Abstract
This study identified four new keratin-associated protein genes (KRTAP19-n) in sheep: sKRTAP19-1, sKRTAP19-2, sKRTAP19-4, and sKRTAP19-6. These genes are closely related to the previously identified sheep genes KRTAP19-3 and KRTAP19-5, as well as to human KRTAP19-n genes. However, no clear orthologous relationships were found, suggesting complex evolutionary dynamics for this gene family. Extensive nucleotide sequence variation was observed across the four genes. sKRTAP19-1 had four variants, defined by four synonymous single-nucleotide polymorphisms (SNPs) and a variable number of "GGCTAC" hexanucleotide repeats. sKRTAP19-2 had five variants involving seven SNPs, three of which were non-synonymous. sKRTAP19-4 had five variants with nine SNPs (three being non-synonymous) and a three-nucleotide deletion. sKRTAP19-6 had eight variants, defined by 13 SNPs and a two-nucleotide consecutive substitution, with four of the SNPs being non-synonymous. One distinct variant each of sKRTAP19-4 and sKRTAP19-6 was found exclusively in Yanchi Tan sheep, with seven unique nucleotide differences compared to other variants. These unique variants were identical to the Romanov sheep genome in the region amplified (excluding the primer binding regions), suggesting a shared ancestral origin. The findings highlight considerable genetic diversity in ovine KRTAP19-n and lay a foundation for future research into their role in regulating wool fibre characteristics.