Expression And Analysis Of Four Keratin Family Genes Of Liaoning New-breeding Cashmere Goat

Liaoning new breed of cashmere goat is a valuable genetic resource and cashmere output from these goats is the highest in china. Keratin components are closely related to the quality of cashmere fiber, and the quality between cashmere and goat hair is different significantly though their keratin component is similar. Therefore, identification of differently expressed keratin genes should be the key clue of controlling cashmere quality.The formation of fiber is mainly related to the expression of hair keratins and their associated proteins (KAP). In this study, we constructed a skin cDNA library of Liaoning new-breeding cashmere goat during follicle anagen. A total of 1986 ESTs were sequenced from the skin library and 14 unisequences that encoded structural proteins of cashmere fiber. Then, we did two aspects of research:First, we analyzed the expression of glycine/tyrosine-rich keratin-associated protein genes (KAP6-1.2, KAP6-1.4 and KAP8.1) in skin. (1) We analyzed the different expression of three genes in primary and secondary follicles by Real Time PCR. The results showed that the expression level of KAP6-1.4 in secondary follicles was about 1.5 (P< 0.05) times higher than that of primary follicles. While the expression level of KAP6-1.2 and KAP8.1 genes were similar in the two follicle populations. (2) The expression analysis of three genes in epithelial tissues was performed via RT-PCR. The results demonstrated that the KAP6-1.2, KAP6-1.4 and KAP8.1 all expressed specifically in skin. (3) In situ hybridization analyses of anagen follicles showed that the signals of three genes were all detected in upper/middle cortex of secondary follicles. Interestingly, KAP6-1.2 was asymmetrically expressed in primary follicles, while KAP8.1 with either asymmetrical or symmetrical expression was present and weak expression was observed on the inner side of the bulb deflection. Surprisingly, all three genes were detected in inner root sheath of primary and secondary follicle populations and weak expression of KAP8.1 was found in medulla of primary follicles. Therefore, we proposed that KAP6-1.2, KAP6-1.4 and KAP8.1 genes play an important role in controlling cashmere fiber diameter and have influence on the unique cashmere quality of Liaoning new-breeding cashmere goat.Second, we also isolated a full-length cDNA clone, which showed high homology with another known sequences, termed keratin 26 (K26). (1) The K26 protein consisted of 468 amino acids, exhibited a high amount of histidine, lysine and methionine, but low content of arginine, isoleucine and cysteine, and possessed a glycine-rich region. Additionally, K26 contained a relatively high proportion ofα-helix structures and showed a close relationship with K25 and K27. (2) RT-PCR analysis showed that K26 were only present in goat skin. The above results point to K26 being a novel cashmere goat keratin family member.