Gene expression profiles of novel caprine placental prolactin-related proteins similar to bovine placental prolactin-related proteins

RNA-seq and nuclear proteomics provide insights into the lactation regulation mechanism of goat transfected IGF-I and GH recombinant vectors

There exists little available information on the mechanisms of lactation regulation until now. In order to explore the underlying mechanism, we injected IGF-I and GH recombinant vectors into the mammary gland, then RNA-seq analysis and nuclear proteomics were used for rapid high-throughput screening of DEGs and DEPs in the two groups linked to lactation regulation. KEGG analysis of 206 DEGs showed that the same 4 of top 10 enrichment pathways (ECM receptor interaction, protein digestion and absorption, focal adhesion and phagosome) involved in 4 co-expressed genes (IDO, BTG1, ITGB6 and keratin 83), the two groups enriched different metabolic pathways yet. Nuclear proteomics analysis showed 75 and 36 DEPs in the IGF-I and GH group respectively; Sixteen common proteins were identified between the IGF-I group and GH group, four of which (ALB, TPT1, CXXC-5 and ACTR2) significantly decreased and three of which (PRP1, PAG-9 and Hsp70) significantly increased. Similarly, DEPs in the two groups were enriched in same one of top 10 enrichment pathways (PI3K-Akt signaling pathway). Protein-protein interaction networks highlighted the contribution of glycosphingolipid biosynthesis, porphyrin and chlorophyll metabolism and the Jak-STAT signaling pathway to lactation regulation of GH and IGFI. GH and IGF-I improve milk yield, which may be linked to important nodal proteins (ALB and ACTB). Our research advances the understanding of the mammary gland transcriptome and nuclear proteomics during GH and IGF-I overexpression. Individual genes, proteins and pathways in this study point towards potential targets for lactation regulation.

Evolution of placentation in cattle and antelopes

Bovids have enjoyed great evolutionary success as evidenced by the large number of extant species. Several important domestic animals are from this family. They derive from both subfamilies: cattle and their kin belong to Bovinae and sheep and goats to Antilopinae. The premise of this review, therefore, is that evolution of reproduction and placentation is best understood in a context that includes antelope-like bovines and antelopes. Many key features of placentation, including hormone secretion, had evolved before bovids emerged as a distinct group. Variation nevertheless occurs. Most striking is the difference in fusion of the binucleate trophoblast cell with uterine epithelium that yields a transient trinucleate cell in bovines and many antelopes, but a more persistent syncytium in wildebeest, sheep and goat. There is considerable variation in placentome number and villus branching within the placentome. Many antelopes have right-sided implantation in a bicornuate uterus whilst others have a uterus duplex. Finally, there has been continued evolution of placental hormones with tandem duplication of PAG genes in cattle, differences in glycosylation of placental lactogen and the emergence of placental growth hormone in sheep and goats. The selection pressures driving this evolution are unknown though maternal-fetal competition for nutrients is an attractive hypothesis.

Evolution of the growth hormone, prolactin, prolactin 2 and somatolactin family

Growth hormone (GH), prolactin (PRL), prolactin 2 (PRL2) and somatolactin (SL) belong to the same hormone family and have a wide repertoire of effects including development, osmoregulation, metabolism and stimulation of growth. Both the hormone and the receptor family have been proposed to have expanded by gene duplications in early vertebrate evolution. A key question is how hormone-receptor preferences have arisen among the duplicates. The first step to address this is to determine the time window for these duplications. Specifically, we aimed to see if duplications resulted from the two basal vertebrate tetraploidizations (1R and 2R). GH family genes from a broad range of vertebrate genomes were investigated using a combination of sequence-based phylogenetic analyses and comparisons of synteny. We conclude that the PRL and PRL2 genes arose from a common ancestor in 1R/2R, as shown by neighboring gene families. No other gene duplicates were preserved from these tetraploidization events. The ancestral genes that would give rise to GH and PRL/PRL2 arose from an earlier duplication; most likely a local gene duplication as they are syntenic in several species. Likewise, some evidence suggests that SL arose from a local duplication of an ancestral GH/SL gene in the same time window, explaining the lack of similarity in chromosomal neighbors to GH, PRL or PRL2. Thus, the basic triplet of ancestral GH, PRL/PRL2 and SL genes appear to be unexpectedly ancient. Following 1R/2R, only SL was duplicated in the teleost-specific tetraploidization 3R, resulting in SLa and SLb. These time windows contrast with our recent report that the corresponding receptor genes GHR and PRLR arose through a local duplication in jawed vertebrates and that both receptor genes duplicated further in 3R, which reveals a surprising asynchrony in hormone and receptor gene duplications.

