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Inbreeding and loss of genetic diversity are serious problems in local Chinese pig breeds. Runs of homozygosity (ROHs) are contiguous lengths of homozygous genotypes that can provide information on inbreeding levels, mating schemes, selection pressure, and genetic events. The Anqing six-end-white (AQ) pig, an important autochthonous pig breed bred in the Anhui province of China, plays a key role in the local pig industry. In recent decades, AQ pigs have become a closed breed with a small population size in conservation farms, raising the issue of inbreeding decline. In this study, we used 10× resequencing to detect the whole genome of 24 AQ pigs and six Asian wild boars (AWBs). We used the Plink software to analyze the homozygosity of the genome and the distribution of ROHs in the genome based on the resequencing data. We obtained 935.04 Gb of raw data from the resequencing results and more than 45 822 239 SNPs. Additionally, we identified 28 702 ROHs. Compared with AWB, AQ pigs had higher ROH numbers, longer ROH rates, and higher F

(1) Background: Piglet diarrhea is one of the most serious diseases in pigs and has brought great economic losses to the pig industry. Alteration of the gut microbiota is an important factor in the etiology of piglet diarrhea. Therefore, this study aimed to analyze the differences in the gut microbial structures and fecal metabolic profile between post-weaning diarrhea and healthy Chinese Wannan Black pigs. (2) Methods: An integrated approach of 16S rRNA gene sequencing combined with LC/MS-based metabolomics was employed in this study. (3) Results: We found an increase in the relative abundance of the bacterial genus Campylobacter and a decrease in phylum Bacteroidetes and the species Streptococcus gallolyticus subsp. macedonicus. (S. macedonicus) in piglet diarrhea. Meanwhile, obvious changes in the fecal metabolic profile of diarrheic piglets were also detected, particularly higher levels of polyamines (spermine and spermidine). Moreover, there were substantial associations between the disturbed gut microbiota and the altered fecal metabolites, especially a strong positive relationship between spermidine and Campylobacter. (4) Conclusions: These observations may provide novel insights into potential etiologies related to post-weaning diarrhea and further enhance our understanding of the role of gut microbiota in host homeostasis and in modulating gut microbial structure.

Copy number variation (CNV) has been widely used to study the evolution of different species. We first discovered different CNVs in 24 Anqingliubai pigs and 6 Asian wild boars using next-generation sequencing at the whole-genome level with 10× depth to understand the relationship between genetic evolution and production traits in wild boars and domestic pigs. A total of 97,489 CNVs were identified and divided into 10,429 copy number variation regions (CNVRs), occupying 32.06% of the porcine genome. Chromosome 1 had the most CNVRs, and chromosome 18 had the least. Ninety-six CNVRs were selected using VST 1% based on the signatures of all CNVRs, and sixty-five genes were identified in the selected regions. These genes were strongly correlated with traits distinguishing groups by enrichment in Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathways, such as growth (CD36), reproduction (CIT, RLN), detoxification (CYP3A29), and fatty acid metabolism (ELOVL6). The QTL overlapping regions were associated with meat traits, growth, and immunity, which was consistent with CNV analysis. Our findings increase the understanding of evolved genome structural variations between wild boars and domestic pigs, and provide new molecular biomarkers to guide breeding and the efficient use of available genetic resources.

