Identification of differentially expressed genes in longissimus muscle of pigs with high and low intramuscular fat content using RNA sequencing.

Intramuscular fat (IMF) content in pork is an important element of consumer preference and is positively correlated with meat quality, including tenderness and juiciness. With advances in RNA sequencing technologies, transcriptome-related differences can be associated with specific traits in animals. The objective of this study was to investigate differentially expressed genes (DEGs) closely related to IMF content in porcine longissimus muscle using RNA sequencing. A total of 107 Berkshire pigs were used for IMF content measurements, and significant differences between extremely high (H, n = 3) and low (L, n = 3) IMF content groups were found (P < 0.0001). From multi-dimensional scaling analyses, it was observed that the relationships between H and L groups were similar to each other. Here, we identified a total of 134 genes that were differentially expressed between the groups (false discovery rate <0.05; fold change ≥2). Functional analyses with DEGs revealed that lipid metabolism (SCD and FASN) was one of the significant biological processes related to IMF content determination. In addition, we found that DEGs related to muscle regeneration (MYOG and VEGFA) and extracellular matrix (COL1A1, COL1A2, COL5A1, COL14A1 and COL15A1) were changed among individuals with extreme IMF contents. These results will aid in understanding the regulation of IMF content in pigs.

A genome-wide analysis of the ultimate pH in swine.

Meat pH is an important factor influencing meat quality traits in swine. This study evaluated a large number of genetic variants that covered all of the swine chromosomal regions. Approximately 68,000 single nucleotide polymorphisms (SNPs), found on Illumina Porcine SNP chips, were tested for associations with meat pH values. A genome-wide association study (GWAS) found that 19 SNPs on Sus scrofa chromosome 4 were significantly associated with pH. Two major candidate genomic regions were defined: a 1.08-Mb region (at nucleotide 30118313 to 31207050) contained 10 significant SNPs, based on an effect value of 5.0; and a 2.7-Mb genomic region (at nucleotide 73293076 to 76023681) contained 9 significant SNPs. Three putative genes--PKHD1L1, VCPIP1, and LOC102166532--were identified by GWAS near significant SNPs. These genes may account for variations in pH levels. Three pseudogenes and two non-coding RNAs were also detected by GWAS analysis. Estimations of expected and observed P values for pH revealed significant departures from the null hypothesis. A total of 9 haplotype blocks (HB) were constructed: HBs 1, 3, and 5 showed significant effects on pH24 and pH45, whereas an association was not confirmed between pH24 and HBs 4, 6, and 8. Findings from this study indicate that the three genes identified may influence pH of pig meat.

Genetic variation of FASN is associated with fatty acid composition of Hanwoo.

The objective of this study was to identify genetic variants in the bovine fatty acid synthase (FASN) gene and to evaluate associations with fatty acid composition from longissimus lumborum muscle using 90 purebred Hanwoo steers. Sequence alignments observed 6 genetic variants located in exons 20, 24, 32, 34, and 39, and PCR-RFLP analysis confirmed these variations. Genotypes of the g.15532A>C locus were significantly associated with Linolenic acid (C18:3), and genotypes of the g.17924G>A locus were significantly associated with Palmitic (C16:0), Palmitoleic (C16:1), Oleic (C18:1), saturated fatty acids, and unsaturated fatty acids. The analysis revealed that SFA and UFA showed significant correlations with fatty acid composition (Myristic (C14:0), Palmitic (C16:0), Stearic (C18:0), Oleic (C18:1), and Eicosenoic (C20:1) acids). Oleic acid (C18:1) was negatively correlated with Myristic (C14:0), Palmitic (C16:0), and Palmitoleic (C16:1) acids (P<0.001).

Genetic Polymorphisms of the Bovine NOV Gene Are Significantly Associated with Carcass Traits in Korean Cattle.

The objective of this study was to investigate single nucleotide polymorphisms (SNPs) in the bovine nephroblastoma overexpressed (NOV) gene and to evaluate whether these polymorphisms affect carcass traits in the Korean cattle population. We resequenced to detect SNPs from 24 unrelated individuals and identified 19 SNPs within the full 8.4-kb gene, including the 1.5-kb promoter region. Of these 19 SNPs, four were selected for genotyping based on linkage disequilibrium (LD). We genotyped 429 steers to assess the associations of these four SNPs with carcass traits. Statistical analysis revealed that g.7801T>C and g.8379A>C polymorphisms in the NOV gene were associated with carcass weight (p = 0.012 and 0.008, respectively), and the g.2005A>G polymorphism was associated with the back fat thickness (BF) trait (p = 0.0001). One haplotype of the four SNPs (GGTA) was significantly associated with BF (p = 0.0005). Our findings suggest that polymorphisms in the NOV gene may be among the important genetic factors affecting carcass yield in beef cattle.

