Identification of the ovine keratin-associated protein 22-1 (KAP22-1) gene and its effect on wool traits

Keratin-associated proteins (KAPs) are structural components of wool and hair fibers. To date, eight high glycine/tyrosine KAP (HGT-KAP) families have been identified in humans, but only three have been identified in sheep. In this study, the putative ovine homolog of the human KAP22-1 gene (KRTAP22-1) was amplified using primers designed based on a human KRTAP22-1 sequence. Polymerase chain reaction-single stranded conformational polymorphism (PCR-SSCP) was used to screen for variation in KRTAP22-1 in 390 Merino × Southdown-cross lambs and 75 New Zealand (NZ) Romney sheep. Three PCR-SSCP banding patterns were detected and DNA sequencing revealed that the banding patterns represented three different nucleotide sequences (A-C). Two single nucleotide polymorphisms (SNPs) were identified in these sequences. Variant B was most common with a frequency of 81.3% in NZ Romney sheep, while in the Merino × Southdown-cross lambs, A was more common with a frequency of 51.8%. The presence of B was found to be associated with increased wool yield and decreased mean fiber curvature (MFC). Sheep of genotype BB or AB had a higher wool yield than those of genotype AA. These results suggest that ovine KRTAP22-1 variation may be useful when developing breeding programs based on increasing wool yield, or decreasing wool curvature