PRKAG3 Research Articles

Transcriptomic investigation of meat tenderness in two Italian cattle breeds

Our objectives for this study were to understand the biological basis of meat tenderness and to provide an overview of the gene expression profiles related to meat quality as a tool for selection. Through deep mRNA sequencing, we analyzed gene expression in muscle tissues of two Italian cattle breeds: Maremmana and Chianina. We uncovered several differentially expressed genes that encode for proteins belonging to a family of tripartite motif proteins, which are involved in growth, cell differentiation and apoptosis, such as TRIM45, or play an essential role in regulating skeletal muscle differentiation and the regeneration of adult skeletal muscle, such as TRIM32. Other differentially expressed genes (SCN2B, SLC9A7 and KCNK3) emphasize the involvement of potassium-sodium pumps in tender meat. By mapping splice junctions in RNA-Seq reads, we found significant differences in gene isoform expression levels. The PRKAG3 gene, which is involved in the regulation of energy metabolism, showed four isoforms that were differentially expressed. This distinct pattern of PRKAG3 gene expression could indicate impaired glycogen storage in skeletal muscle, and consequently, this gene very likely has a role in the tenderization process. Furthermore, with this deep RNA-sequencing, we captured a high number of expressed SNPs, for example, we found 1462 homozygous SNPs showing the alternative allele with a 100% frequency when comparing tender and tough meat. SNPs were then classified into categories by their position and also by their effect on gene coding (174 non-synonymous polymorphisms) based on the available UMD_3.1 annotations.

Variation in the ovine PRKAG3 gene

The 5′AMP-activated protein kinase (AMPK) is a heterotrimeric enzyme that controls cellular energy homeostasis in response to environmental or nutritional stress. The PRKAG3 gene (PRKAG3) encodes the γ3 subunit of the AMPK. Variation in this gene has been found to be associated with meat quality traits in pigs. In this study, we used polymerase chain reaction-single stranded conformational polymorphism (PCR-SSCP) to investigate variation in exon 3 and exons 4–6 of ovine PRKAG3. In 160 New Zealand Suffolk sheep, two variant sequences (named a and b) were identified in the exon 3 region of the gene and three variant sequences (named A, B and C) were identified in the exon 4–6 region of the gene, respectively. A total of three nucleotide substitutions were revealed and these were located in intron 4, exon 4 and intron 5, respectively. The nucleotide substitution identified in the exon 4 (g.2656 C>T) could nominally lead to an amino acid substitution of tryptophan to arginine at position 230 (R230W) in ovine PRKAG3. In comparison with the PRKAG3 amino acid sequences in other species, this R230W substitution appeared to occur only in sheep. This is the first report of genetic variation in ovine PRKAG3, and the variation found in this study could be functionally important for AMPK activity, which in turn may affect meat quality traits in sheep.

Polimorfismos de los genes CAPN1, CAST, DES, PRKAG3 Y RYR1 asociados a la capacidad de retención de agua en crudo y cocinado en carne de bovino en cruces Bos indicus y Bos taurus en Colombia

La capacidad de retención de agua (CRA) es uno de los parámetros de calidad de la carne más importante, dado que posee asociación con la percepción de jugosidad y la pérdida de peso de la pieza cárnica durante procedimientos como la maduración, la cocción y otro tipo de procesamiento tecnológico. La CRA en crudo y cocinado (CRAr y CRAc respectivamente) fue evaluada en 164 machos castrados cruzados, en los cuales se realizó la genotipificación de 23 regiones genómicas de los genes CAPN1, CAST, DES, PRKAG3 y RYR1. El marcador CAST2959 presentó asociación con el parámetro CRAr en el músculo Longissimus dorsi (LD) siendo el genotipo AA el de mejor comportamiento. El marcador RYR1-11195 se encontró asociado con el parámetro CRAc en LD, siendo la carne de animales con los genotipos GG y GA, la de mayor pérdida de peso, si son comparados con carne proveniente de animales con genotipo AA. Lo anterior permite establecer estos marcadores como posibles polimorfismos de importancia en procesos de selección y mejoramiento animal de este parámetro de calidad cárnica (CRAr y CRAc) en bovinos, posterior a un proceso de validación.

