Evidence for New Alleles in the Protein Kinase Adenosine Monophosphate-Activated γ3-Subunit Gene Associated With Low Glycogen Content in Pig Skeletal Muscle and Improved Meat Quality

Abstract

Several quantitative trait loci (QTL) affecting muscle glycogen content and related traits were mapped to pig chromosome 15 using a three-generation intercross between Berkshire × Yorkshire pigs. On the basis of the QTL location the PRKAG3 (protein kinase, AMP-activated, γ3-subunit) gene was considered to be a good candidate for the observed effects. Differences in the PRKAG3 gene sequences of the founder animals of the intercross were analyzed. The RN− mutation previously reported was not present in the cross but three missense substitutions and a polymorphic short interspersed element (SINE) were identified. To confirm the hypothesis that at least one of these mutations was associated with differences in meat quality, >1800 animals from several unrelated commercial lines were genotyped for the candidate substitutions and an association study was performed. The results demonstrate the presence of new economically important alleles of the PRKAG3 gene affecting the glycogen content in the muscle and the resulting meat quality. Haplotype analysis was shown to resolve the effects of PRKAG3 more clearly than analysis of individual polymorphisms. Because of their prevalence in the more common commercial breeds, the potential implications for the pig industry and consumers are considerably greater than the original discovery of the RN− mutation. Furthermore, these results illustrate that additional alleles of genes involved in major mutations may play a significant role in quantitative trait variation.

Genetic Diversity of Meat Quality Related Genes in Argentinean Pigs

“…On the other hand, the protein encoded by the PRKAG3 gene is a regulatory subunit of the AMP activated protein kinase (AMPK), which plays a key role in the regulation of glucose and energy metabolism in skeletal muscle. Glycogen content is determinant of multiple meat quality traits, such as pH, meat color, drip loss or tenderness(Ciobanu et al, 2001). The ampli ed PCR product for PRKAG3 or RN (199I>V and 200R>Q) SNP was 114 bp in length, which was similar to the ndings ofJosell et al (2003) andLindahl et al (2004).…”

“…Pairwise linkage disequilibrium between SNPs was used to measure the linkage disequilibrium (LD). This study provides an overview of LD patterns between SNPs related to meat quality in different subpopulations of Creole (11) and commercial pigs (13). It is observed that not all pairs of SNPs present statistically signi cant associations.…”

“…dominant homozygote (CC) with a fragment size of 92 and 42 bp and heterozygote (Ct) with a fragment size of 134, 92 and 42 bp. Two mutations described at the PRKAG3 locus by Milan et al (2000) and Ciobanu et al (2001), namely I199V and R200Q, were analyzed by PCR-RFLP. A fragment size of 114, 81 and 33 bp; and 81 and 33 bp, respectively was observed for heterozygote QR and wild homozygote RR genotype Three genotypes were observed at PRKAG3 c.199I>V SNP locus: a restriction fragments size of 114, 82, and 32 bp was observed for VI, 114 bp for homozygote II.…”

“…AMPK γ3 has a role in the metabolic plasticity of fast-glycolytic muscle and is primarily expressed in white (fast-twitch, type IIb) skeletal muscle bers (Mahlapuu et al, 2004). Non-synonymous single nucleotide polymorphisms (SNPs) in this gene such as I199V and R200Q are associated with important pork quality traits (WHC and pH) (Ciobanu et al, 2001;Josell et al, 2003;Lindahl et al, 2004;Granlund et al, 2011). Both mutations are located in a highly conserved region of the cystathionine β-synthase domain which is believed to act as a sensor of cellular energy status (Ryan et al, 2012).…”

“…The PRKAG3 R200Q SNP appears in Hampshire breed or derived synthetic lines and the mutant allele was absent in several European local porcine breeds(Muñoz et al, 2018). On the other hand, the I allele (rn*) is widely reported to have a positive effect on pH, color and water holding capacity in diverse pig breed populations(Ciobanu et al, 2001;Lindahl et al, 2004, Otto et al, 2007. In both populations, the allele rn* is highly represented (37.35% and 42.21%).…”