Deep sequencing of the porcine endometrial transcriptome on day 14 of pregnancy

Identification of Genes Related to Growth and Lipid Deposition from Transcriptome Profiles of Pig Muscle Tissue

Transcriptome profiles established using high-throughput sequencing can be effectively used for screening genome-wide differentially expressed genes (DEGs). RNA sequences (from RNA-seq) and microRNA sequences (from miRNA-seq) from the tissues of longissimus dorsi muscle of two indigenous Chinese pig breeds (Diannan Small-ear pig [DSP] and Tibetan pig [TP]) and two introduced pig breeds (Landrace [LL] and Yorkshire [YY]) were examined using HiSeq 2000 to identify and compare the differential expression of functional genes related to muscle growth and lipid deposition. We obtained 27.18 G clean data through the RNA-seq and detected that 18,208 genes were positively expressed and 14,633 of them were co-expressed in the muscle tissues of the four samples. In all, 315 DEGs were found between the Chinese pig group and the introduced pig group, 240 of which were enriched with functional annotations from the David database and significantly enriched in 27 Gene Ontology (GO) terms that were mainly associated with muscle fiber contraction, cadmium ion binding, response to organic substance and contractile fiber part. Based on functional annotation, we identified 85 DEGs related to growth traits that were mainly involved in muscle tissue development, muscle system process, regulation of cell development, and growth factor binding, and 27 DEGs related to lipid deposition that were mainly involved in lipid metabolic process and fatty acid biosynthetic process. With miRNA-seq, we obtained 23.78 M reads and 320 positively expressed miRNAs from muscle tissues, including 271 known pig miRNAs and 49 novel miRNAs. In those 271 known miRNAs, 20 were higher and 10 lower expressed in DSP-TP than in LL-YY. The target genes of the 30 miRNAs were mainly participated in MAPK, GnRH, insulin and Calcium signaling pathway and others involved cell development, growth and proliferation, etc. Combining the DEGs and the differentially expressed (DE) miRNAs, we drafted a network of 46 genes and 18 miRNAs for regulating muscle growth and a network of 15 genes and 16 miRNAs for regulating lipid deposition. We identified that CAV2, MYOZ2, FRZB, miR-29b, miR-122, miR-145-5p and miR-let-7c, etc, were key genes or miRNAs regulating muscle growth, and FASN, SCD, ADORA1, miR-4332, miR-182, miR-92b-3p, miR-let-7a and miR-let-7e, etc, were key genes or miRNAs regulating lipid deposition. The quantitative expressions of eight DEGs and seven DE miRNAs measured with real-time PCR certified that the results of differential expression genes or miRNAs were reliable. Thus, 18,208 genes and 320 miRNAs were positively expressed in porcine longissimus dorsi muscle. We obtained 85 genes and 18 miRNAs related to muscle growth and 27 genes and 16 miRNAs related to lipid deposition, which provided new insights into molecular mechanism of the economical traits in pig.

Endometrial gene expression profile of pregnant sows with extreme phenotypes for reproductive efficiency

Prolificacy can directly impact porcine profitability, but large genetic variation and low heritability have been found regarding litter size among porcine breeds. To identify key differences in gene expression associated to swine reproductive efficiency, we performed a transcriptome analysis of sows' endometrium from an Iberian x Meishan F2 population at day 30-32 of gestation, classified according to their estimated breeding value (EBV) as high (H, EBV > 0) and low (L, EBV < 0) prolificacy phenotypes. For each sample, mRNA and small RNA libraries were RNA-sequenced, identifying 141 genes and 10 miRNAs differentially expressed between H and L groups. We selected four miRNAs based on their role in reproduction, and five genes displaying the highest differences and a positive mapping into known reproductive QTLs for RT-qPCR validation on the whole extreme population. Significant differences were validated for genes: PTGS2 (p = 0.03; H/L ratio = 3.50), PTHLH (p = 0.03; H/L ratio = 3.69), MMP8 (p = 0.01; H/L ratio =4.41) and SCNN1G (p = 0.04; H/L ratio = 3.42). Although selected miRNAs showed similar expression levels between H and L groups, significant correlation was found between the expression level of ssc-miR-133a (p < 0.01) and ssc-miR-92a (p < 0.01) and validated genes. These results provide a better understanding of the genetic architecture of prolificacy-related traits and embryo implantation failure in pigs.