Placentation in different mammalian species

The placenta is a complex, transient organ associated with viviparity, which is located at the interface of the dam and fetus during pregnancy. It is formed after attachment, or implantation, of the blastocyst on the uterine lining and derives from complex cellular and molecular interactions between uterine and embryonic tissues. In mammals, there are many forms of placentation but this organ has the same function in all species: it is responsible for orchestrating materno-fetal exchanges, together with endocrine and immunological functions.

Expression of basigin in the early phase of acute myocardial ischemia in rats

Basigin may be involved in cardiovascular disease. In our previous study, suppression subtractive hybridization results indicated that basigin may be associated with the early phase of acute myocardial ischemia (AMI) within 1 h. However, little is known regarding the expression of basigin in the early phase of AMI. The aim of the present study was to evaluate the temporal and spatial expression patterns of basigin mRNA and protein levels in AMI in rats. We constructed an AMI model in rats that received left anterior descending coronary artery ligation for 0, 15, 30, 60, 120 or 240 min. Real‑time quantitative PCR and in situ hybridization (ISH) were conducted to reveal the basigin mRNA levels in the early ischemic myocardium (EIM) and non‑ischemic myocardium (NIM). The expression levels of basigin protein were detected using western blot analysis and immunohistochemistry. The expression levels of basigin mRNA and protein significantly changed in the EIM as early as 30 min from ischemia, and the changes continued to be present throughout the ischemic period (P<0.05). The expression levels of basigin mRNA were significantly reduced, whilst those of the protein underwent a significant ~2-fold increase in the EIM. However, there were no significant differences in the basigin mRNA or protein expression levels from 0‑240 min in the NIM (P>0.05). We failed to detect a signal for basigin mRNA in the myocardium by ISH. Our findings indicated that basigin may be involved in acute myocardial ischemia following continual ischemia for >30 min.

Expression of endogenous retrovirus-like transcripts in bovine trophoblastic cells

Endogenous retrovirus envelope elements are considered to participate in trophoblastic cell fusion and multinucleate cell formation in humans, mice, and sheep. However, there is limited information about their roles in the ruminant placenta.

OBJECTIVES

We explore and identify the endogenous retrovirus envelope element genes expressed in bovine trophoblasts.

METHODS

The NCBI UniGene database (Build #97 Bos taurus) was screened by in silico analysis. After cloning endogenous retrovirus envelope element-like transcript (ERVE), expression profiles were analyzed with quantitative RT-PCR and in situ hybrizaidation.

RESULTS

Two UniGene clusters, UniGene ID: Bt.68042 and Bt.85243, were detected, and ERVE-A gene was cloned. Weak expression of this gene was first detected on Day 20 of gestation, and the intensity of its expression increased up to Day 70 of gestation. The intensity of its expression was maintained throughout gestation in the placenta, and its specific expression in trophoblastic binucleate cells was confirmed by in situ hybridization.

CONCLUSIONS

bERVE-A has a similar sequence to human syncytin-1, although it lacks an intact envelope sequence, and is specifically expressed in binucleate cells. This is the first evidence that endogenous retrovirus envelope element genes are expressed in bovine binucleate cells.

