melanogenic

Melanogenic is an adjective describing processes, substances, or factors that promote or pertain to melanin formation, the biosynthesis of the pigment melanin in specialized cells called melanocytes. Melanin production occurs mainly in the epidermis, particularly the basal layer of the epidermis and within hair follicles, and also in ocular tissues such as the retinal pigment epithelium.

In melanocytes, melanin is synthesized in organelles called melanosomes. The enzyme tyrosinase catalyzes the rate-limiting steps, converting tyrosine to DOPA and then to dopaquinone; tyrosinase-related proteins TYRP1 and TYRP2/DCT modify the pathway, leading to production of eumelanin (brown/black pigment) and pheomelanin (red/yellow pigment). The final pigment is transported to keratinocytes and contributes to skin and hair coloration.

Melanogenic activity is tightly regulated. MITF is a master transcription factor controlling expression of TYR, TYRP1, and DCT. Signaling through MC1R and increased intracellular cAMP activates PKA, CREB, and MITF, enhancing eumelanin synthesis. Ultraviolet radiation and hormonal signals such as alpha-melanocyte-stimulating hormone bias production toward eumelanin.

Variation in melanogenic capacity underlies human hair and skin color diversity and can be altered in disease. Defects in melanogenesis cause oculocutaneous albinism; other conditions modify pigmentation, including some pigmentary disorders and melanoma. Researchers study melanogenic pathways to understand pigmentary biology and to develop cosmetic or therapeutic agents; modulation can involve inhibitors or activators that influence signaling pathways.

Etymology: melanogenic derives from melanin and -genic, meaning producing. The term is used in biology and medicine to describe factors that influence melanin synthesis.