A functional regulatory variant of MYH3 influences muscle fiber-type composition and intramuscular fat content in pigs.

Muscle development and lipid accumulation in muscle critically affect meat quality of livestock. However, the genetic factors underlying myofiber-type specification and intramuscular fat (IMF) accumulation remain to be elucidated. Using two independent intercrosses between Western commercial breeds and Korean native pigs (KNPs) and a joint linkage-linkage disequilibrium analysis, we identified a 488.1-kb region on porcine chromosome 12 that affects both reddish meat color (a*) and IMF. In this critical region, only the MYH3 gene, encoding myosin heavy chain 3, was found to be preferentially overexpressed in the skeletal muscle of KNPs. Subsequently, MYH3-transgenic mice demonstrated that this gene controls both myofiber-type specification and adipogenesis in skeletal muscle. We discovered a structural variant in the promotor/regulatory region of MYH3 for which Q allele carriers exhibited significantly higher values of a* and IMF than q allele carriers. Furthermore, chromatin immunoprecipitation and cotransfection assays showed that the structural variant in the 5'-flanking region of MYH3 abrogated the binding of the myogenic regulatory factors (MYF5, MYOD, MYOG, and MRF4). The allele distribution of MYH3 among pig populations worldwide indicated that the MYH3 Q allele is of Asian origin and likely predates domestication. In conclusion, we identified a functional regulatory sequence variant in porcine MYH3 that provides novel insights into the genetic basis of the regulation of myofiber type ratios and associated changes in IMF in pigs. The MYH3 variant can play an important role in improving pork quality in current breeding programs.

Genome scan linkage analysis identifies a major quantitative trait loci for fatty acid composition in longissimus dorsi muscle in an F2 intercross between Landrace and Korean native pigs.

OBJECTIVE: This study was conducted to locate quantitative trait loci (QTL) influencing fatty acid (FA) composition in a large F2 intercross between Landrace and Korean native pigs. METHODS: Eighteen FA composition traits were measured in more than 960 F2 progeny. All experimental animals were genotyped with 165 microsatellite markers located throughout the pig autosomes. RESULTS: We detected 112 QTLs for the FA composition; Forty seven QTLs reached the genome-wide significant threshold. In particular, we identified a cluster of highly significant QTLs for FA composition on SSC12. QTL for polyunsaturated fatty acid on pig chromosome 12 (F-value = 97.2 under additive and dominance model, nominal p-value 3.6×10-39) accounted for 16.9% of phenotypic variance. In addition, four more QTLs for C18:1, C18:2, C20:4, and monounsaturated fatty acids on the similar position explained more than 10% of phenotypic variance. CONCLUSION: Our findings of a major QTL for FA composition presented here could provide helpful information to locate causative variants to improve meat quality traits in pigs.

Association of a missense mutation in the positional candidate gene glutamate receptor-interacting protein 1 with backfat thickness traits in pigs.

OBJECTIVE: Previously, we reported quantitative trait loci (QTLs) affecting backfat thickness (BFT) traits on pig chromosome 5 (SW1482-SW963) in an F2 intercross population between Landrace and Korean native pigs. The aim of this study was to evaluate glutamate receptor-interacting protein 1 (GRIP1) as a positional candidate gene underlying the QTL affecting BFT traits. METHODS: Genotype and phenotype analyses were performed using the 1,105 F2 progeny. A mixed-effect linear model was used to access association between these single nucleotide polymorphism (SNP) markers and the BFT traits in the F2 intercross population. RESULTS: Highly significant associations of two informative SNPs (c.2442 T>C, c.3316 C>G [R1106G]) in GRIP1 with BFT traits were detected. In addition, the two SNPs were used to construct haplotypes that were also highly associated with the BFT traits. CONCLUSION: The SNPs and haplotypes of the GRIP1 gene determined in this study can contribute to understand the genetic structure of BFT traits in pigs.

Association of the Single Nucleotide Polymorphisms in RUNX1, DYRK1A, and KCNJ15 with Blood Related Traits in Pigs.

