Integrated analysis of the DNA methylome and RNA transcriptome during the development of skeletal muscle in Duroc pigs.

BACKGROUND: Skeletal muscle development plays a crucial role in yield and quality of pork; however, this process is influenced by various factors. In this study, we employed whole-genome bisulfite sequencing (WGBS) and transcriptome sequencing to comprehensively investigate the longissimus dorsi muscle (LDM), aiming to identify key genes that impact the growth and development of Duroc pigs with different average daily gains (ADGs). RESULTS: Eight pigs were selected and divided into two groups based on ADGs: H (774.89 g) group and L (658.77 g) group. Each pair of the H and L groups were half-siblings. The results of methylation sequencing revealed 2631 differentially methylated genes (DMGs) involved in metabolic processes, signalling, insulin secretion, and other biological activities. Furthermore, a joint analysis was conducted on these DMGs and the differentially expressed genes (DEGs) obtained from transcriptome sequencing of the same individual. This analysis identified 316 differentially methylated and differentially expressed genes (DMEGs), including 18 DMEGs in promoter regions and 294 DMEGs in gene body regions. Finally, LPAR1 and MEF2C were selected as candidate genes associated with muscle development. Bisulfite sequencing PCR (BSP) and quantitative real-time PCR (qRT-PCR) revealed that the promoter region of LPAR1 exhibited significantly lower methylation levels (P < 0.05) and greater expression levels (P < 0.05) in the H group than in the L group. Additionally, hypermethylation was observed in the gene body region of MEF2C, as was a low expression level, in the H group (P < 0.05). CONCLUSIONS: These results suggest that the differences in the ADGs of Duroc pigs fed the same diet may be influenced by the methylation levels and expression levels of genes related to skeletal muscle development.

Expression of lipid metabolism genes provides new insights into intramuscular fat deposition in Laiwu pigs.

OBJECTIVE: The objective of this study was to measure the special expression pattern of lipid metabolism genes and investigate the molecular mechanisms underlying intramuscular fat (IMF) deposition in Longissimus dorsi muscle of Laiwu pigs. METHODS: Thirty-six pigs (Laiwu n = 18; Duroc×Landrace×Yorkshire n = 18) were used for the measurement of the backfat thickness, marbling score, IMF content, and expression of lipid metabolism genes. RESULTS: Significant correlations were found between IMF content and the mRNA expression of lipid metabolism genes. Of the 14 fat deposition genes measured, fatty acid synthase (FASN) showed the strongest correlation (r = 0.75, p = 0.001) with IMF content, and of the 6 fat removal genes, carnitine palmitoyl transferase 1B (CPT1B) exhibited the greatest negative correlation (r = -0.66, p = 0.003) with IMF content in Laiwu pig. Multiple regression analysis showed that CPT1B, FASN, solute carrier family 27 member 1 (SLC27A1), and fatty acid binding protein 3 (FABP3) contributed 38% of the prediction value for IMF content in Laiwu pigs. Of these four variables, CPT1B had the greatest contribution to IMF content (14%) followed by FASN (11%), SLC27A1 (9%), and FABP3 (4%). CONCLUSION: Our results indicate that the combined effects of an upregulation in fat deposition genes and downregulation in fat removal genes promotes IMF deposition in Laiwu pigs.

Analysis and preliminary validation of the molecular mechanism of fat deposition in fatty and lean pigs by high-throughput sequencing.

Fat deposition in muscle includes intramuscular fat (IMF) and intermuscular fat. IMF content is an index of pork quality; however, because IMF content is difficult to measure in vivo in young animals, conventional breeding for IMF content is difficult to carry out. The mechanism and progression of animal fat deposition is not well understood, and there are currently no effective control methods. In this study, using Laiwu and large white pigs as the research subjects and RNA sequencing technology, we analyzed the genetic mechanism of animal fat deposition in pigs. Specifically, we analyzed the features of lncRNAs and their potential target genes. We obtained 464 million clean reads, from which 907 lncRNAs were identified. The cis and trans analysis identified target genes, including genes that were upregulated (286) and downregulated (621) in the fatty and lean pigs. ENSSSCG00000008692_ADD1, ENSSSCG00000023124_ADD1 and ENSSSCG00000005918_DGAT1 were validated as target genes of the lncRNAs and were shown to be closely related to fat deposition. These results provide a basis for studying the different metabolic lncRNA expression of IMF deposition. In addition, as the valuable model animal to study the mechanisms of obesity, pigs may represent a new avenue for studying human obesity.