Maternal N-Carbamylglutamate Supplementation during Early Pregnancy Enhances Embryonic Survival and Development through Modulation of the Endometrial Proteome in Gilts

BACKGROUND

Early pregnancy loss is a major concern in humans and animals. N-carbamylglutamate (NCG) has been found to enhance embryonic survival during early pregnancy in rats. However, little is known about the key factors in the endometrium involved in the improvement of embryonic implantation and development induced by maternal NCG supplementation.

OBJECTIVES

Our objectives were to investigate whether NCG supplementation during early gestation enhanced embryonic survival and development in gilts and to uncover the related factors using the approach of endometrium proteome analysis with isobaric tags for relative and absolute quantification (iTRAQ).

METHODS

Uteruses and embryos/fetuses were obtained on days 14 and 28 of gestation from gilts fed a basal diet that was or was not supplemented with 0.05% NCG. The iTRAQ-based quantitative proteomics approach was performed to explore the endometrium proteome altered by NCG supplementation.

RESULTS

Maternal NCG supplementation significantly increased the number of total fetuses and live fetuses on day 28 of gestation by 1.32 and 1.29, respectively (P < 0.05), with a significant decrease in embryonic mortality (P < 0.05). iTRAQ results indicated that a total of 59 proteins showed at least 2-fold differences (P < 0.05), including 52 proteins that were present at higher abundance and 7 proteins present at lower abundance in NCG-supplemented gilts. The differentially expressed proteins primarily are involved in cell adhesion, energy metabolism, lipid metabolism, protein metabolism, antioxidative stress, and immune response. On day 14 of gestation, several proteins closely related to embryonic implantation and development, such as integrin-αv, integrin-β3, talin, and endothelial nitric oxide synthase, were upregulated (3.7-, 4.1-, 2.4-, and 5.4-fold increases, respectively) by NCG supplementation.

CONCLUSION

To our knowledge, our results provide the first evidence that altered abundance of the endometrial proteome induced by NCG supplementation is highly associated with the improvement of embryonic survival and development in gilts.

Transcriptome Analysis Revealed the Embryo-Induced Gene Expression Patterns in the Endometrium from Meishan and Yorkshire Pigs

The expression patterns in Meishan- and Yorkshire-derived endometrium during early (gestational day 15) and mid-gestation (gestational days 26 and 50) were investigated, respectively. Totally, 689 and 1649 annotated genes were identified to be differentially expressed in Meishan and Yorkshire endometrium during the three gestational stages, respectively. Hierarchical clustering analysis identified that, of the annotated differentially expressed genes (DEGs), 73 DEGs were unique to Meishan endometrium, 536 DEGs were unique to Yorkshire endometrium, and 228 DEGs were common in Meishan and Yorkshire endometriums. Subsequently, DEGs in each of the three types of expression patterns were grouped into four distinct categories according to the similarities in their temporal expression patterns. The expression patterns identified from the microarray analysis were validated by quantitative RT-PCR. The functional enrichment analysis revealed that the common DEGs were enriched in pathways of steroid metabolic process and regulation of retinoic acid receptor signaling. These unique DEGs in Meishan endometrium were involved in cell cycle and adherens junction. The DEGs unique to Yorkshire endometrium were associated with regulation of Rho protein signal transduction, maternal placenta development and cell proliferation. This study revealed the different gene expression patterns or pathways related to the endometrium remodeling in Meishan and Yorkshire pigs, respectively. These unique DEGs in either Meishan or Yorkshire endometriums may contribute to the divergence of the endometrium environment in the two pig breeds.

Characterization of the Transcriptional Complexity of the Receptive and Pre-receptive Endometria of Dairy Goats

Endometrium receptivity is essential for successful embryo implantation in mammals. However, the lack of genetic information remains an obstacle to understanding the mechanisms underlying the development of a receptive endometrium from the pre-receptive phase in dairy goats. In this study, more than 4 billion high-quality reads were generated and de novo assembled into 102,441 unigenes; these unigenes were annotated using published databases. A total of 3,255 unigenes that were differentially expressed (DEGs) between the PE and RE were discovered in this study (P-values < 0.05). In addition, 76,729–77,102 putative SNPs and 12,837 SSRs were discovered in this study. Bioinformatics analysis of the DEGs revealed a number of biological processes and pathways that are potentially involved in the establishment of the RE, notably including the GO terms proteolysis, apoptosis, and cell adhesion and the KEGG pathways Cell cycle and extracellular matrix (ECM)-receptor interaction. We speculated that ADCY8, VCAN, SPOCK1, THBS1, and THBS2 may play important roles in the development of endometrial receptivity. The de novo assembly provided a good starting point and will serve as a valuable resource for further investigations into endometrium receptivity in dairy goats and future studies on the genomes of goats and other related mammals.

