Expression of trophoblast cell-specific pregnancy-related genes in somatic cell-cloned bovine pregnancies

Early pregnancy diagnosis in cows using corpus luteum blood flow analysis based on colour Doppler ultrasonography and mRNA analysis

BACKGROUND

Reproductive efficiency is paramount in the dairy industry, where early pregnancy detection of dairy cows will allow to detect the non-pregnant animals early, thus enabling to re-synchronize them and getting them pregnant leading to decrease in calving interval, which, in turn, is critical for maximizing productivity and economic gain. The objective of this study was to evaluate the colour Doppler ultrasonography (CDUS) and peripheral blood leukocytes (PBLs)-based pregnancy-associated biomarker mRNAs expression for the earliest detection of pregnancy status in the dairy cows at post insemination. Intensively managed animals were ovulation synchronized and subjected to timed artificial insemination (TAI). On day 20, corpus luteum blood flow (CLBF) was evaluated using CDUS in 30 cows. The percentage of the incoming blood flow (as an area) of the corpus luteum (CL) was determined using an image analysis software. On day 35, the same operator performed a final pregnancy diagnosis using transrectal ultrasonography to confirm the pregnancy. Blood samples were collected on day 20 and 28 after TAI for biomarkers analysis. The mRNA expression levels of ISG15, MX1, MX2, and PAG9 genes in PBLs were determined by quantitative polymerase chain reaction (qPCR).

RESULTS

The identified CLBF cutoff point resulted 100% sensitivity and negative predictive value (NPV) in determining non-pregnant status on day 20 in the cows. Overall, MX2 and ISG15 mRNAs showed the most significant (P < 0.05) expression levels in pregnant animals on day 20 and 28 compared to non-pregnant animals. Among them, MX2 showed the highest expression levels on both days, ascertaining it as the better candidate biomarker for the earliest identification of pregnancy.

CONCLUSIONS

The CDUS-based CLBF analysis on day 20 after TAI can be potentially used for the early identification of non-pregnancy status in dairy cows and MX2 could be a potential mRNA candidate for the identification of pregnancy in cows. Further studies should be conducted in large scale to validate these findings due to the small sample number used in the current study.

Nuclear transfer alters placental gene expression and associated histone modifications of the placental-specific imprinted gene pleckstrin homology-like domain, family A, member 2 (PHLDA2) in cattle

Abnormal placental development is frequent in nuclear transfer (NT) pregnancies and is likely to be associated with altered epigenetic reprogramming. In the present study, fetal and placental measurements were taken on Day 60 of gestation in cows with pregnancies produced by AI, IVF and NT. Placentas were collected and subjected to histological evaluation, the expression of genes important in trophoblast differentiation and expression of the placental imprinted gene pleckstrin homology-like domain, family A, member 2 (PHLDA2), as well as chromatin immunoprecipitation (ChIP) for histone marks within the promoter of PHLDA2. Fewer binucleated cells were observed in NT cotyledons, followed by IVF and AI cotyledons (P<0.05). Expression of heart and neural crest derivatives expressed 1 (HAND1), placental lactogen (PL), pregnancy-associated glycoprotein 9 (PAG-9) and PHLDA2 was elevated in NT cotyledons compared with AI cotyledons. Expression of PHLDA2 was higher in IVF than AI samples (P<0.05). ChIP revealed an increase in the permissive mark dimethylation of lysine 4 on histone H3 (H3K4me2), surprisingly associated with the silent allele of PHLDA2, and a decrease in the inhibitory mark H3K9me2 in NT samples. Thus, genes critical for placental development were altered in NT placentas, including an imprinted gene. Allele-specific changes in the permissive histone mark in the PHLDA2 promoter indicate misregulation of imprinting in clones. Abnormal trophoblast differentiation could have resulted in lower numbers of binucleated cells following NT. These results suggest that the altered expression of imprinted genes associated with NT are also caused by changes in histone modifications.

