Exploring Variation in Ovine KRTAP19-5 and Its Effect on Fine Wool Fibre Curvature in Chinese Tan Sheep

Sheep's wool is known to have unique biological, physical and chemical properties. The fibre primarily consists of proteins, but these have amino acid sequence variation, and at the phenotypic level wool fibre varies considerably. This can affect its utility and value. Unravelling the genetic factors that underpin the protein and phenotypic variability is crucial if we are to contemplate improving wool quality. Accordingly, this study investigates the high glycine and tyrosine content keratin-associated protein 19-5 gene (KRTAP19-5) in sheep. PCR-single strand confirmation polymorphism analysis, coupled with DNA sequencing of a region spanning whole coding sequence, revealed six sequence variants containing seven single nucleotide polymorphisms (SNPs). Five of the SNPs were located within the coding region, with four leading to amino acid changes if expressed. In 247 Chinese Tan sheep derived from 10 sire-lines, and renowned for their distinct 'spring-like' crimped wool at up to approximately 35 days after birth, one of the variants was found to be associated with decreased curvature of the fine wool fibres in the fleece. No associations were detected with other fibre traits or with variation in the heterotypic hair fibres of the Tan sheep. While these findings may be useful for developing gene markers to alter mean wool fibre curvature and improve sheep breeding, many other genes and environmental factors are known to contribute to variation in fibre traits.