Comparison of the meat quality, post-mortem muscle energy metabolism, and the expression of glycogen synthesis-related genes in three pig crossbreeds

Post-mortem muscle energy metabolism plays an important role in pork quality. To analyse the differences of meat quality and energy metabolism, three commercial pig crossbreeds frequently used in China were studied, they were DT (Duroc × Taihu; n = 16), PIC (five-way crossbreed from Pig Improvement Co., UK; n = 29) and DLY (Duroc × (Landrace × Yorkshire); n = 19) pigs. The results showed that DT pigs had a higher post-mortem pH45 min and pH24 h, lower shear force and drip loss, higher muscle free-glucose and glycogen contents, and lower lactic acid content than did PIC and DLY pigs. Post-mortem muscle free-glucose content of these three pig crossbreeds changed little, from 45 min to 96 h post-mortem. The expression levels of PRKAG3 (encoding a regulatory subunit of the AMP-activated protein kinase) and GYS1 (encoding muscle glycogen synthase) genes of DT pigs were significantly lower than those of PIC and DLY pigs. DT pigs had a higher expression level of glycogenin-1-like (encoding glycogenin) gene than did PIC and DLY pigs. In conclusion, DT pigs had better meat quality than did the other two pig crossbreeds. We deduced that the post-mortem muscle energy status and metabolism of DT pigs might be an important reason for their good meat quality, and future research should focus on the molecular and physiological mechanism of post-mortem muscle energy metabolism to find ways to improve meat quality.

Allelic frequencies ofPRKAG3 in several pig breeds and its technological consequences on aDuroc × Landrace‐LargeWhite cross

The allelic frequencies of PRKAG3 gene (the RN gene) have been investigated in several pig breeds. R200Q mutation appear only in Hampshire pigs, whereas V199I mutation is most abundant in Iberian, Porco Celta or Bizaro, and less in breeds selected for muscularity as Duroc, Landrace and Pietrain. A thorough study of phenotypic effects of V1991 has been performed in a Duroc×Landrace-Large White cross. 199I homozygous pigs show increased pH24 values in ham homogenates and loin (0.14 and 0.16 pH units, respectively) compared to 199V homozygous ones. Meat of 199I homozygous pigs exudates 42.6% less fluid and is darker (2.46 'L'-value units). 199I homozygous pigs are fatter (4.2mm more backfat thickness) and contain less muscle mass in ham (1.0 percentage points) and shoulder (2.7 percentage points), than 199V homozygous ones. 199I homozygous pigs contain 7.3% less protein in the belly and 8.5% more fat in shoulder muscle mass than 199V homozygous pigs. 199I homozygous pigs have also superior functional properties: better gelling (22.8% larger G' value) and emulsion capacities (14 percentage points less of total exuded fluid), and higher curing yield in the belly (6 percentage points more). These data support the adipogenic character of the V199I mutation. The advantages and disadvantages of selecting any of the two PRKAG3 alleles for position 199 are discussed.

Polymorphisms in AKT3, FIGF, PRKAG3, and TGF-β genes are associated with myofiber characteristics in chickens

Muscle characteristics such as myofiber diameter, density, and total number are important traits in broiler breeding and production. In the present study, 19 SNP of 13 major genes, which are located in the vicinity of quantitative trait loci affecting breast muscle weight, including INS, IGF2, PIK3C2A, AKT3, PRKAB2, PRKAG3, VEGFA, RPS6KA2/3, FIGF, and TGF-β1/2/3, were chosen to be genotyped by high-throughput matrix-assisted laser desorption/ionization time-of-flight mass spectrometry in a broiler population. One hundred twenty birds were slaughtered at 6 wk of age. Body weight, breast muscle weight, myofiber diameter, density, and total number were determined for each bird. Six SNP with a very low minor allele frequency (<1%) were excluded for further analysis. The remaining 13 SNP were used for the association study with muscle characteristics. The results showed that SNP in TGF-β1/2/3 had significant effects on myofiber diameter. A SNP in PRKAG3 had a significant effect on myofiber density (P < 0.05). A C > G mutation in FIGF was strongly associated with total fiber number (P < 0.05). Additionally, birds with the GG genotype of the C > G mutation in AKT3 had significantly larger myofiber numbers (P < 0.05) than birds with the CC or GC genotype. The SNP identified in the present study might be used as potential markers in broiler breeding.

