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Juvenile poliosis, also known as premature canities, occurs in young adults. The incidence of this condition is about 15-32% in the Chinese population. The mechanism of juvenile poliosis is currently poorly understood but is thought to be related to inheritance and nutrition. Hair pigmentation depends entirely on the presence of melanin, produced by melanocytes. The active melanocytes of the bulb are essential, because they produce and transfer melanin to the cortical keratinocytes of the shaft (1, 2). A reduction in tyrosinase (TYR) activity, suboptimal melanocyte-cortical keratinocyte interactions, and defective migration of melanocytes can all lead to pigment dilution or true grayness (3). Melanocytes of the follicular pigmentary unit are derived from the neural crest and melanogenesis is tightly regulated by several factors, including microphthalmia-associated transcription factor (MITF), the Paired box 3 (Pax3), the Sry-related HMG box 10 (Sox10), tyrosine kinase receptor c-Kit and others (4). MITF-M isoforms have been reported to be expressed in the hair bulb and in the melanocyte stem cells in the bulge area. MITF-M is a key transcription factor regulating the expression of tyrosinase, and is also associated with the migration, survival, and differentiation/proliferation of melanocytes (5). Pax3 can increase MITF expression by binding to its promoter and simultaneously prevent MITF from activating downstream genes by competition for enhancer occupancy in melanocyte precursors. Sox10 is expressed in melanoblasts, which can directly transactivate the MITF gene and cooperate with MITF to activate tyrosinase expression (6, 7). The tyrosine kinase receptor, c-Kit, is also important for melanocyte survival during development, and mutations in these genes result in unpigmented hairs (8). Furthermore, immature melanocytes must express c-Kit as a prerequisite for migration into the stem cell factor-supplying hair follicle epithelium. Differentiating c-Kit-positive melanocytes appear to target the hair bulb (4). The present study seeks to explore the expression of genes related to melanogenesis in relation to the mechanism of juvenile poliosis.

Downregulation of c-Kit/MITF-M in Graying Hair of Juvenile Poliosis