Transcriptome profiling of different developmental stages of corpus luteum during the estrous cycle in pigs

Transcriptome analysis of corpora lutea in domestic cats (Felis catus) reveals strong differences in gene expression of various hormones, hormone receptors and regulators across different developmental stages

In the domestic cat (Felis catus), the corpus luteum (CL) is the main source of progestogen during pregnancy. Here, we studied gene expression changes in different life cycle stages of the CL of pseudopregnant cats to identify potential regulatory factors. Results revealed no support for different regression substages, which were previously defined on the basis of morphological examination analysis and intraluteal hormone content, as only a very low number of differentially expressed genes and no subclusters in PCA plot were detected. By comparing the regression stage with the developmental/maintenance stage, we detected a total of 6174 differentially expressed genes in the sample set, of which 2882 were upregulated and 3292 were downregulated. The large changes in the expression levels of some genes indicate that the endocrine function of the CL may not be restricted to progesterone (P4) secretion. The findings suggest that domestic cat CLs could also be a source of adipokines such as adiponectin or APELA. The expression of these genes is highly variable and reversed between stages. The life cycle and activity of CLs seem to be regulated by different factors, as genes encoding for the hormone receptors LHCGR and PAQR5 were more highly expressed in the development/maintenance stage, in contrast to this encoding for LEPR, which is higher expressed in regression stage. For regression stage, we identified different potential ways to modulate the cholesterol level and/or P4 concentration. Furthermore, we found differences from previous studies in other species for many genes that were studied in more detail, as well as when analysing functions and pathways. Our findings support the hypothesis that different stages of the CL life cycle in domestic cats can be characterized by changes in gene regulation and that CL life cycles are partly differentially regulated between species.

Complete mitochondrial genome sequence analysis revealed double matrilineal components in Indian Ghoongroo pigs

This research aimed to characterize the mitochondrial genome of the Ghoongroo (GH) pig, a notable breed in India, along with its crossbred varieties, to elucidate their matrilineal components, evolutionary history, and implications for conservation. Seven pigs (5 GH, 2 crossbred, namely Rani and Asha) were sequenced for complete mitochondrial genome, while 24 pigs (11 GH, 6 Rani, and 7 Asha) were sequenced for the complete D-loop of the mitochondrial genome. The genome size of these pigs was determined to be 16,690 bp. Analysis of the mitochondrial sequences and phylogenetics uncovered two distinct matrilineal components within the GH population, a phenomenon also observed in its crossbred counterparts, Rani and Asha. Phylogenetic analysis demonstrated a clear clustering of GH sequences into two clades, indicating the presence of two independent maternal lineages. The phylogenetic study using complete mitogenome also indicated that GH pigs were originated locally from Indian wild boar independently from Asian and European pig population. Haplotype analysis from complete D-loop sequences revealed 10 different haplotypes, with some sequences shared among GH, Rani, and Asha, while others differed due to varying matrilineal origins. The haplotype analysis using complete mitogenome sequences revealed 16 different haplotypes with some shared sequences among GH. Furthermore, examination of tRNA genes and nucleotide composition of different genes namely rRNAs, COX1, COX2, ATP6, ND4, ND5, ND6, Cytb offered insights into genetic diversity within these pigs. The findings suggest that geographical isolation and historical events likely contributed to the emergence of distinct maternal lineages within the GH breed. This study underscores the significance of mitochondrial DNA analysis in uncovering hidden genetic diversity within seemingly uniform populations. The molecular insights gained into the genetic makeup of GH pigs could aid in designing effective breeding programs for conservation efforts and highlight its significance in understanding the broader context of pig domestication in India.

Transcriptional dynamics of porcine granulosa cells during cellular acclimation to thermal challenge

