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

The Complexity of the Ovine and Caprine Keratin-Associated Protein Genes

Sheep (Ovis aries) and goats (Capra hircus) have, for more than a millennia, been a source of fibres for human use, be it for use in clothing and furnishings, for insulation, for decorative and ceremonial purposes, or for combinations thereof. While use of these natural fibres has in some respects been superseded by the use of synthetic and plant-based fibres, increased accounting for the carbon and water footprint of these fibres is creating a re-emergence of interest in fibres derived from sheep and goats. The keratin-associated proteins (KAPs) are structural components of wool and hair fibres, where they form a matrix that cross-links with the keratin intermediate filaments (KIFs), the other main structural component of the fibres. Since the first report of a complete KAP protein sequence in the late 1960s, considerable effort has been made to identify the KAP proteins and their genes in mammals, and to ascertain how these genes and proteins control fibre growth and characteristics. This effort is ongoing, with more and more being understood about the structure and function of the genes. This review consolidates that knowledge and suggests future directions for research to further our understanding.

Variation in a Newly Identified Caprine KRTAP Gene Is Associated with Raw Cashmere Fiber Weight in Longdong Cashmere Goats

Keratin-associated proteins (KAPs) and keratins determine the physical and chemical properties of cashmere fibers as they are the main components of the fibers. It has been reported that ovine KRTAP1-2 affects clean fleece weight, greasy fleece weight and yield in sheep, but the gene has not been described in goats and its effects on fiber traits are unknown. In this study, we identify the keratin-associated protein 1-2 gene (KRTAP1-2) in the goat genome and describe its effect on cashmere fiber traits in 359 Longdong cashmere goats. Six sequence variants (named CAPHI-KRTAP1-2*A to CAPHI-KRTAP1-2*F) were revealed using polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) analysis. These sequences have the highest homology with ovine KRTAP1-2 sequences. There were a 60-bp deletion, a 15-bp insertion and five single nucleotide polymorphisms (SNPs) including two non-synonymous SNPs in the coding sequence. The caprine KRTAP1-2 gene was expressed in the skin tissue, but a signal was not observed for the kidneys, liver, lungs, spleen, heart and longissimus dorsi muscle. Variation in caprine KRTAP1-2 was found to be associated with raw cashmere fiber weight, but not with fiber diameter and length.

Expression analysis of KAP9.2 and Hoxc13 genes during different cashmere growth stages by qRT-PCR method

Keratin-associated protein 9.2 (KAP9.2) and Homeobox C13 (Hoxc13) genes were chosen to study because of their biological functions involving hair formation. KAP9.2 gene belongs to the ultra high sulfur KAPs, which is important for hair formation and may have association with cashmere. Hoxc13 takes part in the formation of cashmere keratin and maintaining the normal structure of follicle. It has been reported that Hoxc13 gene exists binding site of KP and KAP genes at its promoter regions in mouse. So the expression of KAP9.2 and Hoxc13 genes was detected at anagen stage vs telogen stage by qRT-PCR. The data showed that KAP9.2 and Hoxc13 gene had similar expression trend at different stages, which indicated that there was interaction between them. KAP9.2 and Hoxc13 gene had lower expression level in anagen than that of in telogen of cashmere growth. In anagen, KAP9.2 and Hoxc13 expressed lower in high cashmere yield individuals than that of in low cashmere yield ones. In telogen, the result was reverse. The study would provide the evidence of involvement of KAP9.2 and Hoxc13 in hair periodic growth.

Variation and expression of KAP9.2 gene affecting cashmere trait in goats

Keratin-associated proteins 9.2 (KAP9.2) gene encodes one of the ultra high sulfur KAPs. Variation in KAP genes may affect the structure of KAPs and hence cashmere characteristics. In order to test the association between the polymorphism of KAP9.2 gene and cashmere trait, DNA sequencing was used to detect a novel C/T polymorphism of KAP9.2 gene from a genomic DNA pool. The mutation could be recognized by Pst I restriction enzyme. To Shanbei white cashmere goat, Inner Mongolia white cashmere goat and Guanzhong dairy goat, the genotypic frequencies of TT, TC and CC from total 1,236 animals were as follows: 0.047, 0.519 and 0.434; 0.180, 0.592 and 0.228; 0.431, 0.544 and 0.025. The allelic frequencies of T and C were 0.307 and 0.693; 0.476 and 0.524; 0.703 and 0.297, respectively, in breeds mentioned above. The frequency of C allele between cashmere and dairy goat was significant (P < 0.01). To provide support for the hypothesis that SNP 586 was responsible for KAP9.2 expression, quantitative real-time PCR analysis revealed that the expression level of KAP9.2 was reduced in individuals bearing genotype CC compared with TT individuals, suggesting that C was the nucleotide causing decreased expression of KAP9.2 or was in linkage disequilibrium with the causative SNP. The 586C/T SNP found in this study might control translation or stability of KAP9.2 mRNA, which would be beneficial for marker assistant selection in cashmere goat breeding.