Identification of interferon-tau isoforms expressed by the peri-implantation goat (Capra hircus) conceptus

Molecular characterization of IFN-T expressed in buffalo embryonic trophoblasts and expression of recombinant BuIFN-T1a2 and BuIFN-T8 isoforms in E. coli

Interferon tau (IFN-T) acts as a signaling molecule for maternal recognition of pregnancy (MRP) in ruminants. Aim of the present study was to identify various Buffalo Interferon tau (BuIFN-T) transcripts in buffalo trophoblast, phylogenetic comparison of these sequences with known mRNA sequences of buffalo, bovine, caprine and ovine and to express and purify the recombinant BuIFN-T (rBuIFN-T) isoforms. Following RNA extraction from trophectodermal cells, RT-PCR was performed using Ifn-t gene specific primers. 13 distinct cDNA variants encoding eight different BuIFN-T proteins were identified. BuIFN-T1a2 and BuIFN-T8 were expressed in prokaryotic expression system at 37 °C, 25 °C and 16 °C with 1 mM IPTG for 12 h and the recombinant proteins expressed at 16 °C were partially purified by Immobilised Metal Affinity Chromatography (IMAC). BuIFN-T isoforms have greater nucleotide and amino acid homology with caprine (98-100%, 96-100%), ovine (94-97%, 90-95%) and bovine (89.6-90.6%, 82-86%). These novel BuIFN-T isoforms contained pronounced nucleotide and amino acid sequence identity with one another (99.1-99.8%, 98-99%) but moderate sequence identity with previously identified buffalo IFN-T (90-92%, 82-86%). Solubility of expressed recombinant isoforms (rBuIFN-T1a2 and rBuIFN-T8) was highest at 16 °C. In conclusion, 13 distinct Ifn-t gene variants exist in trophectoderm of in vitro developed buffalo blastocysts that encode eight different proteins. rBuIFN-T1a2 and rBuIFN-T8 were successfully expressed in soluble form in Escherichia coli expression system at 16 °C with 1 mM IPTG and the resulting recombinant proteins were partially purified by IMAC.

Biological activity of recombinant bovine interferon τ produced by a silkworm-baculovirus gene expression system

Bovine interferon (bIFN) τ plays a crucial role in maternal-fetal recognition and was expressed using a Bombyx mori (Bm) nuclear polyhedrosis virus (silkworm baculovirus) gene expression system. The biological effects of Bm-recombinant bIFNτ (rbIFNτ) on prostaglandin (PG) F_2α synthesis were investigated in cultured bovine endometrial epithelial cells with oxytocin (OT, 100 nM) and on the in vitro development of bovine embryos. Bm-rbIFNτ and OT were shown to suppress PGF_2α production in a dose-dependent manner. When in vitro produced morula stage embryos were cultured for 72 hr in modified CR1aa medium supplemented with or without rbIFNτ, Bm-rbIFNτ (10 ng/ml) significantly promoted development to the expanded blastocyst stage. In conclusion, Bm-rbIFNτ was suggested to have the same bioactivity as native IFNτ.

Molecular characterization of novel variants of interferon-tau (IFNT) gene in Garole breed of sheep (Ovis aries)

The survivability of embryo, especially during the early embryonic life is dependent on the effective maternal recognition of pregnancy. Interferon-tau (IFNT), secreted from the elongating blastocyst, acts as the primary signal for maternal recognition of pregnancy in ruminant ungulates. IFNT has been studied extensively in many domesticated and wild ruminant species. In the present study, we have cloned and characterized the IFNT gene of Garole sheep, a popular Indian micro-sheep breed, which is known across the world for its high prolificacy and fecundity. The 588 bp sequences of two variants of IFNT gene described in this study are novel variants, compared to the variants reported previously in sheep. It exhibited more than 96% identity with other ovine IFNT variants and phylogenetically placed in a single clad containing the ovine, caprine and musk ox IFNT variants. The IFNT of Garole sheep demonstrated the highest identity with the genomic derived and highly expressed ovine IFNT variants.