As a distinguished Chinese indigenous pig breed that exhibits disease resistance and high meat quality, the Anqing six-end-white (AQ) pig represents a valuable germplasm resource for improving the quality of the pig breeding industry. In this study, 24 AQ pigs that were distantly blood-related and 6 Asian Wild Boar (AWB) were selected for 10× deep-genome resequencing. The signatures of the selection were analyzed to explore the genetic basis of their germplasm characteristics and to identify excellent germplasm-related functional genes based on NGS data. A total of 49,289,052 SNPs and 6,186,123 indels were detected across the genome in 30 pigs. Most of the genetic variations were synonym mutations and existed in the intergenic region. We identified 275 selected regions (top 1%) harboring 85 genes by applying a crossover approach based on genetic differentiation (FST) and polymorphism levels (π ratio). Some genes were found to be positively selected in AQ pigs’ breeding. The SMPD4 and DDX18 genes were involved in the immune response to pseudorabies virus (PRV) and porcine reproductive and respiratory syndrome virus (PRRSV). The BCL6 and P2RX6 genes were involved in biological regulation of immune T cells and phagocytes. The SLC7A4 and SPACA4 genes were related to reproductive performance. The MSTN and HIF1A genes were related to fat deposition and muscle development. Moreover, 138 overlapping regions were detected in selected regions and ROH islands of AQ pigs. Additionally, we found that the QTLs with the most overlapping regions were related to back fat thickness, meat color, pH value, fatty acid content, immune cells, parasitic immunity, and bacterial immunity. Based on functional enrichment analysis and QTLs mapping, we conducted further research on the molecular genetic basis of germplasm traits (disease resistance and excellent meat quality). These results are a reliable resource for conserving germplasm resources and exploiting molecular markers of AQ pigs.

Background Porcine epidemic diarrhea virus (PEDV) is a causative agent of serious viral enteric disease in suckling pigs. Such diseases cause considerable economic losses in the global swine industry. Enhancing our knowledge of PEDV-induced transcriptomic responses in host cells is imperative to understanding the molecular mechanisms involved in the immune response. Here, we analyzed the transcriptomic profile of intestinal porcine epithelial cell line J2 (IPEC-J2) after infection with a classical strain of PEDV to explore the host response. Results In total, 854 genes were significantly differentially expressed after PEDV infection, including 716 upregulated and 138 downregulated genes. Functional annotation analysis revealed that the differentially expressed genes were mainly enriched in the influenza A, TNF signaling, inflammatory response, cytokine receptor interaction, and other immune-related pathways. Next, the putative promoter regions of the 854 differentially expressed genes were examined for the presence of transcription factor binding sites using the MEME tool. As a result, 504 sequences (59.02%) were identified as possessing at least one binding site of signal transducer and activator of transcription (STAT), and five STAT transcription factors were significantly induced by PEDV infection. Furthermore, we revealed the regulatory network induced by STAT members in the process of PEDV infection. Conclusion Our transcriptomic analysis described the host genetic response to PEDV infection in detail in IPEC-J2 cells, and suggested that STAT transcription factors may serve as key regulators in the response to PEDV infection. These results further our understanding of the pathogenesis of PEDV.

With the development of high-throughput genotyping techniques, selection signatures in the genome of domestic pigs have been extensively interrogated in the last decade. The Duroc, a major commercial pig breed famous for its fast growth rate and high lean ratio, has not been extensively studied focusing on footprints of intensively artificial selection in their genomes by a lot of re-sequencing data. The goal of this study was to investigate genomic regions under artificial selection and their contribution to the unique phenotypic traits of the Duroc using whole-genome resequencing data from 97 pigs. Three complementary methods (di, CLR, and iHH12) were implemented for selection signature detection. In Total, 464 significant candidate regions were identified, which covered 46.4 Mb of the pig genome. Within the identified regions, 709 genes were annotated, including 600 candidate protein-coding genes (486 functionally annotated genes) and 109 lncRNA genes. Genes undergoing selective pressure were significantly enriched in the insulin resistance signaling pathway, which may partly explain the difference between the Duroc and other breeds in terms of growth rate. The selection signatures identified in the Duroc population demonstrated positive pressures on a set of important genes with potential functions that are involved in many biological processes. The results provide new insights into the genetic mechanisms of fast growth rate and high lean mass, and further facilitate follow-up studies on functional genes that contribute to the Duroc’s excellent phenotypic traits.