Analysis of circulating DNA distribution in pregnant and nonpregnant dairy cows

Circulating nucleic acids (CNAs) are free-floating, cell-free DNA and RNA molecules in the circulation of healthy and diseased humans and animals. The aim of this study was to identify differences in CNA distribution in serum samples from multiparous pregnant (n = 24) and nonpregnant (n = 16) dairy cows at different days of gestation (Days 0, 20, and 40). A modified serial analysis of gene expression procedure was used to generate concatemerized short sequence tags from isolated serum DNA. A total of 6.1 × 10(6) tags were recovered from analyzed samples (n = 40). Significant differences between the pregnant and nonpregnant groups were detected in chromosomal regions, protein-coding sequences, and single genes (P < 0.05). Approximately 23% (1.4 × 10(6) tags) of the total sequence pool were present exclusively in the analyzed serum samples of pregnant cows. Of these tag sequences, seven originated from genomic regions and 13 from repetitive elements. Comparative BLAST analysis identified the repetitive tags as BovB (non-long terminal repeat retrotransposons/long interspersed nuclear elements), Art2A, BovA2, and Bov-tA2 (short interspersed nuclear elements). To our knowledge, this is the first study to comprehensively characterize the circulating, cell-free DNA profile in sera from pregnant and nonpregnant cows across early gestation.

Generation of colonies of induced trophoblast cells during standard reprogramming of porcine fibroblasts to induced pluripotent stem cells

During reprogramming of porcine mesenchymal cells with a four-factor (POU5F1/SOX2/KLF4/MYC) mixture of vectors, a fraction of the colonies had an atypical phenotype and arose earlier than the recognizable porcine induced pluripotent stem (iPS) cell colonies. Within days after each passage, patches of cells with an epithelial phenotype formed raised domes, particularly under 20% O(2) conditions. Relative to gene expression of the iPS cells, there was up-regulation of genes for transcription factors associated with trophoblast (TR) lineage emergence, e.g., GATA2, PPARG, MSX2, DLX3, HAND1, GCM1, CDX2, ID2, ELF5, TCFAP2C, and TEAD4 and for genes required for synthesis of products more typical of differentiated TR, such as steroids (HSD17B1, CYP11A1, and STAR), pregnancy-associated glycoproteins (PAG6), and select cytokines (IFND, IFNG, and IL1B). Although POU5F1 was down-regulated relative to that in iPS cells, it was not silenced in the induced TR (iTR) cells over continued passage. Like iPS cells, iTR cells did not senesce on extended passage and displayed high telomerase activity. Upon xenografting into immunodeficient mice, iTR cells formed nonhemorrhagic teratomas composed largely of layers of epithelium expressing TR markers. When cultured under conditions that promoted embryoid body formation, iTR cells formed floating spheres consisting of a single epithelial sheet whose cells were tethered laterally by desmosome-like structures. In conclusion, reprogramming of porcine fibroblasts to iPS cells generates, as a by-product, colonies composed of self-renewing populations of TR cells, possibly containing TR stem cells.

Trophoblast stem cells

Trophoblast stem cells (TSC) are the precursors of the differentiated cells of the placenta. In the mouse, TSC can be derived from outgrowths of either blastocyst polar trophectoderm (TE) or extraembryonic ectoderm (ExE), which originates from polar TE after implantation. The mouse TSC niche appears to be located within the ExE adjacent to the epiblast, on which it depends for essential growth factors, but whether this cellular architecture is the same in other species remains to be determined. Mouse TSC self-renewal can be sustained by culture on mitotically inactivated feeder cells, which provide one or more factors related to the NODAL pathway, and a medium supplemented with FGF4, heparin, and fetal bovine serum. Repression of the gene network that maintains pluripotency and emergence of the transcription factor pathways that specify a trophoblast (TR) fate enables TSC derivation in vitro and placental formation in vivo. Disrupting the pluripotent network of embryonic stem cells (ESC) causes them to default to a TR ground state. Pluripotent cells that have acquired sublethal chromosomal alterations may be sequestered into TR for similar reasons. The transition from ESC to TSC, which appears to be unidirectional, reveals important aspects of initial fate decisions in mice. TSC have yet to be derived from domestic species in which remarkable TR growth precedes embryogenesis. Recent derivation of TSC from blastocysts of the rhesus monkey suggests that isolation of the human equivalents may be possible and will reveal the extent to which mechanisms uncovered by using animal models are true in our own species.

