| Keratins-associated proteins（KRTAPs）are the main structural components of wool fibers which are encoded by the KAPs gene families.KARTAP6 gene family belong to the member of high glycine / tyrosine keratin（HGT-KRTAPs）.Fatty acid synthase（FASN）is a key enzyme for fatty acid synthesis and metabolism,and plays a key role in the synthesis of fatty acids in animal body fat and milk fat.In this study,PCR-SSCP technique was used to detect the mutations of KRTAP6 gene familiy coding regions and FASN gene promoter region and exon 34 in Gannan yak,Tianzhu white yak,Qinghai yak and wild-blood yak,the polymorphism and sequence variation characteristics were analyzed,the effects of FASN gene mutation on milk quality traits were analyzed by combining the quality traits of Gannan yak.The main results were showed as follows:1.Polymorphism were richer in coding regions of KRTAP6 gene family of yak.（1）Five alleles A1,B1,C1,D1 and E1 were identified in the KRTAP6-1 gene,sequence alignment revealed four SNPs and a 45-bp insertion/ deletion mutation,where nonsynonymous mutation（c.173G>C and c.175G>T）that resulted in p.Cys58 Ser and p.Gly59 Cys changes,as well as a 45-bp insertion/ deletion that led to 16 amino-acid residue changes;A1 was the most common allele with the frequency of 56.5%76.0%;The yak populations presented moderate polymorphism with PIC value in range of 0.3930.467 except Gannan yak with low polymorphism as their PIC = 0.222 in coding regions of KRTAP6-1 gene;（2）Three alleles A2,B2 and C-2 were identified in the KRTAP6-2,sequence alignment revealed three SNPs and a 6-bp insertion/deletion mutation,where nonsynonymous mutation（c.248A>G）that resulted in p.Tyr19 Cys changes,as well as a 6-bp insertion/deletion that led to 2 amino-acid residue changes;A-2 was the most common allele with the frequency of 73.2%87.3%;The yak populations presented low polymorphism with PIC value in range of 0.2030.246 except Gannan yak with moderate polymorphism as their PIC=0.387 in coding regions of KRTAP6-2 gene;（3）Five alleles A3,B3,C3,D3 and E-3 were identified in the KRTAP6-4,sequence alignment revealed six SNPs,where nonsynonymous mutation（c.118A>G）that resulted in p.Ser40 Gly changes;A3 was the most common allele with the frequency of 73.7%82.8%;The yak populations showed moderate polymorphism with PIC value in range of 0.2650.387 in KRTAP6-4 gene.（4）The coding regions of KRTAP6-1,KRTAP6-2 and KRTAP6-4 genes significantly deviated from Hardy-Weinberg equilibrium in Gannan yak.2.Sequence and cluster analysis showed that KRTAP6-1,KRTAP6-2 and KRTAP6-4 gene were located on chromosome 1;the cluster analysis of KRTAP6-1 gene showed that yak,cattle,goat and sheep were the highest on homology and the phylogenetic distance consistent with their genetics relationship.3.Polymorphism were richer in promoter region and exon 34 of FASN gene in yak.（1）Three alleles A,B and C were identified in the promoter region of FASN gene,sequence alignment found c.1-1948.T>C and c.1-1910C>A mutations;A was the most common allele with the frequency of 74.4%75.2%;The yak populations presented moderate polymorphism with PIC value in range of 0.3660.376.（2）Two alleles D and E were identified in the exon 34 of FASN gene,sequence alignment found c.15281+74 A>T mutations;D was the most common allele with the frequency of 77.6%79.5%;The yak populations presented moderate polymorphism with PIC value in range of 0.2720.286.（3）Four haplotypes were formed between promoter and exon 34 region mutation sites;which haplotype D1A2 frequency highest is 66.74%,haplotype D1B2 frequency lowest is 6.96%;The two regions mutation between extent of linkage and close linkage equilibrium.4.FASN gene mutations affect milk quality traits in part Gannan yak.The milk fat rate of genotype AA was significantly higher than that of genotype AB and AC individuals（P<0.05）;the milk fat rate of exon 34 region genotype DD was significantly higher than genotype DE（P<0.05）;the percentage of lactose genotype DE was significantly higher than DD（P<0.05）. |
