Pregnancy associated glycoprotein-1, -6, -7, and -17 are major products of bovine binucleate trophoblast giant cells at midpregnancy

Genomic diversity and relationship analyses of endangered German Black Pied cattle (DSN) to 68 other taurine breeds based on whole-genome sequencing

German Black Pied cattle (Deutsches Schwarzbuntes Niederungsrind, DSN) are an endangered dual-purpose cattle breed originating from the North Sea region. The population comprises about 2,500 cattle and is considered one of the ancestral populations of the modern Holstein breed. The current study aimed at defining the breeds closest related to DSN cattle, characterizing their genomic diversity and inbreeding. In addition, the detection of selection signatures between DSN and Holstein was a goal. Relationship analyses using fixation index (F_ST), phylogenetic, and admixture analyses were performed between DSN and 68 other breeds from the 1000 Bull Genomes Project. Nucleotide diversity, observed heterozygosity, and expected heterozygosity were calculated as metrics for genomic diversity. Inbreeding was measured as excess of homozygosity (F_Hom) and genomic inbreeding (F_RoH) through runs of homozygosity (RoHs). Region-wide F_ST and cross-population-extended haplotype homozygosity (XP-EHH) between DSN and Holstein were used to detect selection signatures between the two breeds, and RoH islands were used to detect selection signatures within DSN and Holstein. DSN showed a close genetic relationship with breeds from the Netherlands, Belgium, Northern Germany, and Scandinavia, such as Dutch Friesian Red, Dutch Improved Red, Belgian Red White Campine, Red White Dual Purpose, Modern Angler, Modern Danish Red, and Holstein. The nucleotide diversity in DSN (0.151%) was higher than in Holstein (0.147%) and other breeds, e.g., Norwegian Red (0.149%), Red White Dual Purpose (0.149%), Swedish Red (0.149%), Hereford (0.145%), Angus (0.143%), and Jersey (0.136%). The F_Hom and F_RoH values in DSN were among the lowest. Regions with high F_ST between DSN and Holstein, significant XP-EHH regions, and RoH islands detected in both breeds harbor candidate genes that were previously reported for milk, meat, fertility, production, and health traits, including one QTL detected in DSN for endoparasite infection resistance. The selection signatures between DSN and Holstein provide evidence of regions responsible for the dual-purpose properties of DSN and the milk type of Holstein. Despite the small population size, DSN has a high level of diversity and low inbreeding. F_ST supports its relatedness to breeds from the same geographic origin and provides information on potential gene pools that could be used to maintain diversity in DSN.

A multiplexed parallel reaction monitoring assay to monitor bovine pregnancy-associated glycoproteins throughout pregnancy and after gestation

Bovine pregnancy-associated glycoproteins (boPAGs) are extensively glycosylated secretory proteins of trophoblast cells. Roughly 20 different boPAG members are known but their distribution patterns and degree of glycosylation during pregnancy are not well characterized. The objective of the present study was the development of a parallel reaction monitoring-based assay for the profiling of different boPAGs during pregnancy and after gestation. Furthermore, we investigated the effects of N-glycosylation on our analytical results. BoPAGs were purified from cotyledons of four different pregnancy stages. The assay detects 25 proteotypic peptides from 18 boPAGs in a single run. The highest abundances were found for boPAG 1 in both, glycosylated and deglycosylated samples. Strongest effects of glycosylation were detected during mid and late pregnancy as well as in afterbirth samples. Furthermore, we identified different boPAG-clusters based on the observed relative protein abundances between glycosylated and deglycosylated samples. A linkage between the impact of glycosylation and potential N-glycosylation sites or phylogenetic relation was not detected. In conclusion, the newly developed parallel reaction monitoring-based assay enables for the first time a comprehensive semi-quantitative profiling of 18 different boPAGs during pregnancy and post-partum on protein level, thereby investigating the influence of glycosylation. The results of this study provide new and important starting points to address further research on boPAGs to better understand their physiological role during pregnancy and for the development of new pregnancy detection tests.

