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<pubmed limit=5>Bovine Embryology</pubmed>
<pubmed limit=5>Bovine Development</pubmed>
PLoS One. 2018 Nov 19;13(11):e0207682. doi: 10.1371/journal.pone.0207682. eCollection 2018. Fetal age assessment for Holstein cattle.
Krog CH1,2, Agerholm JS2, Nielsen SS1. Author information Abstract Although transport and slaughter of cattle during the last 10% of the gestation period is prohibited in the European Union, such cattle are sometimes sent for slaughter. The late term pregnancy is usually not recognized by the authorities until the uterus is inspected after slaughter and a near term fetus is observed. Accurate post mortem determination of age of bovine fetuses is therefore of major importance as evidence for the subsequent prosecution of the owner. Fetometric measurements such as crown-rump length (CRL) have been used, but these existing estimators have often been established based on insufficiently described study populations or phenotypes that may have changed in the past decades. Morphological characteristics are also used, but few data are available on the correlation between fetal age and the development of these characteristics. The objectives of this study were to investigate the correlation between fetal age and morphological features of bovine Holstein fetuses and to evaluate the use of these features alone and in combination with fetometric measurements to predict fetal age. We collected fetuses from 274 pregnant Holstein cows with recorded insemination dates slaughtered at a Danish abattoir. Gender, teeth development, occurrence of pigmentation, coat, tactile hair and other morphological features were recorded along with CRL, head width, head length and body weight (BW). The gestational length was calculated based on recorded insemination and slaughter dates, and coefficients of variation (R2) were determined for all recorded variables. Notably, the highest R2 was recorded for head length (0.985) followed by CRL (0.979) and head width (0.974). The categorical (morphological) variables were less informative. When used in multivariable models, they did offer statistically significance, but for practical purposes, limited additional information. A multivariable model including the fetometric variables head length and width in combination with CRL resulted in R2 = 0.99 with predictions that were roughly within +/- 11-12 days in 95% of cases. We conclude that the model based on the fetometric variables only provided the most precise predictions, while combination with morphological features such as eruption of teeth, pigmentation and coat mostly increased the width of the prediction intervals. PMID: 30452469 DOI: 10.1371/journal.pone.0207682
Role of ROCK Signaling in Formation of the Trophectoderm of the Bovine Preimplantation Embryo
Mol Reprod Dev. 2018 Mar 15. doi: 10.1002/mrd.22976.
Negrón-Pérez VM1, Rodrigues LT2, Mingoti GZ2, Hansen PJ1.
Rho-associated coiled-coil containing protein kinases (ROCK1 and ROCK2) are activated by binding to RHO GTPases and phosphorylate a variety of downstream targets including actinomyosin. In the mouse embryo, ROCK signaling acts to promote formation of trophectoderm (TE) and inhibit formation of the inner cell mass (ICM) by polarizing outer cells of the embryo to inactivate Hippo signaling (Kono et al., 2014; Mihajlović and Bruce, 2016). This article is protected by copyright. All rights reserved. KEYWORDS: trophectoderm, ROCK, bovine, blastocyst
PMID: 29542836 DOI: 10.1002/mrd.22976
Sexually Dimorphic Gene Expression in Bovine Conceptuses at the Initiation of Implantation
Biol Reprod. 2016 Aug 3. pii: biolreprod.116.139857. [Epub ahead of print]
Forde N, Maillo V, Ó Gaora P, Simintiras CA, Sturmey RG, Ealy AD, Spencer TE, Gutierrez-Adan A, Rizos D, Lonergan P.
