Transcriptome studies of bovine endometrium reveal molecular profiles characteristic for specific stages of estrous cycle and early pregnancy

The endometrium undergoes marked functional changes during estrous cycle and pregnancy. As the adjacent environment of the conceptus, it represents the maternal interface for embryo-maternal communication, which is essential to maintain pregnancy. Transcriptome studies provide the unique opportunity to assess molecular profiles changing in response to endocrine or metabolic stimuli or to embryonic pregnancy recognition signals. Here we review the current state of transcriptome profiling techniques and the results of a series of transciptome studies comparing bovine endometrium samples during the estrous cycle or endometrium samples from pregnant vs. non-pregnant animals. These studies revealed specific mRNA profiles which are characteristic for the functional status of the endometrium. Transcriptome studies of endometrial samples recovered during the pre-attachment period identified many interferon-stimulated genes, genes that are possibly involved in embryo-maternal immune modulation ( C1S, C1R, C4, SERPING1, UTMP, CD81, IFITM1, BST2), as well as genes affecting cell adhesion ( AGRN, CD81, LGALS3BP, LGALS9, GPLD1, MFGE8, and TGM2) and remodeling of the endometrium ( CLDN4, MEP1B, LGMN, MMP19, TIMP2, TGM2, MET, and EPSTI1). The results of these transcriptome studies were compared to those of similar microarray analyses in human, mouse and Rhesus monkey to identify similarities in endometrial biology between mammalian species and species-specific differences. Future studies will cover dynamic transcriptome changes between different stages of early pregnancy, the relationship between metabolic problems in dairy cows and the functionality of reproductive tissues as well as endometrium transcriptome profiles in recipients of somatic cell nuclear transfer embryos.

175 TRANSCRIPTOME ANALYSIS OF BOVINE DAY 150 FETAL LIVER AND COTYLEDON REVEALS GENES INVOLVED IN FETAL GROWTH

Major problems in breeding of modern dairy cows include increasing rates of stillbirth and dystocia, associated with elevated costs for veterinary intervention (caesarean section) and loss of production animals (cows and calves). Rates of stillbirth as high as 12% have been reported, primarily caused by fetal overgrowth and increased birth weight. In order to discover molecular markers for selection against stillbirth, we developed a model for the inheritance of fetal growth traits. A Fleckvieh bull segregating for paternal stillbirth was used for insemination of 36 cows that were slaughtered at Day 150 of pregnancy in order to recover and phenotype the fetuses. The mode of inheritance indicated involvement of imprinting. Mapping results suggested an imprinted region on chromosome 9 as candidate for the stillbirth QTL. Due to the complexity of the trait, we opted for a holistic approach that is not restricted to the QTL candidate region but allows identification of genes and networks that influence fetal growth. Transcriptome profiles of liver and cotyledon samples from the fetuses with the highest (n = 10) and the lowest total weight n = 10) were analyzed using Affymetrix Bovine GeneChips (Affymetrix, Inc., Santa Clara, CA, USA). Analysis with the program SAM showed 41 up- and 4 down-regulated genes in liver samples of the heavy-weight group. Most of these genes are involved in immune response. Interestingly, many of these genes are reported to be regulated by vitamin D. Furthermore, vitamin D is closely connected to the IGF1 system and thus the most important fetal growth regulation circuit. Seasonal effects on vitamin D levels could mostly be excluded by the experimental design and did not correlate with growth traits. Most likely, the mRNA levels of our candidate genes were influenced by alterations in the IGF1/vitamin D circuit and did not cause the observed weight differences. The imprinted candidate genes showed no correlation with fetal weight. Gene set enrichment analysis indicated enhanced metabolic activity in the liver of heavy-weight fetuses. Genes from the QTL region showed a clear enrichment in correlation with fetal weight, confirming their involvement in fetal growth. The gene with the best correlation, GHITM (growth hormone inducible transmembrane protein), could give an explanation for the enhanced metabolic activity, as it is reported to function as a metabolic regulator. Simultaneous analysis of the data sets for liver and placenta in a linear model (R-package LIMMA; Smyth 2004 Stat. Applic. Genet. Mol. Biol. 3, art. 3) yielded essentially the same differentially expressed genes for liver and a higher number of differentially expressed genes for placenta (89 up- and 114 down-regulated), with little overlap between the two tissues. This work was supported by Grant BMBF FUGATO-Fertilink.

