Expression profiling analysis for genes related to meat quality and carcass traits during postnatal development of backfat in two pig breeds

The competitive equilibrium of fatty acid biosynthesis and oxidation in vivo determines porcine subcutaneous fat thickness (SFT) and intramuscular fat (IMF) content. Obese and lean-type pig breeds show obvious differences in adipose deposition; however, the molecular mechanism underlying this phenotypic variation remains unclear. We used pathway-focused oligo microarray studies to examine the expression changes of 140 genes associated with meat quality and carcass traits in backfat at five growth stages (1–5 months) of Landrace (a leaner, Western breed) and Taihu pigs (a fatty, indigenous, Chinese breed). Variance analysis (ANOVA) revealed that differences in the expression of 25 genes in Landrace pigs were significant (FDR adjusted permutation, P<0.05) among 5 growth stages. Gene class test (GCT) indicated that a gene-group was very significant between 2 pig breeds across 5 growth stages (P _ErmineJ<0.01), which consisted of 23 genes encoding enzymes and regulatory proteins associated with lipid and steroid metabolism. These findings suggest that the distinct differences in fat deposition ability between Landrace and Taihu pigs may closely correlate with the expression changes of these genes. Clustering analysis revealed a very high level of significance (FDR adjusted, P<0.01) for 2 gene expression patterns in Landrace pigs and a high level of significance (FDR adjusted, P<0.05) for 2 gene expression patterns in Taihu pigs. Also, expression patterns of genes were more diversified in Taihu pigs than those in Landrace pigs, which suggests that the regulatory mechanism of micro-effect polygenes in adipocytes may be more complex in Taihu pigs than in Landrace pigs. Based on a dynamic Bayesian network (DBN) model, gene regulatory networks (GRNs) were reconstructed from time-series data for each pig breed. These two GRNs initially revealed the distinct differences in physiological and biochemical aspects of adipose metabolism between the two pig breeds; from these results, some potential key genes could be identified. Quantitative, real-time RT-PCR (QRT-PCR) was used to verify the microarray data for five modulated genes, and a good correlation between the two measures of expression was observed for both 2 pig breeds at different growth stages (R=0.874±0.071). These results highlight some possible candidate genes for porcine fat characteristics and provide some data on which to base further study of the molecular basis of adipose metabolism.     

Expression profiling analysis for genes related to meat quality and carcass traits during postnatal development of backfat in two pig breeds

The competitive equilibrium of fatty acid biosynthesis and oxidation in vivo determines porcine sub-cutaneous fat thickness(SFT) and intramuscular fat(IMF) content.Obese and lean-type pig breeds show obvious differences in adipose deposition;however, the molecular mechanism underlying this phenotypic variation remains unclear.We used pathway-focused oligo microarray studies to examine the expression changes of 140 genes associated with meat quality and carcass traits in backfat at five growth stages(1―5 months) of Landrace(a leaner, Western breed) and Taihu pigs(a fatty, indigenous, Chinese breed).Variance analysis(ANOVA) revealed that differences in the expression of 25 genes in Landrace pigs were significant(FDR adjusted permutation, P<0.05) among 5 growth stages.Gene class test(GCT) indicated that a gene-group was very significant between 2 pig breeds across 5 growth stages(PErmineJ<0.01), which consisted of 23 genes encoding enzymes and regulatory proteins associ-ated with lipid and steroid metabolism.These findings suggest that the distinct differences in fat deposition ability between Landrace and Taihu pigs may closely correlate with the expression changes of these genes.Clustering analysis revealed a very high level of significance(FDR adjusted, P<0.01) for 2 gene expression patterns in Landrace pigs and a high level of significance(FDR adjusted, P<0.05) for 2 gene expression patterns in Taihu pigs.Also, expression patterns of genes were more diversified in Taihu pigs than those in Landrace pigs, which suggests that the regulatory mechanism of micro-effect polygenes in adipocytes may be more complex in Taihu pigs than in Landrace pigs.Based on a dy-namic Bayesian network(DBN) model, gene regulatory networks(GRNs) were reconstructed from time-series data for each pig breed.These two GRNs initially revealed the distinct differences in physiological and biochemical aspects of adipose metabolism between the two pig breeds;from these results, some potential key genes could be identified.Quantitative, real-time RT-PCR(QRT-PCR) was used to verify the microarray data for five modulated genes, and a good correlation between the two measures of expression was observed for both 2 pig breeds at different growth stages(R=0.874±0.071).These results highlight some possible candidate genes for porcine fat characteristics and provide some data on which to base further study of the molecular basis of adipose metabolism.     

