Sequences and Differential Expression of Three Novel Human Type-II Hair Keratins

The study characterized three novel human type-II hair keratins, hHb3, hHb5, and hHb6, revealing their cDNA and amino acid sequences, which showed high conservation with sheep wool keratins. The research highlighted distinct expression patterns of these keratins in human anagen hair follicles. hHb5 mRNA synthesis began at the base of the hair bulb and extended into the lower cortex, while hHb1 and hHb3 mRNA synthesis started higher in the cortex and continued beyond hHb5. hHb6 mRNA synthesis initiated even higher and extended into the keratogenous zone. The findings indicated that hair differentiation, marked by keratin expression, started earlier than previously thought, beginning in the lower matrix cells and continuing through a late cortical phase involving multiple type-II keratins.