Proteomic analysis of the major cellular proteins of bovine trophectoderm cell lines derived from IVP, parthenogenetic and nuclear transfer embryos: Reduced expression of annexins I and II in nuclear transfer-derived cell lines

Trophectoderm cell lines were established from 8-day in vitro-cultured embryos of cattle derived from fertilization (IVF), somatic cell nuclear transfer (NT), or parthenogenetic activation (P) of in vitro-matured oocytes and from five 8-day-old in vivo (V) embryos. The most abundant cellular proteins of 5 V-, 16 NT-, 12 P-, and 16 IVF-derived cell lines were compared by 2D-gel electrophoresis and mass spectrometry; that is, the unaltered thiourea/urea extract of each cell culture was analyzed. Common protein spots (n=118) were examined, and 95% were identified with significant scores from protein and gene database searches. Of the proteins detected and identified, actin and cytokeratin-8 were found to be the most abundant. Other prominent cellular proteins were metabolic enzymes such as aldose reductase, phosphoglycerate mutase, enolase, triosephosphate isomerase, cytoskeletal interacting proteins transgelin and stratifin, anti-oxidant proteins peroxiredoxin 1 and anti-oxidant protein 2, and the calcium-dependent lipid-binding proteins annexins I and II. In comparative analysis of the 2D-gels, the NT-derived trophectoderm had less annexins I and II in comparison to the IVF- and P-derived trophectoderm. Because annexins I and II are abundant in the placenta and have functions important to the maintenance of placentation, the down-regulation of the annexin genes in the cultured NT trophectoderm may be related to the frequent failures of NT pregnancies.

Genetic reprogramming of transcription factor ap-2gamma in bovine somatic cell nuclear transfer preimplantation embryos and placentomes

Bovine somatic cell nuclear transfer (SCNT) efficiency remains very low despite a tremendous amount of research devoted to its improvement over the past decade. Frequent early and mid-gestational losses are commonly accompanied by placental abnormalities. A transcription factor, activating protein AP-2gamma, has been shown to be necessary for proper placental development in the mouse. We first evaluated the expression of the gene coding for AP-2gamma (Tfap2c) in several bovine fibroblast donor cell lines and found it was not expressed. Subsequently we determined the expression profile of Tfap2c in oocytes and various stages of preimplantation in vitro fertilized (IVF) embryos. Tfap2c was undetectable in oocytes and early embryos, and was detectable at relatively high levels in morula and blastocyst IVF embryos. The lack of expression in oocytes and donor cells means Tfap2c must be induced in the zygote at the morula stage in properly reprogrammed embryos. SCNT embryos expressed Tfap2c at the eight-cell stage, 2 days earlier than control embryos. Control embryos first expressed Tfap2c at the morula stage, and at this stage Tfap2c was significantly lower in the SCNT embryos. No differences in expression were detected at the blastocyst stage. To determine whether Tfap2c was properly reprogrammed in the placenta of SCNT pregnancies, we evaluated its expression in cotyledons and caruncles of SCNT and control pregnancies between days 55 and 90 gestation. Expression of Tfap2c in caruncles significantly increased between days 55 and 90, while expression in cotyledons was relatively consistent over that same period. Expression levels in SCNT tissues were not different from controls. This data indicates Tfap2c expression is altered in early preimplantation SCNT embryos, which may have developmental consequences resulting from genes influenced by Tfap2c, but expression was not different at the blastocyst stage and in placentomes.

Review Paper: A Review of the Pathology of Abnormal Placentae of Somatic Cell Nuclear Transfer Clone Pregnancies in Cattle, Sheep, and Mice

Cloning of cattle, sheep, and mice by somatic cell nuclear transfer (SCNT) can result in apparently healthy offspring, but the probability of a successful and complete pregnancy is less than 5%. Failures of SCNT pregnancy are associated with placental abnormalities, such as placentomegaly, reduced vascularisation, hypoplasia of trophoblastic epithelium, and altered basement membrane. The pathogenesis of these changes is poorly understood, but current evidence implicates aberrant reprogramming of donor nuclei by the recipient oocyte cytoplast, resulting in epigenetic modifications of key regulatory genes essential for normal placental development. The purpose of this review is to provide an overview of the anatomic pathology of abnormal placentae of SCNT clones and to summarize current knowledge concerning underlying pathogenetic mechanisms.

