Expression of the porcine adrenergic receptor beta 2 gene in longissimus dorsi muscle is affected by cis-regulatory DNA variation.

The beta-2 adrenergic receptor (AR) mediates metabolic actions of catecholamines, including glycogenolysis, lipolysis and proteolysis, in muscle and adipose tissue. Factors influencing the density of beta-2 ARs thus might affect carcass composition and meat quality. One such factor might represent cis-regulatory DNA variation affecting mRNA expression of the adrenergic receptor beta 2 (ADRB2) gene in relevant tissues. To identify potential cis-regulatory DNA variation of porcine ADRB2, we comparatively sequenced part of the 5' flanking region and identified 10 single nucleotide polymorphisms (SNPs). The SNP at position g.673C>T (AF000134) resides in an evolutionarily conserved region (ECR) in an in silico predicted androgen response element. Quantification of total transcript levels and allelic expression imbalance (AEI) revealed significant variability in mRNA expression of ADRB2 in longissimus dorsi muscle of slaughter pigs, partly attributable to cis-regulatory DNA variation. However, the g.673C>T SNP has, in the given temporo-spatial context, no significant effect but is apparently in linkage disequilibrium with the causal cis-regulatory DNA variant. We used the g.673C>T SNP as a marker to study the association of ADRB2 variation with carcass and meat quality in four commercial lines. We found association with the pH of loin at 45 min and 24 h postmortem (p.m.) and with the pH of ham at 24 h p.m. Supporting evidence for ADRB2 as a candidate gene for pork quality is provided by our assignment of the gene to the telomeric end of the q arm of porcine chromosome 2, where several quantitative trait loci for meat quality were reported.