Investigations on heat stress induced transcriptomic changes is critical to characterization of candidate genes for thermal adaptability in livestock. Continues spells of high ambient temperature due to climate change has amplified reproductive dysfunctions, necessitating immediate attention. The present study aimed to explore the transcriptomic signature of heat stressed granulosa cells (GCs) and signalling pathways regulating their adaptability to thermal challenge. The GCs were collected from small follicles (3-6 mm) of pig ovary. The GCs primary culture was subjected to in vitro heat stress challenge at 42 OC for 6 h. RNA sequencing was conducted for heat stress (treated) and non-heat stress (control) groups using Illumina NextSeq2000 sequencing platform. The significant DEGs were selected using NOISeq R package with cut-offs, probability value ≥ 0.95 and log2 fold change ≥1. Bioinformatics analysis was conducted for exploring gene ontology enrichment, functional pathways, hub genes in protein-protein interaction network and functional clusters regulating cellular homeostasis and survivability during heat stress challenge. The analysis pipeline yielded a total of 12156 protein coding transcripts, which were expressed during heat stress challenge in GCs, out of which 4904 were differentially (prob. ≥ 0.95) expressed; 2936 were upregulated and 1968 were downregulated. The large number of DEGs and gene ontologies in the study specifies the concerted mechanisms involving multiple signalling pathways like MAPK, HIPPO, WNT, PI3-AKT, NFKB, NOTCH and many more operating in the cell to maintain cellular homeostasis. Thermal stress induced differentially expressed hub genes HSP90, HSPA8, HSPA5, TGFB1 and PPARG are key elements in stress, regulating multiple pathways and expression of transcription factors. The TNF signalling pathway, phosphatidyl inositol signalling system and DERL3 gene network linked ubiquitin-dependent endoplasmic reticulum associated protein degradation pathway, which regulates cell viability, proliferation, apoptosis and estrogen synthesis, can be regarded as novel regulators involved in stress adaptation in pigs.

A tale of two endothelins: the rise and fall of the corpus luteum

Endothelins are small 21 amino acid peptides that interact with G-protein-coupled receptors. They are highly conserved across species and play important roles in vascular biology as well as in disease development and progression. Endothelins, mainly endothelin-1 and endothelin-2, are intricately involved in ovarian function and metabolism. These two peptides differ only in two amino acids but are encoded by different genes, which suggests an independent regulation and a cell-specific mode of expression. This review aims to comprehensively discuss the distinct regulation and roles of endothelin-1 and endothelin-2 regarding corpus luteum function throughout its life span.

Elucidation of novel SNPs affecting immune response to classical swine fever vaccination in pigs using immunogenomics approach

The host genetic makeup plays a significant role in causing the within-breed variation among individuals after vaccination. The present study was undertaken to elucidate the genetic basis of differential immune response between high and low responder Landlly (Landrace X Ghurrah) piglets vis-à-vis CSF vaccination. For the purpose, E2 antibody response against CSF vaccination was estimated in sampled animals on the day of vaccination and 21-day post-vaccination as a measure of humoral immune response. Double-digestion restriction associated DNA (ddRAD) sequencing was undertaken on 96 randomly chosen Landlly piglets using Illumina HiSeq platform. SNP markers were called using standard methodology. Genome-wide association study (GWAS) was undertaken in PLINK program to identify the informative SNP markers significantly associated with differential immune response. The results revealed significant SNPs associated with E2 antibody response against CSF vaccination. The genome-wide informative SNPs for the humoral immune response against CSF vaccination were located on SSC10, SSC17, SSC9, SSC2, SSC3 and SSC6. The overlapping and flanking genes (500Kb upstream and downstream) of significant SNPs were CYB5R1, PCMTD2, WT1, IL9R, CD101, TMEM64, TLR6, PIGG, ADIPOR1, PRSS37, EIF3M, and DNAJC24. Functional enrichment and annotation analysis were undertaken for these genes in order to gain maximum insights into the association of these genes with immune system functionality in pigs. The genetic makeup was associated with differential immune response against CSF vaccination in Landlly piglets while the identified informative SNPs may be used as suitable markers for determining variation in host immune response against CSF vaccination in pigs.

CRISPR/Cas genome editing revealed non-angiogenic role of VEGFA gene in porcine luteal cells: a preliminary report

BACKGROUND

The angiogenic cytokine vascular endothelial growth factor A (VEGFA) also exerts non-angiogenic effects on endocrine functionality of porcine luteal cells critical for progesterone (P4) production.

METHOD AND RESULTS

The expression dynamics of VEGFA-FLT/KDR system were investigated using RT-qPCR during luteal stages and VEGFA gene knock out (KO) porcine luteal cells were generated using CRISPR/Cas9 technology. The downstream effects of VEGFA ablation were studied using RT-qPCR, Annexin V, MTT, ELISA for P4 estimation and scratch wound assay. Bioinformatics analysis of RNA-Seq data of porcine mid-luteal stage was conducted for exploring protein-protein interaction network, KEGG pathways, transcription factors and kinase mapping for VEGFA-FLT/KDR interactomes. The VEGFA-FLT/KDR system expressed throughout the luteal stages with highest expression during mid- luteal stage. Cellular morphology, structure and oil-red-o staining for lipid droplets did not differ significantly between VEGFA KO and wild type cells, however, VEGFA KO significantly decreased (p < 0.05) viability and proliferation efficiency of edited cells on subsequent passages. Expression of apoptotic gene, CASP3 and hypoxia related gene, HIF1A were significantly (p < 0.05) upregulated in KO cells. The relative mRNA expression of VEGFA and steroidogenic genes STAR, CYP11A1 and HSD3B1 decreased significantly (p < 0.05) upon KO, which was further validated by the significant (p < 0.05) decrease in P4 output from KO cells. Bioinformatics analysis mapped VEGFA-FLT/KDR system to signalling pathways associated with steroidogenic cell functionality and survival, which complemented the findings of the study.

