Isolation and Characterization of Human Repetin, a Member of the Fused Gene Family of the Epidermal Differentiation Complex

The study isolated and characterized the human repetin gene, part of the fused gene family in the epidermal differentiation complex on chromosome 1q21. Repetin, a 784 amino acid protein, contained EF hands of the S100 type and internal tandem repeats, typical of cell envelope precursor proteins. It was strongly expressed in specific epidermal areas, such as the acrosyringium and inner hair root sheath, and was a component of keratohyalin granules in the stratum granulosum. The study showed that repetin's EF hands could reversibly bind calcium, confirming its role in epidermal differentiation, similar to profilaggrin and trichohyalin. Repetin was prominently expressed in the tongue and inner root sheath of hair follicles, suggesting a role in hair follicle biology. Its expression increased significantly when terminal differentiation was disrupted, indicating a potential compensatory role in the absence of other structural proteins like loricrin. The research faced challenges in expressing full-length repetin in mammalian cells, limiting further functional analysis.