Short Communication: Maternal obesity alters ovine endometrial gene expression during peri-implantation development

Exposure to maternal obesity in utero is associated with marked developmental effects in offspring that may not be evident until adulthood. Mechanisms regulating the programming effects of maternal obesity on fetal development have been reported, but little is known about how maternal obesity affects the earliest periods of embryonic development. This work explored how obesity influences endometrial gene expression during the peri-implantation period using a sheep model. Ewes were assigned randomly to diets that produced an obese state or maintained a lean state. After 4 mo, obese and lean ewes were bred and then euthanized at day 14 post-breeding. The uterus was excised, conceptuses were flushed, and endometrial tissue was collected. Isolated RNA from endometrial tissues (n = 6 ewes/treatment) were sequenced using an Illumina-based platform. Reads were mapped to the Ovis aries genome (Oar_4.0). Differential gene expression was determined, and results were filtered (false discovery rate ≤ 0.05 and ≥2-fold change, ≥0.2 reads/kilobase/million reads). Differentially expressed genes (DEGs) were identified (n = 699), with 171 downregulated and 498 upregulated in obese vs. lean endometrium, respectively. The most pronounced gene ontology categories identified were cellular process, metabolic process, and biological regulation. Enrichments were detected within the DEGs for genes involved with immune system processes, negative regulation of apoptosis, cell growth, and cell adhesion. A literature search revealed that 125 DEGs were associated with either the trophoblast lineage or the placenta. Genes within this grouping were involved with wingless/integrated signaling, angiogenesis, and integrin signaling. In summary, these data indicate that the peri-implantation endometrium is responsive to maternal obesity. Transcript profile analyses suggest that the endometrial immune response, adhesion, and angiogenesis may be especially susceptible to obesity. Thus, alterations in uterine transcript profiles during early embryogenesis may be a mechanism responsible for developmental programming following maternal obesity exposure in utero.

Using commercial enzyme immunoassay for measuring pregnancy-associated glycoproteins to diagnose pregnancy in dairy cows under field conditions in Algeria

The purpose of the present work was to study effectiveness for early pregnancy diagnosis in cattle of the new enzyme immunoassay (EIA) sandwich kit commercially available based on the measurement of pregnancy-associated glycoproteins (PAGs). 120 Holstein-Friesian cattle of mixed age and parity were comprised from different dairy herds. The pregnant females (n = 68) were diagnosed by ultrasonography at day 35-40 after artificial insemination and confirmed by transrectal exploration at 2-3 months after AI. The non-pregnant females (n = 52) were housed in the absence of males during the experimental period. Blood samples were collected from coccygeal vessels of females into EDTA tubes. The serum was obtained by centrifugation and the serum was stored at - 20 C until assay. The PAG concentrations in pregnant and non-pregnant females were determined in serum by EIA kit. The reproducibility inter- and intra-assay of the PAG-EIA is satisfactory (2.78 and 13.19 %, respectively). The accuracy ( 94.8 %) and the test of parallelism were largely acceptable. No cross-reaction was observed with the different hormones tested at different dilutions. PAG-EIA system gave 100 % sensitivity and negative predictive values. Whereas, specificity and positive predictive value were 91.93 and 71.15 %, respectively. The accuracy of pregnancy diagnosis by PAG-EIA was 87.5 %. In conclusion, the present study shows clearly that the EIA kit can be used to measure PAG in serum cows for the detection of gestation in Algeria. Therefore, this alternative technique could be recommended to replace the radioactive methods in immunoassays to improve the reproductive performances and an efficient tool for reproductive management of dairy cattle.

Bioinformatics analysis, codon optimization and expression of ovine pregnancy associated Glycoprotein-7 in HEK293 cells

Pregnancy-associated glycoproteins (PAGs) are widely used as powerful markers for early pregnancy diagnosis in livestock. To improve expression efficiency of recombinant ovine pregnancy-associated glycoprotein-7 (ovPAG-7) in HEK293 cells, the codon usage bias of the ovPAG-7 gene was analyzed using bioinformatic approaches, after which the DNA sequence encoding ovPAG-7 was designed, synthesized, and expressed in HEK293. The structure and function of ovPAG-7 were predicted using bioinformatics software and online databases. The results showed that the effective number of codons (NEC) of the ovPAG-7 gene was 56.82, indicating that the ovPAG-7 gene was weakly biased. ovPAG-7 gene had 26 biased codons (relative synonymous codon usage (RSCU) > 1), 15 of which were biased towards G/C at the third position. After codon optimization, the codon adaptation index of the ovPAG-7 gene increased from 0.74 to 0.96, and its GC content changed from 46.6 to 58.6%. The amino acid sequence encoded by the optimized gene was entirely consistent with those published in Gen Bank. Western blot analysis indicated that the recombinant ovPAG-7 protein with a relative molecular mass of 48 kDa was successfully expressed in HEK293 cells. The bioinformatics prediction results showed that ovPAG-7 protein contained 3 N-glycosylation sites, 13 B-cell epitopes, and a signal peptide consisting of 15 amino acids at the N terminus. The secondary structure of the ovPAG-7 protein was predicted to consist of random coils (46.85%), extended strands (32.05%), α-helices (16.16%), and β-turns (4.93%). This study provided a tool for the screening of monoclonal antibodies and functional research on ovPAG-7.