181 MESSENGER RNA PROFILING OF BOVINE ENDOMETRIUM DURING THE ESTROUS CYCLE USING A CUSTOM-MADE cDNA ARRAY

The endometrium provides the optimal conditions for the transport of sperm to the oviduct, to the site of fertilization, and later on for the reception of the embryo. This is reflected by specific morphological and functional changes during the estrous cycle, which are mainly regulated by the hormones progesterone, estradiol, and oxytocin. To study these changes on the level of messenger RNA, a microarray analysis of endometrial tissue samples was performed. Tissue samples were collected from 20 cyclic heifers (Deutsches Fleckvieh, between 17 and 31 months of age) after slaughter at Days 0, 3.5, 12, and 18 of the estrous cycle. The Day 18 group split into two subgroups, one with high and one with low progesterone levels in peripheral blood. Altogether there were 4 heifers in each experimental group. RNA was extracted from these tissue samples and analyzed with a custom-made bovine oviduct and endometrium (BOE) cDNA array (Bauersachs et al. 2007 J. Dairy Sci. 90, in press). The cDNAs present on the array were derived from several previously conducted differential gene expression studies of bovine endometrium between different stages of the estrous cycle, during early pregnancy, and from studies of bovine oviduct epithelial cells. In all of these studies, cDNAs of differentially expressed genes were identified using a combination of subtracted cDNA libraries and cDNA array hybridization. Redundant cDNA clones were removed, resulting in 1440 cDNA fragments on the array, representing 950 different genes. Twenty radioactively (33P) labeled cDNA samples (n = 4 for each cycle stage) were hybridized with the BOE array. After normalization of raw data (using BioConductor open source software) and significance analysis (SAM, FDR 1%), 272 mRNAs were identified that showed alterations of their concentration during the estrous cycle. Expression data from cDNAs with significant changes during the estrous cycle were used for cluster analyses with MultiExperiment Viewer 4.0 (Saeed et al. 2003 Biotechniques 34, 374–378). The main clusters represented genes upregulated either during the estrus or during the diestrus phase. Quantitatively enriched Gene Ontology (GO) categories were identified to find relevant functional groups and prominent biological processes. At estrus, e.g., GO categories extracellular matrix, cytoskeleton organization, and growth factor activity indicate changes in the composition of the endometrium during the estrous cycle. At diestrus, only a few overrepresented GO categories were found, mostly related to immune response and metabolism. The genes of known function were further analyzed in the context of interaction and regulatory networks. One of a number of central factors was TGF-β, which controls the expression of 12 genes upregulated at estrus and 8 at diestrus. In conclusion, the present study extended the results of our previously conducted analysis of bovine endometrium between the estrus and diestrus stages (Bauersachs et al. 2005 J. Mol. Endocrinol. 32, 449–466), revealed distinct temporal expression profiles, and identified additional genes differentially expressed during the estrous cycle. This work was supported by Grant BMBF FUGATO-Fertilink.

Technical Note: Bovine Oviduct and Endometrium Array Version 1: A Tailored Tool for Studying Bovine Endometrium Biology and Pathophysiology

Fertility problems are the main reason for slaughter of high-performance milk cows, because elongated calving intervals result in financial losses for the farmer and retard genetic progress. Genetic improvement of fertility would be of great benefit, but functional traits for effective selection are missing. Recent advances in functional genomics tools like DNA microarrays could be the key to identify gene expression patterns in the endometrium that correlate with maternal fertility. Therefore, a first version of a bovine oviduct and endometrium cDNA array was established that contains a set of 1,440 cDNA clones and long oligonucleotides representing 950 different genes. The major part of these genes has been identified in a series of differential gene expression studies in endometrium (different stages of the estrous cycle, d 18 pregnant vs. nonpregnant) and in oviduct epithelial cells (different stages of the estrous cycle) using a combination of subtracted cDNA libraries and cDNA array hybridization. Furthermore, cDNA clones of genes, which showed no changes in their mRNA levels in the analyzed tissues, were added as controls. Reproducibility of the array hybridization, a comparison with the Affymetrix bovine genome array, and confirmation of differential gene expression with reverse transcription-quantitative PCR is shown. Potential future applications include systematic studies of interactions between metabolic status and functionality of the endometrium to identify genes that could be used for differential diagnosis of fertility problems. Further, endometrium transcriptome profiles may serve as novel traits to improve fertility by genetic selection.