Cellular localisation of the pregnancy-associated glycoprotein family (PAGs) in the synepitheliochorial placenta of the European bison

This paper describes the cellular immuno-localisation of the PAG family in synepitheliochorial (cotyledonary) placenta of the European bison (Eb). Uteri were harvested from pregnant wild Eb (n=4; 45-150 days post coitum-dpc); and additionally from cattle (30, 45 dpc) and pigs (42 dpc)--both domestic species were used as positive controls for cellular PAG immunodetection. Placentas were sectioned, fixed, dehydrated and subjected to double fluorescent immunohistochemistry (dF-IHC) with the use of Alexa 488 fluorochrom (A488) and propidium iodide (PI). Native positive EbPAG signals were detected by heterologous (ht; cross-species) dF-IHC with primary rabbit anti-PAG polyclonals against native or recombinant porcine PAG antigens (anti-pPAG); then visualised with secondary anti-rabbit goat immunoglobulins--conjugated to A488. Our htdF-IHC indicated an unequivocal localisation to the mono- and bi-nuclear trophectoderm (chorionic epithelium) cells expressing the PAGs (A488-green) among all placental cells, in which PI (red) stained nuclei. This is the first paper reporting the EbPAG family expression examined by htdF-IHC at the feto-maternal interface in wild Pecoran species. The cross-reactivity of anti-pPAG polyclonals with the EbPAGs suggests that shared epitopes are present in these molecules. It seems that the EbPAG family, which is robustly expressed in mono- and bi-nucleated trophectoderm cells, is associated with events taking place during placenta development. Our study also provided a proficient ht-system to identify various PAGs that could be useful as prenatal protein markers for pregnancy diagnoses, which is essential for effective reproductive management of endangered mammals.

Pleiotropy and Redundancy of STAT Proteins in Early Pregnancy

Signal transducers and activators of transcription (STATs) are a group of proteins involved in signal transduction from numerous bioactive substances. Hormones and cytokines such as leukaemia inhibitory factor, interferon-tau and prolactin, which play key roles during early pregnancy, activate the Janus kinase (JAK)/STAT signalling pathway. The STATs are thus involved in the regulation of implantation, establishing uterine receptivity and regulation of the maternal immune response. It seems that STATs can orchestrate signals from hormones and cytokines in different cell types and may therefore generate numerous biological effects, despite the relatively small number of receptors activating the JAK/STAT pathway. This review summarizes the participation of STATs in the main processes of early pregnancy, especially regarding their pleiotropy and redundancy.

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

Background

This study reports the identification of a full-length cDNA sequence for two novel caprine prolactin-related proteins (cPRP1 and cPRP6), and their localization and quantitative expression in the placenta. Caprine PRPs are compared with known bovine PRPs. We examined their evolution and role in the ruminant placenta.

Results

Full-length cPRP1 and cPRP6 cDNA were cloned with a 717- and 720- nucleotide open-reading frame corresponding to proteins of 238 and 239 amino acids. The cPRP1 predicted amino acid sequence shares a 72% homology with bovine PRP1 (bPRP1). The cPRP6 predicted amino acid sequence shares a 74% homology with bovine PRP6 (bPRP6). The two cPRPs as well as bPRPs were detected only in the placentome by RT-PCR. Analysis by in situ hybridization revealed the presence of both cPRPs mRNA in the trophoblast binucleate cells. These mRNA were quantified by real-time RT-PCR analysis of the placentome at 30, 50, 90 and 140 days of pregnancy. Both new cPRP genes were able to translate a mature protein in a mammalian cell-expression system. Western blotting established the molecular sizes of 33 kDa for cPRP1 with FLAG-tag and 45 kDa for cPRP6 with FLAG-tag. The sequence properties and localized expression of cPRP1 and cPRP6 were similar to those of bovine. However, their expression profiles differed from those in bovine placenta. Although this study demonstrated possible roles of PRPs in caprine placenta, PRPs may regulate binucleate-cell functions like those in bovine, but their crucial roles are still unclear.

Conclusion

We have identified the novel PRPs in caprine placenta. Localization and quantitative expression of caprine PRPs were compared with bovine PRPs. The data indicate that PRP genes in caprine placenta have coordination functions for gestation, as they do in bovine. This is the first study of PRPs function in caprine placenta.

Trophoblast cells of ruminant placentas—A minireview

The ruminant placenta is classified as cotyledonary and synepitheliochorial on the basis of its gross anatomical features and histological characteristics, respectively. The richly vascularized embryonic chorioallantois is lined on its external surface by cells of the trophectodermal epithelium. These cells which assume specialized functions are referred to as trophoblast cells. Two morphologically and functionally distinct cell types have been recognized in the trophectoderm of the placenta of ruminant animals. These are the mononucleate trophoblast cells and the binucleate trophoblast cells. The occurrence, morphological characteristics, and specialized functions of these trophoblast cells, in relation to conceptus nutrition and survival in utero are discussed in this review.