Introgression events and population admixture occurred among Sus species across the Eurasian mainland in the Middle Pleistocene, which reflects the local adaption of different populations and contributes to evolutionary novelty. Previous findings on these population introgressions were largely based on extensive genome-wide single-nucleotide polymorphism information, ignoring structural variants (SVs) as an important alternative resource of genetic variations. Here, we profiled the genome-wide SVs and explored the formation of pattern-related SVs, indicating that PRE1-SS is a recently active subfamily that was strongly associated with introgression events in multiple Asian and European pig populations. As reflected by the three different combination haplotypes from two specific patterns and known phylogenetic relationships in Eurasian boars, we identified the Asian Northern wild pigs as having experienced introgression from European wild boars around 0.5–0.2 Ma and having received latitude-related selection. During further exploration of the influence of pattern-related SVs on gene functions, we found substantial sequence changes in 199 intron regions of 54 genes and 3 exon regions of 3 genes (HDX, TRO, and SMIM1), implying that the pattern-related SVs were highly related to positive selection and adaption of pigs. Our findings revealed novel introgression events in Eurasian wild boars, providing a timeline of population admixture and divergence across the Eurasian mainland in the Middle Pleistocene.

Background Reproductive performance of livestock is an economically important aspect of global food production. The Chinese Meishan pig is a prolific breed, with an average of three to five more piglets per litter than European breeds; however, the genetic basis for this difference is not well understood. Results In this study, we investigated copy number variations (CNVs) of 32 Meishan pigs and 29 Duroc pigs by next-generation sequencing. A genome-wide analysis of 61 pigs revealed 12,668 copy number variable regions (CNVRs) that were further divided into three categories based on copy number (CN) of the whole population, i.e., gain (n = 7,638), and loss (n = 5,030) CNVRs. We then compared Meishan and Duroc pigs and identified 17.17 Mb of 6,387 CNVRs that only existing in Meishan pigs CNVRs that overlapped the reproduction-related gene encoding the aryl hydrocarbon receptor (AHR) gene. We found that normal AHR CN was more frequent than CN loss in four different pig breeds. An association analysis showed that AHR CN had a positive effect on litter size (P P P Conclusions The present study provides comprehensive CNVRs for Meishan and Duroc pigs through large-scale population resequencing. Our results provide a supplement for the high-resolution map of copy number variation in the porcine genome and valuable information for the investigation of genomic structural variation underlying traits of interest in pig. In addition, the association results provide evidence for AHR as a candidate gene associated with reproductive traits that can be used as a genetic marker in pig breeding programs.

Structural variants (SVs) represent essential forms of genetic variation, and they are associated with various phenotypic traits in a wide range of important livestock species. However, the distribution of SVs in the pig genome has not been fully characterized, and the function of SVs in the economic traits of pig has rarely been studied, especially for most domestic pig breeds. Meishan pig is one of the most famous Chinese domestic pig breeds, with excellent reproductive performance. Here, to explore the genome characters of Meishan pig, we construct an SV map of porcine using whole-genome sequencing data and report 33,698 SVs in 305 individuals of 55 globally distributed pig breeds. We perform selective signature analysis using these SVs, and a number of candidate variants are successfully identified. Especially for the Meishan pig, 64 novel significant selection regions are detected in its genome. A 140-bp deletion in the Indoleamine 2,3-Dioxygenase 2 (IDO2) gene, is shown to be associated with reproduction traits in Meishan pig. In addition, we detect two duplications only existing in Meishan pig. Moreover, the two duplications are separately located in cytochrome P450 family 2 subfamily J member 2 (CYP2J2) gene and phospholipase A2 group IVA (PLA2G4A) gene, which are related to the reproduction trait. Our study provides new insights into the role of selection in SVs' evolution and how SVs contribute to phenotypic variation in pigs.

Alternative splicing (AS) is a process during gene expression that results in a single gene coding for different protein variants. AS contributes to transcriptome and proteome diversity. In order to characterize AS in pigs, genome-wide transcripts and AS events were detected using RNA sequencing of 34 different tissues in Duroc pigs. In total, 138,403 AS events and 29,270 expressed genes were identified. An alternative donor site was the most common AS form and accounted for 44% of the total AS events. The percentage of the other three AS forms (exon skipping, alternative acceptor site, and intron retention) was approximately 19%. The results showed that the most common AS events involving alternative donor sites could produce different transcripts or proteins that affect the biological processes. The expression of genes with tissue-specific AS events showed that gene functions were consistent with tissue functions. AS increased proteome diversity and resulted in novel proteins that gained or lost important functional domains. In summary, these findings extend porcine genome annotation and highlight roles that AS could play in determining tissue identity.

