Trichohyalin-like 1 (TCHHL1, also known as THHL1, S100A17), is a member of the fused-type S100 protein family. The TCHHL1 gene is located on chromosome 1q21.3 that encodes an S100 family protein of unknown function. This gene is evolutionarily conserved; its expression appears to be hair-specific and spatially restricted within the distal inner root sheath of the hair follicle. It thus may have an important role in hair morphogenesis. The deduced amino acid sequence of TCHHL1 contains an EF-hand domain in the N-terminus, one trans-membrane domain and a nuclear localization signal. This protein is expressed in the basal layer of the normal epidermis.