Identification of the ovine keratin-associated protein 15-1 gene (KRTAP15-1) and genetic variation in its coding sequence

Keratin-associated proteins (KAPs) are the major component of wool fibres. The gene encoding the high sulphur-protein KAP15-1 has been described in humans and mice, but it has not been identified in sheep. A BLAST search of the Ovine Genome Assembly v4.0 using the coding sequence of caprine KRTAP15-1, identified a putative ovine KAP15-1 gene clustered within eleven other KAP genes on chromosome 1. PCR-Single Stranded Conformational Polymorphism (PCR-SSCP) analysis was used to screen amplicons derived from the gene in 732 sheep from six Chinese sheep breeds. Four different PCR-SSCP patterns, representing four unique DNA sequences (designated A-D) were detected. These sequences shared lower identity with other ovine KRTAP sequences, but the highest similarity was found with goat and human KRTAP15-1 sequences. This suggests that the sequences are variants of ovine KRTAP15-1. Among these four sequences, six nucleotide substitutions were identified in the coding region and four of the substitutions were non-synonymous. Breed differences in variant frequencies were observed. A was the most common variant in all the breeds. The next common variant differed in frequency between breeds. These results indicate that ovine KRTAP15-1 is variable and the differences between the Chinese breeds investigated suggest the variation might underpin variation in wool traits.