Changing expression of the genes related to human hair graying.

Hair graying is one of the prototypical signs of human aging, but its mechanism is largely unknown. To elucidate the mechanism of hair graying, we investigated gene expression related to melanogenesis in human hair. The key molecules in melanogenesis, microphthalmia-associated transcription factor-M (MITF-M), Sox10, Pax3, tyrosine related protein-1 (TRP-1), and tyrosinase, were absent or greatly reduced in the bulbs of white hair compared to black hair. Melanocyte stem cells (MSCs) or melanocytes express markers for neural crest cells, Sox10, Pax3, and MITF-M. Taken together, our data suggest that hair graying is caused by defective migration of MSCs into the bulb area of hair.