Abstract
Prolactin plays an important role in mammary gland development, milk section initiation and maintenance of lactation, so the bovine prolactin gene is considered as a potential quantitative trait locus affecting milk performance traits in dairy cattle. In this study, to determine the association between prolactin and milk performance traits, the genetic polymorphisms of a part of the prolactin gene were detected in a population of 649 cows of Chinese Holstein Dairy Cattle. Three SNPs in the promoter and one SNP in the intronl of prolactin were identified, which was A/C (-767), G/T (-485), C/A (-247), and C/T (427), respectively. Statistical results indicated that one of SNP within promote, CHBP2, was significantly associated with milk yield (p<0.01), fat yield (p<0.05), protein yield (p<0.01), and protein percentage (p<0.05). The cows with genotype BB of CHBP2 had significantly higher milk yield (p<0.01), fat yield (p<0.05), and protein yield (p<0.01) than those of cows with genotype AA, while cows with genotype AA showed the highest protein percentage (p<0.05). In addition, based on the nine major haplotypes constructed from the four SNPs, the association analysis between diplotypes and milk performance trait was carried out. Results showed that the least square mean for fat yield of diplotype H2H8 was significantly higher than those of other eleven diplotypes (p<0.05). Our findings implied that CHBP2 and H2H8 of prolactin would be useful genetic markers in selection program on milk performance traits in Holstein Dairy Cattle.
Highlights
Prolactin is a polypeptide hormone and plays crucial roles in mammary gland development, initiation and maintenance of lactation, which is synthesized in lactotrophic cells of the anterior pituitary gland of vertebrate
Statistical results indicated that, among the 4 SNPs, only CHBP2 in the promoter was significantly associated with milk yield (p
We found that the least square mean of fat yield for diplotype H2H8 was significantly higher than those of other diplotypes (p
Summary
Prolactin is a polypeptide hormone and plays crucial roles in mammary gland development, initiation and maintenance of lactation, which is synthesized in lactotrophic cells of the anterior pituitary gland of vertebrate. Single nucleotide polymorphisms (SNPs), one base changes including deletion, insertion and substitution, may play important roles in the regulation of genes transcription and amino acids sequences of mature proteins, which has been used to the association studies between candidate genes and complex traits in domestic animals (Kim et al, 2005; Meng et al, 2005; Yoon et al, 2005). For, several SNPs within the bovine prolactin gene have been reported, but most studies only described its restriction fragment length polymorphism (RFLP) and single strandedconformation polymorphism (SSCP) patterns without indicating their nucleotide changes and locations within the gene (Cowan et al, 1989; Hart et al, 1993; Zhang et al, 1994; Chung, 1997). Based on the sequences of 4 cDNA clones, 7 nucleotide substitutions were described by
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