Prolactin family of the guinea pig, Cavia porcellus

Prolactin (PRL) is a multifunctional hormone with prominent roles in regulating growth and reproduction. The guinea pig (Cavia porcellus) has been extensively used in endocrine and reproduction research. Thus far, the PRL cDNA and protein have not been isolated from the guinea pig. In the present study, we used information derived from the public guinea pig genome database as a tool for identifying guinea pig PRL and PRL-related proteins. Guinea pig PRL exhibits prominent nucleotide and amino acid sequence differences when compared with PRLs of other eutherian mammals. In contrast, guinea pig GH is highly conserved. Expression of PRL and GH in the guinea pig is prominent in the anterior pituitary, similar to known expression patterns of PRL and GH for other species. Two additional guinea pig cDNAs were identified and termed PRL-related proteins (PRLRP1, PRLRP2). They exhibited a more distant relationship to PRL and their expression was restricted to the placenta. Recombinant guinea pig PRL protein was generated and shown to be biologically active in the PRL-responsive Nb2 lymphoma cell bioassay. In contrast, recombinant guinea pig PRLRP1 protein did not exhibit PRL-like bioactivity. In summary, we have developed a new set of research tools for investigating the biology of the PRL family in an important animal model, the guinea pig.

Cleaved bovine prolactin-related protein-I stimulates vascular endothelial cell proliferation

Prolactin-related protein-I (PRP1) is a member of a non-classical prolactin (PRL)/growth hormone family in cattle. However, its function is still unknown. PRL, when cleaved by cathepsin D and matrix metalloproteinases (MMPs), resulted in cleaved N-terminal 16kDa fragments (16K-PRL) that have antiangiogenetic properties in human and rodents. We examined the possibility of similar activity of bovine PRP1. PRP1 (normally 33kDa) was cleaved by cathepsins (CTSs), MMPs, and bovine cotyledonary-conditioned medium (BCCM), and generated mainly 26kDa N-terminal fragments. Two specific enzyme families, CTSs and MMPs cleaved intact PRP1, and BCCM also contained PRP1 cleavage activity. Bioactivity for pro- or anti-angiogenesis of the cleaved PRP1 was examined in a cell proliferation assay using bovine brain vascular endothelial cells. The cleaved PRP1 proliferated the endothelial cells in vitro. The endothelial cell proliferation activity of cleaved PRP1 may be shared in specific bovine placentomal angiogenesis.

Expression of extracellular matrix metalloproteinase inducer (EMMPRIN) and its related extracellular matrix degrading enzymes in the endometrium during estrous cycle and early gestation in cattle

BACKGROUND

Extracellular matrix metalloproteinase inducer (EMMPRIN) regulates several biological functions involving the modulation of cell behaviors via cell-cell and cell-matrix interactions. According to its diverse functions, we hypothesized that EMMPRIN may play an important role in endometrial remodeling and establishment of pregnancy in cow.

METHODS

In this study, endometrial tissues from the cyclic cows during before ovulation, after ovulation and middle of estrous cycle; and pregnant endometrial tissues from Day 19 to 35 of gestation have been used. Expression of mRNA was analyzed by RT-PCR, qPCR and in situ hybridization whereas protein expression by immunohistochemistry and western blot analysis.

RESULTS

EMMPRIN mRNA was expressed in both cyclic and pregnant endometrium and significantly higher in the endometrium at Day 35 of gestation than the cyclic endometrium. In Western blot analysis, an approximately 65 kDa band was detected in the endometrium, and approximately 51 kDa in the cultured bovine epithelial cells and BT-1 cells, respectively. Both in situ hybridization and immunohistochemistry data showed that EMMPRIN was primarily expressed in luminal and glandular epithelium with strong staining on Day 19 conceptus. At Day 19 of gestation, expression of EMMPRIN mRNA on luminal epithelium was decreased than that observed at middle of estrous cycle, however, on Day 30 of gestation, slightly increased expression was found at the site of placentation. Expression of matrix metalloproteinase-2 (MMP-2) and MMP-14 mRNA were mainly detected in stroma and their expression also decreased at Day 19 of gestation however it was also expressed at the site of placentation at Day 30 of gestation as observed for EMMPRIN. Expression of MMP-1 or -9 mRNA was very low and was below the detection limit in the cyclic and pregnant endometrium.