In cattle, maternal recognition of pregnancy occurs on Day 16 via secretion of interferon tau (IFNT) by the conceptus. The endometrium can distinguish between embryos with different developmental competencies. In eutherian mammals, X-chromosome inactivation (XCI) is required to ensure an equal transcriptional level of most X-linked genes for both male and female embryos in adult tissues, but this process is markedly different in cattle than mice. We examined how sexual dimorphism affected conceptus transcript abundance and amino acid composition as well as the endometrial transcriptome during the peri-implantation period of pregnancy. Of the 5132 genes that were differentially expressed on Day 19 in male compared to female conceptuses, 2.7% were located on the X-chromosome. Concentrations of specific amino acids were higher in the uterine luminal fluid with male compared to female conceptuses, while female conceptuses had higher transcript abundance of specific amino acid transporters (SLC6A19 and SLC1A35). Of note, the endometrial transcriptome was not different in cattle gestating a male or a female conceptus. These data support the hypothesis that, far from being a blastocyst specific phenomenon, XCI is incomplete before and during implantation in cattle. Despite differences in transcript abundance and amino acid utilization in male versus female conceptuses, the sex of the conceptus itself does not elicit a different transcriptomic response in the endometrium. Copyright 2016 by The Society for the Study of Reproduction. KEYWORDS: Amino acids; Endometrium; Gene expression; Uterine luminal fluid; XCI
Cell death is involved in sexual dimorphism during preimplantation development
Mech Dev. 2016 Jan 2. pii: S0925-4773(15)30038-1. doi: 10.1016/j.mod.2015.12.001. [Epub ahead of print]
Oliveira CS1, Saraiva NZ2, Lima MR3, Oliveira LZ4, Serapião RV5, Garcia JM3, Borges CA6, Camargo LS6.
In bovine preimplantation development, female embryos progress at lower rates and originate smaller blastocysts than male counterparts. Although sex-specific gene expression patterns are reported, when and how sex dimorphism is established is not clear. Differences among female and male early development can be useful for human assisted reproductive medicine, when X-linked disorders risk is detected, and for genetic breeding programs, especially in dairy cattle, which requires female animals for milk production. The aim of this study was to characterize the development of female and male embryos, attempting to identify sex effects during preimplantation development and the role of cell death in this process. Using sex-sorted semen from three different bulls for fertilization, we compared kinetics of bovine sex-specific embryos in six time points, and cell death was assessed in viable embryos. For kinetics analysis, we detected an increased population of female embryos arrested at 48 and 120h.p.i., suggesting this time points as delicate stages of development for female embryos that should be considered for testing improvement strategies for assisted reproductive technologies. Assessing viable embryos quality, we found 144h.p.i. is the first time point when viable embryos are phenotypically distinct: cell number is decreased, and apoptosis and cell fragmentation are increased in female embryos at this stage. These new results lead us to propose that sex dimorphism in viable embryos is established during morula-blastocyst transition, and cell death is involved in this process. Copyright © 2015. Published by Elsevier Ireland Ltd. KEYWORDS: apoptosis; caspase 3; female embryo; preimplantation development; sexual dimorphism
Remodeling of the Nuclear Envelope and Lamina during Bovine Preimplantation Development and Its Functional Implications
PLoS One. 2015 May 1;10(5):e0124619. doi: 10.1371/journal.pone.0124619. eCollection 2015.
Popken J1, Graf A2, Krebs S2, Blum H2, Schmid VJ3, Strauss A4, Guengoer T5, Zakhartchenko V5, Wolf E6, Cremer T7.