Analysis on differential expressed genes of ovarian tissue between high- and low-yield laying hen.

In order to elucidate molecular genetic mechanism of laying hen reproduction at the transcriptional level and the structure of significantly differential genes, the mRNA differential display and reverse northern dot-blot were used to detect the differential expression of genes in the ovary tissue of low-yield laying hens and high-yield laying hens in the present study. Sixteen 32-week-old CAU-pink laying hens divided into two groups were used and the laying performance was measured. The results showed that only the egg numbers were significantly different between the two groups; and from 15 primer pairs, a total of 336 bands were displayed of which 59 cDNA bands were found to be differentially expressed in both high-yield and low-yield laying hen. The sequence analysis indicated that the expression of such bands as H-AP5, H-P5, and H-P4 was significantly potentiated in high-yield laying hen using primer pairs AP5/HT11G, P5/HT11G and P4/HT11G and these transcripts had high homology (98%) to HoxDb, HoxCa, and HoxBa, respectively. The differentially expressed gene fragments may be relevant to the progression of the high-yield hens to the egg-laying stage. And further study is required to elucidate the molecular function to improve the productivity of laying hens.

Pangenome obtained by long-read sequencing of 11 genomes reveal hidden functional structural variants in pigs.

Long-read sequencing (LRS) facilitates both the genome assembly and the discovery of structural variants (SVs). Here, we built a graph-based pig pangenome by incorporating 11 LRS genomes with an average of 94.01% BUSCO completeness score, revealing 206-Mb novel sequences. We discovered 183,352 nonredundant SVs (63% novel), representing 12.12% of the reference genome. By genotyping SVs in an additional 196 short-read sequencing samples, we identified thousands of population stratified SVs. Particularly, we detected 7,568 Tibetan specific SVs, some of which demonstrate significant population differentiation between Tibetan and low-altitude pigs, which might be associated with the high-altitude hypoxia adaptation in Tibetan pigs. Further integrating functional genomic data, the most promising candidate genes within the SVs that might contribute to the high-altitude hypoxia adaptation were discovered. Overall, our study generates a benchmark pangenome resource for illustrating the important roles of SVs in adaptive evolution, domestication, and genetic improvement of agronomic traits in pigs.

Molecular cloning, characterization and expression of cathepsin D from grass carp (Ctenopharyngodon idella).

Cathepsin D is a lysosomal aspartic proteinase which participates in various degradation functions within the cell. In this current study, we cloned and characterized the complete cDNA of grass carp cathepsin D through 5'- and 3'-RACE. The cathepsin D contained a 56 bp 5' terminal untranslated region (5'-UTR), a 1197 bp open reading frame encoding 398 amino acids, and a 394 bp 3'-UTR. Grass carp cathepsin D shared high similarity with those from other species, and showed the highest amino acid identity of 91% to Danio rerio. Unlike many other organisms, the grass carp cathepsin D contains only one N-glycosylation site closest to the N-terminal. Real-time quantitative RT-PCR demonstrated that Cathepsin D expressed in all twelve tissues (bladder, brain, liver, heart, gill, muscle, fin, eye, intestines, spleen, gonad and head kidney). The relative expression levels of Cathepsin D in gonad and liver were 26.58 and 24.95 times as much as those in fin, respectively. The expression level of Cathepsin D in muscle approximately 16-fold higher, in intestines and spleen were 12-fold higher. The cathepsin D expression showed an upward trend during embryonic development. After challenged with Aeromonas hydrophil, the expression of grass carp cathepsin D gene showed significant changes in the four test tissues (liver, head kidney, spleen and intestines). The fact that the bacterial infection can obviously improve the cathepsin D expression in immune-related organs, may suggest that cathepsin D plays an important role in the innate immune response of grass carp.

