Study On Associations Between Gene Polymorphysms Of Prlr And Stat4and Production Traits In The Cattle

Novel single nucleotide polymorphisms (SNPs) of the PRLR and STAT4genes were investigated in966Chinese cattle of three breeds (Chinese Holstein, Luxi Yellow and Bohai Black cattle) by PCR-SSCP, PCR-RFLP and DNA sequencing methods in the present study. The relationships between polymorphisms and haplotype of the PRLR and STAT4genes and the milk performance traits were analyzed in Chinese Holstein cattle, for the purpose of selecting molecular maker information to improve the breeding efficiency of high milk yiled and milk quality.1. Associations between polymorphisms of the PRLR gene and bovine performance traitsProlactin receptor (PRLR) is thought to play a central role in signal transmitting from prolactin to milk protein genes. It binds prolactin and contributes to activation of JAK2kinases and subsequent phosphorylation of STAT5transcription factors which bind to recognition sequences located in promoters of milk protein genes. Therefore, PRLR is suggested as candidate gene associated with milk protein yield and content in dairy cattle.Eleven SNPs were investigated in PRLR gene. Among them,42054A>G mutation could be genotyped into three genotypes (AA, AG and GG) with PCR-RFLP method using Tas I. The genotype frequencies were different among the three breeds of cattle studied. AG genotype was dominant in Chinese Holstein, while in Luxi Yellow and Bohai Black, GG genotype frequency was the highest. In addition, another SNP (42275C>T) was genotyped into three genotypes (CC, TC and TT) by Msp Ⅰ. In Chinese Holstein, CC genotype was dominant, but TT dominant in in Luxi Yellow and Bohai Black. Statistical results of χ2test indicated that both loci in the populations studied were in Hardy-Weinberg equilibrium (P>0.05).However,42054A>G and42275C>T polymorphisms had no significant relationships with the milk production traits (P>0.05). The further analysis of haplotype suggested that the fat content of cows with haplotype AACC were significantly higher than that of AGCC, AGTC and GGTC (P<0.05). Therefore, offsprings of AACC cattle may have a good milk composition.2. Associations between polymorphisms of the STAT4gene and bovine performance traitsSignal transducer and activator of transcription4(STAT4) plays important roles in the activation of milk protein genes and the development of mammary glands. Four SNPs (g.62624A>C ssl75327225, g.60330A>G ssl75327226, g.63823G>C ssl75327227, g.66912C>T ss175327228) were identified in comparison with the reference sequence. Among them, two SNPs (g.62624A>C and g.63823G>C) were not found in the three breeds of cattle. The SNP (g.60330A>G ss175327226) could be genotyped into three genotypes (AA, AG and GG) with PCR-RFLP using Msp Ⅰ and another SNP (g.66912C>T ss175327228) only into two genotypes (CC and TC) by PCR-SSCP. The allelic frequencies of the SNP (g.60330A>G) were different among the three different cattle breeds. The associations between polymorphisms of the STAT4gene and dairy performance traits were analyzed in793Chinese Holstein cattle. The SNP (g.60330A>G), in particular, remarkablely affected the305d matured equivalency (P<0.05) and fat content (P<0.05), but not on the protein content, fat yield and protein yield (P>0.05). However, the SNP (g.66912C>T) had no significant relationship with the milk production traits (P>0.05). Together, the SNP (g.60330A>G) of the STAT4gene may be as a molecular marker for the differentiation of various populations and selection of the milk yield and fat content in the bovine breeding program.Haplotype of g.60330A>G and g.66912OT loci in the STAT4gene were analyzed and6haplotypes were found in695Chinese Holstein cattle. The cows with haplotype AATC and AACC had higher milk fat percentage than that of AGCC (P<0.05). The protein content of AGTC haplotype cows were significantly higher than AGCC (P<0.05). In addition, AGCC haplotype had significant relationship with305d matured equivalency, which are higher than GGCC and GGTC haplotypes (P<0.05). In the last, AATC haplotype, for its advantages in protein content, milk fat content and3O5d matured equivalency, may be used as a molecular marker for selecting cattle population of higher milk yield and quality.