Cellular and molecular features of mammalian pigmentation--tyrosinase and TRP

Melanin pigments are found in all biological kingdoms. At the cellular level, correct pigmentation depends not only on correct migration of pigment cells (melanocytes) and their precursors (melanoblasts), but also on specialized cytoplasmic organelles, melanosomes. Three pigment cell-specific enzymes inside melanosomes are involved in melanogenesis: tyrosinase, TRP-1 and TRP-2/DOPA-chrome tautomerase. A point mutation of tyrosinase is sufficient to give rise to a nonfunctional enzyme, leading to albinism and associated decreased visual acuity. Several regulatory elements have been identified within the promoters of the genes encoding these three enzymes. These promoter fragments have been used to target the expression of heterogeneous genes in pigment cells of transgenic mice.