172 DOES ESTRADIOL-17β CAUSE CYCLE-DEPENDENT MODULATIONS OF UTERINE MILK PROTEIN IN BOVINE ENDOMETRIUM?

Uterine secretion from the endometrial glandular epithelium provides optimal conditions for early embryonic development. The uterine milk protein (UTMP), a member of the serine proteinase inhibitor superfamily, has been demonstrated to be a major progesterone-induced glycoprotein secreted by the endometrium during pregnancy. Previous transcriptomic analysis revealed that UTMP was highly abundant at estrus in the bovine endometrium (Bauersachs et al. 2005 J. Mol. Endocrinol. 34, 889–908). Here we describe a detailed characterization of UTMP mRNA expression at several time points during the bovine estrous cycle and the pre-implantation period. Simmental heifers were monitored with respect to serum progesterone (P4) and estradiol-17β (E2), and slaughtered at estrus or 3.5, 12, 15, or 18 days after estrus, or at Day 15 or 18 of pregnancy (n = 4 per group). The uterus was divided into corpus and caudal, middle and cranial parts of the ipsilateral uterine horn for sampling of intercaruncular endometrium. In addition, effects of steroid hormones were investigated by stimulating an endometrial cell culture obtained from Day 8 animals (n = 4) with physiological doses of P4 or E2. In all cases, UTMP mRNA was quantified by real-time RT-PCR. Pronounced changes of UTMP mRNA abundance were detected during the estrous cycle. Expression was highest at estrus, followed by a remarkable decrease at Day 3.5. There was no difference between pregnant and non-pregnant animals at Day 15. Cycling animals displaying a high P4 and low E2 content (P4 > 2 ng mL-1 and E2 < 1 pg mL-1) revealed a lower expression of UTMP at Day 18 compared to the pregnant heifers, whereas animals at Day 18 progressing toward estrus (P4 < 1.5 ng mL-1 and E2 > 3 pg mL-1) exceeded the mRNA expression of the pregnant group. Following stimulation with estradiol-17β, the in vitro UTMP transcripts increased significantly. These results indicate that two different interfering stimulatory events might take place. While estradiol-17β appeared to increase UTMP mRNA expression at estrus, a second factor, most probably embryo-derived or embryo-induced, is assumed to be responsible for the UTMP rise during early pregnancy. The distinct gradient from the cranial uterine horn to the corpus at estrus was less pronounced at Day 3.5 and absent at Days 12, 15, and 18, pointing toward functional implications regarding the passing gametes, particularly sperm. An antibody raised against bovine UTMP will further validate the observed mRNA regulations on the protein level. In conclusion, bovine UTMP seems to play a decisive role for precise cyclic regulation of the bovine uterine milieu and during early embryo-maternal communication. This work was supported by the DFG FOR 478.

Region-specific expression of nitric oxide synthases in the bovine oviduct during the oestrous cycle and in vitro

Nitric oxide synthases (NOS) account for the endogenous production of nitric oxide (NO), a small and permeable bioreactive molecule. NO is known to act as a paracrine mediator during various processes associated with female reproduction. In the present study, the mRNA expression of the endothelial (eNOS) and inducible (iNOS) NO synthases were examined in bovine oviduct epithelial cells (BOEC) during the oestrous cycle. In addition, eNOS and iNOS mRNA and protein were localised by in situ hybridisation and immunocytochemistry respectively. Furthermore, the effects of exogenously applied oestradiol-17beta and progesterone on NOS mRNA regulation were studied in a suspension culture of BOEC. The eNOS mRNA abundance was low around ovulation (day 0) and increased significantly until pro-oestrus (day 18) in the ampulla. Immunoreactive protein of eNOS was detected predominantly in endothelial cells as well as in secretory oviduct epithelial cells at pro-oestrus. The iNOS mRNA concentration was significantly reduced in the isthmus at pro-oestrus (day 18) and oestrus (day 0) compared with persistently high levels in the ampulla. By in situ hybridisation, specific iNOS transcripts were additionally demonstrated in the oviduct epithelium. Immunoreactive iNOS protein was localised in secretory epithelial cells as well as in the lamina muscularis. The in vitro stimulation showed that both NOS were stimulated by progesterone, but not by oestradiol-17beta. The region-specific modulated expression of eNOS and iNOS provides evidence for an involvement of endogenously produced NO in the regulation of oviductal functions.

