Identification of llama KRTAP7-1 and KRTAP8-1 fiber genes and polymorphism screening
Keratin-associated proteins (KAP) are one of the main structural components of hair fiber. Within this protein group, high glycine tyrosine (HGT)-KAP play a crucial role in the definition of their physical-mechanical properties. Polymorphisms in HGT genes have been associated with the variation of different wool traits in sheeps and goats. The Argentine llama is a fiber-producing animal which is valued by the textile industry. However, the genes encoding for fiber proteins have not yet been identified in this species. Here, we focus on studying the HGT-KRTAP7-1 and KRTAP8-1 genes and their variation using the High Resolution Melting (HRM) technique in a sample of 117 llamas. Four single nucleotide polymorphisms (SNPs) were detected in KRTAP7-1, two of which were non-synonymous substitutions leading to amino acid changes in the protein. Of the 5 polymorphisms identified in KRTAP8-1, c.1-5A > G was located in the Kozak sequence, known to regulate protein synthesis level. The other four, two SNPs and one double nucleotide polymorphism (DNP), were found in the coding region and produced three amino acid replacement: c.43 T > C and c.45C > A (p.Y15Q), c.46 G > T (p.G16W) and c.173 A > G (p.Y58C). In summary, most of the polymorphisms found in both KRTAP7-1 and KRTAP8-1 genes produce non-conservative amino acid changes involving tyrosine and glycine residues, which are essential to maintain HGT protein properties. Therefore, these mutations as well as the regulatory SNP here identified could modify the fiber characteristics. We discuss the possible impact of these polymorphisms on KAP7-1 and KAP8-1 structure and/or interaction with other fiber proteins.