Polymorphisms in adrenergic receptor genes in Qinchuan cattle show associations with selected carcass traits.

The beta-adrenergic receptors coded by the ADRB1, ADRB2 and ADRB3 genes play important roles in mediating metabolic effects, especially lipolysis, insulin resistance and energy balance. This study investigated the expression levels of these three genes in different tissues of Qinchuan cattle by real-time polymerase chain reaction (RT-PCR). Expressed levels of RNA from the ADRB2 gene were generally much higher than for ADRB1 and ADRB3. ADRB1 and ADRB2 expression levels were highest in subcutaneous fat and lower in muscle, whereas ADRB3 expression was higher in muscle tissue. Eight single nucleotide polymorphisms (SNPs) were discovered in 503 Qinchuan cattle by DNA sequencing, containing three missense mutations (g.1148G>C in ADRB1, g.1293C>T and g.1311T>C in ADRB2), four synonymous mutations (g.1054T>C, g.1122C>T and g.1143G>T in ADRB1 and g.506A>G in ADRB3), as well as one mutation in 3'untranslated region (3'UTR) (g.2799G>A in ADRB3). Interestingly, five of them were located in regions predicted to contain multiple repeats of CG nucleotides (CpG islands). Association analysis showed relationships between most of those SNPs or combined haplotypes and carcass traits of Qinchuan cattle. This study association analysis suggests that polymorphisms in these genes might be useful for selection in beef cattle breeding.