SNP variation in the promoter of the PRKAG3gene and association with meat quality traits in pig

BackgroundThe PRKAG3 gene encodes the γ3 subunit of adenosine monophosphate activated protein kinase (AMPK), a protein that plays a key role in energy metabolism in skeletal muscle. Non-synonymous single nucleotide polymorphisms (SNPs) in this gene such as I199V are associated with important pork quality traits. The objective of this study was to investigate the relationship between gene expression of the PRKAG3 gene, SNP variation in the PRKAG3 promoter and meat quality phenotypes in pork.ResultsPRKAG3 gene expression was found to correlate with a number of traits relating to glycolytic potential (GP) and intramuscular fat (IMF) in three phenotypically diverse F1 crosses comprising of 31 Large White, 23 Duroc and 32 Pietrain sire breeds. The majority of associations were observed in the Large White cross. There was a significant association between genotype at the g.-311A>G locus and PRKAG3 gene expression in the Large White cross. In the same population, ten novel SNPs were identified within a 1.3 kb region spanning the promoter and from this three major haplotypes were inferred. Two tagging SNPs (g.-995A>G and g.-311A>G) characterised the haplotypes within the promoter region being studied. These two SNPs were subsequently genotyped in larger populations consisting of Large White (n = 98), Duroc (n = 99) and Pietrain (n = 98) purebreds. Four major haplotypes including promoter SNP’s g.-995A>G and g.-311A>G and I199V were inferred. In the Large White breed, HAP1 was associated with IMF% in the M. longissmus thoracis et lumborum (LTL) and driploss%. HAP2 was associated with IMFL% GP-influenced traits pH at 24 hr in LTL (pHULT), pH at 45 min in LTL (pH45LT) and pH at 45 min in the M. semimembranosus muscle (pH45SM). HAP3 was associated with driploss%, pHULT pH45LT and b* Minolta. In the Duroc breed, associations were observed between HAP1 and driploss% and pHUSM. No associations were observed with the remaining haplotypes (HAP2, HAP3 and HAP4) in the Duroc breed. The Pietrain breed was monomorphic in the promoter region. The I199V locus was associated with several GP-influenced traits across all three breeds and IMF% in the Large White and Pietrain breed. No significant difference in promoter function was observed for the three main promoter haplotypes when tested in vitro.ConclusionGene expression levels of the porcine PRKAG3 are associated with meat quality phenotypes relating to glycolytic potential and IMF% in the Large White breed, while SNP variation in the promoter region of the gene is associated with PRKAG3 gene expression and meat quality phenotypes.

PRKAG3 and CAST genetic polymorphisms and quality traits of dry-cured hams—III. Associations in Slovenian dry-cured ham Kraški pršut and their dependence on processing

The aim of the present study, the third in a series of three papers, is to show the effects of PRKAG3 and CAST gene polymorphisms on the quality traits of the Slovenian dry-cured ham “Kraški pršut” and their interaction with ham producers. Significant interaction of polymorphisms with producer in the case of salt content, lipid oxidation (PRKAG3 Ile199Val), proteolysis index (CAST Arg249Lys) and pastiness (CAST Ser638Arg) indicated that genotype manifestation was reliant on the manufacturing practice. PRKAG3 Ile199Val polymorphism affected several physico-chemical, rheological and sensory traits. The Ile/Ile genotype yielded less salty and softer hams, indicating beneficial effects on dry-cured ham quality. The effect of CAST polymorphisms was less pronounced, although the observed associations with pastiness, proteolysis index and several free amino acid concentrations indicate its possible influence on proteolysis, with haplotype CAST 249Arg/638Ser being associated with a higher degree of proteolysis.