Effect of ovarian hormones on the healthy equine uterus: a global gene expression analysis

The physiological changes associated with the varying hormonal environment throughout the oestrous cycle are linked to the different functions the uterus needs to fulfil. The aim of the present study was to generate global gene expression profiles for the equine uterus during oestrus and Day 5 of dioestrus. To achieve this, samples were collected from five horses during oestrus (follicle >35 mm in diameter) and dioestrus (5 days after ovulation) and analysed using high-throughput RNA sequencing techniques (RNA-Seq). Differentially expressed genes between the two cycle stages were further investigated using Gene Ontology and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses. The expression of 1577 genes was found to be significantly upregulated during oestrus, whereas 1864 genes were expressed at significantly higher levels in dioestrus. Most genes upregulated during oestrus were associated with the extracellular matrix, signal interaction and transduction, cell communication or immune function, whereas genes expressed at higher levels in early dioestrus were most commonly associated with metabolic or transport functions, correlating well with the physiological functions of the uterus. These results allow for a more complete understanding of the hormonal influence on gene expression in the equine uterus by functional analysis of up- and downregulated genes in oestrus and dioestrus, respectively. In addition, a valuable baseline is provided for further research, including analyses of changes associated with uterine inflammation.

Differential gene expression in ovaries of Qira black sheep and Hetian sheep using RNA-Seq technique

The Qira black sheep and the Hetian sheep are two local breeds in the Northwest of China, which are characterized by high-fecundity and low-fecundity breed respectively. The elucidation of mRNA expression profiles in the ovaries among different sheep breeds representing fecundity extremes will helpful for identification and utilization of major prolificacy genes in sheep. In the present study, we performed RNA-seq technology to compare the difference in ovarian mRNA expression profiles between Qira black sheep and Hetian sheep. From the Qira black sheep and the Hetian sheep libraries, we obtained a total of 11,747,582 and 11,879,968 sequencing reads, respectively. After aligning to the reference sequences, the two libraries included 16,763 and 16,814 genes respectively. A total of 1,252 genes were significantly differentially expressed at Hetian sheep compared with Qira black sheep. Eight differentially expressed genes were randomly selected for validation by real-time RT-PCR. This study provides a basic data for future research of the sheep reproduction.

Uterine responses to the preattachment embryo in domestic ungulates: recognition of pregnancy and preparation for implantation

The endometrium is a tissue newly evolved with the development of mammalian species. Its main function is the support of embryonic growth and development and the nutrition of the fetus. The species-specific differences in establishment and maintenance of pregnancy make the study of this tissue in various mammalian organisms particularly interesting. With the application of omics technologies to various mammalian species, many systematic studies of endometrial gene expression changes during the phase of establishment of pregnancy have been performed to obtain a global view of regulatory events associated with this biological process. This review summarizes the results of trancriptome studies of bovine, porcine, and equine endometrium. Furthermore, the results are compared between these species and to humans. Because an increasing number of studies suggest an important role of small regulatory RNAs (i.e., microRNAs), recent findings related to the regulation of endometrial functions and the development of the conceptus are presented.

Global gene expression profiling of porcine endometria on Days 12 and 16 of the estrous cycle and pregnancy

The objective of the study was to investigate transcriptomic profile of pig endometrium on Days 12 and 16 of pregnancy in comparison with the respective days of the estrous cycle. Labeled complementary DNA was hybridized to Porcine Long Oligo microarray containing 13,297 oligonucleotide probes, which represented complementary DNA and expressed sequence tags. Statistical analysis revealed 110 differentially expressed genes (DEGs) on Day 12 of pregnancy and 179 DEGs on Day 16 of pregnancy. In silico analysis of gene function and functionality networks revealed links between genes implicated in cell death and survival, protein synthesis, lipid metabolism, cellular movement, tissue development, and cell-to-cell signaling. On Day 12 of pregnancy, estrogen, transforming growth factor (TGF) β1, and fibroblast growth factor (FGF) 2, and on Day 16 of pregnancy, epidermal growth factor (EGF), insulin, interleukin 11 (IL-11), and FGF family members were indicated as possible upstream regulators of several DEGs. Obtained results showed changes in global endometrial gene expression at the time of maternal recognition of pregnancy and embryo implantation. Additionally, these data revealed signaling molecules, which together with E2, may evoke molecular changes in the uterus, leading to successful pregnancy establishment.

