The Roles of the Lrig1- and Lgr6-Positive Stem Cells in the Skin and the Functions of the Molecular Markers That Define Them

The study explored the roles of Lrig1- and Lgr6-positive stem cells in the hair follicle of adult mouse skin. Lrig1-positive cells were found in the junctional zone and were involved in maintaining the hair follicle infundibulum, with their activity influenced by treatments like 12-O-tetradecanoylphorbol-13-acetate. Mutations in Hras or Kras in these cells led to distinct phenotypes, such as wavy hair or oily skin, and contributed to papilloma development, although they were not common origins of chemically induced tumors. Lgr6-positive cells, located in the central isthmus, were identified as markers for cutaneous squamous cancer stem cells. Knockdown of Lgr6 increased growth in squamous tumor cell lines and accelerated papilloma development, suggesting Lgr6's role in regulating Wnt signaling and restraining epidermal lineage commitment during homeostasis and tumor development.