Comparison of the interferon-tau expression from primary trophectoderm outgrowths derived from IVP, NT, and parthenogenote bovine blastocysts

The expression of interferon-tau (IFN-tau) is essential for bovine embryo survival in the uterus. An evaluation of IFN-tau production from somatic cell nuclear transfer (NT)-embryo-derived primary trophectoderm cultures in comparison to trophectoderm cultured from parthenogenote (P) and in vitro matured, fertilized, and cultured (IVP) bovine embryos was performed. In Experiment 1, the success/failure ratio for primary trophectoderm colony formation was similar for IVP and NT blastocysts [IVP = 155/29 (84%); NT 104/25 (81%)], but was decreased (P = .05) for P blastocysts [54/43 (56%)]. Most trophectoderm colonies reached diameters of at least 1 cm within 3-4 weeks, and at this time, 72 hr conditioned cell culture medium was measured for IFN-tau concentration by antiviral activity assay. The amount of IFN-tau produced by IVP-outgrowths [4311 IU/mL (n = 155)] was greater (P < .05) than that from NT- [626 IU/mL (n = 104)] and P - [1595 IU/mL (n = 54)] derived trophectoderm. Differential expression of IFN-tau was confirmed by immunoblotting. In Experiment 2, colony formation was again similar for IVP and NT blastocysts [IVP = 70/5 (93%); NT 67/1 (99%)] and less (P < .05) for P blastocysts [65/27 (70%)]. Analysis of trophectoderm colony size after 23 days in culture showed a similar relationship with P-derived colonies being significantly smaller in comparison to IVP and NT colonies. A differential expression of IFN-tau was also observed again, but this time as measured over time in culture. Maximal IFN-tau production was found at day-14 of primary culture and diminished to a minimum by the 23rd day.

Radioimmunoassay of bovine placental lactogen using recombinant and native preparations: determination of fetal concentrations across gestation

Concentrations of bovine placental lactogen (bPL) were determined in fetal plasma samples by twelve double-antibody competitive radioimmunoassay systems (RIA I-XII) based on either recombinant bPL (non-glycosylated) or native bPL (glycosylated). Both preparations were used as standard and tracer, and for primary antisera production. The minimum detection limit measured by these RIA varied from 0.02 to 0.6 ng bPL mL(-1). The coefficients of correlation of different bPL RIA systems were up to 90% (P < 0.0001) when each RIA was tested against the average values of all twelve RIA systems. All developed RIA were used to investigate the incidence of different bPL isoforms in bovine fetal serum samples (n = 71). Fetal concentrations ranged from 11.8 to 35.7 ng mL(-1) at the third month and from 1.1 to 13.5 ng mL(-1) at the ninth month of gestation. They tended to decrease with advancing gestation. In general, those RIA systems that used recombinant bPL as the standard measured higher values than those using the native bPL preparation. These differences decreased toward the end of gestation (P < 0.05), suggesting a lower rate of glycosylation. Our results provide evidence of different glycosylated isoforms of bPL in fetal serum at different gestation periods.

Establishment of a bovine blastocyst-derived cell line collection for the comparative analysis of embryos created in vivo and by in vitro fertilization, somatic cell nuclear transfer, or parthenogenetic activation

Tools and methods for analyzing differences in embryos resulting from somatic cell nuclear transfer (NT) in comparison to those derived from normal fertilization are needed to define better the nature of the nuclear reprogramming that occurs after NT. To this end, a collection of bovine blastocyst-derived cell lines was created. In vitro expanded or hatched blastocysts, used as primary culture tissue, were from NT; in vitro maturation, fertilization, and culture (IVF); or parthenogenetic (P) activation. Also, five in vivo-fertilized and developed blastocysts were collected by uterine flushing on the eighth d postfertilization. Whole blastocysts were physically attached to STO feeder layers to initiate all of the cell lines generated. The majority of the cell lines in the collection are trophectoderm, 38 NT-derived, 6 in vivo-derived, 20 IVF-derived, and 13 P-derived. Trophectoderm identity was ascertained by morphology and, in many cases, interferon-tau production. Several visceral endoderm cell lines and putative parietal endoderm cell lines were also established. At approximately 5% efficiency, epiblast masses from NT and IVF blastocysts survived and were isolated in culture. Two epiblast masses were also isolated from P blastocysts. Spontaneous differentiation from the epiblast outgrowths resulted in the establishment of fibroblast cell lines. The use of the trophectoderm cell lines as a comparative in vitro model of bovine trophectoderm and placental function is discussed in relation to NT reprogramming.