Comparative transcriptomic analysis to identify differentially expressed genes in fat tissue of adult Berkshire and Jeju Native Pig using RNA-seq

Pork is a major source of animal protein for humans. The subcutaneous, intermuscular and the intramuscular fat are the factors responsible for meat quality. RNA-seq is rapidly adopted for the profiling of the transcriptomes in the studies related to gene regulation. The discovery of differentially expressed genes (DEGs) between adult animals of Jeju Native Pig (JNP) and Berkshire breeds are of particular interest for the current study. RNA-seq was used to investigate the transcriptome profiling in the fat tissue. Sequence reads were obtained from Ilumina HiSeq2000 and mapped to the pig genome using Tophat2. Total 153 DEGs were identified and 71 among the annotated genes, have BLAST matches in the non- redundant database. Metabolic, immune response and protein binding are enriched pathways in the fat tissue. In our study, biological adhesion, cellular, developmental and multicellular organismal processes in fat were up-regulated in JNP as compare to Berkshire. Multicellular organismal process, developmental process, embryonic morphogenesis and skeletal system development were the most significantly enriched terms in fat of JNP and Berkshire breeds (p = 1.17E-04, 0.044, 3.47E-04 and 4.48E-04 respectively). COL10A1, COL11A2, PDK4 and PNPLA3 genes responsible for skeletal system morphogenesis and body growth were down regulated in JNP. This study is the first statistical analysis for the detection of DEGs from RNA-seq data generated from fat tissue sample. This analysis can be used as stepping stone to understand the difference in the genetic mechanisms that might influence the identification of novel transcripts, sequence polymorphisms, isoforms and noncoding RNAs.

Comprehensive analysis of the whole transcriptomes from two different pig breeds using RNA-Seq method

Next-generation sequencing RNA-Seq technology is a powerful tool that creates new possibilities for whole-transcriptome analysis. In our study, the RNA-Seq method was applied to analyze global changes in transcriptome from muscle tissue (m. semimembranosus) in two pig breeds (Pietrain and Polish Landrace, PL). The breeds differ in terms of muscularity, growth rate and reproduction traits. Using three different approaches (deseq, cufflinks and edger) and taking into account the most restrictive criteria, 35 genes differentially expressed between Pietrain and PL pigs were identified. In both breeds, the most abundant were transcripts encoding ribosomal and cytoskeletal proteins (TPM3, TCAP, TMOD4, TPM2, TNNC1) and calcium-binding proteins involved in muscle contraction, calcium-mediated signaling or cation transport (CASQ1, MLC2V, SLC25A4, MYL3). In PL pigs, we identified up-regulation of several genes that play crucial roles in reproduction: female gamete generation (BDP1, PTPN21, USP9X), fertilization (EGFR) and embryonic development (CPEB4). In the Pietrain breed, only seven genes were over-expressed (CISH, SPP1, TUBA8, ATP6V1C2, IGKC, predicted LOC100510960 and LOC100626400), and they play important roles in, for example, negative regulation of apoptosis, immune response, cell-cell signaling, cell growth and migration as well as the metabolic process. The functions of the majority of selected genes were consistent with phenotypic variation in investigated breeds; thus, we proposed a new panel of candidate genes that can be associated with economically important pig traits.

Comparative transcriptomic analysis by RNA-seq to discern differential expression of genes in liver and muscle tissues of adult Berkshire and Jeju Native Pig

RNA-seq is being rapidly adopted for the profiling of the transcriptomes in different areas of biology, especially in the studies related to gene regulation. The discovery of differentially expressed genes (DEGs) between adult animals of Jeju Native Pig (JNP) and Berkshire breeds of Sus scrofa, is of particular interest for the current study. For the better understanding of the gene expression profiles of the liver and longissimus dorsi muscle, DEGs were identified via RNA-seq. Sequence reads were obtained from Illumina HiSeq2000 and mapped to the pig reference genome (Sscrofa10.2) using Tophat2. We identified 169 and 39 DEGs in the liver and muscle of JNP respectively, by comparison with Berkshire breed. Out of all identified genes, 41 genes in the liver and 9 genes in the muscle have given significant expression. Gene ontology (GO) terms of developmental process and KEGG pathway analysis showed that metabolic, immune response and protein binding were commonly enriched pathways in the two tissues. Further the heat map analysis by ArrayStar has shown the different levels of expression in JNP with respect to the Berkshire breed. The validation through real time PCR and western blotting also confirmed the differential expression of genes in both breeds. Genes pertaining to metabolic process and inflammatory and immune system are more enriched in Berkshire breed. This comparative transcriptome analysis of two tissues suggests a subset of novel marker genes which expressed differently between the JNP and Berkshire.