The present study demonstrates a major remodeling of the nuclear envelope and its underlying lamina during bovine preimplantation development. Up to the onset of major embryonic genome activation (MGA) at the 8-cell stage nuclei showed a non-uniform distribution of nuclear pore complexes (NPCs). NPCs were exclusively present at sites where DNA contacted the nuclear lamina. Extended regions of the lamina, which were not contacted by DNA, lacked NPCs. In post-MGA nuclei the whole lamina was contacted rather uniformly by DNA. Accordingly, NPCs became uniformly distributed throughout the entire nuclear envelope. These findings shed new light on the conditions which control the integration of NPCs into the nuclear envelope. The switch from maternal to embryonic production of mRNAs was accompanied by multiple invaginations covered with NPCs, which may serve the increased demands of mRNA export and protein import. Other invaginations, as well as interior nuclear segments and vesicles without contact to the nuclear envelope, were exclusively positive for lamin B. Since the abundance of these invaginations and vesicles increased in concert with a massive nuclear volume reduction, we suggest that they reflect a mechanism for fitting the nuclear envelope and its lamina to a shrinking nuclear size during bovine preimplantation development. In addition, a deposit of extranuclear clusters of NUP153 (a marker for NPCs) without associated lamin B was frequently observed from the zygote stage up to MGA. Corresponding RNA-Seq data revealed deposits of spliced, maternally provided NUP153 mRNA and little unspliced, newly synthesized RNA prior to MGA, which increased strongly at the initiation of embryonic expression of NUP153 at MGA. PMID 25932910
Genome-Wide DNA Methylation Patterns of Bovine Blastocysts Developed In Vivo from Embryos Completed Different Stages of Development In Vitro
PLoS One. 2015 Nov 4;10(11):e0140467. doi: 10.1371/journal.pone.0140467. eCollection 2015.
Salilew-Wondim D1, Fournier E2, Hoelker M1, Saeed-Zidane M1, Tholen E1, Looft C1, Neuhoff C1, Besenfelder U3, Havlicek V3, Rings F1, Gagné D2, Sirard MA2, Robert C2, A Shojaei Saadi H2, Gad A4, Schellander K1, Tesfaye D1.
Early embryonic loss and altered gene expression in in vitro produced blastocysts are believed to be partly caused by aberrant DNA methylation. However, specific embryonic stage which is sensitive to in vitro culture conditions to alter the DNA methylation profile of the resulting blastocysts remained unclear. Therefore, the aim of this study was to investigate the stage specific effect of in vitro culture environment on the DNA methylation response of the resulting blastocysts. For this, embryos cultured in vitro until zygote (ZY), 4-cell (4C) or 16-cell (16C) were transferred to recipients and the blastocysts were recovery at day 7 of the estrous cycle. Another embryo group was cultured in vitro until blastocyst stage (IVP). Genome-wide DNA methylation profiles of ZY, 4C, 16C and IVP blastocyst groups were then determined with reference to blastocysts developed completely under in vivo condition (VO) using EmbryoGENE DNA Methylation Array. To assess the contribution of methylation changes on gene expression patterns, the DNA methylation data was superimposed to the transcriptome profile data. The degree of DNA methylation dysregulation in the promoter and/or gene body regions of the resulting blastocysts was correlated with successive stages of development the embryos advanced under in vitro culture before transfer to the in vivo condition. Genomic enrichment analysis revealed that in 4C and 16C blastocyst groups, hypermethylated loci were outpacing the hypomethylated ones in intronic, exonic, promoter and proximal promoter regions, whereas the reverse was observed in ZY blastocyst group. However, in the IVP group, as much hypermethylated as hypomethylated probes were detected in gene body and promoter regions. In addition, gene ontology analysis indicated that differentially methylated regions were found to affected several biological functions including ATP binding in the ZY group, programmed cell death in the 4C, glycolysis in 16C and genetic imprinting and chromosome segregation in IVP blastocyst groups. Furthermore, 1.6, 3.4, 3.9 and 9.4% of the differentially methylated regions that were overlapped to the transcriptome profile data were negatively correlated with the gene expression patterns in ZY, 4C, 16C and IVP blastocyst groups, respectively. Therefore, this finding indicated that suboptimal culture condition during preimplantation embryo development induced changes in the DNA methylation landscape of the resulting blastocysts in a stage dependent manner and the altered DNA methylation pattern was only partly explained the observed aberrant gene expression patterns of the blastocysts.
Influence of Sex on Basal and Dickkopf-1 Regulated Gene Expression in the Bovine Morula
PLoS One. 2015 Jul 21;10(7):e0133587. doi: 10.1371/journal.pone.0133587. eCollection 2015.
Denicol AC1, Leão BC2, Dobbs KB1, Mingoti GZ2, Hansen PJ1.
