Nucleotide sequence polymorphisms of beta1‐, beta2‐, and beta3‐adrenergic receptor genes on Jinhua,Meishan, Duroc and Landrace pigs

The full amino acid coding sequences of adrenergic receptor genes beta1, beta2, and beta3 (ADRB1, ADRB2, and ADRB3)were determined for Jinhua, Meishan, Duroc and Landrace pigs. Non‐synonymous substitution of Arg458Pro was found in the porcine ADRB1 gene, resulting in a 469 amino acid sequence. Continuous substitutions of Asn29Asp and Glu30Gln were found in the porcine ADRB2 gene, resulting in a 418 amino acid sequence. Additionally, a Lys30 polymorphism of the ADRB2 gene was found in the Jinhua pigs. There were three non‐synonymous substitutions of Asn24Thr, Arg264Gln and Asn398Asp on the porcine ADRB3 gene. A thymine insertion in the ADRB3 gene, resulting in a protein with two fewer amino acids, was found in the Jinhua and Meishan pigs. To assess the effect of ADRB polymorphisms on porcine subcutaneous fat layer thickness, we calculated the genetic frequency of the variants in fatty and lean groups, each consisting of 24 pigs that were crossbreds of Duroc and Jinhua pigs. The effect of the ADRB3 gene polymorphism was not evaluated, because there was insufficient variation on the ADRB3 gene in the examined groups. Although Fisher's exact test showed no significant difference in the frequency of ADRB1 and ADBR2 variants between the two groups, the Arg458 variant of ADRB1 was higher (P = 0.11) in the lean group, and pigs in that group had a thinner fat layer than did those with the Pro458 variant. These results imply a possibility of ADRB1 polymorphism as a minor factor in porcine fat layer thickness. The Asp29 variant of ADRB2 was higher in the lean group (P = 0.11), and the Glu30 variant was higher in the fatty group (P = 0.15), but the Asp29 variant was found only in the Chinese pigs. Thus, the effect of ADRB2 polymorphisms was not clear in this study.