Somatic cell nuclear transfer alters peri-implantation trophoblast differentiation in bovine embryos

Abnormal placental development limits success in ruminant pregnancies derived from somatic cell nuclear transfer (SCNT), due to reduction in placentome number and consequently, maternal/fetal exchange. In the primary stages of an epithelial–chorial association, the maternal/fetal interface is characterized by progressive endometrial invasion by specialized trophoblast binucleate/giant cells (TGC). We hypothesized that dysfunctional placentation in SCNT pregnancies results from aberration in expression of genes known to be necessary for trophoblast proliferation (Mash2), differentiation (Hand1), and function (IFN-τ and PAG-9). We, therefore, compared the expression of these factors in trophoblast from bovine embryos derived from artificial insemination (AI),in vitrofertilization (IVF), and SCNT prior to (day 17) and following (day 40 of gestation) implantation, as well as TGC densities and function. In preimplantation embryos, Mash2 mRNA was more abundant in SCNT embryos compared to AI, while Hand1 was highest in AI and IVF relative to SCNT embryos. IFN-τ mRNA abundance did not differ among groups. PAG-9 mRNA was undetectable in SCNT embryos, present in IVF embryos and highest in AI embryos. In postimplantation pregnancies, SCNT fetal cotyledons displayed higher Mash2 and Hand1 than AI and IVF tissues. Allelic expression of Mash2 was not different among the groups, which suggests that elevated mRNA expression was not due to altered imprinting status of Mash2. The day 40 SCNT cotyledons had the fewest number of TGC compared to IVF and AI controls. Thus, expression of genes critical to normal placental development is altered in SCNT bovine embryos, and this is expected to cause abnormal trophoblast differentiation and contribute to pregnancy loss.

Ultrasound fetal measurements and pregnancy associated glycoprotein secretion in early pregnancy in cattle recipients carrying somatic clones

Somatic cloning in the bovine species leads to high levels of fetal losses which occur throughout pregnancy. These losses are most often associated with fetal overgrowth, a syndrome known as large offspring syndrome (LOS), and excessive maternal plasma pregnancy serum protein 60 (PSP60), a protein similar to a pregnancy-associated glycoprotein of 67 kDa (PAG I67) produced by the bovine placenta. Predicting the outcome of pregnancies initiated from cloned embryos has become an important issue both to prevent potential harm to the mother because of excessive fetal size at birth and also to get a better understanding of the relationships between growth, differentiation and placental functions in developing cloned fetuses. Here, we report on a systematic analysis of fetal and placental development in the first trimester of pregnancy performed by ultrasonographic imaging and by measurement of the maternal concentrations of pregnancy associated glycoproteins (PAGS), using four different radioimmunoassays (RIA) (two homologous RIA systems with PSP60 and PAG I67; two heterologous RIA systems with PAG I67 as standard and tracer, and antisera anti-caprine PAGs). We showed that crown-rump length (CRL) in clones appeared smaller than controls at 35, 50 and 62 days (P<0.05). At 62 days of pregnancy, CRL in cloned fetuses that died before 90 days was smaller compared to the other cloned fetuses (P<0.05) whereas the width of the fetal sack and the biparietal diameter (BPD) was larger in fetuses that developed LOS in late gestation (P<0.05). Maternal PAGs concentrations were statistically different between controls and all clone recipients as early as Day 34, suggesting early abnormal placental glycoprotein synthesis for clone pregnancies regardless of pregnancy outcome. This work provides a practical, non-invasive tool to follow up clone pregnancies and suggests that primary growth retardation and abnormal placental function precedes excessive fetal and placental growth at later stages of pregnancy.

