Keratin intermediate filament (KIF) and keratin-associated protein (KAP) genes encode the majority of wool proteins. In comparison to the 17 KIF genes reported to be expressed in human hair, only eight ovine homologues have been reported to date (1, 2). In this study, ovine KIFs were identified based on conservation among the mammalian species using an ovine contiguous cDNA library, or by PCR amplification with primers derived from bovine and human gene homologues. Nine previously unknown wool KIF genes (KRT32, KRT33B, KRT34, KRT36, KRT39, KRT40, KRT82, KRT84 and KRT87) were found. The analogue of human KRT37 (type I) was unable to be identified, while KRT87 (type II) is uniquely present in sheep. As a result, 10 type I and seven type II wool KIF genes were identified, compared to the 11 and six genes, respectively, reported in the human. Phylogenetic analysis of all available annotated hair KIF sequences from human, cattle and sheep reveals consistent relationships between members in both gene families in the three species. Localisation of KIF gene expression in wool follicles using in situ hybridisation indicated the involvement of all 17 KIFs, including KRT84 and KRT87, in wool formation. The expression patterns of all wool KIF genes were investigated and they displayed many similarities, but also some significant differences, to their human orthologues. The variation in co-expression of KIF genes may affect intermediate filament assembly, thus the fibre characteristics. Further comparative studies of their expression in sheep producing wool of contrasting characteristics may facilitate an improved understanding of their roles in the determination of fibre attributes.
References:
1. Langbein, L., and Schweizer, J. (2005) Int Rev Cytol 243: 1-78.
2. Yu, et al (2009) Differentiation 77: 307-316.