Association analysis of polymorphisms in six keratin genes with wool traits in sheep.

OBJECTIVE

The purpose of this study was to investigate the genetic effects of six keratin () genes on the wool traits of 418 Chinese Merino (Xinjiang type) (CMXT) individuals.

METHODS

To explore the effects and association of six genes on sheep wool traits, The polymerase chain reaction-based single-strand conformation polymorphism (PCR-SSCP), DNA sequencing, and the gene pyramiding effect methods were used.

RESULTS

We report 20 mutation sites (single-nucleotide polymorphisms) within the six genes, in which twelve induced silent mutations; five induced missense mutations and resulted in Ile→Thr, Glu→Asp, Gly→Ala, Ala→Ser, Se→His; two were nonsense mutations and one was a same-sense mutation. Association analysis showed that two genotypes of the gene were significantly associated with fiber diameter (p<0.05); three genotypes of the gene were significantly associated with wool fineness score and fiber diameter (p<0.05), three genotypes of the gene were significantly associated with the number of crimps (p< 0.05); and three genotypes of the gene were significantly associated with wool crimps score, body size, and fiber diameter (p<0.05). Analysis of the gene pyramiding effect between the different genotypes of the gene loci , , and , each genotype in a gene locus was combined with all the genotypes of another two gene loci and formed the different three loci combinations, indicated a total of 26 types of possible combined genotypes in the analyzed population. Compared with the other combined genotypes, the combinations CC-GG-II, CC-HH-IJ, CC-HH-JJ, DD-HH-JJ, CC-GH-IJ, and CC-GH-JJ at gene loci , , and , respectively, had a greater effect on wool traits (p<0.05).

CONCLUSION

Our results indicate that the mutation loci of , , , and genes, as well as the combinations at gene loci , , and in CMXT have significant effects on wool traits, suggesting that these genes are important candidate genes for wool traits, which will contribute to sheep breeding and provide a molecular basis for improved wool quality in sheep.