The aim of this study was to detect positional candidate genes located within the support interval (SI) regions based on the results of red blood cell, mean corpuscular volume (MCV), and mean corpuscular hemoglobin quantitative trait locus (QTL) in Sus scrofa chromosome 13, and to verify the correlation between specific single-nucleotide polymorphisms (SNPs) located in the exonic region of the positional candidate gene and the three genetic traits. The flanking markers of the three QTL SI regions are SW38 and S0215. Within the QTL SI regions, 44 genes were located, and runt-related transcription factor 1, dual-specificity tyrosine-(Y)-phosphorylation regulated kinase 1A (DYRK1A), and potassium inwardly-rectifying channel, subfamily J, member 15 KCNJ15-which are reported to be related to the hematological traits and clinical features of Down syndrome-were selected as positional candidate genes. The ten SNPs located in the exonic region of the three genes were detected by next generation sequencing. A total of 1,232 pigs of an F2 resource population between Landrace and Korean native pigs were genotyped. To investigate the effects of the three genes on each genotype, a mixed-effect model which is the considering family structure model was used to evaluate the associations between the SNPs and three genetic traits in the F2 intercross population. Among them, the MCV level was highly significant (nominal p = 9.8×10-9) in association with the DYRK1A-SNP1 (c.2989 G

Genome-wide QTL analysis of meat quality-related traits in a large F2 intercross between Landrace and Korean native pigs.

BACKGROUND: We conducted a genome-wide linkage analysis to identify quantitative trait loci (QTL) that influence meat quality-related traits in a large F2 intercross between Landrace and Korean native pigs. Thirteen meat quality-related traits of the m. longissimus lumborum et thoracis were measured in more than 830 F2 progeny. All these animals were genotyped with 173 microsatellite markers located throughout the pig genome, and the GridQTL program based on the least squares regression model was used to perform the QTL analysis. RESULTS: We identified 23 genome-wide significant QTL in eight chromosome regions (SSC1, 2, 6, 7, 9, 12, 13, and 16) (SSC for Sus Scrofa) and detected 51 suggestive QTL in the 17 chromosome regions. QTL that affect 10 meat quality traits were detected on SSC12 and were highly significant at the genome-wide level. In particular, the QTL with the largest effect affected crude fat percentage and explained 22.5% of the phenotypic variance (F-ratio = 278.0 under the additive model, nominal P = 5.5 × 10(-55)). Interestingly, the QTL on SSC12 that influenced meat quality traits showed an obvious trend for co-localization. CONCLUSIONS: Our results confirm several previously reported QTL. In addition, we identified novel QTL for meat quality traits, which together with the associated positional candidate genes improve the knowledge on the genetic structure that underlies genetic variation for meat quality traits in pigs.

Association of the gene encoding stearoyl-CoA desaturase (SCD) with fatty acid composition in an intercross population between Landrace and Korean native pigs.

Fatty acid (FA) composition is one of the most important parameters for the evaluation of meat quality. The stearoyl-CoA desaturase (SCD) gene is considered a positional candidate gene affecting FA composition in SSC14, based on previous quantitative trait loci studies. To evaluate the association of the SCD gene with FA composition in a Korean native pig × Landrace F(2) intercross population, we genotyped six single nucleotide polymorphisms (SNPs) of the SCD gene located in promoter region [2 SNPs (g.-353T>C, g.-233T>C)], exonic region [1 SNP (g.817C>T) in exon 2] and 3' UTR [3 SNPs (g.13311C>G, g.14384G>A, and g.14424C>T)] identified by massively parallel sequencing technology. Eighteen FA composition traits were measured in more than the 950 F(2) animals. A mixed-effect model was used to evaluate associations between these SNPs and FA composition traits in the F(2) intercross population. A detailed investigation detected that the five FA composition traits [palmitoleic acid (C16:1), stearic acid (C18:0), arachidic acid (C20:0), saturated FA, and unsaturated FA] were highly significant (P < 4.7 × 10(-5); C20:0) in association with the SNP g.-233T>C, SNP g.817C>T, SNP g.13311C>G and SNP g.14384G>A in the SCD gene, whereas SNP g.14424C>T was only significantly associated with palmitoleic acid (C16:1, P = 1.4 × 10(-3)). No significant association of FA composition traits with SNP g.-353T>C was detected. In particular, the SNP g.14384G>A accounted for 30.6 % of the additive genetic variance of palmitoleic acid (P = 1.9 × 10(-10)). These results suggest the SCD gene has a strong effect on FA composition in the crossbred pig population.

A missense mutation (c.1963A

Serum Ca(++) levels play important roles in the humoral immunity. The aim of this study was to detect quantitative trait loci and the associated positional candidate genes affecting baseline serum Ca(++) concentrations. A genome-wide association study was conducted in an F(2) intercross population between Landrace and Korean native pigs using the porcine single nucleotide polymorphism (SNP) 60 K beadchip and the PLINK program based on linear regression. Data used in the study included 410 F(2) pigs. All experimental animals were genotyped with 36,613 SNP markers located throughout the pig autosomes. We identified a strong association between a SNP marker on chromosome 7 and serum Ca(++) levels (DIAS0002191, genomic control-corrected P = 7.7 × 10(-5)). The position of DIAS0002191 was closely located to SLA class III region containing the C2 gene encoding the complementary component 2 protein, a protein which is important in the humoral immune responses. De novo sequencing of the porcine C2 gene revealed a missense mutation [c.1963A

QTL analysis of back fat thickness and carcass pH in an F2 intercross between Landrace and Korean native pigs.