Sex affects function of the developing mammalian embryo as early as the preimplantation period. There were two goals of the current objective. The first was to determine the degree and nature of differences in gene expression between female and male embryos in the cow at the morula stage of development. The second objective was to determine whether DKK1, a molecule known to alter differentiation of the blastocyst, would affect gene expression differently for female and male morulae. In Experiment 1, female and male embryos were treated with DKK1 at Day 5 after insemination. Morulae were harvested 24 h after treatment, pooled in groups of 20 for microarray analysis and RNA subjected to analysis of gene expression by microarray hybridization. There were 662 differentially expressed genes between females and males and 128 of these genes had a fold change ≥ 1.5 between the two sexes. Of the genes upregulated in females, 49.5% were located in the X chromosome. Functional analysis predicted that cell survival was greater in female embryos. Experiment 2 involved a similar design except that transcripts for 12 genes previously reported to be affected by sex, DKK1 or the interaction were quantified by quantitative polymerase chain reaction. Expression of all genes tested that were affected by sex in experiment 1 was affected in a similar manner in Experiment 2. In contrast, effects of DKK1 on gene expression were largely not repeatable in Experiment 2. The exception was for the Hippo signaling gene AMOT, which was inhibited by DKK1. In Experiment 3, embryos produced by fertilization with unsorted sperm were treated with DKK1 at Day 5 and abundance of transcripts for CDX2, GATA6, and NANOG determined at Days 5, 6 and 7 after insemination. There was no effect of DKK1 on expression of any of the three genes. In conclusion, female and male bovine embryos have a different pattern of gene expression as early as the morula stage, and this is due to a large extent to expression of genes in the X chromosomes in females. Differential gene expression between female and male embryos is likely the basis for increased resistance to cell death signals in female embryos and disparity in responses of female and male embryos to changes in the maternal environment.
Morphological and Gene Expression Changes in Cattle Embryos from Hatched Blastocyst to Early Gastrulation Stages after Transfer of In Vitro Produced Embryos
PLoS One. 2015 Jun 15;10(6):e0129787. doi: 10.1371/journal.pone.0129787. eCollection 2015.
van Leeuwen J1, Berg DK2, Pfeffer PL3.
A detailed morphological staging system for cattle embryos at stages following blastocyst hatching and preceding gastrulation is presented here together with spatiotemporal mapping of gene expression for BMP4, BRACHYURY, CERBERUS1 (CER1), CRIPTO, EOMESODERMIN, FURIN and NODAL. Five stages are defined based on distinct developmental events. The first of these is the differentiation of the visceral hypoblast underlying the epiblast, from the parietal hypoblast underlying the mural trophoblast. The second concerns the formation of an asymmetrically positioned, morphologically recognisable region within the visceral hypoblast that is marked by the presence of CER1 and absence of BMP4 expression. We have termed this the anterior visceral hypoblast or AVH. Intra-epiblast cavity formation and the disappearance of the polar trophoblast overlying the epiblast (Rauber's layer) have been mapped in relation to AVH formation. The third chronological event involves the transition of the epiblast into the embryonic ectoderm with concomitant onset of posterior NODAL, EOMES and BRACHYURY expression. Lastly, gastrulation commences as the posterior medial embryonic ectoderm layer thickens to form the primitive streak and cells ingress between the embryonic ectoderm and hypoblast. At this stage a novel domain of CER1 expression is seen whereas the AVH disappears. Comparison with the mouse reveals that while gene expression patterns at the onset of gastrulation are well conserved, asymmetry establishment, which relies on extraembryonic tissues such as the hypoblast and trophoblast, has diverged in terms of both gene expression and morphology.
The Transcriptome Signature of the Receptive Bovine Uterus Determined at Early Gestation
Changes in sub-cellular localisation of trophoblast and inner cell mass specific transcription factors during bovine preimplantation development
BMC Dev Biol. 2013 Aug 13;13:32. doi: 10.1186/1471-213X-13-32.