Comparative Analysis on Antioxidative Ability of Muscle between Laiwu Pig and Large White.

This study was conducted to evaluate effects of storage temperatures (4°C and 20°C) and pig breeds (Laiwu pig and Large White pig) on the main antioxidative enzymes (superoxide dismutase, catalase, and glutathione peroxidase) activity and lipid oxidation in porcine Longissimus dorsi muscle. Activities of antioxidative enzymes (AOE) decreased slightly during storage, regardless of storage temperatures. Muscle antioxidative enzymes activities stored at 4°C were higher than that stored at 20°C. Laiwu pig's enzymes activities were significantly (p<0.01) higher than Large White's. The level of malondialdehyde is a direct expression of the grade of lipid oxidation in meat. In our study, the malondialdehyde contents increased after 6 days storage. However, malondialdehyde contents of Laiwu pig were significantly (p<0.01) lower than Large White's. A lower content of malondialdehyde corresponds to a lower oxidation of lipids. These results indicated the muscle antioxidative ability of Laiwu pig was higher than Large White pig. It also implied that antioxidative enzymes were involved in the essentials and deciding mechanisms of meat quality by quenching oxygen free radicals and inhibiting lipid oxidation in muscle.

Characteristics of circRNAs expression profiles in the piglets intestine induced by oxidative stress.

BACKGROUD: Oxidative stress (OS) can affect the expression of key genes and destroy the intestinal structure. However, it is unclear how OS regulates the expression of circular RNAs (circRNAs), microRNAs (miRNAs) and mRNAs. OBJECTIVE: The aim of this study was to examine the expression of circRNAs, miRNAs and mRNAs exposed to OS. METHODS: Piglets were exposed to diquat (DQ), a herbicide, and the activity of antioxidant enzymes and the morphology of the intestine were investigated. We utilized whole transcriptome sequencing to examine the global expression of circRNAs, miRNAs and mRNAs in the jejunum. RESULTS: Compared to controls, 751 circRNAs, 731 miRNAs and 164 mRNAs were differentially expressed in diquat-treated piglets. Kyoto Encyclopedia of Genes and Genomes pathway analysis indicated that oxidative phosphorylation, RNA degradation and ubiquitin-mediated proteolysis were closely associated with OS. CONCLUSIONS: Our results indicated that diquat-induced OS alters the intestinal structure, resulting in the differential expression of circRNAs, miRNAs and mRNAs in the jejunum of piglets. Meanwhile, OS weakened the enzyme antioxidant system in serum of piglets. Our results provide a foundation for further studies on the mechanisms involved in the response to OS in the jejunum.

circGLI3 Inhibits Oxidative Stress by Regulating the miR-339-5p/VEGFA Axis in IPEC-J2 Cells.

As a new type of noncoding RNA, circular RNA (circRNA) is stable in cells and not easily degraded. This type of RNA can also competitively bind miRNAs to regulate the expression of their target genes. The role of circRNA in the mechanism of intestinal oxidative stress (OS) in weaned piglets is still unclear. In our research, diquat (DQ) was used to induce OS in small intestinal epithelial cells (IPEC-J2) to construct an OS cell model. Mechanistically, dual luciferase reporter assays, fluorescence in situ hybridization (FISH), and western blotting were performed to confirm that circGLI3 directly sponged miR-339-5p and regulated the expression of VEGFA. Overexpression of circGLI3 promoted IPEC-J2 cell proliferation, increased the proportion of S-phase cells (P < 0.01), and reduced reactive oxygen species (ROS) generation when IPEC-J2 cells were subjected to OS. circGLI3 can increase the activity of glutathione peroxidase (GSH-Px) and the total antioxidant capacity (T-AOC) in IPEC-J2 cells and reduce the malondialdehyde (MDA) content and levels of inflammatory factors. Therefore, overexpression of circGLI3 reduced oxidative damage, whereas miR-339-5p mimic counteracted these effects. We identified a regulatory network composed of circGLI3, miR-339-5p, and VEGFA and verified that circGLI3 regulates VEGFA by directly binding miR-339-5p. The expression of VEGFA affects IPEC-J2 cell proliferation, cell cycle progression, and ROS content and changes the levels of antioxidant enzymes and inflammatory factors. This study reveals the molecular mechanism by which circGLI3 inhibits OS in the intestine of piglets and provides a theoretical basis for further research on the effect of OS on intestinal function.

