Ontogeny and Regional Variability of Keratin 2e in Developing Human Fetal Skin: A Unique Spatial and Temporal Pattern of Keratin Expression in Development

The study investigated the expression of keratin 2e (K2e) in developing human fetal skin, revealing a unique spatial and temporal pattern distinct from other epidermal keratins. K2e was first detected at 10 weeks estimated gestational age (EGA) in the presumptive nail bed and later shifted to the proximal nail fold by 13.5 weeks EGA. It was excluded from developing hair follicles and sweat glands, with expression patterns varying across different body regions. By 19 weeks EGA, K2e+ cells were observed at the level of the matrix in fetal hair follicles. The study highlighted the distinct regulation and function of K2e compared to other keratins, with some overlap in staining with K10 and K9, but mostly unique filamentous patterns.