Madeja ZE, Sosnowski J, Hryniewicz K, Warzych E, Pawlak P, Rozwadowska N, Plusa B, Lechniak D. Source Department of Genetics and Animal Breeding, Poznan University of Life Sciences, Wolynska 33, Poznan 60-673, Poland. firstname.lastname@example.org
BACKGROUND: Preimplantation bovine development is emerging as an attractive experimental model, yet little is known about the mechanisms underlying trophoblast (TE)/inner cell mass (ICM) segregation in cattle. To gain an insight into these processes we have studied protein and mRNA distribution during the crucial stages of bovine development. Protein distribution of lineage specific markers OCT4, NANOG, CDX2 were analysed in 5-cell, 8-16 cell, morula and blastocyst stage embryos. ICM/TE mRNA levels were compared in hatched blastocysts and included: OCT4, NANOG, FN-1, KLF4, c-MYC, REX1, CDX2, KRT-18 and GATA6. RESULTS: At the mRNA level the observed distribution patterns agree with the mouse model. CDX2 and OCT4 proteins were first detected in 5-cell stage embryos. NANOG appeared at the morula stage and was located in the cytoplasm forming characteristic rings around the nuclei. Changes in sub-cellular localisation of OCT4, NANOG and CDX2 were noted from the 8-16 cell onwards. CDX2 initially co-localised with OCT4, but at the blastocyst stage a clear lineage segregation could be observed. Interestingly, we have observed in a small proportion of embryos (2%) that CDX2 immunolabelling overlapped with mitotic chromosomes. CONCLUSIONS: Cell fate specification in cattle become evident earlier than presently anticipated - around the time of bovine embryonic genome activation. There is an intriguing possibility that for proper lineage determination certain transcription factors (such as CDX2) may need to occupy specific regions of chromatin prior to its activation in the interphase nucleus. Our observation suggests a possible role of CDX2 in the process of epigenetic regulation of embryonic cell fate. PMID 23941255
Mutations in genes involved in oestrous cycle associated expression of oestrus
Anim Reprod Sci. 2013 Oct 2. pii: S0378-4320(13)00282-0. doi: 10.1016/j.anireprosci.2013.09.018. [Epub ahead of print]
Homer EM, Derecka K, Webb R, Garnsworthy PC. Source University of Nottingham, School of Biosciences, Sutton Bonington Campus, Loughborough LE12 5RD, UK.
Detection of oestrus is a key determinant of profitability of dairy herds, but oestrus is increasingly difficult to observe in the modern dairy cow, with shorter duration and less intense oestrus. Concurrent with the unfavourable correlation between milk yield and fertility, oestrous detection rates have decreased to less than 50%. A number of mutations have been identified in genes associated with fertility and production traits, but, to date, no single nucleotide polymorphism (SNP) has been associated with oestrous expression. Therefore, the objective of this study was to investigate SNPs, linked to fertility, for the association with oestrous expression. Blood was collected from 205 Holstein Friesian dairy cows and genotyped at 41 loci of 18 genes chosen for their roles in the oestrous cycle and milk production. SNPs were then examined for correlations with increase in activity at oestrus, recorded via activity monitors, using generalised linear models. Physical activity increased at oestrus between two and four fold. Larger increases were associated with mutant alleles in oestrogen receptor-α and gonadotrophin releasing hormone receptor genes (P<0.05) and in the STAT5A gene (P<0.05). Smaller increases were associated with mutant alleles of the activin receptor type IIB and prolactin receptor genes (P<0.10). In conclusion, alleles in these five genes provide the opportunity for selection of animals displaying greater oestrous activity which could aid reversal of the decrease in oestrous detection and thereby contribute to sustainability of the dairy industry worldwide. Copyright © 2013 The Authors. Published by Elsevier B.V. All rights reserved. KEYWORDS: Dairy cow, Oestrus, Polymorphism, SNP
Effects of long-term in vitro culturing of transgenic bovine donor fibroblasts on cell viability and in vitro developmental potential after nuclear transfer
In Vitro Cell Dev Biol Anim. 2013 Mar 22. [Epub ahead of print]
Bressan FF, Miranda MS, Bajgelman MC, Perecin F, Mesquita LG, Fantinato-Neto P, Merighe GF, Strauss BE, Meirelles FV. Source Department of Veterinary Medicine, Faculty of Animal Sciences and Food Engeneering, University of São Paulo, São Paulo, Brazil, email@example.com.
