Document Detail

Redefining the skin's pigmentary system with a novel tyrosinase assay.
MedLine Citation:
PMID:  12100495     Owner:  NLM     Status:  MEDLINE    
In mammalian skin, melanin is produced by melanocytes and transferred to epithelial cells, with the epithelial cells thought to receive pigment only and not generate it. Melanin formation requires the enzyme tyrosinase, which catalyzes multiple reactions in the melanin biosynthetic pathway. Here, we reassess cutaneous melanogenesis using tyramide-based tyrosinase assay (TTA), a simple test for tyrosinase activity in situ. In the TTA procedure, tyrosinase reacts with biotinyl tyramide, causing the substrate to deposit near the enzyme. These biotinylated deposits are then visualized with streptavidin conjugated to a fluorescent dye. In the skin and eye, TTA was highly specific for tyrosinase and served as a sensitive indicator of pigment cell distribution and status. In clinical skin samples, the assay detected pigment cell defects, such as melanocytic nevi and vitiligo, providing confirmation of medical diagnoses. In murine skin, TTA identified a new tyrosinase-positive cell type--the medullary cells of the hair--providing the first example of cutaneous epithelial cells with a melanogenic activity. Presumably, the epithelial tyrosinase originates in melanocytes and is acquired by medullary cells during pigment transfer. As tyrosinase by itself can generate pigment from tyrosine, it is likely that medullary cells produce melanin de novo. Thus, we propose that melanocytes convert medullary cells into pigment cells by transfer of the melanogenic apparatus, an unusual mechanism of differentiation that expands the skin's pigmentary system.
Rong Han; Howard P Baden; Janice L Brissette; Lorin Weiner
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S.; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Pigment cell research / sponsored by the European Society for Pigment Cell Research and the International Pigment Cell Society     Volume:  15     ISSN:  0893-5785     ISO Abbreviation:  Pigment Cell Res.     Publication Date:  2002 Aug 
Date Detail:
Created Date:  2002-07-08     Completed Date:  2003-01-14     Revised Date:  2014-04-08    
Medline Journal Info:
Nlm Unique ID:  8800247     Medline TA:  Pigment Cell Res     Country:  Denmark    
Other Details:
Languages:  eng     Pagination:  290-7     Citation Subset:  IM    
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MeSH Terms
Biotin / analogs & derivatives*,  diagnostic use
Enzyme Inhibitors / pharmacology
Epidermis / cytology,  metabolism
Fluorescent Antibody Technique, Direct / methods
Melanins / biosynthesis*
Melanocytes / cytology,  metabolism*
Monophenol Monooxygenase / metabolism*
Nevus, Pigmented / metabolism,  pathology
Predictive Value of Tests
Proto-Oncogene Proteins c-kit / metabolism
Pyrones / pharmacology
Reproducibility of Results
Skin / cytology,  metabolism*
Tissue Fixation / methods
Tyramine / analogs & derivatives*,  diagnostic use
Grant Support
Reg. No./Substance:
0/Enzyme Inhibitors; 0/Melanins; 0/Pyrones; 0/biotinyltyramide; 6K23F1TT52/kojic acid; 6SO6U10H04/Biotin; EC Monooxygenase; EC Proteins c-kit; X8ZC7V0OX3/Tyramine

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