CONCLUSION

EMMPRIN from the luminal epithelium may regulate the expression of stromal MMP-2 and -14 suggesting its crucial role in adhesion and fusion of embryo to luminal epithelium by directly itself through physiological tissues remodeling and developmental process, and/or stimulating MMPs to compensate endometrial functions.

Cloning and expression of SOLD1 in ovine and caprine placenta, and their expected roles during the development of placentomes

Background

The Ly-6 (Ly-6/uPAR) superfamily members share the Ly-6 domain defined by distinct disulfide bonding patterns between 8 or 10 cysteine residues. They comprise membrane- and secretory-type proteins. We recently reported the gene and protein characterization of the bovine secreted protein of Ly-6 domain 1 (SOLD1). Bovine SOLD1 is expressed in trophoblast mononucleate cells (TMCs) and is localized in the cotyledonary mesenchyme. Here, we compared the expression and functionality of SOLD1 among the ruminants. We examined mRNA expression by chorionic fibroblasts as a measure of one of the SOLD1 functions.

Results

Ovine and caprine SOLD1 mRNAs have 303 bp open reading frames and encode for deduced SOLD1 proteins with 100 amino acids, including a 22-aa-long signal peptide at the N-terminal. Both of the SOLD1 amino acid sequences have high similarities with the bovine sequence. Both SOLD1 mRNAs were also expressed in TMCs of cotyledons and intercotyledonary membranes. The mature SOLD1 proteins were localized in the mesenchymal villi of cotyledons after secretion. Bovine, ovine and caprine SOLD1 affected gene expression in mesenchymal fibroblasts in vitro; nucleoredoxin expression was upregulated and BCL2-like 13 was downregulated. Thus, we suggest that SOLD1 acts as a modulator of cell proliferation and apoptosis.

Conclusion

Expressing cells and protein localization of SOLD1 coincided among the three ruminants. SOLD1 participated in regulating nucleoredoxin and BCL2-like 13 expression in chorionic fibroblasts. SOLD1 is produced specifically in the cotyledons and intercotyledonary membranes in ruminants and appears to be involved in the construction of the ruminant placenta.

Evaluation of real-time PCR endogenous control genes for analysis of gene expression in bovine endometrium

Background

Quantitative real-time PCR gene expression results are generally normalised using endogenous control genes. These reference genes should be expressed at a constant level across all sample groups in a study, and should not be influenced by study treatments or conditions. There has been no systematic investigation of endogenous control genes for bovine endometrium to date. The suitability of both commonly used and novel endogenous control genes was evaluated in this study, with the latter being selected from stably expressed transcripts identified through microarray analysis of bovine endometrium. Fifteen candidate endogenous control genes were assessed across different tissue subtypes in pregnant and cycling Holstein-Friesian dairy cows from two divergent genetic backgrounds.

Results

The expression profiles of five commonly used endogenous control genes (GAPDH, PPIA, RPS9, RPS15A, and UXT) and 10 experimentally derived candidate endogenous control genes (SUZ12, C2ORF29, ZNF131, ACTR1A, HDAC1, SLC30A6, CNOT7, DNAJC17, BBS2, and RANBP10) were analysed across 44 samples to determine the most stably expressed gene. Gene stability was assessed using the statistical algorithms GeNorm and Normfinder. All genes presented with low overall variability (0.87 to 1.48% CV of Cq). However, when used to normalise a differentially expressed gene (oxytocin receptor - OXTR) in the samples, the reported relative gene expression levels were significantly affected by the control gene chosen. Based on the results of this analysis, SUZ12 is proposed as the most appropriate control gene for use in bovine endometrium during early pregnancy or the oestrus cycle.

