Recent advances in understanding the molecular basis of melanogenesis in melanocytes

F1000Res. 2020 Jun 15:9:F1000 Faculty Rev-608. doi: 10.12688/f1000research.24625.1. eCollection 2020.

Abstract

Melanin pigments are responsible for human skin and hair color, and they protect the body from harmful ultraviolet light. The black and brown melanin pigments are synthesized in specialized lysosome-related organelles called melanosomes in melanocytes. Mature melanosomes are transported within melanocytes and transferred to adjacent keratinocytes, which constitute the principal part of human skin. The melanosomes are then deposited inside the keratinocytes and darken the skin (a process called tanning). Owing to their dark color, melanosomes can be seen easily with an ordinary light microscope, and melanosome research dates back approximately 150 years; since then, biochemical studies aimed at isolating and purifying melanosomes have been conducted. Moreover, in the last two decades, hundreds of molecules involved in regulating melanosomal functions have been identified by analyses of the genes of coat-color mutant animals and patients with genetic diseases characterized by pigment abnormalities, such as hypopigmentation. In recent years, dynamic analyses by more precise microscopic observations have revealed specific functions of a variety of molecules involved in melanogenesis. This review article focuses on the latest findings with regard to the steps (or mechanisms) involved in melanosome formation and transport of mature melanosomes within epidermal melanocytes. Finally, we will touch on current topics in melanosome research, particularly on the "melanosome transfer" and "post-transfer" steps, and discuss future directions in pigment research.

Keywords: BLOC; Rab small GTPase; melanogenic enzymes; melanosome maturation; membrane traffic.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Animals
  • Humans
  • Keratinocytes
  • Melanins / biosynthesis*
  • Melanocytes / metabolism*
  • Melanosomes / metabolism*
  • Skin / cytology
  • Skin Pigmentation

Substances

  • Melanins

Grants and funding

This work was supported in part by Grant-in-Aid for Scientific Research (C) from the Ministry of Education, Culture, Sports, Science, and Technology (MEXT) of Japan (grant number 19K06653 to N.O.), Grant-in-Aid for Scientific Research (B) from the MEXT (grant number 19H03220 to M.F.), and Japan Science and Technology Agency (JST) CREST (grant number JPMJCR17H4 to M.F.).