Establishment of a Sandwich-ELISA for simultaneous quantification of bovine pregnancy-associated glycoprotein in serum and milk

Bovine pregnancy-associated glycoproteins (boPAG) are expressed by trophoblast cells in the bovine placenta. The multigene family of boPAG belongs to the group of aspartic proteases. The accumulation and circulation in maternal blood and milk has made boPAG very useful and important for pregnancy diagnosis in cattle. The goal of the present study was to develop and validate a new Sandwich-ELISA which allows the detection of boPAG in maternal serum and whole milk. Therefore, 984 serum and 928 milk samples were collected monthly from 231 Holstein Friesian cows (Bos Taurus) from one week after insemination (p.i.) until six weeks postpartum. The ELISA is able to identify a cow as being pregnant at day 30 p.i. in serum and at day 40 p.i in milk with threshold values of 1.0 ng/ml in serum and 0.0165 ng/ml in milk. The postpartum half-life of boPAG was estimated to be 6.4 days in serum and 7.1 days in milk. The boPAG profile established during pregnancy in serum and milk showed a typical pattern. The amount of boPAG found in milk was 1.5 % of the amount of boPAG present in serum. In conclusion, a Sandwich-ELISA has been developed to quantify boPAG in serum and in whole milk simultaneously with the same test procedure. This is time saving for farmers and more efficient for laboratories.

Pregnancy-Specific Protein B in Yankasa Ewes During Pregnancy and Postpartum Periods

Pregnancy-specific protein B (PSPB) is produced by mono and binucleate trophoblast cells in the placenta of ruminants during pregnancy. This study was designed to determine the pattern of serum PSPB in Yankasa ewes during pregnancy and postpartum periods. Mature cycling Yankasa ewes were synchronized and divided into two groups A (n=11) and B (n=13). Group A was bred, while group B was unbred. Blood samples for PSPB assessment were collected from the ewes starting from the day of breeding until 4 weeks post-lambing. All pregnant Yankasa ewes lambed with singleton lambs after an average of 151.18 days. There was a significant (p<0.05) increase in PSPB in pregnant compared with the non-pregnant ewes in the period between 3 weeks post-breeding and 3 weeks post-lambing. Peaks were detected in the first (100.60 ng/ml), second (133.90 ng/ml), and third (114.82 ng/ml) trimesters at 5, 10 and 21 weeks of gestation, respectively, but steadily decreased within 4 weeks (2.38 ng/ml) postpartum. In conclusion, PSPB detected pregnancy in Yankasa ewes from 3 weeks post-breeding with peak levels at 5, 10 and 21 weeks post-breeding in the first, second, and third trimesters, respectively. PSPB decreased gradually after lambing until 4 weeks postpartum.

Relationship of foetal number and parity in Barbari goats to plasma profile of caprine pregnancy-associated glycoprotein (caPAG) during gestation and the early postpartum period

This study was conducted to characterise pregnancy-associated glycoprotein (caPAG) in peripheral plasma during gestation and postpartum periods of nulliparous and multiparous does with one or two foetuses using a caPAG specific two-step sandwich ELISA system. Earliest time-points for detection of pregnancy and foetal number with appropriate cut-off values were identified. Plasma samples from 15 pregnant (multiparous: n = 8; nulliparous: n = 7; during pregnancy and postpartum period) and six non-pregnant (during oestrous cycle) goats were collected and analysed. Mean caPAG concentration was greater than the threshold for pregnancy detection (S-N = 0.40) on d22, peaked on d45 and remained unchanged until parturition. From d45 until parturition, caPAG concentration in multiparous does with two foetuses was 1.4 to 1.8 fold greater (P < 0.001) than those with one foetus. For the ELISA, 0.83 (S-N) was the most appropriate cut-off to differentiate does with two from those with a single foetus with an overall sensitivity and accuracy of 88.9% and 84.7%, respectively. Circulating caPAG concentration in multiparous goats was greater (P < 0.05) compared with nulliparous goats during the early pregnancy and postpartum periods. After parturition, caPAG concentrations markedly decreased and were basal within 14 days postpartum. In conclusion, using the caPAG specific ELISA, results indicated there were unique gestational and postpartum profiles for caPAG concentrations that are affected by number of foetuses and parity of the doe. The marked decrease in concentration of caPAG following parturition indicates there would not be compromising of the detection of subsequent pregnancies in goats using this technique.