The Polymorphism in 5 'Regulatory Region and Exon 13 of PRKAG3 Gene and its Distribution Pattern in Different Goat Breeds

The Polymorphism in 5 'Regulatory Region and Exon 13 of PRKAG3 Gene and its Distribution Pattern in Different Goat Breeds

English

The bovine PRKAG3 gene encodes a muscle-specific isoform of the regulatory gamma-subunit of adenosine monophosphate activated protein kinase (AMPK), which plays a key role in regulating energy homeostasis in eukaryotes. It is well known that mutations in the PRKAG3 gene affect high glycogen content in the porcine skeletal muscle and, consequently, meat quality. Therefore, this gene has been proposed as a positional and functional candidate gene for a quantitative trait locus (QTL) with an effect on meat quality traits. In this study, we detected four single nucleotide polymorphisms (SNPs) at the PRKAG3 gene (DQ082736) in 267 beef cattle. The SNP marker association analysis indicated that the SNP markers T2885C was significantly associated with tenderness trait. Animals with the TT genotype had lower Warner-Bratzler shear force (WBS) than those with the other genotypes. Results of this study suggest that the PRKAG3-gene-specific SNP may be a useful marker for meat quality traits in future marker-assisted selection programmes in beef cattle. Key words : Association analysis, beef cattle, single nucleotide polymorphism (SNP) polymorphism, PRKAG3 gene.

Association of Prkag3 Gene Polymorphisms with Meat Quality Traits in Chinese Meat-Type Quality Chicken Populations

In this study, we aimed to detect the single nucleotide polymorphism (SNPs) of the chicken PRKAG3 gene and discern the potential association with meat quality traits. A total of 240 meat-type quality chickens were screened by using single-strand conformational polymorphism analysis (SSCP) and DNA sequencing. Two SNPs (g.1744G&gt;C and g.3207A&gt;G) were identified in chicken PRKAG3 with medium polymorphism (0.25C were significantly associated with water content, crude protein, and crude ash (P&lt;0.05/0.01). The SNP genotypes g.3207A&gt;G were significantly associated with water content, and crude protein (P&lt;0.01). The results suggested that PRKAG3 gene is potential major genes or is in close linkage disequilibrium with the QTL affecting meat quality traits in this population of chickens.

Association between polymorphism in bovine PRKAG3 gene and milk production traits

The aim of the conducted study was to evaluate correlation between genotypes and PRKAG3 compound genotypes and milk production traits (yield of milk, milk fat and milk protein, and protein and fat content in milk). The study covered a herd of 180 Jersey cows. PCR-RFLP method was used for genotyping. The frequencies of alleles that occur mostly and combined genotypes were as follows: T1526G G - 0.57, G 1609A G - 0.92 and for T1526G/G1609A TG/GG - 0.54. The results obtained in the study demonstrated the correlation between analyzed genotypes and selected milk production traits; however they are not statistically significant.

Dry-cured ham Kraški pršut seasoning losses as affected by PRKAG3 and CAST polymorphisms

Association between polymorphisms on PRKAG3 (Ile199Val) and CAST (Lys249Arg and Ser638Arg) genes and dry ham seasoning losses was studied. A total of 724 green hams (same pig crossbreed, same pig producer) were selected, genotyped (PCR-RFLP) and processed according to the rules of consortium for dry-cured ham Kraški pršut. Weight losses after each processing phase were recorded. We observed significant effect of interaction between gene polymorphism and dry ham producer on seasoning losses, indicating that the effect of studied genes differ in relation to manufacturing practice or product type, despite narrow consortium constraints. The analysis was thus made separately for each producer; in case of producer B, PRKAG3 affected salting, resting and overall losses (Val/Val higher than Ile/Ile or Ile/Val) but in case of producer A, the effect of PRKAG3 was significant only for salting losses (Ile/Val lower than Ile/Ile or Val/Val). Effects of CAST polymorphisms were significant only in case of producer A; CAST249 Arg/Arg hams showed the highest first salting, drying, and overall seasoning losses, whereas CAST638 Arg/Arg hams had the highest drying, ripening, and overall seasoning losses. In conclusion, PRKAG3 and CAST polymorphisms were associated with seasoning losses, important from economic viewpoint, but also for salt intake and product quality.