2 IDENTIFICATION OF GENES INDUCED BY THE CONCEPTUS IN THE BOVINE ENDOMETRIUM DURING THE PRE-IMPLANTATION PERIOD

Early embryonic development, implantation, and maintenance of a pregnancy are critically dependent on an intact embryo-maternal communication. So far, only few signals involved in this dialogue have been identified. In ruminants, interferon tau (IFN�) plays a key role in the process of maternal recognition of pregnancy by exhibiting antiluteolytic activity. Even though many experimental findings indicate a pivotal role of IFN� in the context of embryo-maternal communication in ruminants, a number of other systems may be involved. To identify genes induced in the bovine endometrium by the signaling of the embryo, a combination of subtracted cDNA libraries and cDNA array hybridization was applied. Monozygotic twin pairs (n = 5) were used as the biological model. Pregnancy was created in one twin by transferring two in vitro-produced embryos on Day 7 of the estrous cycle; the other twin received a sham embryo transfer. Pregnant and nonpregnant twins were slaughtered at Day 18; endometrial tissue samples were recovered and processed for transcriptome analysis as described (Bauersachs et al. 2005 J. Mol. Endocrinol. 34, 889-908). Screening of 4608 clones of two subtracted libraries revealed 90 different up-regulated genes and mRNAs, of which almost 50% are known to be stimulated by type I interferons. Among these interferon-stimulated genes, the ISG15 system is assumed to be of particular interest, and several components were studied in more detail using in situ hybridization. The pattern of mRNA expression suggests that modification of endometrial proteins through ISG15ylation plays a fundamental role during the pre-implantation period. A classification of the identified genes based on Gene Ontologies revealed the prevalence of genes involved in regulation of gene expression, cell communication, cell growth, cell differentiation, cell proliferation, and cell adhesion, and also the prevalence of genes with immune-related functions. These results underline the intense response of the endometrium to the presence of a conceptus, culminating in the preparation of the maternal environment for embryonic implantation. Further, for eleven selected genes the expression in the endometrium was quantified by the use of real-time RT-PCR. Overall, the results of quantitative RT-PCR and array hybridization correlated very well. To our knowledge this study provides the first holistic gene expression analysis of the bovine endometrium during the pre-implantation period. The results underline the importance of IFN� as an embryo-derived pregnancy recognition signal and depict the molecular mechanisms at the mRNA level underlying the intense embryo-maternal dialog taking place at Day 18 of gestation.

Gene expression profiling of bovine endometrium during the oestrous cycle: detection of molecular pathways involved in functional changes

The endometrium plays a central role among the reproductive tissues in the context of early embryo-maternal communication and pregnancy. It undergoes typical changes during the sexual/oestrous cycle, which are regulated by the ovarian hormones progesterone and oestrogen. To identify the underlying molecular mechanisms we have performed the first holistic screen of transcriptome changes in bovine intercaruncular endometrium at two stages of the cycle--end of day 0 (late oestrus, low progesterone) and day 12 (dioestrus, high progesterone). A combination of subtracted cDNA libraries and cDNA array hybridisation revealed 133 genes showing at least a 2-fold change of their mRNA abundance, 65 with higher levels at oestrus and 68 at dioestrus. Interestingly, genes were identified which showed differential expression between different uterine sections as well. The most prominent example was the UTMP (uterine milk protein) mRNA, which was markedly upregulated in the cranial part of the ipsilateral uterine horn at oestrus. A Gene Ontology classification of the genes with known function characterised the oestrus time by elevated expression of genes, for example related to cell adhesion, cell motility and extracellular matrix and the dioestrus time by higher expression of mRNAs encoding for a variety of enzymes and transport proteins, in particular ion channels. Searching in pathway databases and literature data-mining revealed physiological processes and signalling cascades, e.g. the transforming growth factor-beta signalling pathway and retinoic acid signalling, which are potentially involved in the regulation of changes of the endometrium during the oestrous cycle.

Functional genomics: tools for improving farm animal health and welfare

The first genome sequence assemblies of farm animal species are now accessible through public domain databases, and further sequencing projects are in rapid progress. In addition, large collections of expressed sequences have been obtained, which will aid in constructing annotated transcript maps for many economically important species. Thus, the breeding of farm animals is entering the post-genome era. Functional genomics, defined as applying global experimental approaches to assess gene function, by using the information and reagents provided by structural genomics (i.e. mapping and sequencing), has become the focus of interest. Combining a holistic view of phenotypes at the molecular level with genetic marker data seems a particularly promising approach for improving health and welfare traits in farm animals. These traits are often difficult to define. They suffer from low heritabilities and a corresponding lack of genetic gain in conventional selection and breeding programmes. At the same time, genomic information from micro-organisms and parasites offers the potential for new vaccines and therapeutics. This review describes major functional genomics tools, lists genomic resources available for farm animals and discusses the prospects and challenges of functional genomics in improving the health and welfare of farm animals.

