FOXN1 Is Critical for Onycholemmal Terminal Differentiation in Nude (Foxn1nu) Mice

Nude mice with a Foxn1(nu) mutation exhibited downregulation of hair keratins, leading to structurally weak hair fibers that break off. Their nails were deformed due to altered onychocyte differentiation, with decreased sulfur concentrations and lack of keratin 1 expression in the nail matrix. The differentiation process shifted towards an epidermis-like pattern, producing filaggrin-containing keratohyalin granules. The nail plates were thinner, weak, and prone to breaking. These findings highlighted the critical role of Foxn1 in normal onycholemmal differentiation and provided insights into the molecular controls of nail formation, offering a model for studying nail diseases.