Validation of a paternally imprinted QTL affecting pH24h distinct from PRKAG3 on SSC15

We previously performed a genome scan in a White Duroc × Erhualian F(2) population and identified a QTL on SSC15 with strong effect on pH24h in M. Longissimus dorsi and M. Semimembranous muscle tissue. At that time, the mode of inheritance of this QTL was not clarified, and it was also unclear whether the observed QTL effect was completely or partially caused by mutations in the PRKAG3 gene, which is the only major gene on SSC15 so far known to influence pH24h. In this study, effects of the PRKAG3 gene on meat quality traits were estimated by association analyses. Two substitutions in PRKAG3, p.Ile199Val (p.I199V) and p.Thr30Asn (p.T30N), were found to be segregating in the F(2) population and to significantly affect pH24h and total glycogen in meat, respectively. However, we excluded PRKAG3 as a causative gene for the detected QTL based on the following reasons: (i) the gene was located outside of the QTL confidence interval; (ii) when the PRKAG3 substitution was included as a fixed effect in the QTL model, the F-ratio for the QTL increased rather than decreased; (iii) favourable alleles for pH24h at the QTL and at the PRKAG3 p.I199V locus originated from Erhualian and White Duroc founders, respectively; (iv) more importantly, this QTL showed exclusive maternal expression, differing from the Mendelian expression of PRKAG3. In conclusion, this study is the first to report a maternally-expressed QTL for pH24h on SSC15, which is distinct from PRKAG3.

Comparison of PRKAG3 and RYR1 gene effect on carcass traits and meat quality in Slovenian commercial pigs

The effect of polymorphisms at &lt;I&gt;PRKAG3&lt;/I&gt; (&lt;I&gt;R200Q&lt;/I&gt; and &lt;I&gt;I199V&lt;/I&gt;) and &lt;I&gt;RYR1&lt;/I&gt; (&lt;I&gt;R615C&lt;/I&gt;) genes on carcass traits and meat quality was examined in a sample of 257 commercial pigs, crosses of Landrace × Large White as maternal line and Pietrain (&lt;I&gt;N&lt;/I&gt; = 96), Pietrain × Landrace (&lt;I&gt;N&lt;/I&gt; = 42) or Pietrain × Hampshire (&lt;I&gt;N&lt;/I&gt; = 119) as paternal line. Pigs were genotyped (PCR-RFLP) and traits of interest were measured (which included carcass and ham weight, measurements of fatness, meatiness, ultimate pH, colour parameters and drip loss). The observed genotype frequencies at &lt;I&gt;PRKAG3&lt;/I&gt; gene were 9.7%, 38.9%, 32.7%, 6.2% and 12.5% for &lt;I&gt;R/R-I/I, R/R-I/V, R/R-V/V, Q/R-I/V&lt;/I&gt; and &lt;I&gt;Q/R-V/V&lt;/I&gt; genotype, respectively. &lt;I&gt;RYR1&lt;/I&gt; genotype frequencies were 57.2% for &lt;I&gt;N/N&lt;/I&gt; and 42.8% for &lt;I&gt;N/n&lt;/I&gt; genotype. Studied polymorphisms exhibited a significant effect on meat quality, but mainly an insignificant effect on carcass traits. No significant interaction between &lt;I&gt;PRKAG3&lt;/I&gt; and &lt;I&gt;RYR1&lt;/I&gt; was found. Carriers of &lt;I&gt;RYR1&lt;/I&gt; mutant allele “&lt;I&gt;n&lt;/I&gt;” had less intense &lt;I&gt;longissimus dorsi&lt;/I&gt; muscle colour (subjective score, Minolta &lt;I&gt;L&lt;/I&gt;* and &lt;I&gt;b&lt;/I&gt;*) and higher drip loss. Regarding &lt;I&gt;PRKAG3&lt;/I&gt;, the ultimate pH decreased and Minolta &lt;I&gt;L&lt;/I&gt;*, &lt;I&gt;a&lt;/I&gt;*, &lt;I&gt;b&lt;/I&gt;* and drip loss increased in the following order: &lt;I&gt;R/R-I/I, R/R-I/V, R/R-V/V, Q/R-I/V&lt;/I&gt; and &lt;I&gt;Q/R-V/V&lt;/I&gt;, according to the presence of &lt;I&gt;199I&lt;/I&gt; and absence of &lt;I&gt;200Q&lt;/I&gt; alleles. The study shows that the &lt;I&gt;I199V&lt;/I&gt; polymorphism is an important source of variation in pigs free of &lt;I&gt;200Q&lt;/I&gt;. In particular the &lt;I&gt;199I&lt;/I&gt; proves beneficial for meat quality. The results of combining the &lt;I&gt;RYR1&lt;/I&gt; and &lt;I&gt;PRKAG3&lt;/I&gt; genotypes indicate that &lt;I&gt;R/R-I/I&lt;/I&gt; genotype could be used in counterbalancing the negative effects of “&lt;I&gt;n&lt;/I&gt;” allele on meat quality.&lt;B&gt;&lt;/B&gt;