[CDS cloning and relationship between intramuscular fat content and mRNA expression of PID1 gene in pig].

To explore the relationship between the expression of PID1 gene and fat deposition, we cloned CDS of PID1 from porcine fat and muscle tissues by RT-PCR using degenerate primers, and investigated expression of this gene in various tissues (i.e., liver, backfat, and muscle tissues) of different breeds (i.e., Yorkshire, Laiwu, and Lulai Black) by real-time fluorescence quantitative PCR. The results showed that 654 bp CDS of porcine PID1 was obtained by sequencing and was 93.88%, 66.94% and 88.07% identical to those of the human, rat, and Bos taurus, respectively. The expression of PID1 mRNA in various tissues and breeds, on the whole, tended to be liver > fat > muscle and Laiwu > Lulai Black > Yorkshire, respectively. For different breeds, PID1 mRNA abundance in liver had significant difference (P < 0.05), but had no significant differences in fat and muscle tissues between Laiwu and Lulai Black (P > 0.05). For the three groups of Laiwu pigs with high (LWH), intermediate (LWI), and low IMF content (LWL), PID1 mRNA level was higher in liver tissue of LWH than that of LWL significantly (P < 0.05), and was higher in muscle tissue of LWH than that of LWI and LWL significantly (P < 0.05). PID1 mRNA abundance was not correlated with IMF in these three tissues of Laiwu breed, but it was positively correlated with IMF in the tissues of these three breeds (P < 0.05). These results implied that the expression of PID1 may be related to fat deposition.

[Cloning, expression and functional analysis of CuZnSOD gene in swine.].

In order to understand the structure and function of CuZnSOD gene, reveal the effect of the anti-oxidant in swine, and find the molecule marker correlated with meat traits, the cDNA of CuZnSOD gene was cloned and sequenced from muscle of Laiwu black swine by RACE (rapid amplification of cDNA end) techniques. The structure and function of CuZnSOD were analyzed by bioinformatics, and the gene expression profile in different tissues was examined by real-time PCR. The results showed that the full sequence of CuZnSOD cDNA is 658 bp (GU944822), containing 76 bp sequence of 5' UTR and 120 bp sequence of 3' UTR, and coding region (CDS, 462 bp) encodes 153 amino acids. The isoelectric point (pI) of the protein is 6.03, and the molecular weight is 15.9 kDa. There were one O-glycosylation site at the third amino acid and one N-glycosylation site at the eighty-fourth amino acid. The percentage of alpha helix was 1.31%. The alignment similarities of the CDS sequence of swine CuZnSOD with those of cattle, human, rat, and mouse were 87.74%, 87.66%, 83.44%, and 83.23%, and the similarities of amino acid sequence were 90.26%, 94.12%, 92.21%, and 91.50%, respectively. CuZnSOD possesses the typical metal binding ligands (GFHVHQFGDNT). The phylogenic tree based on CuZnSOD protein sequence detected the closest relationship between swine and cattle. CuZnSOD mRNA is a broad-spectrum expression gene, which was detected in brain, heart, spleen, liver, kidney, lung, large intestine, small intestine, spinal cord, muscle, backfat, and stomach. In particular, high expression levels of CuZnSOD mRNA were detected in kidney, small intestine and lung, but low expressions were observed in heart and muscle tissues.

[Relationship of genetic polymorphism of PRLR and RBP4 genes with litter size traits in pig].