Comparison of microRNAs in adipose and muscle tissue from seven indigenous Chinese breeds and Yorkshire pigs

Elucidation of the pig microRNAome is essential for interpreting functional elements of the genome and understanding the genetic architecture of complex traits. Here, we extracted small RNAs from skeletal muscle and adipose tissue, and we compared their expression levels between one Western breed (Yorkshire) and seven indigenous Chinese breeds. We detected the expression of 172 known porcine microRNAs (miRNAs) and 181 novel miRNAs. Differential expression analysis found 92 and 12 differentially expressed miRNAs in adipose and muscle tissue respectively. We found that different Chinese breeds shared common directional miRNA expression changes compared to Yorkshire pigs. Some miRNAs differentially expressed across multiple Chinese breeds, including ssc‐miR‐129‐5p, ssc‐miR‐30 and ssc‐miR‐150, are involved in adipose tissue function. Functional enrichment analysis revealed that the target genes of the differentially expressed miRNAs are associated mainly with signaling pathways rather than metabolic and biosynthetic processes. The miRNA–target gene and miRNA–phenotypic traits networks identified many hub miRNAs that regulate a large number of target genes or phenotypic traits. Specifically, we found that intramuscular fat content is regulated by the greatest number of miRNAs in muscle tissue. This study provides valuable new candidate miRNAs that will aid in the improvement of meat quality and production.     

Differences in hepatic gene expression as a major distinguishing factor between Korean native pig and Yorkshire

There are phenotypic differences between Korean native pig (KNP) and Yorkshire (YS) breeds due to different interests in selection. YS has been selected for industrial interests such as a growth rate and lean meat production, while KNP has been maintained as a regional breed with local interests such as disease resistance and fat content in and between muscle. A comparison of gene expression profiles from liver tissue reflected overall long-term effects of artificial selection for these two pig breeds. Based on minimum positive false discovery rate (less than 10%) and fold change (|FC|>1.5), 73 differentially expressed genes (DEGs) were identified. Functional analysis of these DEGs indicated clear distinctions in signaling capacity related to epidermal growth factor (EGF), extracellular structure, protein metabolism, and detoxification. Hepatic DEGs demonstrated the importance of hormonal and metabolic capabilities to differences between these two pig breeds.     

Comparison of stomach microRNA transcriptomes of Tibetan and Yorkshire pigs by deep sequencing

MiRNAs regulate the expression of target genes in diverse cellular processes and hence play important roles in different physiological processes, yet little is known about the stomach microRNAome (miRNAome) of the Tibetan pig. The objective of this experiment was to investigate differentially expressed stomach miRNAs participating in digestion. Firstly, we isolated total RNA by Trizol reagent from three Tibetan and three Yorkshire purebred pigs stomach samples at 90-day-old. Secondly, a comprehensive analysis of Tibetan and Yorkshire pig stomach miRNAomes was performed by small RNA sequencing in the Illumina HiSeq 2000 system. Finally, SYBR Green Real-time RT-PCR was performed to validate the differentially expressed miRNAs. We identified 318 unique miRNAs, 260 were co-expressed in both libraries, 17 and 31 miRNAs were specifically expressed in Tibetan and Yorkshire pigs respectively. Fifty six differentially expressed miRNAs were identified by the identifying differentially expressed genes 6 (IDEG6). Kyoto encyclopedia of genes and genomes analysis revealed that some of the differentially expressed miRNAs were associated with protein and fat digestion. Two differentially expressed miRNAs (miR-214-3p and ssc-un39) participating in the digestion of lipid were identified. Additionally, qRT-PCR results suggested that a higher expression of miR-214-3p in the Tibetan pig stomach could lead to relatively lower expression of calcium-dependent phospholipase A2, which is an enzyme important for the digestion of glycerol phospholipid. This study has delineated the different stomach miRNAs expression patterns of Tibetan and Yorkshire pigs, which would help explain the regulatory mechanisms of miRNAs in digestion of Tibetan pigs, and contribute to utilize a the unique digestion merits of Tibetan pig in future porcine hybridization breeding.     