Effects of exercise on muscle glycogen synthesis signalling and enzyme activities in pigs carrying the PRKAG3 mutation

The dominant RN mutation in pigs results in excessive glycogen storage in skeletal muscle. The mutation is situated in the PRKAG3 gene, which encodes a muscle-specific isoform of the AMP-activated protein kinase (AMPK) gamma3 subunit. AMPK is an important regulator of carbohydrate and fat metabolism in mammalian cells. The aim of the present study was to examine the effect of exercise on glycogen synthesis signalling pathways in muscle and to study enzyme activities of importance in carbohydrate metabolism in pigs with or without the PRKAG3 mutation. Glycogen content, metabolic enzyme activities and expression or phosphorylation of signalling proteins were analysed in skeletal muscle specimens obtained at rest, after a single treadmill exercise bout and after 3 h recovery. The PRKAG3 mutation carriers had higher glycogen content, a tendency for lower expression of AMPK (P < 0.07) and higher hexokinase and phosphorylase activities, whereas citrate synthase, 3-hydroxyacyl-CoA dehydrogenase and glycogen synthase activities did not differ between genotypes. Carriers and non-carriers of the RN mutation showed a similar degradation of glycogen after exercise, whereas the rate of resynthesis was faster in the carriers. Acute exercise stimulated Akt phosphorylation on Ser(473) in both genotypes, and the effect was greater in the carriers than in the non-carriers. Acute exercise also stimulated phosphorylation of Akt substrate of 160 kDA and Glycogen synthase kinase 3 in the carriers and GSK3alpha in the non-carriers. In conclusion, the increased rate of glycogen synthesis following exercise in pigs carrying the PRKAG3 mutation correlates with an increased signalling response of Akt and its substrate, AS160, and a higher activity of hexokinase, indicating an increased glucose influx and phosphorylation of glucose, directed towards glycogen synthesis.

Association of PRKAG3 and CAST genetic polymorphisms with traits of interest in dry-cured ham production: Comparative study in France, Slovenia and Spain

Two genes ( PRKAG3 and CAST) were screened for genotype incidence and their effect on green ham traits in pigs suitable for dry-cured ham production from three commercial crosses (in three countries France, Slovenia and Spain). Hams were genotyped for PRKAG3 Ile199Val, CAST Lys249Arg and CAST Ser638Arg polymorphisms and the traits of interest (green ham weight and fat thickness, pH in M. semimembranosus (SM), M. gluteus medius (GM) colour) were measured. The genotype frequencies as well as the effect of the studied genes varied according to the country, which used different genetic crosses and selection criteria for dry-cured ham processes. Regarding the association with traits of interest, we observed a significant effect of PRKAG3 Ile199Val polymorphism on green ham weight and colour grade in the French cross, on green ham fat thickness, colour grade and GM Minolta L⁎ and a⁎ values in the Slovenian cross, and on SM pH in the Spanish cross. The CAST Lys249Arg polymorphism affected green ham weight in Slovenian cross, whereas CAST Ser638Arg affected green ham colour grade in French cross. No effect of CAST polymorphisms on the traits of interest was found in Spanish cross. According to our results, PRKAG3 gene seems to be more influential on green ham traits important for dry ham production than CAST gene. However the results were different for each country, indicating possible interaction with other genetic or environmental factors.