231 TEMPORAL AND SPATIAL GENE EXPRESSION ANALYSIS OF THE BOVINE OVIDUCT EPITHELIUM

The fallopian tube plays a central role in reproduction, providing the appropriate environmental conditions for oocyte maturation as well as for sperm capacitation. Furthermore, fertilization and the first cleavage stages of embryonic development take place in the oviduct. At the molecular level, only fragmentary data are available regarding the physiological changes in the oviduct epithelium during the estrous cycle. Therefore, we performed a systematic study of gene expression changes in bovine ipsilateral oviduct epithelial cells derived from either the ampulla or the isthmus part of the oviduct at four different time points of the estrous cycle. A cDNA array consisting of approximately 400 candidate genes, primarily identified in different studies in the context of gene expression regulation in the oviduct, was designed and hybridized with 33P-labeled cDNA probes prepared from 28 different tissue samples. These tissue samples were collected from cyclic Simmental heifers at Day 0 (n = 3), Day 3.5 (n = 3), Day 12 (n = 4) and Day 18 (n = 4) of the estrous cycle. Ipsilateral epithelial cells were separately collected from ampulla and isthmus. After array evaluation (AIDA Image Analyzer, version 3.41, Raytest, Straubenhardt, Germany), the raw data were normalized to internal reference cDNAs on the arrays. Statistical analysis was done using ANOVA and the Tukey post-hoc test (GeneSpring® version 6.1, Silicon Genetics, Redwood City, CA, USA). For selected genes, differential expression was verified by real-time RT-PCR. A simplified Gene Ontology was built for the genes present on the array and a pathway analysis was performed to elucidate gene networks involved in the regulation of oviduct epithelial cell function. The expression patterns of two functional groups of genes are presented here: genes that are related to immune functions and genes of the secretory pathway or encoding secreted proteins. Messenger-RNA levels of immune-related genes were higher in epithelial cells of the ampulla compared to the isthmus part of the oviduct. This implies that certain immune functions may be differentially regulated in ampulla and isthmus. Furthermore, mRNAs of genes of the secretory pathway showed highest levels mainly in the ampulla around time of estrus, which may be explained with the increase of the secretory activity in the epithelium of the ampulla beginning at pre-estrus. In general, this study shows the importance of a separate analysis of the oviduct compartments and the influence of the estrous cycle on the expression level of a variety of genes. In the context of fertilization and early embryo-maternal communication, these results could provide an insight into the physiological changes during the estrous cycle, which are the bases for these processes. This work was supported by the Deutsche Forschungsgemeinschaft (Research Unit “Mechanisms of Embryo-Maternal Communication”; FOR 478/1).

211 TEMPORAL AND SPATIAL EXPRESSION PROFILE OF THE UTERINE MILK PROTEIN — A MEMBER OF THE SERINE PROTEASE INHIBITOR SUPERFAMILY — IN THE BOVINE ENDOMETRIUM

A combination of subtracted cDNA libraries and cDNA array hybridization was applied to identify differentially expressed genes in the bovine intercaruncular endometrium at estrus and diestrus. Six cyclic Simmental heifers were cycle-synchronized and slaughtered the morning after standing heat occurred (n = 3) or 12 days after estrus (n = 3), respectively. The uterus was divided into seven sections: corpus, plus the caudal, middle, and cranial parts of both uterine horns. Samples were collected from the epithelial layer of the lamina propria of the intercaruncular endometrium. Two subtracted libraries were prepared and analyzed by array hybridization with probes produced from the 42 tissue samples. More than 130 differentially expressed genes were identified. Among these genes, the mRNA for the uterine milk protein (UTMP) showed a much higher expression level at estrus versus diestrus. Furthermore, the expression level differed markedly between the uterus sections. Statistical significance was tested using ANOVA and Student Newman Keuls post-hoc test (GeneSpring® version 6.1, Silicon Genetics, Redwood City, CA, USA). There was a pronounced expression gradient from both cranial uterine horns (highest) to the corpus (lowest) at estrus. UTMP mRNA level was highest in the ipsilateral cranial horn. A more accurate quantification was done by quantitative real-time RT-PCR using the same RNA samples as for array hybridization and, in addition, samples from further time points of the estrous cycle and early pregnancy. The results obtained by array hybridization were clearly confirmed. UTMPs, also known as uterine serpins (US), were previously shown to be the major products secreted by the uteri of cattle, sheep, and pigs during pregnancy. The US are glycoproteins belonging to the serpin (serine proteinase inhibitor) superfamily of proteins. However, no inhibitory activity to any serine proteinase has been found. The ovine uterine serpin (OvUS) has been shown to inhibit a wide variety of immune responses, including mixed lymphocyte reaction, T cell-dependent antibody production, and NK (natural killer)-like activity, indicating a major role in protecting the conceptus from maternal immune reactions. The four members of the US family form a clade distinct from other serpins, which have probably adopted important biological functions in the reproductive biology of Artiodactyla. Therefore, the identified expression gradient of the UTMP mRNA at estrus may be of particular importance, e.g. for sperm selection, and deserves further investigation at the protein level and in functional studies. This work was supported by the Deutsche Forschungsgemeinschaft (Research Unit “Mechanisms of Embryo-Maternal Communication”; FOR 478/1).