CONCLUSION

The ablation of VEGFA gene resulted in decreased steroidogenic capability of luteal cells, which suggests that VEGFA exerts additional non-angiogenic regulatory effects in luteal cell functionality.

Androgen receptor gene deficiency results in the reduction of steroidogenic potential in porcine luteal cells

Luteal steroidogenesis is critical to implantation and pregnancy maintenance in mammals. The role of androgen receptors (AR) in the progesterone (P4) producing luteal cells of porcine corpus luteum (CL) remains unexplored. The aim of the present study was to establish AR gene knock out (KO) porcine luteal cell culture system model by CRISPR/Cas9 genome editing technology and to study the downstream effects of AR gene deficiency on steroidogenic potential and viability of luteal cells. For this purpose, genomic cleavage detection assay, microscopy, RT-qPCR, ELISA, annexin, MTT, and viability assay complemented by bioinformatics analysis were employed. There was significant downregulation (p < 0.05) in the relative mRNA expression of steroidogenic marker genes STAR, CYP11A1, HSD3B1 in AR KO luteal cells as compared to the control group, which was further validated by the significant (p < 0.05) decrease in the P4 production. Significant decrease (p < 0.05) in relative viability on third passage were also observed. The relative mRNA expression of hypoxia related gene HIF1A was significantly (p < 0.05) downregulated in AR KO luteal cells. Protein-protein interaction analysis mapped AR to signaling pathways associated with luteal cell functionality. These findings suggests that AR gene functionality is critical to luteal cell steroidogenesis in porcine.

Comparative muscle transcriptome of Mali and Hampshire breeds of pigs: a preliminary study

Muscle development is an important priority of pig breeding programs. There is a considerable variation in muscularity between the breeds, but the regulation mechanisms of genes underlying myogenesis are still unclear. Transcriptome data from two breeds of pigs with divergent muscularity (Mali and Hampshire) were integrated with histology, immunofluorescence and meat yield to identify differences in myogenesis during the early growth phase. The muscle transcriptomics analysis revealed 17,721 common, 1413 and 1115 unique transcripts to Hampshire and Mali, respectively. This study identified 908 differentially expressed genes (p < 0.05; log2FC > ±1) in the muscle samples, of which 550 were upregulated and 358 were downregulated in Hampshire pigs, indicating differences in physiological process related to muscle function and development. Expression of genes related to myoblast fusion (MYMK), skeletal muscle satellite cell proliferation (ANGPT1, CDON) and growth factors (HGF, IGF1, IGF2) were higher in Hampshire than Mali, even though transcript levels of several other myogenesis-related genes (MYF6, MYOG, MSTN) were similar. The number of fibers per fascicle and the expression of myogenic marker proteins (MYOD1, MYOG and PAX7) were more in Hampshire as compared to Mali breed of pig, supporting results of transcriptome studies. The results suggest that differences in muscularity between breeds could be related to the regulation of myoblast fusion and myogenic activities. The present study will help to identify genes that could be explored for their utility in the selection of animals with different muscularities.

Ovarian follicle transcriptome dynamics reveals enrichment of immune system process during transition from small to large follicles in cyclic Indian Ghoongroo pigs