Primary structures of different isoforms of buffalo pregnancy-associated glycoproteins (BuPAGs) during early pregnancy and elucidation of the 3-dimensional structure of the most abundant isoform BuPAG 7

Pregnancy-associated glycoproteins (PAGs) are expressed during pregnancy by the trophoectodermal cells of fetus. Presence of PAGs in dam's circulation has been widely used in pregnancy diagnosis. The present study reports the identification and characterization of different PAG isoforms in buffalo during early stages of pregnancy. The PAG mRNAs isolated from fetal cotyledons (Pregnancy stages: 45, 75 and 90 days) were successfully cloned in pJET1.2 vector and transformed in E. coli. A total of 360 random clones were sequenced and correlated with their stages of expression. A total of 12 isoforms namely, BuPAG 1, 2, 4, 6, 7, 8, 9, 13, 15, 16, 18 and one new isoform were identified. BuPAG 7 was found as the most abundant isoform in all three stages followed by BuPAG 18. Further, a large number of variants were found for most of these isoforms. Phylogenetic relationship of identified BuPAGs showed that BuPAG 2 belonged to an ancient group while other members clustered with modern group. Three-dimensional (3D) structure of BuPAG 7 was determined by homology modeling and molecular dynamic (MD) simulations which displayed a typical fold represented by other aspartic proteinase (AP) family members. Molecular docking of Pepstatin inhibitor with BuPAG 7 revealed to interact through various hydrogen bonding and hydrophobic interactions. Various amino acid substitutions were observed in peptide-binding cleft of BuPAG 7. Superimposition of BuPAG 7 with homologous structures revealed the presence of a 35-41 amino acid long insertion (alpha helix connected by two loops) near the N- terminus which seems to be a unique feature of BuPAG 7 in AP family. This is the first report on identification and sequence characterization of PAG isoforms in buffalo with unique finding that these isoforms represent many transcript variants. We also report 3D structure of the most abundant isoform BuPAG 7 for the first time.

Identification of pregnancy-associated glycoproteins and alpha-fetoprotein in fallow deer (Dama dama) placenta

BACKGROUND

This paper describes the isolation and characterization of pregnancy-associated glycoproteins (PAG) from fetal cotyledonary tissue (FCT) and maternal caruncular tissue (MCT) collected from fallow deer (Dama dama) pregnant females. Proteins issued from FCT and MCT were submitted to affinity chromatographies by using Vicia villosa agarose (VVA) or anti-bovine PAG-2 (R#438) coupled to Sepharose 4B gel. Finally, they were characterized by SDS-PAGE and N-terminal microsequencing.

RESULTS

Four distinct fallow deer PAG (fdPAG) sequences were identified and submitted to Swiss-Prot database. Comparison of fdPAG with PAG sequences identified in other ruminant species exhibited 64 to 83% identity. Additionally, alpha-fetoprotein was identified in fetal and maternal tissues.

CONCLUSION

Our results demonstrate the efficacy of VVA and bovine PAG-2 affinity chromatographies for the isolation of PAG molecules expressed in deer placenta. This is the first report giving four specific amino acid sequences of PAG isolated from feto-maternal junction (FCT and MCT) in the Cervidae family.

Specific expression patterns and cell distribution of ancient and modern PAG in bovine placenta during pregnancy

Pregnancy-associated glycoproteins (PAGs) constitute a multigenic family of aspartic proteinases expressed in the trophoblast of the ruminant placenta. In Bos taurus, this family comprises 21 members segregated into ancient and modern phylogenetic groups. Ancient PAGs have been reported to be synthesized throughout the trophoblastic cell layer whereas modern PAGs are produced by binucleate cells of cotyledons. The aim of this study was to investigate modern and ancient PAGs during gestation in cotyledonary and intercotyledonary tissues. To obtain convincing and innovative results despite the high sequence identity shared between PAGs, we designed specific tools such as amplification primers and antibodies. Using real-time RT-PCR, we described the transcript expression of 16 bovine PAGs. Overall, PAGs are characterized by an increase in their expression during gestation. However, we demonstrated a segregation of modern PAGs in cotyledons and of ancient PAGs in the intercotyledonary chorion, except for the ancient PAG2 expressed in cotyledons. By raising specific antibodies against the modern PAG1 and ancient PAG11 and PAG2, we established the expression kinetics of the proteins using western blotting. Immunohistochemistry showed that PAGs were produced by specific cellular populations: PAG1 by binucleate cells in the whole trophoblastic layer, PAG11 was localized in binucleate cells of the intercotyledonary trophoblast and the chorionic plate of the cotyledon, while PAG2 was produced in mononucleate cells of the internal villi of the cotyledon. These results revealed a highly specific regulation of PAG expression and cell localization as a function of their phylogenetic status, suggesting distinct biological functions within placental tissues.

