052 Asymmetrical Expression of a Keratin Intermediate Filament in Ferret Hair Follicles

Z.D. Yu1,2, A.J. Nixon1, R.J. Wilkins2, and A.J. Pearson1 1AgResearch Ruakura, Hamilton, New Zealand. 2Dept. Biological Sciences, University of Waikato, Hamilton, New Zealand

The cortex of hair fibres is largely comprised of keratin intermediate filament (IF) and keratinassociated proteins (KAPs). The highly ordered and sequential expression of different keratin IFs and KAPs underlies the formation of the mature hair fibre. Whereas some KAPs have been found to be asymmetrically expressed within the follicle, previously reported IFs are expressed uniformly across the cortex. Here, we report on the unusual pattern of expression of a ferret keratin IF gene. This transcript was identified by differential display of RNA extracted from the skin of prepubertal ferrets administered with melatonin to synchronise winter hair growth. Two adjacent cDNA bands specific to the mid/late proanagen stage were cloned and sequenced. The sequences were found to have limited homology to a region in the 3’ untranslated region (UTR) of human hair acidic keratin 8 (hHa8). Northern blot analysis confirmed that a mRNA of 2.8 kb existed only in skin samples containing hair follicles in which fibre keratinisation was advanced. In situ hybridisation using probes labelled with digoxigenin demonstrated that the expression of this gene was restricted to the cortex of the keratinisation zone. Although expression of fHa8 was in a similar zone of keratinisation to that observed in human hair follicles, it showed a distinct asymmetry, varying from small patches to half of the follicle in both longitudinal and transverse sections. The full ferret Ha8 cDNA generated by rapid amplification of cDNA ends (RACE) was 2769 bp; of similar length to the human orthologue (2837 bp). The two transcripts had high sequence homology in the coding region, but reduced homology in the 3’ UTR. Both encode proteins of 456 amino acids, which share 83% positive and 76% identical residues. The asymmetrical expression of ferret Ha8 distinguishes it from that previously reported in humans, and suggests additional functions in ferret hair follicles. The expression of this keratin may also represent a marker of a different cell differentiation pathway.