c-Maf and MafB transcription factors are differentially expressed in Huxley's and Henle's layers of the inner root sheath of the hair follicle and regulate cuticle formation

Background: The hair follicle of mammalian skin consists of a group of concentric epithelial cell layers. The inner root sheath (IRS), which surrounds the hardening hair shaft beneath the skin surface, is subdivided into three layers, termed the cuticle of the IRS, Huxley's layer, and Henle's layer. The IRS forms a follicular wall in the hair canal and helps guide the developing hair shaft. c-Maf and MafB, members of the Maf family of transcription factors, play important roles in the developmental processes of various tissues and in cell type-specific gene expression.

Objective: The aim of this study is to reveal the pattern of expression and functional roles of c-Maf and MafB in the hair follicle.

Methods: We determined the precise location of c-Maf and MafB expression using immunofluorescent staining of mouse skin sections with layer-specific markers. We also analyzed whiskers of c-maf- and mafB-null mice (c-maf(-/-) and mafB(-/-), respectively) using scanning electron microscopy.

Results: c-Maf and MafB were differentially expressed in the Huxley's and Henle's layers of the IRS. Scanning electron microscopic analysis showed irregular cuticle patterning of whiskers of c-maf(-/-) and mafB(-/-) mice. The cuticles of mafB(-/-) mice were also thinner than those of wild-type mice.

Conclusion: c-Maf and MafB are expressed in the IRS layers in a lineage-restricted manner and are involved in hair morphogenesis.