Int J Biol Sci 2020; 16(7):1264-1273. doi:10.7150/ijbs.38415

Research Paper

SASH1 promotes melanin synthesis and migration via suppression of TGF-β1 secretion in melanocytes resulting in pathologic hyperpigmentation

Hongzhou Cui1,2,3*, Shuping Guo1*, Hongxia He1, Huina Guo2,3, Yuliang Zhang2,3, Binquan Wang1,2,3✉

1. Department of Dermatology, the First Hospital, Shanxi Medical University, Taiyuan, Shanxi, China
2. Shanxi Key Laboratory of Otorhinolaryngology Head and Neck Cancer, Shanxi Medical University, Taiyuan, Shanxi, China
3. The Key Scientific and Technological Innovation Platform for Precision Diagnosis and Treatment of Head and Neck Cancer, Shanxi Province, Taiyuan 030001, Shanxi, China
* Hongzhou Cui and Shuping Guo contributed equally as first authors.

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Citation:
Cui H, Guo S, He H, Guo H, Zhang Y, Wang B. SASH1 promotes melanin synthesis and migration via suppression of TGF-β1 secretion in melanocytes resulting in pathologic hyperpigmentation. Int J Biol Sci 2020; 16(7):1264-1273. doi:10.7150/ijbs.38415. Available from http://www.ijbs.com/v16p1264.htm

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Abstract

Dyschromatosis universalis hereditaria (DUH) is an autosomal dominant pigmentary genodermatosis characterized by the presence of patches of hyperpigmentation and hypopigmented macules distributed over the body, with most cases reported in Asia. DUH is a heterogeneous disease and a small portion of patients carry the ABCB6 variant. In the present study, exome sequencing of four generations of a Chinese family with DUH identified a c.1761C>G (p.Ser587Arg) mutation in exon 15 of SAM and SH3 domain containing 1 (SASH1) that was found to co-segregate in some family members. Immunohistological analysis of biopsy specimens showed that SASH1 was diffusely distributed in all layers of the epidermis, suggesting increased transepithelial migration of melanocytes (MCs). The point mutation c.1761C>G of SASH1 was successfully induced in immortalized human melanocyte (PIG1) cells, which resulted in the downregulation of SASH1 expression. Bioinformatics analysis showed that mutated SASH1 downregulated thrombospondin 1 (THBS1) expression and inactivated transforming growth factor beta 1 (TGF-β1) signaling. TGF-β1 expression by PIG1cells was found to negatively regulate SASH1 protein expression. Transwell migration and wound-healing assays showed an increase in the migration and invasion capabilities of the cells carrying the mutation. Further, SASH1 mutations induced downregulation of melanin content. The study results suggest cross-talking between SASH1-TGF-β1 signaling, demonstrating the proposed MC migration modulation models and affecting melanin trafficking in the epithelium.