Purification of pregnancy-associated glycoproteins from late-pregnancy Bubalus bubalis placentas and development of a radioimmunoassay for pregnancy diagnosis in water buffalo females

Background

Pregnancy-associated glycoproteins (PAGs) were first described as placental antigens present in the blood serum of the mother soon after implantation. Here, we describe the purification of several pregnancy-associated glycoproteins from water buffalo placenta (wbPAGs). A specific radioimmunoassay (RIA) was developed for early pregnancy diagnosis in buffalo species.

Results

Amino-terminal microsequencing of immunoreactive placental proteins allowed the identification of eleven wbPAGs sequences [Swiss-Prot accession numbers: P86369 to P86379]. Three polyclonal antisera (AS#858, AS#859 and AS#860) were raised in rabbits against distinct wbPAG fractions. A new RIA (RIA-860) was developed and used to distinguish between pregnant (n = 33) and non-pregnant (n = 26) water buffalo females.

Conclusions

Our results confirmed the multiplicity of PAG expression in buffalo placenta. In addition, the RIA-860 system was shown to be sensitive, linear, reproducible, accurate and specific in measuring PAG concentrations in buffalo plasma samples from Day 37 of gestation onwards.

Assessment of pregnancy-associated glycoprotein (PAG) concentrations in swamp buffalo samples from fetal and maternal origins by using interspecies antisera

Pregnancy-associated glycoproteins (PAG) constitute a large family of glycoproteins found in the outer placental epithelial cell layer of the placenta in Eutherian species. In ruminants, they are noted to be structurally closely related among the different species. This study was designed to determine PAG concentrations in maternal and fetal plasma, allantoic and amniotic fluids in buffalo species. Antisera (AS) generated in rabbits against distinct PAG molecules were used in three radioimmunoassay (RIA)-PAG systems: RIA-1 (antiserum raised against bovine PAG67kDa; AS#497), RIA-2 (antiserum raised against caprine PAG55 + 62 kDa; AS#706) or RIA-3 (antiserum raised against buffalo PAG; AS#859). Samples were collected at a slaughterhouse (n = 67). PAG concentrations determined by RIA-2 gave significantly higher results in both allantoic and amniotic fluids (12.7 ± 2.1 ng/mL and 24.0 ± 7.3 ng/mL, respectively). Regarding maternal and fetal plasma, PAG concentrations obtained by RIA-2 (21.8 ± 2.4 ng/mL and 20.2 ± 2.5 ng/mL, respectively) and RIA-3 (25.0 ± 2.2 ng/mL and 21.9 ± 3.2 ng/mL, respectively) were higher than those obtained by RIA-1 (15.5 ± 1.4 ng/mL and 16.1 ± 1.8 ng/mL, respectively). The correlation among the three systems was very high. The study clearly reveals the ability of different PAG-RIA systems to measure PAG concentration in swamp buffalo samples.

Pregnancy-associated glycoprotein (PAG) family localized in chorionic cells within the epitheliochorial/diffuse placenta of the alpaca (Lama pacos)

Pregnancy-associated glycoproteins (PAGs) are abundant embryo-originated products expressed in the pre-placental trophoblast and later in the post-implantational chorionic epithelium of some ungulate species. This paper describes the cellular immunolocalization of the chorionic PAG family in the epitheliochorial placenta type of the alpaca (Lama pacos-Lp), in which the PAGs were named 'LpPAGs'. Placental Lp sections (5 μm) of different females near mid-pregnancy (150 days post coitum; dpc), advanced pregnancy (244-263 dpc) and late pregnancy (347 dpc) were used for cross-species (heterologous-ht) double fluorescent immunohistochemistry (htdF-IHC). The htdF-IHC was performed with primary rabbit polyvalent anti-porcine PAG polyclonals. The LpPAG immuno-complexes were visualized with secondary goat anti-rabbit immunoglobulins-conjugated with Alexa 488 fluorophore (green), among all nuclei of placental cells stained with propidium iodide (red). This is the first study reporting the immunolocalization of the LpPAG family identified by htdF-IHC at the feto/maternal interface during different pregnancy stages of the alpaca. The most dominant and strongest immune-positive LpPAG signals were found in the well-developed chorionic cell layer. Our htdF-IHC indicated relatively high epitope resemblance to that of the PAGs in camelids and pigs. These data increase our general knowledge of chorionic PAG localization during pregnancy-stage dependent development of the epitheliochorial diffuse placenta type in the alpaca.

