The peripheral clock regulates human pigmentation

J Invest Dermatol. 2015 Apr;135(4):1053-1064. doi: 10.1038/jid.2014.442. Epub 2014 Oct 13.

Abstract

Although the regulation of pigmentation is well characterized, it remains unclear whether cell-autonomous controls regulate the cyclic on-off switching of pigmentation in the hair follicle (HF). As human HFs and epidermal melanocytes express clock genes and proteins, and given that core clock genes (PER1, BMAL1) modulate human HF cycling, we investigated whether peripheral clock activity influences human HF pigmentation. We found that silencing BMAL1 or PER1 in human HFs increased HF melanin content. Furthermore, tyrosinase expression and activity, as well as TYRP1 and TYRP2 mRNA levels, gp100 protein expression, melanocyte dendricity, and the number gp100+ HF melanocytes, were all significantly increased in BMAL1 and/or PER1-silenced HFs. BMAL1 or PER1 silencing also increased epidermal melanin content, gp100 protein expression, and tyrosinase activity in human skin. These effects reflect direct modulation of melanocytes, as BMAL1 and/or PER1 silencing in isolated melanocytes increased tyrosinase activity and TYRP1/2 expression. Mechanistically, BMAL1 knockdown reduces PER1 transcription, and PER1 silencing induces phosphorylation of the master regulator of melanogenesis, microphthalmia-associated transcription factor, thus stimulating human melanogenesis and melanocyte activity in situ and in vitro. Therefore, the molecular clock operates as a cell-autonomous modulator of human pigmentation and may be targeted for future therapeutic strategies.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • ARNTL Transcription Factors / metabolism*
  • Biological Clocks*
  • Epidermis / metabolism
  • Gene Silencing
  • Hair Follicle / metabolism
  • Humans
  • Keratinocytes / cytology
  • Melanins / chemistry
  • Melanins / metabolism
  • Melanocytes / cytology
  • Microphthalmia-Associated Transcription Factor / metabolism
  • Monophenol Monooxygenase / metabolism
  • Period Circadian Proteins / metabolism*
  • Pigmentation*
  • Skin / metabolism
  • gp100 Melanoma Antigen / metabolism

Substances

  • ARNTL Transcription Factors
  • BMAL1 protein, human
  • Melanins
  • Microphthalmia-Associated Transcription Factor
  • PER1 protein, human
  • Period Circadian Proteins
  • gp100 Melanoma Antigen
  • Monophenol Monooxygenase