Extensive expression differences along porcine small intestine evidenced by transcriptome sequencing

The aim of this study was to analyse gene expression along the small intestine (duodenum, jejunum, ileum) and in the ileal Peyer's patches in four young pigs with no clinical signs of disease by transcriptome sequencing. Multidimensional scaling evidenced that samples clustered by tissue type rather than by individual, thus prefiguring a relevant scenario to draw tissue-specific gene expression profiles. Accordingly, 1,349 genes were found differentially expressed between duodenum and jejunum, and up to 3,455 genes between duodenum and ileum. Additionally, a considerable number of differentially expressed genes were found by comparing duodenum (7,027 genes), jejunum (6,122 genes), and ileum (6,991 genes) with ileal Peyer's patches tissue. Functional analyses revealed that most of the significant differentially expressed genes along small intestinal tissues were involved in the regulation of general biological processes such as cell development, signalling, growth and proliferation, death and survival or cell function and maintenance. These results suggest that the intrinsic large turnover of intestinal tissues would have local specificities at duodenum, ileum and jejunum. In addition, in concordance with their biological function, enteric innate immune pathways were overrepresented in ileal Peyer's patches. The reported data provide an expression map of the cell pathway variation in the different small intestinal tissues. Furthermore, expression levels measured in healthy individuals could help to understand changes in gene expression that occur in dysbiosis or pathological states.

Identification of genes regulating growth and fatness traits in pig through hypothalamic transcriptome analysis

Previous studies on Iberian × Landrace (IBMAP) pig intercrosses have enabled the identification of several quantitative trait locus (QTL) regions related to growth and fatness traits; however, the genetic variation underlying those QTLs are still unknown. These traits are not only relevant because of their impact on economically important production traits, but also because pig constitutes a widely studied animal model for human obesity and obesity-related diseases. The hypothalamus is the main gland regulating growth, food intake, and fat accumulation. Therefore, the aim of this work was to identify genes and/or gene transcripts involved in the determination of growth and fatness in pig by a comparison of the whole hypothalamic transcriptome (RNA-Seq) in two groups of phenotypically divergent IBMAP pigs. Around 16,000 of the ∼25.010 annotated genes were expressed in these hypothalamic samples, with most of them showing intermediate expression levels. Functional analyses supported the key role of the hypothalamus in the regulation of growth, fat accumulation, and energy expenditure. Moreover, 58,927 potentially new isoforms were detected. More than 250 differentially expressed genes and novel transcript isoforms were identified between the two groups of pigs. Twenty-one DE genes/transcripts that colocalized in previously identified QTL regions and/or whose biological functions are related to the traits of interest were explored in more detail. Additionally, the transcription factors potentially regulating these genes and the subjacent networks and pathways were also analyzed. This study allows us to propose strong candidate genes for growth and fatness based on expression patterns, genomic location, and network interactions.

HOXA10 mRNA expression and promoter DNA methylation in female pig offspring after in utero estradiol-17β exposure

Early exposure to environmental estrogens may exert lasting impacts on health. In rodents, homeobox A10 (HOXA10) was demonstrated to be a target of early endocrine disruption, as indicated by persistent changes in uterine HOXA10 expression and promoter DNA methylation in the offspring. This study aimed at analyzing long-term effects of estradiol-17β on porcine uterine HOXA10. Therefore, offspring were exposed in utero to low (0.05 and 10μg/kg body weight/day) and high (1000μg/kg body weight/day) doses, respectively. We, furthermore, investigated whether promoter DNA methylation was generally involved in regulating HOXA10 expression. Unexpectedly, the maternal estrogen exposure did not distinctly impact HOXA10 expression and promoter DNA methylation in either pre- or postpubertal offspring. Although differential HOXA10 expression was observed in endometrial tissue during the estrous cycle and the pre-implantation period, no concurrent substantial changes occurred regarding promoter DNA methylation. However, by comparing several tissues displaying larger differences in transcriptional abundance, HOXA10 expression correlated with promoter DNA methylation in prepubertal, but not postpubertal, gilts. Thus, promoter DNA methylation could affect gene expression in pigs, depending on their stage of development. Clearly, early estrogen exposure exerted other effects in pigs as known from studies in rodents. This may be due to endocrine differences as well as to species-specific peculiarities of tissue sensitivity to estradiol-17β during critical windows of development.