Characterization and In Silico Analysis of Pregnancy-Associated Glycoprotein-1 Gene of Buffalo (Bubalus bubalis)

Pregnancy-Associated Glycoproteins (PAGs) are trophoblastic proteins belonging to the Aspartic proteinase family secreted by different placental cells of many mammalian species. They play a pivotal role in placentogenesis, foetomaternal unit remodeling, and implantation. The identification of the genes encoding those proteins will be helpful to unravel the intricate embryogenomic functions during pregnancy establishment. Considering importance of these proteins, the present study was undertaken to characterize the pregnancy associated glycoprotein-1 gene of buffalo. An 1181 base pairs buffalo Pregnancy-Associated Glycoprotein PAG-1 gene was PCR amplified from the RNA obtained from the fetal cotyledons. BLAST analysis of the buffalo PAG-1 sequence retrieved a total of 20 cattle, 5 goat, and 4 sheep PAG sequences, exhibiting more than 80% similarity. Buffalo PAG-1 gene contained an uninterrupted open reading frame of 1140 base pairs encoding 380 amino acids that possess a 15 amino acid signal peptide and mature peptide of 365 amino acids. The phylogenetic study of the buffalo PAG-1 gene revealed buffalo PAG-1 is more related to cattle, goat, and sheep PAG-1 sequences. By this study characterization of buffalo PAG-1 gene and its evolutionary relationship was deduced for the first time.

The glycosylation pattern of secretory granules in binucleate trophoblast cells is highly conserved in ruminants

The binucleate trophoblast cells (BNCs) in the ruminant placenta are a unique feature of this taxon. These cells produce several secretory proteins and transfer these across the fetomaternal barrier into the dam. We used lectin histochemistry with a panel of 24 lectins to characterise the glycosylation pattern of BNC secretory granules in a variety of ruminants. Seven species out of three ruminant families were thus investigated: greater malayan chevrotain (Tragulidae); fallow deer, red deer, chinese water deer (Cervidae); and domestic goat, springbok, impala (Bovidae). BNC granules in all species studied strongly expressed tri-/tetraantennary complex N-glycans and bisecting N-acetylglucosamine [GlcNAc] as shown by binding of leuco- and erythroagglutins of Phaseolus vulgaris respectively. The presence of terminal N-acetylgalactosamine [GalNAc]) in BNC granules is shown by intense staining with lectins from Dolichos biflorus, Vicia villosa and Wisteria floribunda. Terminal galactose or GalNAc was also present, bound by Glycine max agglutinin. Treatment of slides with neuraminidase strongly intensified staining of Erythrina cristagalli lectin (ECA) to terminal lactosamine in all species studied; this was otherwise absent except in goat. Sambucus nigra-1 lectin bound to BNC granules in all species except in Impala, indicating the presence of abundant alpha2,6 linked sialic acid. These results indicate that these unusual highly branched glycans, with bisecting GlcNAc and terminal GalNAc are a general feature of BNC granules in Ruminants, including the most basal Tragulid branch. It therefore appears that the specific glycosylation pattern of BNC granules evolved early in ruminant phylogenesis, together with the appearance of BNC. The conserved glycan structure in BNC secretory granules indicates that this pattern of glycosylation is likely to be of considerable functional importance for the secretory glycoproteins of ruminant BNC.