Identification and cloning of caprine uterine serpin

The uterine serpins have been described in sheep, cattle, and pigs as a highly diverged group of the large superfamily of serpin proteins that typically function as serine proteinase inhibitors. Here, the range of species that possess and express a uterine serpin gene is extended to the goat. Sequencing of cDNA amplified from total RNA from a pregnant goat at day 25 of pregnancy resulted in a 1,292 bp full-length consensus cDNA sequence for caprine uterine serpin (CaUS). The predicted amino acid sequence of the caprine precursor showed 96%, 82%, 55%, and 56% identity to OvUS, BoUS, PoUS1, and PoUS2, respectively. The signal peptide extends from amino acids 1 to 25, resulting in a secreted protein of 404 amino acids and 46,227 Mr (excluding carbohydrate). Both the goat and sheep uterine serpins have a nine amino acid insert in the Helix I region that is not found in bovine or porcine uterine serpins. A total of 13 amino acids in CaUS are different than those for the nearest homologue, ovine uterine serpin. One of these is in the site of cleavage of the signal sequence, where a single nucleotide substitution (G --> C) changed the cysteine for the sheep, bovine, and porcine genes to a serine. In addition, the amino acid at the putative P1-P1' site (the scissile bond for antiproteinase activity) is a valine for CaUS, BoUS, PoUS1, and PoUS2 versus an alanine for OvUS. The hinge region of all five of the uterine serpins (P17-P9) is distinct from the consensus pattern for inhibitory sequences and it is unlikely, therefore, that the uterine serpins possess prototypical proteinase inhibitory activity. The goat uterine serpin was immunolocalized to the glandular epithelium of the endometrium from a pregnant nanny at day 25 of pregnancy. There was also immunoreactive product in scattered luminal epithelial cells. No immunoreaction product was detected in endometrium from a nanny at day 5 of the estrous cycle. Western blotting of uterine fluid collected from the pregnant uterine horn of a unilaterally-pregnant goat revealed the presence of a protein band at Mr approximately 56,000 that reacted with monoclonal antibody to OvUS. In conclusion, the range of species in which uterine serpins are present and expressed in the uterus includes the goat in addition to the previously described sheep, cow, and pig. In all of these species, the uterine serpin is derived primarily from glandular epithelium, is secreted into the uterine lumen, and contains sequence characteristics suggesting it is not an inhibitory serpin.

Identification of bovine and novel interferon-? alleles in the American plains bison (bison bison) by analysis of hybrid cattle x bison blastocysts

The objective of this study was to generate bison x cattle hybrid embryos by in vitro fertilization, to assess their developmental potential, to determine the pattern of secretion of the embryonic signaling molecule interferon-tau (IFN-tau), and to identify novel IFN-tau mRNA polymorphism in the American plains bison. A total of 600 bovine oocytes were inseminated with frozen-thawed bison semen. Of these, 40.7% cleaved and 14.8% proceeded to the blastocyst stage. Individual blastocysts were cultured on a basement membrane (Matrigel) and their ability to attach and form outgrowths was monitored. A total of 36 blastocysts were cultured of which 22 formed outgrowths. During individual culture, medium samples were collected and their IFN-tau concentration was measured. On day 6 after onset of individual culture, attached outgrowths produced significantly more IFN-tau than unattached viable or degenerate blastocysts. At this time, female conceptuses also produced significantly more IFN-tau than their male cohorts. However, by day 12 this difference had disappeared. Total mRNA was extracted from three individual outgrowths and analyzed by RT-PCR. Subsequent sequencing of 28 clones showed several known bovine IFN-tau sequences as well as two novel sequences termed bisIFN-tau1 and 2. To determine the origin of these, DNA was extracted from bison semen and analyzed by PCR. One bovine IFN-tau sequence (bovIFN-tau1d) as well as bisIFN-tau2 and a third novel sequence bisIFN-tau3 were detected. This study demonstrates the feasibility of using hybrid embryos for the analysis of developmentally regulated gene expression in species where embryos may not be available.