In this study, we conducted a genome-wide linkage analysis to identify the quantitative trait loci (QTL) that influence back fat thickness and carcass pH in an F(2) intercross between Landrace and Korean native pigs. Eight phenotypes related with back fat thickness and carcass pH were measured in more than 960 F(2) progeny. All experimental animals were subjected to genotypic analysis using 173 microsatellite markers located throughout the pig genome. The GridQTL program, based on the least squares regression model, was used to perform the QTL analysis. We identified 22 genome-wide significant QTL in 9 chromosomal regions (SSC1, 2, 5, 6, 7, 8, 12, 15, and 16) and 29 suggestive QTL in 16 chromosomal regions (SSC2, 3, 4, 5, 6, 7, 8, 10, 11, 12, 14, 15, 16, 17, 18, and X). On SSC5, we detected a QTL affecting back fat thickness that accounted for 4.8 % of the phenotypic variance, which was the highest test statistic (F-ratio = 50.3 under the additive model, nominal P value = 2.5 × 10(-12)) observed in this study. Additionally, we showed that there were significant QTL on SSC16 affecting carcass pH traits. In conclusion, the QTL identified in this study together with associated positional candidate genes could play an important role in determining the genetic structure underlying the variation of back fat thickness and carcass pH in pigs.

QTL analysis of clinical-chemical traits in an F2 intercross between Landrace and Korean native pigs.

Clinical-chemical traits are essential when examining the health status of individuals. The aim of this study was to identify quantitative trait loci (QTL) and the associated positional candidate genes affecting clinical-chemical traits in a reciprocal F(2) intercross between Landrace and Korean native pigs. Following an overnight fast, 25 serum phenotypes related to clinical-chemical traits (e.g., hepatic function parameters, renal function parameters, electrolyte, lipids) were measured in >970 F(2) progeny. All experimental samples were subjected to genotyping analysis using 165 microsatellite markers located across the genome. We identified eleven genome-wide significant QTL in six chromosomal regions (SSC 2, 7, 8, 13, 14, and 15) and 59 suggestive QTL in 17 chromosomal regions (SSC 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 13, 14, 15, 16, 17, and 18). We also observed significant effects of reciprocal crosses on some of the traits, which would seem to result from maternal effect, QTL on sex chromosomes, imprinted genes, or genetic difference in mitochondrial DNA. The role of genomic imprinting in clinical-chemical traits also was investigated. Genome-wide analysis revealed a significant evidence for an imprinted QTL in SSC4 affecting serum amylase levels. Additionally, a series of bivariate linkage analysis provided strong evidence that QTL in SSC 2, 13, 15, and 18 have a pleiotropic effect on clinical-chemical traits. In conclusion, our study detected both novel and previously reported QTL influencing clinical-chemical traits in pigs. The identified QTL together with the positional candidate genes identified here could play an important role in elucidating the genetic structure of clinical-chemical phenotype variation in humans and swine.

The robust phylogeny of Korean wild boar (Sus scrofa coreanus) using partial D-loop sequence of mtDNA.

In order to elucidate the precise phylogenetic relationships of Korean wild boar (Sus scrofa coreanus), a partial mtDNA D-loop region (1,274 bp, NC_000845 nucleotide positions 16576-1236) was sequenced among 56 Korean wild boars. In total, 25 haplotypes were identified and classified into four distinct subgroups (K1 to K4) based on Bayesian phylogenetic analysis using Markov chain Monte Carlo methods. An extended analysis, adding 139 wild boars sampled worldwide, confirmed that Korean wild boars clearly belong to the Asian wild boar cluster. Unexpectedly, the Myanmarese/Thai wild boar population was detected on the same branch as Korean wild boar subgroups K3 and K4. A parsimonious median-joining network analysis including all Asian wild boar haplotypes again revealed four maternal lineages of Korean wild boars, which corresponded to the four Korean wild boar subgroups identified previously. In an additional analysis, we supplemented the Asian wild boar network with 34 Korean and Chinese domestic pig haplotypes. We found only one haplotype, C31, that was shared by Chinese wild, Chinese domestic and Korean domestic pigs. In contrast to our expectation that Korean wild boars contributed to the gene pool of Korean native pigs, these data clearly suggest that Korean native pigs would be introduced from China after domestication from Chinese wild boars.