Detection of quantitative trait Loci affecting fat deposition traits in pigs.

Quantitative trait loci (QTL) associated with fat deposition traits in pigs are important gene positions in a chromosome that influence meat quality of pork. For QTL study, a three generation resource population was constructed from a cross between Korean native boars and Landrace sows. A total of 240 F2 animals from intercross of F1 were produced. 80 microsatellite markers covering chromosomes 1 to 10 were selected to genotype the resource population. Intervals between adjacent markers were approximately 19 cM. Linkage analysis was performed using CRIMAP software version 2.4 with a FIXED option to obtain the map distances. For QTL analysis, the public web-based software, QTL express (http://www.qtl.cap.ed.ac.uk) was used. Two significant and two suggestive QTL were identified on SSC 6, 7, and 8 as affecting body fat and IMF traits. For QTL affecting IMF, the most significant association was detected between marker sw71 and sw1881 on SSC 6, and a suggestive QTL was identified between sw268 and sw205 on SSC8. These QTL accounted for 26.58% and 12.31% of the phenotypic variance, respectively. A significant QTL affecting IMF was detected at position 105 cM between markers sw71 and sw1881 on SSC 6.

Isolation and characterization of the bovine microsatellite loci.

Microsatellite loci were isolated using five repetitive probes for Korean native cattle. Eleven microsatellite loci were developed based on a biotin hybrid capture method, and enrichment of the genomic libraries (AAAT, TG, AG, T, and TGC repeats) was performed using Sau3AI adapters. The isolated markers were tested in two half-sib Korean cattle families and four imported breeds (Angus, Limousine, Holstein, and Shorthorn). Nine informative microsatellite loci were observed, and two microsatellite loci were revealed as monomorphic in Korean cattle. In the imported breeds, however, all of the markers were informative. In total, 213 alleles were obtained at the 11 loci across five breeds, and the average number of alleles found per locus, considering all populations, was 4.26. Heterozygosity was 0.71 (expected) and 0.57 (observed). The range of the polymorphic information content for the markers in all cattle populations was 0.43-0.69. Eleven percent of genetic variation was attributed to differentiation between populations as determined by the mean F (ST) values. The remaining 89% corresponded to differences among individuals. The isolated markers may be used to identify and classify the local breeds on a molecular basis.

Genetic structure of pig breeds from Korea and China using microsatellite loci analysis.

To understand molecular genetic characteristics of Korean pigs, the genetic relationships of nine pig breeds including two Korean pigs (Korean native pig and Korean wild pig), three Chinese pigs (Min pig, Xiang pig, and Wuzhishan pig), and four European breeds (Berkshire, Duroc, Landrace, and Yorkshire) were characterized from a 16-microsatellite loci analysis. The mean heterozygosity within breeds ranged from 0.494 to 0.703. Across multiple loci, significant deviation from Hardy-Weinberg equilibrium was observed in most pig breeds, except for two Chinese pigs (Min pig and Wuzhishan pig). This deviation was in the direction of heterozygote deficit. Across population loci, 36 of 144 significantly deviated (P < 0.05) from Hardy-Weinberg equilibrium. The mean FST, a measure of genetic divergence among subpopulations, of all loci indicated that 26.1% of total variation could be attributed to the breed difference. Relationship trees based on the Nei's DA genetic distance and scatter diagram from principal component analysis consistently displayed pronounced genetic differentiation among the Korean wild pig, Xiang pig, and Wuzhishan pig. Individual assignment test using a Bayesian method showed 100% success in assigning Korean and Chinese individual pigs into their correct breeds of origin and 100% exclusion success from all alternative reference populations at P < 0.001. These findings indicate that the Korean native pig has been experiencing progressive interbreeding with Western pig breeds after originating from a North China pig breed with a black coat color. Considering the close genetic relationship of Korean pigs to the Western breeds such as Berkshire and Landrace, our findings can be used as valuable genetic information for the preservation and further genetic improvement of the Korean native pig.