Characterization of Epithelial Cells in the Hair Follicle With S100 Proteins

S100 proteins are the largest subgroup of Ca²⁺ binding proteins with the EF-hand structural motif. A unique feature of this protein family is that individual members are localized in specific cellular compartments. For example, various S100 proteins are expressed in very restricted regions of the hair follicle: S100A3 and S100A6 in distinct postmitotic differentiated epithelial cells and S100A4 and S100A6 in the epithelial stem cell compartments. Characterization of epithelial cells by their S100 protein expression profiles is therefore useful for a better understanding of the dynamic cellular events associated with hair follicle development and regeneration. This chapter presents our protocols for probe preparations and histochemical analyses of S100 proteins in hair follicle tissue, including simultaneous detection procedures for pulse-labeled proliferating cells.