Systematic identification and characterization of porcine snoRNAs: structural,functional and developmental insights

Small nucleolar RNAs (snoRNAs) are 50‐ to 300‐nt non‐coding RNAs that are involved in critical cellular events, including rRNA/snRNA modification and splicing, ribosome genesis, telomerase formulation and cell proliferation. The identification of snoRNAs in the pig, which is a widely consumed commercial organism that also has important functions in medicine and biology, will enrich the snoRNA kingdom and provide evolutionary clues about snoRNAs. In this study, we performed a systematic identification of snoRNAs in Sus scrofa and obtained 120 candidate snoRNAs, 65 of which were predicted via sequencing from our constructed cDNA library. The others were obtained by computational screening. The primary structural features examined included the sequence length, GC content, conservation of common box motifs and nucleotide diversity. The results indicate that the primary features of H/ACA box snoRNAs are opposite to those of C/D box snoRNAs. Subsequently, based on chromosomal location and host gene determination, we assigned 91 snoRNAs to nine genome organization modes. Gene duplications and translocations are considered to contribute to the high abundant organization in evolution. Functional information about our novel snoRNAs, such as putative targets, modification sites and guide sequences, was predicted by orthologue alignment. A comparative analysis of predicted targets and possible modified loci on U6 snRNA and 5.8S and 18S rRNAs among five species revealed that targets of snoRNA are conserved among species. Furthermore, we performed a quantitative analysis of six representative snoRNA genes in two pig breeds during different developmental stages. Interestingly, all six snoRNAs from one breed expressed in a similar pattern over the tested time points; however, these same six genes had different expression patterns in the other pig breed. Specifically, expression of all six snoRNAs declined significantly from 65 to 90 days post‐coitus (dpc) and then increased slightly during adulthood in Tongcheng pigs, whereas the expression of the same six genes increased slowly from 65 dpc until adulthood in Landrace pigs. This expression pattern suggests that most housekeeping, non‐coding RNAs from a single pig breed may be similarly expressed during development. Our study adds to the knowledge about the snoRNA family by providing the first genome‐wide study of porcine snoRNAs. The comparative analysis of snoRNAs from different pig breeds gave us evolutionary insight into the function of snoRNAs.     

猪脂肪组织中IGF2和IGFBP3基因表达的发育性变化及其品种差异

采用荧光定量PCR技术分析长白猪和太湖猪背部皮下脂肪组织中胰岛素样生长因子2和胰岛素样生长因子结合蛋白3基因在30、60、90、120和150日龄时表达水平的发育性变化。结果表明: (1)品种内日龄间比较, 长白猪IGF2 mRNA 在30日龄时的表达量极显著高于其他日龄(P<0.01), 之后逐渐下降, 至120日龄降到最低, 150日龄时又明显上升; 太湖猪IGF2 mRNA在30~60日龄的表达量较高, 90日龄降至最低, 120日龄迅速回升, 之后又有所下降。两品种IGFBP3 mRNA表达的发育性变化模式基本相同, 30日龄时表达量最高, 60日龄显著下降(P<0.05), 之后趋于平缓但略有波动。(2)品种间同日龄比较, 120日龄时太湖猪IGF2 mRNA的表达量极显著高于长白猪(P<0.01), 150日龄时太湖猪IGFBP3的表达量极显著低于长白猪(P<0.01), 其余日龄间两品种差异均不显著(P>0.05)。研究结果提示: 猪脂肪组织IGF2和IGFBP3基因表达存在明显的发育性变化和品种差异; IGF2基因表达水平的降低可能与脂肪细胞的增殖有关。