Conclusion

This study establishes the suitability of novel endogenous control genes for comparing expression levels in endometrial tissues of pregnant and cycling bovines, and demonstrates the utility of microarray analysis as a method for identifying endogenous control gene candidates.

The characterization of DNA methylation-mediated regulation of bovine placental lactogen and bovine prolactin-related protein-1 genes

Background

Bovine trophoblast binucleate cells (BNC) express a plethora of molecules including bovine placental lactogen (bPL, gene name is bCSH1) and bovine prolactin-related protein-1 (bPRP1). BCSH1 and bPRP1 are members of the growth hormone (GH)/prolactin (PRL) gene family, which are expressed simultaneously in BNC and are central to placentation and the progression of pregnancy in cattle. However, there is a paucity of information on the transcriptional regulatory mechanisms of both the bCSH1 and bPRP1 genes. Recent studies, however, have demonstrated that the expression of a number of genes is controlled by the methylation status of their promoter region. In the present study, we examined the cell-type-specific epigenetic alterations of the 5'-flanking region of the bCSH1 and bPRP1 genes to gain an insight into their regulatory mechanisms.

Results

Analysis of 5-aza-2'-deoxycytidine treatment demonstrated that bCSH1 expression is moderately induced in fibroblast cultures but enhanced in BT-1 cells. Sodium bisulfite based sequencing revealed that bCSH1 is hypomethylated in the cotyledonary tissue but not in the fetal skin, and this pattern was not altered with the progression of pregnancy. On the other hand, the methylation status of bPRP1 was similar between the cotyledon and fetal skin. The bPRP1 gene was exclusively hypermethylated in a bovine trophoblast cell-derived BT-1 cell-line. While the activity of bCSH1 was similar in both BT-1 and bovine fibroblast cells, that of bPRP1 was specific to BT-1. Treatment with a demethylating agent and luciferase assays provided in vitro evidence of the positive regulation of bCSH1 but not bPRP1.

Conclusion

This is the first report to identify the differential regulatory mechanisms of the bCSH1 and bPRP1 genes and indicates that bCSH1 might potentially be the only transcript that is subject to DNA methyltransferase regulation. The data indicates the possibility of novel kinetics of induction of the synchronously expressed BNC-specific bCSH1 and bPRP1 transcripts, which may aid the understanding of the intricate regulation and specific role(s) of these important molecules in bovine placentogenesis and the progression of pregnancy.

Expression and characterization of novel ovine orthologs of bovine placental prolactin-related proteins

Background

The prolactin-related proteins (PRPs) are non-classical placental-specific members of the prolactin/growth hormone family. Among ruminants, they are expressed in the cotyledonary villi of cattle and goat. We investigated placental PRP in sheep in order to gain a comprehensive understanding of the function and evolution of these molecules. We also examined the sequence properties, expression and lactogenic activation of the cloned genes.

Results

We cloned two novel ovine PRPs, named oPRP1 and oPRP2. oPRP2 had a typical PRP sequence similar to bovine PRP1 (bPRP1). oPRP1 had a short sequence identical with bovine or caprine type PRP but the reading frame was shifted. Both oPRPs were expressed in trophoblast giant binucleate cells (BNC) as in cattle and goat. oPRP1 expression declined from the early to the middle stage of gestation. In contrast, oPRP2 expression remained constant throughout the gestation period. oPRP2 was translated to form a mature protein in a mammalian cell expression system. Western blotting showed a molecular mass of 35 kDa for the FLAG-tag fusion oPRP2 protein. This recombinant protein and bPRP1 were bioassayed using Nb2 lymphoma cells; it was confirmed that neither ruminant PRP had lactogenic activity because the Nb2 lymphoma cells did not proliferate.

Conclusion

We have identified two novel PRPs, oPRP1 and oPRP2, in ovine placenta. Both these ovine PRPs were localized and quantitatively expressed in BNC. Absence of lactogenic activity was confirmed for the oPRP2 molecule. It is anticipated that novel and known ruminant PRPs have common functions, except for lactogenic activity.