Long noncoding RNA (lncRNA) play a critical role in mammary development and breast cancer biology. Despite their important role in the mammary gland, little is known of the roles of lncRNA in bovine lactation, particularly regarding the molecular processes underlying it. To characterize the role of lncRNA in bovine lactation, 4 samples of Holstein cow mammary gland tissue at peak and late lactation stages were examined after biopsy. We then profiled the transcriptome of the mammary gland using RNA sequencing technology. Further, functional lncRNA-mRNA coexpression pairs were constructed to infer the function of lncRNA using a generalized linear model, followed by gene ontology and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses. More than 1,000 putative lncRNA were identified, 117 of which were differentially expressed between peak and late lactation stages. Bovine lncRNA were shorter, with fewer exon numbers, and expressed at significantly lower levels than protein-coding genes. Seventy-two differentially expressed (DE) lncRNA were coexpressed with 340 different protein-coding genes. The KEGG pathway analysis showed that target mRNA for DE lncRNA were mainly related to lipid and glucose metabolism, including the peroxisome proliferator-activated receptors and 5' adenosine monophosphate-activated protein kinase signaling pathways. Further bioinformatics and integrative analyses revealed that 12 DE lncRNA potentially played important roles in bovine lactation. Our findings provide a valuable resource for future bovine transcriptome studies, facilitate the understanding of bovine lactation biology, and offer functional information for cattle lactation.

Background Pseudo-phenotypes, such as 305-day yields, estimated breeding values or deregressed proofs, are usually used as response variables for genome-wide association studies (GWAS) of milk production traits in dairy cattle. Computational inefficiency challenges the direct use of test-day records for longitudinal GWAS with large datasets. Results We propose a rapid longitudinal GWAS method that is based on a random regression model. Our method uses Eigen decomposition of the phenotypic covariance matrix to rotate the data, thereby transforming the complex mixed linear model into weighted least squares analysis. We performed a simulation study that showed that our method can control type I errors well and has higher power than a longitudinal GWAS method that does not include time-varied additive genetic effects. We also applied our method to the analysis of milk production traits in the first three parities of 6711 Chinese Holstein cows. The analysis for each trait was completed within 1 day with known variances. In total, we located 84 significant single nucleotide polymorphisms (SNPs) of which 65 were within previously reported quantitative trait loci (QTL) regions. Conclusions Our rapid method can control type I errors in the analysis of longitudinal data and can be applied to other longitudinal traits. We detected QTL that were for the most part similar to those reported in a previous study in Chinese Holstein. Moreover, six additional SNPs for fat percentage and 13 SNPs for protein percentage were identified by our method. These additional 19 SNPs could be new candidate quantitative trait nucleotides for milk production traits in Chinese Holstein. Electronic supplementary material The online version of this article (10.1186/s12711-018-0383-0) contains supplementary material, which is available to authorized users.

Background Mutations in mitochondrial tRNA genes have been widely reported association with human reproductions. It is also important to explore the effect on the number of piglets born alive (NBA). Here, 1017 sows were used to investigate the association between polymorphisms in mitochondrial tRNA genes and NBA. Results In total, 16 mutations were found in mitochondrial tRNA genes, of which 13 mutations were significantly associated with NBA (P

Aim: To construct a comprehensive pig noncoding transcriptome and further enhance porcine noncoding genome annotation. Materials & methods: We performed a tissue-based long noncoding RNA (lncRNA) profiling via exploiting 32,212 nonredundant lncRNA isoforms corresponding to 18,676 lncRNA loci across 34 normal pig tissues using high-throughput sequencing. Furthermore, the potential relationship between our identified lncRNAs and known protein-coding genes were globally assessed via a comprehensive computation-based strategy, developing a genome-wide lncRNA-targeted genome draft for further functional studies on noncoding genes. Results & conclusion: Among these lncRNAs, ubiquitously expressed lncRNA appeared at a higher level compared with tissue-specific one. Findings herein provide insight into comprehensive knowledge of porcine noncoding RNAs and further enhance pig noncoding annotation. For ease of accessing the information of the identified lncRNAs, we deposited those with high confidence in the publicly available NONCODE database, providing a valuable resource for facilitating pig noncoding genomic studies.