Isolation of new pregnancy-associated glycoproteins from water buffalo (Bubalus bubalis) placenta by Vicia villosa affinity chromatography

The present study describes the isolation and characterization of new pregnancy-associated glycoprotein molecules (PAG) from midpregnancy and late-pregnancy placentas in the water buffalo (Bubalus bubalis). After extraction, the homogenates are subjected to acid and ammonium sulfate precipitations followed by DEAE chromatography. Subsequently, the water buffalo PAG (wbPAG) from these solutions are enriched by Vicia villosa agarose (VVA) affinity chromatography. As determined by western blotting with anti-PAG sera, the apparent molecular masses of the immunoreactive bands from the VVA peaks range from 59.5 to 75.8kDa and from 57.8 to 73.3kDa in the midpregnancy and late-pregnancy placentas, respectively. Amino-terminal microsequencing of the immunoreactive proteins has allowed the identification of three distinct wbPAG sequences, which have been deposited in the SwissProt database: RGSXLTIHPLRNIRDFFYVG (acc. no. P85048), RGSXLTILPLRNIID (acc. no. P85049), and RGSXLTHLPLRNI (acc. no. P85050). Their comparison to previously identified proteins has shown that two of them are new because they have not been described before. Our results confirm the suitability of VVA chromatography for the enrichment of the multiple PAG molecules expressed in buffalo placenta.

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.

Identification of novel pregnancy-associated glycoproteins (PAG) expressed by the peri-implantation conceptus of domestic ruminants

Pregnancy-associated glycoproteins (PAG) are a multigene family, related to aspartic proteinases, expressed in the placenta of artiodactyls. Ruminant PAG expression varies spatially as well as temporally during gestation. The aim of this study was the identification of novel PAG expressed around implantation in domestic ruminants and to study their phylogenetic relationships. Day 12, 14, 17 (ovine); day 15, 18 (bovine); and day 12, 14, 15, 16, 18 (caprine) conceptuses were used for reverse transcription-polymerase chain reaction (RT-PCR) performed on RNA extracted from conceptuses pooled on each day of recovery. In ovine, a single PAG was detected on day 14, ovPAG2, from the PAG II group. On day 17, three more PAG were identified. One of them similar to ovPAG1 and two unknown named as ovPAG10 and ovPAG11, apparently from the PAG I group. In bovine, PAG expression was detected by day 15 and two transcripts were identified on day 18. One, boPAG2, from the PAG II group and other was previously unknown, boPAG22, closest to boPAG2. In goats, PAG expression was not detected on non-elongated conceptuses (days 12, 14 and 15). Two different transcripts were identified in both day 16 and 18 elongated conceptuses, one similar to caPAG2, from the PAG II group, whereas the other, caPAG12, apparently from the PAG I group, was previously unknown. Interestingly, the three new early PAG identified in sheep and goats are clustered together within the PAG I group. In summary, a complement of new PAGs expressed at implantation in domestic ruminants has been cloned.

Isolation of pregnancy-associated glycoproteins from placenta of the American bison (Bison bison) at first half of pregnancy

This paper describes the successful purification and characterisation of pregnancy-associated glycoproteins (PAG) extracted from placenta (3-4 months) of American bisons (Amb). Chorionic AmbPAG proteins were purified from foetal cotyledonary tissues (CT) and liquid cotyledonary-carrying proteins (LCP) leaking from damaged cells. Our protocols successfully indicated the usefulness of AmbPAG protein identification, especially from LCP fraction. The AmbPAGs were extracted, precipitated and eluted during DEAE cellulose chromatography. The richest protein fractions were further chromatographed on VVA (Vicia villosa agglutinin affinity column), then characterised by mono- and bi-dimensional electrophoresis, Western blot and N-terminal amino acid (aa) sequence. After being transferred to PVDF membranes, three selected VVA-purified AmbPAG isoforms differing in molecular masses and isoelectric points (Ip 4-4.6) were selected for sequencing. One identified N-terminal 25aa sequence of AmbPAG72kDa CT form was identified as completely new (RGSNLTSLPLQNVIDLFYVGNITIG). Two other AmbPAG proteins purified from different sources (74kDa CT and 76kDa LCP forms; RGSNLTIHPLRNIRDIFYVGNITIG) were identical or corresponded to N-terminus of various bovine PAGs (boPAG). The two AmbPAGs (74kDa CT and 76kDa LCP) revealed identical micro-sequence to boPAG7; and were similar mainly to bovine PAG4, -6, -15 and -17 precursors that were identified by full-length sequencing derived from cDNA cloning. The novel sequence of the AmbPAG (72kDa CT) was related to some boPAG and various other ruminant PAG precursors (caprine and ovine). All three identified AmbPAG sequences were also relatively similar to mature forms of purified native boPAG(56-75kDa) proteins. This is the first report indicating aa sequences of native AmbPAG proteins purified from placenta (CT and LCP) of bison species. The N-terminal sequences of the AmbPAGs have been deposited in the EMBL-EBI database (UniProtKB; Accession Nos.: P84916, P84917 and P84918).