106 GENOMIC IMPRINTING OF IGF2R IN TISSUES OF BOVINE FETUSES GENERATED BY ARTIFICIAL INSEMINATION OR IN VITRO FERTILIZATION

The insulin-like growth factor 2 receptor gene (IGF2R) is involved in fetal growth regulation. A study in sheep associated fetal overgrowth after in vitro embryo culture with abnormal DNA methylation and expression of IGF2R (Young et al. 2001 Nat. Genet. 27, 153–154). This suggested that abnormal IGF2R imprinting is a major cause of fetal overgrowth. To test this hypothesis in bovine fetuses, we developed a microsatellite marker for IGF2R from cDNA sequence data and screened 45 Day-80 fetuses generated in vivo, by artificial insemination (AI), or in vitro, by in vitro fertilization (IVF) procedures, for parent-of-origin-specific gene expression. A total of 17 fetuses were heterozygous, but available parental DNA samples showed that only 12 (8 AI, 4 IVF) allowed unambiguous discrimination of parental alleles. Parent-of-origin-specific allelic expression patterns indicated that bovine IGF2R was expressed predominantly from the maternal allele and thus imprinted in fetal heart, kidney, liver, lung, muscle, and cotyledon tissue. However, the relative amount of expression from the paternal allele was tissue-specific and ranged from 6.4 ± 0.8% in skeletal muscle up to 27.4 ± 0.9% in cotyledon (SPSS or 11.5, ANOVA, P < 0.001). Tissues that originated from the same germ layer showed similar allelic expression ratios whereas significantly different expression ratios (P < 0.05) were observed between tissues originating from different germ layers. Contrary to expectations from sheep data, there was no evidence for gross abnormalities in IGF2R imprinting in tissues from overgrown (n = 2) or normal sized (n = 2) IVF fetuses. However, relative paternal expression levels in several tissues showed significant relationships (P < 0.05–0.001) with growth parameters and pointed to subtle changes in paternal IGF2R expression in overgrown IVF fetuses. We thank W. Scholz and M. Weppert for excellent technical assistance.

Monitoring gene expression changes in bovine oviduct epithelial cells during the oestrous cycle

The oviduct epithelium undergoes marked morphological and functional changes during the oestrous cycle. To study these changes at the level of the transcriptome we did a systematic gene expression analysis of bovine oviduct epithelial cells at oestrus and dioestrus using a combination of subtracted cDNA libraries and cDNA array hybridisation. A total of 3072 cDNA clones of two subtracted libraries were analysed by array hybridisation with cDNA probes derived from six cyclic heifers, three of them slaughtered at oestrus and three at dioestrus. Sequencing of cDNAs showing significant differences in their expression levels revealed 77 different cDNAs. Thirty-seven were expressed at a higher level at oestrus, for the other 40 genes expression levels were higher at dioestrus. The identified genes represented a variety of functional classes. During oestrus especially genes involved in the regulation of protein secretion and protein modification, and mRNAs of secreted proteins, were up-regulated, whereas during dioestrus particularly transcripts of genes involved in transcription regulation showed a slight up-regulation. The concentrations of seven selected transcripts were quantified by real-time RT-PCR to validate the cDNA array hybridisation data. For all seven transcripts, RT-PCR results were in excellent correlation (r>0.92) with the results obtained by array hybridisation. Our study is the first to analyse changes in gene expression profiles of bovine oviduct epithelial cells during different stages of the oestrous cycle, providing a starting point for the clarification of the key transcriptome changes in these cells.

