Association study and expression analysis of MTNR1A as a candidate gene for body measurement and meat quality traits in Qinchuan cattle.

Melatonin receptors, which mediate the functions of melatonin, play an important role in adipocyte differentiation, energy, and lipid metabolism. The aim of this study was to identify single nucleotide polymorphisms (SNPs) in bovine melatonin receptor 1A (MTNR1A) and to determine if these SNPs are associated with body measurement traits (BMTs) and meat quality traits (MQTs) in Qinchuan cattle. We identified three synonymous mutations (A455G, A497G, and C635T) and one missense mutation (G489A) p.Asp224Asn in MTNR1A gene in 420 Qinchuan cattle by sequencing. Association analysis indicated that these four SNPs were associated with some of the BMTs and MQTs (P<0.05). Further, 6 combined haplotypes were constructed to guarantee the reliability of analysis results. Individuals with diplotypes H2H2 (AA-GG-GG-CC) had greater chest depth, heart girth, loin muscle area, and more back fat than the other combinations (P<0.05). Pertaining to G489A mutation, RT-PCR study exhibited a higher mRNA expression of MTNR1A gene among individuals with SNP1/2/4-AG-GA-CT genotype than those with SNP1/2/4-AA-GG-CC genotype (P<0.05). These results suggest that the genotype H2H2 could be used as a molecular marker of the combined genotype for future selection for BMTs and MQTs in Qinchuan cattle.