Transfer of Inner Cell Mass Cells Derived from Bovine Nuclear Transfer Embryos into the Trophoblast of BovineIn Vitro–Produced Embryos

Presence of placental tissues from more normal noncloned embryos could reduce the pregnancy failure of somatic cloning in cattle. In this study, inner cell mass (ICM) cells of in vitro-produced (IVP) embryos was replaced with those of nuclear transfer (NT) embryos to reconstruct bovine blastocysts with ICM and trophoblast cells from NT and IVP embryos, respectively. A total of 65 of these reconstructed embryos were nonsurgically transferred to 20 recipient beef females. Of those, two females were diagnosed pregnant by ultrasonography on day 30 of gestation. One pregnancy was lost at 60-90 days of gestation, and the other recipient cow remained pregnant at day 240 of gestation; however, this female died on day 252 of gestation. Gross pathology of the internal organs of the recipient female, a large fetus, and a large placental tissue mass suggested the massive size of the fetus and placental tissue were likely involved in terminating the life of the recipient female. Biopsy samples were harvested from the skin of the dead recipient cow, the fetus and from cotyledonary tissue. Microsatellite DNA analysis of these samples revealed that the genotype of the fetus was the same as that of the NT donor cells and different from that of the recipient cow. Correspondingly, neither the fetus nor recipient cow had the same genotype with that of the fetal cotyledonary tissue. These results present the first known documented case of a bovine somatic NT pregnancy with nonclone placental tissues after transfer of a blastocyst reconstructed by a microsurgical method to exchange of ICM cells and trophoblast tissue between NT and IVP blastocysts.

Epigenetic characterization of the CpG islands of bovine Leptin and POU5F1 genes in cloned bovine fetuses

Abnormal development and fetal loss during postimplantation period are concerns for production of nuclear transferred animals. Aberrant DNA methylation is one of the reasons for poor survival of cloned animals. In mammalian genome DNA, CpG islands are preferentially located at the start of transcription of housekeeping genes and are associated with tissue-specific genes. The correct and consecutive mechanisms of DNA methylation in the CpG islands are necessary for selective gene expressions that determine the properties of individual cells, tissues, and organs. In this study, we investigated the methylation status of the CpG islands of the bovine Leptin and POU5F1 genes in fetal and placental tissues from fetuses produced by artificial insemination (AI) and nuclear transfer (NT) at days 48 and 59 of pregnancy. Altered DNA methylation was observed in the normal and cloned fetal, placental, and endometrial tissues using bisulfite sequencing and pyrosequencing. Different tissue-specific methylated regions in the bovine Leptin and POU5F1 genes show a variable methylation status in NT fetuses compared to AI control.

Expression profile and protein levels of placental products as indirect measures of placental function in in vitro-derived bovine pregnancies

Bovine conceptus development and its association with placental proteins present in maternal, foetal and neonatal plasma and foetal (amniotic and allantoic) fluids were investigated inin vivo- andin vitro-produced (IVP) concepti and newborn calves. Females were superovulated to obtain control embryos, whereas IVP embryos were derived from establishedin vitroprocedures. Pregnant animals were slaughtered on days 90 or 180 of gestation or allowed to develop to term for the assessment of physical traits. Foetal, maternal and neonatal blood and foetal fluids were collected for the determination of bovine placental lactogen (bPL) and bovine pregnancy-specific protein B (bPSPB) concentrations. Placental transcripts for bPL and bPSPB, determined by quantitative RT-PCR, were elevated in IVP placentomes. No major physical differences were observed between groups on day 90, but concentrations of bPL and bPSPB were higher in foetal plasma and allantoic fluid of IVP concepti in day 180 pregnancies, which were correlated with larger uterine and conceptus traits. Maternal concentrations of bPL in IVP pregnancies were lower than controls during the last 8 weeks of gestation, to become similar as parturition approached. Newborn IVP calves and foetal membranes were larger and displayed higher concentrations of plasma bPL than controls (10 and 60 min after birth). Our results indicated that differential patterns of secretion of bPL and bPSPB into the maternal and foetal systems occurred at distinct stages of gestation, and these were associated with altered conceptus development afterin vitroembryo manipulations, indirectly demonstrating deviations in placental function in IVP pregnancies.