EFFECT OF I199V POLYMORPHISM ON PRKAG3 GENE ON CARCASS AND MEAT QUALITY TRAITS IN SLOVENIAN COMMERCIAL PIGS

ABSTRACT The effect of I199V polymorphism at the PRKAG3 gene on carcass and meat quality of commercial pigs was studied independently from PRKAG3 200Q or RYR1 “n” allele, known to decrease meat quality, i.e., animals were genotyped for RYR1 R615C, PRKAG3 I199V and R200Q substitutions, and only pigs without 200Q and “n” were retained for the analysis of carcass and meat quality traits (n = 274). Genotype frequencies were 12.0, 57.7 and 30.3% for I/I, I/V and V/V, respectively. The I199V polymorphism affected significantly fat thickness and drip loss and tended to affect ultimate pH. Interestingly, I/V were the fattest and significantly different from V/V, with I/I pigs being intermediate. The ultimate pH of I/I was higher than the one of I/V or V/V pigs. Regarding drip loss, significant difference was detected between I/I and V/V pigs. The heterozygous I/V pigs were intermediate with differences to I/I or V/V tending toward significance.PRACTICAL APPLICATIONSOur results provide new evidence about the significant effect of second polymorphism on the PRKAG3 gene (I199V) on carcass and meat quality. Because of low frequencies of I/I genotype in the majority of modern pig breeds, the available literature data for genotype I/I are scarce. Our results confirm a beneficial impact of 199I allele for pork quality, but indicate possible adverse impact for carcass leanness. It would be worthwhile rechecking the interesting position of heterozygous I/V pigs, which turned out to be the fattest. We expect the results to be useful for breeders in search of the compromise between carcass and meat quality.

Investigation of candidate genes for glycolytic potential of porcine skeletal muscle: Association with meat quality and production traits in Italian Large White pigs

The objective of this study was to investigate the association of DNA markers in candidate genes for glycolytic potential on meat quality parameters (pH 1, pH u, glycogen and lactate content and glycolytic potential of semimembranosus muscle) and estimated breeding values (EBVs) for average daily gain, lean cuts, back fat thickness, ham weight, and feed:gain ratio in 272 Italian Large White pigs. Three mutations in the PRKAG3 gene (T30N, G52S and I199V) were investigated as well as single nucleotide polymorphisms in two other skeletal muscle genes ( PGAM2 and PKM2) involved in the glycolytic pathway. Association analysis with the PRKAG3 markers showed significant results ( P < 0.05) only for pH 1 (I199V, with significant additive effect) and lactate content (T30N), confirming, at least in part, the effects of this gene on meat quality traits. Significant association ( P < 0.05) was also observed for PGAM2 and ham weight EBV with significant additive and dominance effects. PKM2 was associated with average daily gain, lean cuts ( P < 0.001), back fat thickness and feed:gain ratio ( P < 0.05), with significant additive and/or dominance effects on these traits. PKM2 encodes for a key enzyme of the muscle glycolytic pathway and maps on porcine chromosome 7 where other studies have reported important QTL for the same traits. These data might suggest an important function of this gene in the mechanisms that produce the observed effects. The results will be important to evaluate the inclusion of some of these DNA polymorphisms in marker assisted selection programs.

New Evidence of Alleles (V199I and G52S) at the PRKAG3 (RN) Locus Affecting Pork Meat Quality

The porcine PRKAG3 (RN) gene encodes the regulatory gamma subunit of adenosine monophosphate-activated protein kinase (AMPK), which is a good candidate gene affecting meat quality. In this study, the effects of two missense mutations A595G (Ile199Val) and G154A (Gly52Ser) in porcine PRKAG3 gene on meat quality traits were studied in M. Longissimus dorsi (LD), M. Semispinalis capitis (SC) and M. Biceps femoris (BF) from different populations of 326 pigs. The PRKAG3 alleles 199I, 199IV, 52S and 52G were identified with PCR-RFLPs and all genotypes - 199I/199I, 199I/199V, 199V/199V, 52S/52S, 52S/52G and 52G/52G - were found. The frequency of V allele was larger than that of I allele in all populations. I allele frequency was zero in Chinese Meishan pigs (population D) especially. G allele frequency was larger than that of S allele in all populations except Large White (population A). Both variations at the PRKAG3 locus significantly affected these meat quality traits. The pork meat quality has not previously been established in Meishan or crosses thereof. The results suggested that generally pH of LD, SC and BF was higher in Meishan pigs than that in other populations. Moreover, Meishan pigs showed higher water-holding capacity and intramuscular fat (IMF), lower water content and water loss percentage compared to other populations in terms of the two variations. The results present here supply new evidence that alleles V199I and G52S at the PRKAG3 locus affect pork meat quality and provide useful information on pork production.