Genetically modified animals have numerous applications, ranging from basic research to livestock production and agriculture. Recent progress in animal cloning by nuclear transfer has made possible the production of transgenic animals using previously genetically modified cell lineages. However, to produce such lineages, an additional time for in vitro culturing and great manipulation is needed. Herein, we aimed to characterize different aspects of genetically modified cells compared to control cells, and we also analyzed the development rate of embryos produced by nuclear transfer by using them as nuclei donors after short or long periods of in vitro culturing (early versus late passages). We hypothesized that the genetic material inserted in the genome of these cells, associated with the prolonged time in culture, ultimately alters cell growth physiology and cell viability, which leads to impaired nuclei reprogramming potential and consequent reduction in the production of cloned blastocysts. Fetal fibroblasts expressing the enhanced Green Fluorescent Protein gene (eGFP) cultured for different periods in vitro were analyzed with respect to chromosomal numeric abnormalities, nuclear DNA fragmentation, the ratio of BAX and BCL2 gene transcripts, and the intensity of mitochondrial membrane potential, and they were then used as nuclei donors for somatic cell nuclear transfer (SCNT). Early passages were defined as fewer than 11 passages, and late passages were 18th passage (18thp) to 21stp. No differences were observed in the percentage of cells with chromosomal abnormalities or in the mitochondrial membrane potential analysis. eGFP cells in late passages and control cells in early passages were not different regarding DNA fragmentation; however, control cells in late passages presented higher fragmentation (P < 0.05). The Bax and Bcl2 gene expression ratio in control and transgenic cells presented different patterns regarding cell conditions during culture. For SCNT experiments, no difference was observed between groups reconstructed with early or late-passage cells when fusion (63.1% and 49%), cleavage (67.7% and 69.9%), eight-cell embryo (36.4% and 44.4%) and blastocyst (21.6% and 20.8%) rates were compared. In conclusion, culture behavior was different between control and eGFP cells. However, when different in vitro culturing periods were compared, long-term cultured transgenic fetal fibroblasts remained competent for blastocyst production when used as nuclei donors in the nuclear transfer technique, a feature needed for the genetic manipulation of cell culture experiments aiming for transgenic animal production.
Global gene expression of the inner cell mass and trophectoderm of the bovine blastocyst
BMC Dev Biol. 2012 Nov 6;12:33. doi: 10.1186/1471-213X-12-33.
Ozawa M, Sakatani M, Yao J, Shanker S, Yu F, Yamashita R, Wakabayashi S, Nakai K, Dobbs KB, Sudano MJ, Farmerie WG, Hansen PJ. Source Department of Animal Sciences and D,H, Barron Reproductive and Perinatal Biology Research Program, PO Box 110910, Gainesville, FL, 32611-0910, USA. Hansen@animal.ufl.edu. Abstract ABSTRACT: BACKGROUND: The first distinct differentiation event in mammals occurs at the blastocyst stage when totipotent blastomeres differentiate into either pluripotent inner cell mass (ICM) or multipotent trophectoderm (TE). Here we determined, for the first time, global gene expression patterns in the ICM and TE isolated from bovine blastocysts. The ICM and TE were isolated from blastocysts harvested at day 8 after insemination by magnetic activated cell sorting, and cDNA sequenced using the SOLiD 4.0 system. RESULTS: A total of 870 genes were differentially expressed between ICM and TE. Several genes characteristic of ICM (for example, NANOG, SOX2, and STAT3) and TE (ELF5, GATA3, and KRT18) in mouse and human showed similar patterns in bovine. Other genes, however, showed differences in expression between ICM and TE that deviates from the expected based on mouse and human. CONCLUSION: Analysis of gene expression indicated that differentiation of blastomeres of the morula-stage embryo into the ICM and TE of the blastocyst is accompanied by differences between the two cell lineages in expression of genes controlling metabolic processes, endocytosis, hatching from the zona pellucida, paracrine and endocrine signaling with the mother, and genes supporting the changes in cellular architecture, stemness, and hematopoiesis necessary for development of the trophoblast.