The polymorphism of prolactin receptor (PRLR) and retinol-binding protein 4 (RBP4) genes was detected by PCR-RFLP method, and the effects of PRLR and RBP4 genes on litter size traits in pig were analyzed by the least square analysis. Data of total number born (TNB) and number born alive (NBA) from 323 sows, including five Shandong local pig breeds and three foreign pig breeds, were collected. The results showed that the polymorphic sites of both PRLR and RBP4 genes were found in all populations tested. The genotype distribution, however, revealed great differences between Shandong local pig breeds and foreign pig breeds. The effects of genotypes on TNB and NBA were significant (P<0.05). The homozygote AA was the most prolific genotype. For PRLR gene, AA genotypic sows of Shandong local pig breeds and foreign pig breeds produced 1.03 TNB, 0.89 NBA, and 1.26 TNB, 1.11 NBA more than BB genotypic sows, respectively. For RBP4 gene, AA genotypic sows of Shandong local pig breeds and foreign pig breeds produced 0.59 TNB, 0.51 NBA and 0.72 TNB, 0.64 NBA more than BB genotypic sows, respectively.

Diquat Determines a Deregulation of lncRNA and mRNA Expression in the Liver of Postweaned Piglets.

Oxidative stress is detrimental to animals and can depress the growth performance and regulate the gene expression of animals. However, it remains unclear how oxidative stress regulates the expression of long noncoding RNAs (lncRNAs) and mRNAs. Therefore, the purpose of this article was to explore the profiles of lncRNAs and mRNAs in the liver of piglets under oxidative stress. Here, we constructed a piglet oxidative stress model induced by diquat and evaluated the effects of oxidative stress on the growth performance and antioxidant enzyme activity of piglets. We also used RNA-Seq to examine the global expression of lncRNAs and mRNAs in piglets under oxidative stress. The targets of lncRNAs and mRNAs were enriched in gene ontology (GO) terms and signaling pathways. The results show that the growth performance and activities of antioxidant enzymes were decreased in piglets under oxidative stress. Moreover, eight lncRNAs (6 upregulated and 2 downregulated) and 30 mRNAs (8 upregulated and 22 downregulated) were differentially expressed in the oxidative stress group of piglets compared to the negative control group. According to biological processes in enriched GO terms, the oxoacid metabolic process, intramolecular oxidoreductase activity, and oxidation-reduction process play important roles in oxidative stress. Pathway analysis showed that the signaling pathways involved in insulin and glucose metabolism had a close relationship with oxidative stress. Further in vitro experiments showed that the expression of the upregulated gene GNMT was significantly increased in primary porcine hepatocytes after diquat stimulation. In contrast, the level of the downregulated gene GCK was significantly decreased at 12 h in primary porcine hepatocytes after diquat stimulation. Our results expand our knowledge of the lncRNAs and mRNAs transcribed in the livers of piglets under oxidative stress and provide a basis for future research on the molecular mechanisms mediating oxidative stress and tissue damage.

Relationships between ultimate pH and antioxidant enzyme activities and gene expression in pork loins.

Ultimate pH (pHu ) is a major determinant factor of meat quality. In this study, we investigated the effects of pHu on the muscle antioxidant capacity, and the relationship between pHu and muscle antioxidant capacity of pigs. A total of 137 pigs from three pig breeds with the same feeding condition were slaughtered and used to measure the pHu , superoxide dismutase (SOD), glutathione peroxidase (GSH-PX), total antioxidant capacity (T-AOC), and malondialdehyde (MDA) content, and gene expression of SOD1 and GPX4. Loins from 137 pigs of three breeds were classified based on pHu into three groups: low (L-pH: ≤5.50), intermediate (I-pH: 5.51-5.90), and high (H-pH: ≥5.91). A majority of loins (47.5%-52%) were classified into the intermediate group. The results suggested that the pHu value was correlated with the activity of SOD, GSH-PX, T-AOC, and MDA, and gene expression of SOD1 and GPX4 in all pigs. In addition, our results also indicated a linear relationship between the pHu value and antioxidant traits. The pHu value accounted for 23%-40% of the variation in the antioxidant traits. These results suggested that increased pHu reduce the lipid peroxidation, and also indicated that pHu may be a key factor explaining the variation in the activity of antioxidant enzymes and gene expression in pork loins.