Ovarian follicular development is a critical determinant of reproductive performance in litter bearing species like pigs, wherein economic gains depend on litter size. The study aimed to gain insight into the differentially expressed genes (DEGs) and signalling pathways regulating follicular growth and maturation in Ghoongroo pigs. Transcriptome profiling of porcine small follicles (SF) and large follicles (LF) was conducted using NovaSeq600 sequencing platform and DEGs were identified using DESeq2 with threshold of Padj. < 0.05 and log2 fold change cut off 0.58 (LF vs. SF). Functional annotations and bioinformatics analysis of DEGs were performed to find out biological functions, signalling pathways and hub genes regulating follicular dynamics. Transcriptome analysis revealed 709 and 479 genes unique to SF and LF stages, respectively, and 11,993 co-expressed genes in both the groups. In total, 507 DEGs (284 upregulated and 223 downregulated) were identified, which encoded for diverse proteins including transcription factors (TFs). These DEGs were functionally linked to response to stimulus, lipid metabolic process, developmental process, extracellular matrix organisation along with the immune system process, indicating wide-ranging mechanisms associated with follicular transition. The enriched KEGG pathways in LF stage consisted of ovarian steroidogenesis, cholesterol and retinol metabolism, cell adhesion molecules, cytokine receptor interaction and immune signalling pathways, depicting intra-follicular control of varied ovarian function. The hub gene analysis revealed APOE, SCARB1, MMP9, CYP17A1, TYROBP as key regulators of follicular development. This study identified candidate genes and TFs providing steroidogenic advantage to LFs which makes them fit for selection into the ovulatory pool of follicles.

Dynamic transcriptome analysis of Maiwa yak corpus luteum during the estrous cycle

Maiwa yak is a special breed of animal living on the Qinghai-Tibet Plateau, which has great economic value, but its fertility rate is low. The corpus luteum (CL) is a temporary tissue that plays a crucial role in maintaining the physiological cycle. However, little is known about the transcriptome profile in Maiwa yak CL. In the present study, the transcriptome of Maiwa yak CL at early (EYCL), middle (MYCL) and late-stages (LYCL) was studied employing high-throughput sequencing. A total of 25,922 transcripts were identified, including 22,277 known as well as 3,645 novel ones. Furthermore, 690 and 212 differentially expressed (DE) mRNAs were detected in the EYCL vs. MYCL and MYCL vs. LYCL groups, respectively. KEGG pathway enrichment analysis of DEGs illustrated that the most enriched pathway was PI3K-Akt pathway. Furthermore, twenty-six DEGs were totally found to be associated with different biological processes of CL development. One of these genes, PGRMC1, displayed a dynamical expression trend during the lifespan of yak CL. The knockdown of PGRMC1 in luteinized yak granulosa cells resulted in defective steroidogenesis. In conclusion, this study analyzed the transcriptome profiles in yak CL of different stages, and provided a novel database for analyzing the gene network in yak CL.HIGHLIGHTSThe manuscript analyzed the transcriptome profiles in yak CL during the estrous cycle.Twenty-six DEGs were found to be associated with the development or function of CL.One of the DEGs, PGRMC1, was found to be responsible for steroidogenesis in luteinized yak granulosa cells.

Time Series Ovarian Transcriptome Analyses of the Porcine Estrous Cycle Reveals Gene Expression Changes during Steroid Metabolism and Corpus Luteum Development

Simple Summary

The estrous cycle, which is divided into follicular and luteal phases based on ovulation, is influenced by reproductive hormones which affect reproduction and cause changes in the reproductive system of the pig. As the main reproductive organ, the ovary is involved in ovulation and changes in the corpus luteum. We aimed to identify dynamic changes in gene expression through differentially expressed gene profiling and to provide a comprehensive understanding of the molecular mechanisms that occur in the pig ovary during the estrous cycle. The transcriptome analysis revealed that the dynamic change in gene expression was more activated in the luteal phase than in the follicular phase. Functional analysis revealed that the metestrus and diestrus periods are important in preparation for pregnancy or the next estrous cycle after ovulation.

Abstract

The porcine estrous cycle is influenced by reproductive hormones, which affect porcine reproduction and result in physiological changes in the reproductive organs. The ovary is involved in ovulation, luteinization, corpus luteum development, and luteolysis. Here, we aimed to provide a comprehensive understanding of the gene expression patterns in porcine ovarian transcriptomes during the estrous cycle through differentially expressed genes profiling and description of molecular mechanisms. The transcriptomes of porcine ovary were obtained during the estrous cycle at three-day intervals from day 0 to day 18 using RNA-seq. At seven time points of the estrous cycle, 4414 DEG were identified; these were classified into three clusters according to their expression patterns. During the late metestrus and diestrus periods, the expression in cluster 1 increased rapidly, and steroid biosynthesis was significant in the pathway. Cluster 2 gene expression patterns represented the cytokine–cytokine receptor interaction in significant pathways. In cluster 3, the hedgehog signaling pathway was selected as the significant pathway. Our study exhibited dynamic gene expression changes with these three different patterns of cluster 1, 2, and 3. The results helped identify the functions and related significant genes especially during the late metestrus and diestrus periods in the estrous cycle.