- "In conclusion, differentiation of blastomeres of the morula-stage embryo into the ICM and TE of the blastocyst is accompanied by differences between the two cell lineages in expression of genes controlling metabolic processes, endocytosis, hatching from the zona pellucida, paracrine and endocrine signaling with the mother, and genes supporting the changes in cellular architecture, stemness, and hematopoiesis necessary for development of the trophoblast. Much of the process leading to this first differentiation event seems to be under the control of genes such as NANOG and GATA3 that play central role in lineage commitment in the mouse. As found by others also [6,42], there are fundamental differences from the mouse. Understanding the nature of the process of preimplantation development in mammals will necessarily require a comparative approach based on study of a variety of animal models."
Expression of pluripotency master regulators during two key developmental transitions: EGA and early lineage specification in the bovine embryo
PLoS One. 2012;7(3):e34110. Epub 2012 Mar 29.
Khan DR, Dubé D, Gall L, Peynot N, Ruffini S, Laffont L, Le Bourhis D, Degrelle S, Jouneau A, Duranthon V. Source INRA UMR 1198 Biologie du Développement et de la Reproduction, Jouy en Josas, France.
Pluripotency genes are implicated in mouse embryonic genome activation (EGA) and pluripotent lineage specification. Moreover, their expression levels have been correlated with embryonic term development. In bovine, however, little information is available about dynamics of pluripotency genes during these processes. In this study, we charted quantitative and/or qualitative spatio-temporal expression patterns of transcripts and proteins of pluripotency genes (OCT4, SOX2 and NANOG) and mRNA levels of some of their downstream targets in bovine oocytes and early embryos. Furthermore, to correlate expression patterns of these genes with term developmental potential, we used cloned embryos, having similar in vitro but different full term development rates. Our findings affirm: firstly, the core triad of pluripotency genes is probably not implicated in bovine EGA since their proteins were not detected during pre-EGA phase, despite the transcripts for OCT4 and SOX2 were present. Secondly, an earlier ICM specification of transcripts and proteins of SOX2 and NANOG makes them pertinent candidates of bovine pluripotent lineage specification than OCT4. Thirdly, embryos with low term development potential have higher transcription rates; nevertheless, precarious balance between pluripotency genes is maintained. This balance presages normal in vitro development but, probably higher transcription rate disturbs it at later stage that abrogates term development.
A small set of extra-embryonic genes defines a new landmark for bovine embryo staging
Reproduction. 2010 Oct 6. [Epub ahead of print]
Degrelle SA, Le Cao KA, Heyman Y, Everts RE, Campion E, Richard C, Ducroix-Crepy C, Tian C, Lewin H, Renard JP, Robert-Granié C, Hue I.
S Degrelle, UMR Biologie du Developpement et Reproduction, INRA, JOUY EN JOSAS, 78350, France. Abstract Axis specification in the mouse is determined by a sequence of reciprocal interactions between embryonic and extra-embryonic tissues so that a few extra-embryonic genes appear as 'patterning' the embryo. Considering these interactions as essential but lacking in most mammals the genetically driven approaches used in the mouse and the corresponding patterning mutants, we examined whether a molecular signature originating from extra-embryonic tissues could relate to the developmental stage of the embryo proper and predict it. To this aim we profiled bovine extra-embryonic tissues at peri-implantation stages, when gastrulation and early neurulation occur, and analysed the subsequent expression profiles through the use of predictive methods as previously reported for tumour classification. A set of 6 genes (CALM1, CPA3, CITED1, DLD, HNRNPDL, TGFB3), half of which had not been previously associated to any extra-embryonic feature, appeared significantly discriminative and mainly dependent on embryonic tissues for its faithful expression. The predictive value of this set of genes for gastrulation and early neurulation stages, as assessed on naïve samples, was remarkably high (93%). In silico connected to the bovine orthologues of the mouse patterning genes, this gene set is proposed as new trait for embryo staging. As such, this will allow saving the bovine embryo proper for molecular or cellular studies. To us, it offers as well new perspectives for developmental phenotyping and modelling of embryonic/extra-embryonic co-differentiation.
