Human trichohyalin gene is clustered with the genes for other epidermal structural proteins and calcium-binding proteins at chromosomal locus 1q21.

Trichohyalin is a major differentiation product of hard keratinizing tissues such as the inner root sheath and medullary cells of the hair follicle and the filiform papillae of the tongue, as well as terminally differentiating epidermal cells. It consists largely of quasi-repeating peptide repeats and functions primarily as an intermediate filament-associated protein in these tissues. By mapping with human-rodent somatic cell hybrids and fluorescent in situ hybridization, we demonstrate that its gene maps to chromosomal region 1q21. Interestingly, genes encoding several other structural proteins expressed during terminal differentiation in the epidermis map to this region, as do also several members of the S-100 class of small calcium-binding proteins.