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AT-A-GLANCE

AT-A-GLANCE

  • Development of Melanocytes

    • Melanocytes are derived from neural crest lineage

    • Transcription factors (MITF, SOX10, PAX3) and signaling pathways (KIT, EDNRB) that are important for development, migration, and survival of melanocytes also play key roles in melanoma

  • Function of melanocytes

    • Key function of melanocytes is to synthesize melanin and transfer to surrounding keratinocytes

    • Melanocytes can produce brown/black melanin (eumelanin) or orange/yellow melanin (pheomelanin)

    • The melanosome, a specialized lysosome-related organelle, is the site of melanin synthesis and storage

  • Regulation of human pigmentation

    • Common human variants in melanocortin 1 receptor (MC1R) lead to the “red hair phenotype”—red hair, fair skin, inability to tan, and increased melanoma risk

    • MC1R signals to the MITF transcription factor to regulate pigmentation and sun-tanning

INTRODUCTION

Melanocytes are specialized cells of the epidermis and hair follicle whose primary function is to synthesize and transfer melanin to adjacent keratinocytes. Melanin synthesis occurs in a specialized organelle, the melanosome; proper melanosome biogenesis and trafficking are required for normal pigmentation. Melanocyte numbers are similar in individuals of different racial backgrounds, and instead differences of pigmentation are a result of the amount and quality of melanin in the skin, in large part driven by variability in the number, size, distribution, and function of melanosomes within keratinocytes.1,2 Analysis of mutations in mice and humans (Table 20-1) that cause pigmentation defects have allowed the identification of key regulators of melanocyte development, survival, and function. Many of these same genes play critical roles in the pathogenesis of melanoma.

Table 20-1Genetic Hypopigmentation and Hyperpigmentation Disorders Caused by Mutations in Genes Important for Melanocyte Development and Biology

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