230TRANSCRIPTOMICS ANALYSIS OF CHANGES IN GENE EXPRESSION IN BOVINE OVIDUCT EPITHELIAL CELLS DURING THE ESTROUS CYCLE

The oviduct epithelium undergoes marked morphological and functional changes during the estrous cycle. It has been shown that a dramatic change in the frequencies of ciliated and non-ciliated cells occurs during the estrous cycle. At estrus the epithelium consists of secretory and ciliated cells and at diestrus mainly of ciliated cells. The oviduct provides the microenvironment for sperm capacitation, fertilization, and early cleavage-stage embryonic development. At the molecular level, only a few genes or proteins are known that change during the estrous cycle and which may be important for fertility, so as the bovine oviduct-specific glycoprotein, the major secretory protein in the oviduct. Therefore, we studied systematically the changes in gene expression in bovine ipsilateral oviduct epithelial cells at estrus and diestrus. To identify differentially expressed genes, a combination of subtracted cDNA libraries and cDNA array hybridization was used. Two subtracted libraries were produced to enrich cDNAs of upregulated genes at estrus and at diestrus. A total of 1536 cDNA clones of each library were analyzed with radioactively (33-P) labeled probes generated from the oviduct epithelial cells of six Simmental heifers, three of them slaughtered at Day 0 (estrus) and three at Day 12 after standing heat (diestrus). After normalization of the raw data and statistical analysis, all cDNAs showing significant differences in their expression levels at estrus compared to diestrus were sequenced. Sequencing revealed 84 different cDNAs;; 42 of them matched bovine genes or their human/mouse homologs with known functions, and 42 matched genes without a known function. Half of the genes (n=42) were expressed at a higher level at estrus;; for the other (n=42) expression levels were higher at diestrus. The regulated genes or their products represented a variety of functional classes, such as genes of the secretory pathway, genes involved in transcription regulation, cell-surface proteins, cell–cell interaction proteins, secreted proteins, members of signal transduction pathways, immune-related proteins, and some enzymes. The identification of genes differentially regulated in ipsilateral oviduct epithelial cells at estrus v. diestrus is the first step of a systematic analysis of differential gene expression during the estrous cycle. Further studies will follow, focusing on different compartments of the bovine oviduct and additional times of the estrous cycle.

Embryo-maternal communication in bovine - strategies for deciphering a complex cross-talk

Early embryonic development, implantation and maintenance of a pregnancy are critically dependent on an intact embryo-maternal communication. So far, only few signals involved in this dialogue have been identified. In bovine and other ruminants, interferon tau is the predominant embryonic pregnancy recognition signal, exhibiting antiluteolytic activity. However, this is just one aspect of the complex process of embryo-maternal signalling, and a number of other systems are more likely to be involved. To gain a more comprehensive understanding of these important mechanisms, integrated projects involving specialists in embryology, reproductive biotechnology and functional genome research are necessary to perform a systematic analysis of interactions between pre-implantation stage embryos and oviduct or uterine epithelial cells, respectively. State-of-the-art transcriptomic and proteomic technologies will identify reciprocal signals between embryos and their maternal environment and the respective downstream reaction cascades. For in vivo studies, the use of monozygotic twins as recipient animals provides elegant model systems, thus eliminating genetic variability as a cause of differential gene expression. In addition, suitable systems for the co-culture of oviduct epithelial or endometrium cells with the respective embryonic stages need to be established for functional validation of candidate genes potentially involved in the dialogue between embryos and their maternal environment. The knowledge of these mechanisms should help to increase the pregnancy rate following embryo transfer and to avoid embryonic losses. Candidate genes involved in embryo-maternal communication will also be used to define new quality criteria for the selection of embryos for transfer to recipients. Another application is the supplementation of embryotrophic factors or components of embryo-maternal signalling in optimized formulations, such as bioartificial matrices. As a long-term goal, signalling mechanisms identified in bovine will also be functionally evaluated in other species, including the human.

Toward a catalog of human genes and proteins: sequencing and analysis of 500 novel complete protein coding human cDNAs

With the complete human genomic sequence being unraveled, the focus will shift to gene identification and to the functional analysis of gene products. The generation of a set of cDNAs, both sequences and physical clones, which contains the complete and noninterrupted protein coding regions of all human genes will provide the indispensable tools for the systematic and comprehensive analysis of protein function to eventually understand the molecular basis of man. Here we report the sequencing and analysis of 500 novel human cDNAs containing the complete protein coding frame. Assignment to functional categories was possible for 52% (259) of the encoded proteins, the remaining fraction having no similarities with known proteins. By aligning the cDNA sequences with the sequences of the finished chromosomes 21 and 22 we identified a number of genes that either had been completely missed in the analysis of the genomic sequences or had been wrongly predicted. Three of these genes appear to be present in several copies. We conclude that full-length cDNA sequencing continues to be crucial also for the accurate identification of genes. The set of 500 novel cDNAs, and another 1000 full-coding cDNAs of known transcripts we have identified, adds up to cDNA representations covering 2%--5 % of all human genes. We thus substantially contribute to the generation of a gene catalog, consisting of both full-coding cDNA sequences and clones, which should be made freely available and will become an invaluable tool for detailed functional studies.

