The Role Of Gsdma3 Gene In Hair Follicle Differentiation And The Research Of Its Mechanisms

Hair follicle is a complex mini-organ that undergoes cyclic process. During embryonic development, hair follicle is initiated as a result of interactions between the primitive epithelium and the underlying mesenchymal. As the epithelium starting a downward growth into the dermis, the key signal centre dermal papilla (DP) cells are enclosed by matrix keratinocytes, which proliferate and differentiate into the multilayered inner root sheath (IRS), composed of Henle's, Huxley's and cuticle layers, and then the hair. The terminal hair shaft is made up of three layers: cuticle, cortex and medulla. The outermost layer hair shaft cuticle (Cuh) interlocks with IRS cuticle to form an interlocking structure, which is necessary for protecting the hair shaft from shedding. The hair follicle differentiation is regulated by multiple signaling pathways, involves Bmp, homeobox genes, and Wnt. Their specific expression patterns in dermal papilla or matrix cells determinate their functions in differentiation. However, the known cellular and molecular mechanisms are limited.Gsdma3 is a novel murine gene and considered to be a mutation hotspot. In previous studies, it was reported as a mutation hotspot and that Gsdma3 mutations showed alopecia and hyperkeratosis phenotypes. All these studies indicated an important role Gsdma3 played in the maintenance of hair follicles. However, little is known about what leads to hair loss in Gsdma3 mutants, and what potential regulatory mechanisms are involved. Earlier studies have shown the Gsdma3 mRNA and protein expression by in situ hybridization and immunohistochemistry respectively, but the results remains inconclusive.In order to verify how the lack of Gsdma3 affects the hair defects, we use alopecia and excoriation mice, a new mouse mutation in this gene, as our research model. The external hairs exhibited a short and curly phenotype in these mutant mice. At postnatal day 25, the mice began to lose their hairs from the head region, and progressing toward the whole back. However, when a new hair cycle was initiated, the hairs regrew. This process was followed by progressive hair loss and regrowth. Ultrastructural and histological analyses show abnormal hair structures and reduced hair keratins in these mutants. The loss of interlocking structures and abnormal constitutive protein indicate defects in anchoring hair shaft in the hair follicle and resisting external forces. Therefore, functional defect of Gsdma3 disrupts IRS and hair shaft differentiation. Immunohistochemistry was used to test that Gsdma3 is expressed in matrix, inner root sheath, and hair shaft, these cell types are associated with hair follicle differentiation. Molecular analysis of Gsdma3 deficiency shows that the master regulators of Msx2 regulatory pathway display a visible down-regulation in the mutants. What is more, Gsdma3 had the same expression pattern with Msx2. When overexpressing Gsdma3 by nake plasmid DNA injection into the skin, all of these genes expression were up-regulated. These results demonstrate that Gsdma3 might regulate Msx2 pathway directly or indirectly. In conclusion, our results show that Gsdma3 is essential in normal hair follicle differentiation and functions by regulating Msx2/Foxn1/acidic hair keratin cascade.