DNA Methylation Profiles of Donor Nuclei Cells and Tissues of Cloned Bovine Fetuses

Methylation of DNA in CpG islands plays an important role during fetal development and differentiation because CpG islands are preferentially located in upstream regions of mammalian genomic DNA, including the transcription start site of housekeeping genes and are also associated with tissue-specific genes. Somatic nuclear transfer (NT) technology has been used to generate live clones in numerous mammalian species, but only a low percentage of nuclear transferred animals develop to term. Abnormal epigenetic changes in the CpG islands of donor nuclei after nuclear transfer could contribute to a high rate of abortion during early gestation and increase perinatal death. These changes have yet to be explored. Thus, we investigated the genome-wide DNA methylation profiles of CpG islands in nuclei donor cells and NT animals. Using Restriction Landmark Genomic Scanning (RLGS), we showed, for the first time, the epigenetic profile formation of tissues from NT bovine fetuses produced from cumulus cells. From approximately 2600 unmethylated NotI sites visualized on the RLGS profile, at least 35 NotI sites showed different methylation statuses. Moreover, we proved that fetal and placental tissues from artificially inseminated and cloned cattle have tissue-specific differences in the genome-wide methylation profiles of the CpG islands. We also found that possible abnormalities occurred in the fetal brain and placental tissues of cloned animals.

Measures of Maternal-Fetal Interaction in Day-30 Bovine Pregnancies Derived from Nuclear Transfer

Embryonic mortality and abnormal placental morphology have been reported by most researchers studying nuclear transfer (NT), and it now is accepted that placental anomalies and poor development of cloned embryos are related. As early as day 50 of gestation, cloned bovine concepti exhibit poor structural organization of the developing placentomes. These experiments were designed to identify alterations in maternal-fetal interactions during establishment of the placentas of NT-derived embryos at day 30 of gestation. Bovine NT embryos were produced using cultured fibroblast cells from a single Hereford donor cow, and control embryos were derived from in vitro fertilization (IVF). Following in vivo culture in ligated sheep oviducts, day-8 blastocysts were transferred to synchronized recipient heifers. Tissues recovered from viable day-30 pregnancies were analyzed by real-time RT-PCR, immunohistochemistry, and quantitative histological techniques. Immunoperoxidase staining of caruncular tissue from NT- and IVF-derived pregnancies revealed no significant differences in expression of the extracellular matrix proteins, collagen type IV and laminin, or the receptor subunits, integrins alpha1 and alpha3, suggesting that altered expression of these proteins at day 30 of gestation is not a primary cause of abnormal placentome structure in cloned concepti. Percentage of binucleate cells (BNC) within the trophoblast also was similar in NT- and IVF-derived pregnancies; however, expression of the BNC-specific placental lactogen (PL) transcript was elevated in NT-derived concepti (p < 0.05). These results indicate that regulation of PL transcription was altered in cloned day-30 placental tissues, suggesting the presence of irregular fetal-maternal signaling patterns that might undermine continued development of NT-derived concepti.

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

Pregnancy associated glycoproteins (PAGs) are extensively glycosylated secretory proteins of ruminant trophoblast cells. In cattle placenta several PAG cDNAs are expressed, but the variety of correspondent proteins and their degree of glycosylation are not well characterized. Thus, we purified PAGs by using a protocol which included a lectin (Vicia villosa agglutinin) affinity chromatography. Due to their specific glycosylation pattern, PAGs derived from binucleate trophoblast giant cells were highly enriched by this protocol. PAGs were purified from cotyledons of 2 day 100 placentas and from a single placenta at day 155 and 180. In all samples three major bands (75; 66; 56 kDa) were detected by one-dimensional SDS-PAGE. Mass-spectrometric analysis identified the 75 kDa band as a mixture of PAG-7 and PAG-6, the 66 kDa band as PAG-1 and the 56 kDa band as PAG-17. N-terminal sequencing of the day 100 sample confirmed the mass spectrometric identifications. Enzymatic release of N-glycans with peptide-N-glycanase-F from PAGs reduced the molecular weight to approximately 37 kDa which corresponds to the theoretical molecular mass of PAGs. Limited peptide-N-glycanase-F treatment revealed that all four N-glycosylation sites are quantitatively occupied in PAG-1. Compared to PAG-1 the number of potential N-glycosylation sites is lower in PAG-17 (three sites) and higher in PAG-6 and -7 (five and six sites, respectively). This suggests that the number of attached N-glycans is the main determinant of molecular mass of bovine PAGs. The degree of glycosylation may be a major factor regulating the plasma half life of PAGs.