The polymorphism of a novel 30 bp-deletion mutation at KAP9.2 locus in the cashmere goat

The keratins and keratin-associated proteins (KAPs) are a large heterogeneous group of proteins that make up about 90% of the cashmere fiber. Keratin-associated proteins 9.2 gene (KAP9.2) is one of the ultra high sulfur KAPs, which might play an important role in the bundling of intermediate filaments. In this study, the deletion/insertion mutation of KAP9.2 gene in 997 cashmere goat samples was firstly detected, at the same time, parts of these samples were sequenced. The results showed that two alleles were detected at this KAP9.2P1 locus, named allele W and D. The frequencies of the KAP9.2-W allele in Inner Mongolia White cashmere (n = 785) and Shaanbei White cashmere goat breeds (n = 212) were 0.878 and 0.790, respectively. The χ²-test showed that the genotype distributions in these two cashmere goat breeds were not in agreement with Hardy–Weinberg equilibrium. According to the classification of polymorphism information content (PIC), Shaanbei White cashmere goat was more polymorphic at this locus. Moreover a 30 bp-deletion mutation was described at KAP9.2P2 locus for the first time and no deletion/insertion was described at KAP9.2P1 locus. The results possibly revealed that the size polymorphism existed in the two Chinese cashmere goat and the 30 bp-deletion mutation was possibly caused by variations in the number of the decapeptide repeat structures.