Abstract
Simple SummaryThe two non-synonymous g.11685G>A and g.11773T>C SNPs of PRLR(L2) were significantly associated with milk yield, fat%, and protein%, and mRNA and protein levels of PRL and PRLR in milk somatic cells. GT-animals had the best milk performance; however, AC-animals had inferior milk production. Thus, the selection of buffaloes with GT haplotypes may enhance milk performance in Egyptian buffaloes.Prolactin (PRL) and its receptor (PRLR) were considered as potential genetic markers for milk production and quality traits in cattle. However, little information is available regarding PRLR genetic diversity and association studies with milk traits in Egyptian water buffaloes. Therefore, the present study was conducted to search for mutations in PRLR and determine their associations with milk performance in these animals. Exon3 (E3) and E10 of PRLR were screened for polymorphisms using single strand conformation polymorphism (SSCP) and sequencing in 400 buffaloes. The associations between haplotypes and milk production (fat%, protein%, lactose%, and solid%) traits as well as mRNA and protein levels of PRL and PRLR were studied. Two single nucleotide polymorphisms (SNPs) in E10 were detected: g.11685G>A (p.Ala494Thr) and g.11773T>C (p.Val523Aal). The G and T alleles were wild (ancestral) alleles, while the A and C alleles were mutant alleles. These SNPs resulted in four haplotypes; AC, AT, GC, and GT. Buffaloes with wild GT haplotypes showed significantly higher milk yield, fat% and protein%, mRNA and protein levels of PRL and PRLR in milk somatic cells than other animals. Animals carrying mutant AC haplotype had inferior milk traits and lowest levels of associated mRNAs and proteins. With these results, we could conclude that the selection of buffaloes with wild GT haplotypes for g.11685G>A and g.11773T>C SNPs of the PRLR gene might improve the milk production traits of Egyptian water buffaloes.
Highlights
High milk production is one of the world’s most important priorities for dairy breeding
Data obtained from sequencing revealed no polymorphisms in PRLR(L1) (Figure S3) among the Egyptian buffaloes
Analysis of PRLR(L2) sequences revealed the presence of two nonsynonymous single nucleotide polymorphisms (SNPs); g.11685G>A (at nucleotide 625 of E10 that changed alanine to threonine amino acid, (p.Ala494Thr)) (Figure 1C,D) and g.11773T>C
Summary
High milk production is one of the world’s most important priorities for dairy breeding. Milk composition characteristics are new breeding goals to cope with healthier dietary demands [1]. The selection of dairy animals with superior milk performance is of a great importance to breeders and consumers. Prolactin (PRL) is necessary for lactation [2] and this lactotrophic potential is facilitated by combining with its receptor, PRLR. PRL/PRLR signaling stimulates the abundant synthesis of milk protein, lactose, and fat, but it regulates their secretion [3], the inhibition of this signaling reduces milk yield [4]. PRLR belongs to the transmembrane cytokine class-1 receptor superfamily. The PRLR gene was mapped to chromosome (buffalo), (cattle), and 16 (sheep), and composed of
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