Molecular cloning, sequence characteristics, and tissue expression analysis of ECE1 gene in Tibetan pig.

Low air pressure and low oxygen partial pressure at high altitude seriously affect the survival and development of human beings and animals. ECE1 is a recently discovered gene that is involved in anti-hypoxia, but the full-length cDNA sequence has not been obtained. For a better understanding of the structure and function of the ECE1 gene and to study its effect in Tibetan pig, the cDNA of the ECE1 gene from the muscle of Tibetan pig was cloned, sequenced and characterized. The ECE1 full-length cDNA sequence consists of 2262 bp coding sequence (CDS) that encodes 753 amino acids with a molecular mass of 85,449 kD, 2 bp 5'UTR and 1507 bp 3'UTR. In addition, the phylogenetic tree analysis revealed that the Tibetan pig ECE1 has a closer genetic relationship and evolution distance with the land mammals ECE1. Furthermore, analysis by qPCR showed that the ECE1 transcript is constitutively expressed in the 10 tissues tested: the liver, subcutaneous fat, kidney, muscle, stomach, heart, brain, spleen, pancreas, and lung. These results serve as a foundation for further insight into the Tibetan pig ECE1 gene.

Developmental changes and effect on intramuscular fat content of H-FABP and A-FABP mRNA expression in pigs.

H-FABP and A-FABP genes are considered as candidates for intramuscular fat (IMF) accretion. The aim of the present study was to assess the expression of H-FABP and A-FABP genes in m. longissimus dorsi (LD) and liver tissues of Laiwu and Lulai Black pig populations of different body weight (BW). Eighty-four barrows at different BW (30, 40, 50, 60, 70, 80, 90 and 100 kg, n = 6 per group) of Laiwu Black pig (no 100 kg group) and Lulai Black pig (no 30 kg group) were used to study the development changes of A-FABP and H-FABP mRNA expression and their relationships to IMF content. The results showed that, in both breeds, the IMF content increased continuously with growing (P < 0.05). The expression of H-FABP and A-FABP genes also increased with growing in LD tissue (P < 0.05), and reached a peak at 50 and 70 kg BW in Laiwu and Lulai Black pig, respectively. However, this regularity was not observed in liver tissue in both breeds. A positive correlation was just found between the A-FABP mRNA expression level in LD tissue and IMF content and BW in both breeds (P < 0.05). In conclusion, the A-FABP gene is strongly related to the development and function of IMF accretion in pigs.

[Isolation of microsatellite markers for Lateolabrax japonicus and polymorphic analysis].

To investigate population structure and marker assisted breeding, fast isolation by AFLP of sequences containing repeats (FIASCO) and GenBank database mining were used to develop novel microsatellite markers for sea perch (Lateolabrax japonicus). Genomic DNA fragments containing SSR sequences were captured by hybridization to (GT)(13) biotin-labeled probe and were ligated to PMD18-T vector. Among 150 randomly chosen clones from the SSR-enriched library, 66 sequences contained microsatellite motif over five repeats. In addition, 540 cDNA sequences and 132 ESTs of Lateolabrax japonicus were downloaded from GenBank and screened for di-, tri- and tetra-nucleotide repeats, while 22 sequences were found to contain microsatellites. As a result, 15 microsatellite loci were shown to be polymorphic in 30 Lateolabrax japonicus individuals, with the alleles ranging from two to ten, the observed heterozygosities from 0.6000-1.0000, and the expected heterozygosities from 0.5079-0.8890. Four loci (SP17, SP52, SP94 and SP468) were deviated from HWE in the sampled population after Bonferroni's correction, and no linkage disequilibrium was found among all loci (P<0.003), whereas null alleles were detected at locus SP52 (P<0.05). Among 15 polymorphic loci, the PIC values, which can be used for related population genetics analysis, were all above 0.5, with the exception of SP17 and SP468.