Identification of the Ovine Keratin-Associated Protein 22-1 (KAP22-1) Gene and Its Effect on Wool Traits

Abstract

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 (<i>KRTAP22-1</i>) was amplified using primers designed based on a human <i>KRTAP22-1</i> sequence. Polymerase chain reaction-single stranded conformational polymorphism (PCR-SSCP) was used to screen for variation in <i>KRTAP22-1</i> 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 (<i>A-C</i>). Two single nucleotide polymorphisms (SNPs) were identified in these sequences. Variant <i>B</i> was most common with a frequency of 81.3% in NZ Romney sheep, while in the Merino × Southdown-cross lambs, <i>A</i> was more common with a frequency of 51.8%. The presence of <i>B</i> was found to be associated with increased wool yield and decreased mean fiber curvature (MFC). Sheep of genotype <i>BB</i> or <i>AB</i> had a higher wool yield than those of genotype <i>AA</i>. These results suggest that ovine <i>KRTAP22-1</i> variation may be useful when developing breeding programs based on increasing wool yield, or decreasing wool curvature.