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SOX9 Protein is Key Regulator of Melanin in Skin Cells

It may play an important role in melanocyte differentiation in response to UVB light

THURSDAY, Aug. 16 (HealthDay News) -- The SOX9 protein, previously known for its role in sexual determinism and skeletal disorders, may play an important role in skin-cell development and melanin production, according to a report published online Aug. 16 in the Proceedings of the National Academy of Sciences.

Thierry Passeron, M.D., of the National Institutes of Health in Bethesda, Md., and colleagues conducted in vitro and in vivo studies to determine whether SOX9 mRNA is expressed in human skin.

The researchers found that the SOX9 protein is expressed by normal human melanocytes in culture and in adult human skin, and that exposure to ultraviolet B up-regulates expression of SOX9 in normal human melanocytes, which increases pigmentation. They also found that the agouti signal protein may decrease pigmentation by reducing the level of SOX9.

"In adult and neonatal melanocytes, SOX9 regulates microphthalmia-associated transcription factor, dopachrome tautomerase, and tyrosinase promoters, leading to an increase in the expression of these key melanogenic proteins and finally to a stimulation of pigmentation," the authors write. "SOX9 completes the complex and tightly regulated process leading to the production of melanin by acting at a very upstream level. This role of SOX9 in pigmentation emphasizes the poorly understood impact of SOX proteins in adult tissues."

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