Toward a catalog of human genes and proteins: sequencing and analysis of 500 novel complete protein coding human cDNAs

With the complete human genomic sequence being unraveled, the focus will shift to gene identification and to the functional analysis of gene products. The generation of a set of cDNAs, both sequences and physical clones, which contains the complete and noninterrupted protein coding regions of all human genes will provide the indispensable tools for the systematic and comprehensive analysis of protein function to eventually understand the molecular basis of man. Here we report the sequencing and analysis of 500 novel human cDNAs containing the complete protein coding frame. Assignment to functional categories was possible for 52% (259) of the encoded proteins, the remaining fraction having no similarities with known proteins. By aligning the cDNA sequences with the sequences of the finished chromosomes 21 and 22 we identified a number of genes that either had been completely missed in the analysis of the genomic sequences or had been wrongly predicted. Three of these genes appear to be present in several copies. We conclude that full-length cDNA sequencing continues to be crucial also for the accurate identification of genes. The set of 500 novel cDNAs, and another 1000 full-coding cDNAs of known transcripts we have identified, adds up to cDNA representations covering 2%--5 % of all human genes. We thus substantially contribute to the generation of a gene catalog, consisting of both full-coding cDNA sequences and clones, which should be made freely available and will become an invaluable tool for detailed functional studies.

A hybrid outer membrane protein antigen for vaccination against Pseudomonas aeruginosa

Recently a hybrid protein containing parts of the outer membrane proteins OprF (aa 190-342) and OprI (aa 21-83) from Pseudomonas aeruginosa fused to the glutathione-S-transferase was shown to protect mice against a 975-fold 50% lethal dose of P. aeruginosa. To omit the use of the GST-protein, the hybrid protein OprF-OprI was expressed in E. coli using distinct modifications which have not to be eliminated after its expression. Using different signal peptides, the yield of the hybrid protein OprF-OprI in E. coli could be increased to 30% of the total cell protein, however, only a very small amount of the hybrid preprotein was processed and could be isolated from the periplasm of the host. A construct containing an N-terminal extension of 11 amino acids from the original OprF gene gave rise to a significantly higher expression in the cytoplasm. Purification was facilitated by the addition of a five histidine tag at the C-terminus. An even higher expression was obtained by a construct in which a six histidine tag was attached to the N-terminus of the hybrid protein. The N-terminal extended OprF-OprI as well as the N-terminal his-tagged OprF-OprI hybrid antigens were purified by immobilized-metal affinity chromatography under native and denaturing conditions and can now be tested for protectivity against P. aeruginosa in animal model systems.

Effects of different levels of dietary selenium and vitamin E on the humoral immunity of rats

The aim of the present study was to investigate whether the level of selenium and selenium/vitamin E supply influences the humoral immunity of rats. In order to detect the effect of Se supply and age, 36 weaned Sprague-Dawley rats divided into two equal groups were killed after 22 or 45 experimental days by decapitation (Exp. I). In Exp. II 9 groups of 10 rats each were exposed to each combination of deficient, normal or excessive selenium with a vitamin E supply and killed after 44 days. The basic (deficiency) diet which was the same in both experiments contained 0.04mg Se and 8mg vitamin E per kg dry matter. The supplementation per kg diet was 0 or 0.2mg Se and 30mg vitamin E in Exp. I and 0, 0.2 or 1mg Se and 0, 30 or 200mg vitamin E in Exp. II. The concentration of selenium in serum, liver and spleen samples and the activity of glutathione peroxidase, which were determined to define the selenium status of the animals, corresponded well to the required supply situation. The immunoglobulins of type IgA, IgM and IgG with the subtypes IgG1, IgG2a, IgG2b and IgG2c were measured by immunoelectrophoresis. In both experiments selenium deficiency decreased the values of the IgG groups only nominally, IgA was not changed. IgM was significantly reduced, especially with prolonged selenium deficiency and simultaneous vitamin E deficiency. An excessive selenium supply compensated to a great extent for the effects of vitamin E deficiency on IgG and IgA.