensional model for the interaction of MSH with the melanocortin-1 receptor. Biochem Biophys Res Commun. 1995;210:205-10. [ Links ]36. Mountjoy KG, Robbins LS, Mortrud MT, Kalvinsh I, Wikberg JE. The cloning of a family of genes that encode the melanocortin receptors. Science. 1992;257:1248-51. [ Links ]37. Valverde P, Healy E, Jackson I, Rees JL, Thody AJ. Variants of the melanocyte-stimulating hormone receptor gene are associated with red hair and fair skin in humans. Nat Genet. 1995;11:328-30. [ Links ]38. Rees JL. The melanocortin 1 receptor (MC1R): more than just red hair. Pigment Cell Res. 2000;13:135-40. [ Links ]39. Tan CP, McKee KK, Weinberg DH, MacNeil T, Palyha OC, Feighner