Modulation of the maternal immune system by the pre-implantation embryo
BMC Genomics. 2010 Aug 13;11:474.
Walker CG, Meier S, Littlejohn MD, Lehnert K, Roche JR, Mitchell MD.
DairyNZ Ltd,, Hamilton, New Zealand. Caroline.Walker@dairynz.co.nz Abstract BACKGROUND: A large proportion of pregnancy losses occur during the pre-implantation period, when the developing embryo is elongating rapidly and signalling its presence to the maternal system. The molecular mechanisms that prevent luteolysis and support embryo survival within the maternal environment are not well understood. To gain a more complete picture of these molecular events, genome-wide transcriptional profiles of reproductive day 17 endometrial tissue were determined in pregnant and cyclic Holstein-Friesian dairy cattle.
RESULTS: Microarray analyses revealed 1,839 and 1,189 differentially expressed transcripts between pregnant and cyclic animals (with > or = 1.5 fold change in expression; P-value < 0.05, MTC Benjamini-Hochberg) in caruncular and intercaruncular endometrium respectively. Gene ontology and biological pathway analysis of differentially expressed genes revealed enrichment for genes involved in interferon signalling and modulation of the immune response in pregnant animals.
CONCLUSION: The maternal immune system actively surveys the uterine environment during early pregnancy. The embryo modulates this response inducing the expression of endometrial molecules that suppress the immune response and promote maternal tolerance to the embryo. During this period of local immune suppression, genes of the innate immune response (in particular, antimicrobial genes) may function to protect the uterus against infection.
"The number of morphologically healthy oocytes in the ovaries of mammals is remarkably variable at birth, ranging, for example, from 350 000 to 1 100 000 in humans [1–3] and approximately 14 000 to 250 000 in cattle [4, 5]"
Dynamics of global transcriptome in bovine matured oocytes and preimplantation embryos
Proc Natl Acad Sci U S A. 2006 Dec 12;103(50):18905-10. Epub 2006 Dec 1.
Misirlioglu M, Page GP, Sagirkaya H, Kaya A, Parrish JJ, First NL, Memili E.
Department of Animal and Dairy Sciences, Mississippi State University, Mississippi State, MS 39762, USA.
Abstract Global activation of the embryonic genome is the most critical event in early mammalian development. After fertilization, a rich supply of maternal proteins and RNAs support development whereas a number of zygotic and embryonic genes are expressed in a stage-specific manner leading to embryonic genome activation (EGA). However, the identities of embryonic genes expressed and the mechanism(s) of EGA are poorly defined in the bovine. Using the Affymetrix bovine-specific DNA microarray as the biggest available array at present, we analyzed gene expression at two key stages of bovine development, matured oocytes (MII) and 8-cell-stage embryos, constituting the ultimate reservoir for life and a stage during which EGA takes place, respectively. Key genes in regulation of transcription, chromatin-structure cell adhesion, and signal transduction were up-regulated at the 8-cell stage as compared with 8-cell embryos treated with alpha-amanitin and MII. Genes controlling DNA methylation and metabolism were up-regulated in MII. These changes in gene expression, related to transcriptional machinery, chromatin structure, and the other cellular functions occurring during several cleavage stages, are expected to result in a unique chromatin structure capable of maintaining totipotency during embryogenesis and leading to differentiation during postimplantation development. Dramatic reprogramming of gene expression at the onset of development also has implications for cell plasticity in somatic cell nuclear transfer, genomic imprinting, and cancer.
Bovine obstetrics (1910) Bruin, M. G. de (Marcelis Gerrit de), https://archive.org/details/cu31924021948413