DNA methylation changes play essential roles in regulating the activities of genes involved in immune responses. Understanding of variable DNA methylation linked to immune responses may contribute to identifying biologically promising epigenetic markers for pathogenesis of diseases. Here, we generated genome-wide DNA methylation and transcriptomic profiles of six pairs of polyinosinic-polycytidylic acid-treated pig peripheral blood mononuclear cell (PBMC) samples and corresponding controls using methylated DNA immunoprecipitation sequencing and RNA sequencing. Comparative methylome analyses identified 5,827 differentially methylated regions and 615 genes showing differential expression between the two groups. Integrative analyses revealed inverse associations between DNA methylation around transcriptional start site and gene expression levels. Furthermore, 70 differentially methylated and expressed genes were identified such as TNFRSF9, IDO1 and EBI3. Functional annotation revealed the enriched categories including positive regulation of immune system process and regulation of leukocyte activation. These findings demonstrated DNA methylation changes occurring in immune responses of PBMCs to poly I:C stimulation and a subset of genes potentially regulated by DNA methylation in the immune responses. The PBMC DNA methylome provides an epigenetic overview of this physiological system in response to viral infection, and we expect it to constitute a valuable resource for future epigenetic epidemiology studies in pigs.

Angiopoietin-like protein 4 (Angptl4) is a secretory protein associated with lipid and energy metabolism. In this study, the expression profile of the bovine Angptl4 gene was detected in different Nanyang cattle tissues by quantitative real-time PCR which was found highly expressed in back fat and abdominal adipose. Meanwhile, three SNPs (snp1145, snp1422 and snp5095) were found by DNA sequencing. Pairs linkage disequilibrium analysis and haplotype construction of the Angptl4 gene were conducted in 424 Chinese native cattle. Four different haplotypes (CA, CT, TA and TT) were derived from snp1422 and snp5095. The association analysis between genetic variants identified and partial growth traits showed that the individual with CCTT combined genotype of snp1422 and snp5095 had significantly higher height at withers, body length, hip width and height at hip cross than those with TTTT. The association analysis of snp1422 demonstrated that the individuals of CC genotype were higher in terms of height at withers, body length, heart girth, hip width, height at hip cross and body weight than those with TT. The effect of the combined genotype on conformation traits was consistent with the snp1422. These results suggest that Angptl4 gene might be an important gene of lipid metabolism and may provide basic, useful molecular information for further studies on growth traits in Chinese indigenous yellow cattle.

Small RNA duodenal libraries were constructed for Escherichia coli F18-sensitive and -resistant weaned piglets in full-sib pair groups and sequenced using Illumina Solexa high-throughput sequencing technology. The identification of differentially expressed miRNAs provides the basis for improved database information on pig miRNAs, understanding the genetic basics of differences in resistance to E. coli F18 between local Chinese and exotic pig breeds, and finding new resistance markers for E. coli F18 infection. The duodenum of all individuals contained more than 90% of known swine miRNAs. A total of 58 differentially expressing miRNAs were identified, of which 46 were increased and 12 were decreased in E. coli F18-sensitive pigs. Of miRNAs with increased expression, ssc-miR-143 was most highly expressed, followed by ssc-let-7f, ssc-miR-192, and ssc-miR-21. We identified a total of 2036 intersection target genes by comparing TargetScan data and previous gene expression profile results. Gene ontology and pathway analysis of intersection genes showed that differentially expressed miRNAs were mainly involved in the immune response and transcriptional regulation. Combining information on differential miRNA expression and their regulatory relationships with transcription factors, identified 12 candidate miRNA disease markers, including 11 miRNAs with increased expression, ssc-miR-143, ssc-let-7f, ssc-miR-30e, ssc-miR-148a, ssc-miR-148b, ssc-miR-181a, ssc-miR-192, ssc-miR-27b, ssc-miR-15b, ssc-miR-21, and ssc-miR-215, and one with decreased expression, ssc-miR-152. Quantitative real-time PCR analysis of candidate miRNA expression in a larger cohort of E coli F18-sensitive and -resistant animals confirmed the high-throughput sequencing results.