Western analyses of pregnancy-associated glycoprotein family (PAG) in placental extracts of various mammals

The present study was conducted in order to analyze the immunoreactivity of placental extracts of several animal species and humans against the following three groups of PAG antisera: anti-boPAG-I (R#497), -boPAG-II (R#435), and -caPAG (R#706). Placental proteins were obtained after extraction at neutral pH, followed by ammonium sulfate (A.S.) precipitation, dialysis, and lyophilization. The immunoreactivity of different placental extracts was revealed by the use of monodimensional SDS-PAGE, followed by blotting on nitrocellulose membrane and the identification of immunoreactive proteins after incubation with PAG antisera (Western blot technique). A strong immunoreactivity of proteins from synepitheliochorial placenta (cattle, sheep, goat, bison, buffalo, and deer) was demonstrated in both 20-50% and 50-80% A.S. fractions using the three antisera. Proteins from species with epitheliochorial placenta presented variable profiles of detected PAG-like proteins: in the sow, many immunoreactive forms were revealed by antisera boPAG-I and boPAG-II, whereas in the dromedary, only two forms were revealed by anti-boPAG-II. Concerning other species, our protocols showed for the first time a cross-reaction between PAG antisera with proteins extracted from dog, alpaca, dromedary, sea lion, and human placenta.

Comparison of five radioimmunoassay systems for PAG measurement: ability to detect early pregnancy in cows

This study was conducted to describe the minimum detection limit, reproducibility, accuracy, specificity and parallelism of different pregnancy-associated glycoprotein radioimmunoassay (PAG-RIA) systems: RIA-497, RIA-706, RIA-780, RIA-809 and RIA-Pool. Their ability to distinguish between non-pregnant and pregnant females at day 30 after artificial insemination (AI) was investigated. The antisera were raised in rabbits against different PAG preparations. All RIA systems proved to be sensitive, repeatable and accurate for measuring PAG concentrations. The dilutions of plasma samples taken at an early stage of pregnancy were found to be parallel to the standard curves. No cross-reaction was observed with different carbohydrates, either with Pregnant Mare Serum Gonadotropin (PMSG) or human Chorionic Gonadotropin (hCG). The concentrations of PAG in pregnant females at day 30 after AI were shown to be higher with the use of antisera R#706, R#780, R#809 and Pool when compared with antiserum R#497. All the RIA systems gave 100% sensitivity and negative predictive values. On the other hand, the use of antisera R#780 and R#809 resulted in lower specificity and positive predictive values. The present study clearly shows that the ability of PAG-RIA systems to diagnose pregnancy specifically at day 30 after AI can be improved by using a combination of antisera raised against different forms of PAG.

The glycosylation of pregnancy-associated glycoproteins and prolactin-related protein-I in bovine binucleate trophoblast giant cells changes before parturition

Binucleate trophoblast giant cells (BNC) in the bovine placenta produce glycoproteins, which are delivered into the mother after fusion of BNC with uterine epithelial cells. During most time of pregnancy, BNC produce pregnancy-associated glycoproteins (PAGs) and prolactin-related protein-I (PRP-I) with asparagine-linked lactosamine-type glycans terminating withN-acetyl-galactosamine. We show by lectin histochemistry that terminalN-acetyl-galactosamine (detected byDolichos biflorusagglutinin, DBA) in placentomal BNC is greatly reduced prior to parturition, while lactosamine-typeN-glycans (detected byPhaseolus vulgarisleucoagglutinin, PHA-L) remain unaltered. The change in DBA-staining showed no statistically significant differences between placentomes of cows with and without retention of fetal membranes. Western blots revealed that, at parturition the apparent molecular mass of PAGs and PRP-I is 1–2 kDa lower than in late pregnancy. These changes are due to alterations of asparagine-linked glycans, since the molecular weight of the peptide backbones after enzymatical release of asparagine-linked glycans is identical at late pregnancy and parturition. Lectin western blots showed a reduction of terminalN-acetyl-galactosamine on PAGs at parturition. A lectin sandwich-ELISAwas used to differentiate DBA- and PHA-L-binding PAGs in sera of pregnant and non-pregnant cows. The values for DBA-binding PAGs at parturition were not significantly different from non-pregnancy, while the values for PHA-L-binding PAGs were significantly higher at parturition. The peripartal changes of PAG- and PRP-I-glycosylation could alter functional properties of these proteins and might therefore be considered for functional studies. The differentiation of PAG glycoforms in maternal serum could be valuable for a further optimization of PAG-based pregnancy diagnosis in cattle.