The rat has been an established experimental animal model within many areas of biological investigation for over one hundred years due to its size, breeding characteristics, and knowledge of its physiology and behaviour. In recent years its status as a leading biomedical model has been somewhat surpassed by the mouse. This is largely the result of the isolation and application of mouse embryonic stem (ES) cells. Mouse ES cells have the capacity for unlimited self-renew in vitro whilst maintaining pluripotency and germline competence, and most importantly are amenable to sophisticated reverse genetics strategies such as gene targeting, which have provided a route to germ line modification. Thus far, the derivation of rat ES cells has proved elusive. The generation of rat ES cells would therefore facilitate equivalent applications to rat genetics and significantly strengthen the rat as an experimental model system. Previous attempts to derive rat ES cells led to the isolation of rat ES-like cells. However, whilst these cells exhibit extensive self-renew in vitro, it was known that they fail to maintain significant levels of the key functional ES cell marker Oct4 and do not contribute to chimeras. Rather, these cells express the trophectoderm markers Cdx2 and CyclinD3, and have been termed ExS cells due to their probable extra-embryonic nature. In the work described in this thesis, further investigation of ExS cells revealed the absence of expression of the key pluripotency gene Nanog, although the expression pattern of Nanog in the rat embryo was shown to be similar to that of mouse. It was hypothesised that expression of exogenous Oct4 and Nanog or Sox2 genes could facilitate reprogramming of ExS cells into a 'true' ES cell state. Initial work described in this thesis demonstrated that it was possible to introduce transgenes into rat ExS cells and obtain stable transformants with long term transgene expression. On this basis Oct 4, Nanog and Sox2 transgene expression vectors were constructed and stably integrated into ExS cells, and transgene expression verified. However, no reactivation of an endogenous gene expression profile, characteristic of a true ES cell-like state, was observed in any of the transgenic lines produced. Concurrent with work on ExS cells, investigations by others using chemically defined, serum-free medium containing small molecule inhibitors of MEK and GSK3 (called 3i/2i medium) had demonstrated that it was possible to readily isolate mouse ES cells, even from strains known to be refractory to ES cell isolation. Therefore, the ability of this culture system to facilitate rat ES cell derivation was investigated. Rat 3i/2i cell lines were established from ICM outgrowths of Fischer, DA and Sprague Dawley E4.5 rat embryos. These cells maintained expression of Oct4 and Nanog and could generate complex teratomas consisting of all three germ layers. They were distinct from epiblast stem cells (EpiSC) in that they expressed Klf4, Rex1 and Stella and most importantly, they could contribute to the formation of adult chimaeras and demonstrated germline competency. Isolation of these authentic rat ES cells paves the way for gene targeting in the rat, a development that should greatly facilitate new biomedical discoveries.

A neoplasia mamária é a doença mais entre as neoplasias em cadelas. As características clínicas dos tumores mamários caninos e sua relação com prognóstico foram discutidos, incluindo idade, raça, estagiamento clínico, diagnóstico histopatológico, hormônios e proliferação celular. Fatores clínicos prognósticos incluindo diâmetro do tumor e comprometimento linfonodal são discutidos em relação a graduação histopatológica e expressão de OCT4 (marcador para célula tronco tumoral). Avaliação imunohistoquímica dos marcadores (RE, RP, Ki-67 e OCT4) de neoplasias mamárias foi descritas. Foi observada marcação positiva para o OCT4, porém não se observou associação com fatores prognósticos clínicos. Assim como a marcação de RE, PR e Ki-67 foram observados. Houve uma forte associação entre graduação histopatológica de malignidade e tipo histológico. / Mammary neoplasms are the most common neoplasm in female dogs. The clinical features of canine mammary gland tumors and their relation to prognosis were discussed, including age, breed, staging, histopathological diagnosis, hormones, cell proliferation. Additional clinical prognostic factors including tumor size, and lymph node status are discussed in relation to graduation histopathological and OCT4 expression (cancer stem cell marker). Immunohistochemical evaluation of the markers (ER, PR, KI-67, OCT4) of the neoplastic canine mammary gland is described. We observed positive staining for OCT4, but was not associated with clinical prognostic factors. And the marking of ER, PR and Ki-67 was observed. There was a strong association between histopathological grade and histological type of malignancy.

A neoplasia mamária é a doença mais entre as neoplasias em cadelas. As características clínicas dos tumores mamários caninos e sua relação com prognóstico foram discutidos, incluindo idade, raça, estagiamento clínico, diagnóstico histopatológico, hormônios e proliferação celular. Fatores clínicos prognósticos incluindo diâmetro do tumor e comprometimento linfonodal são discutidos em relação a graduação histopatológica e expressão de OCT4 (marcador para célula tronco tumoral). Avaliação imunohistoquímica dos marcadores (RE, RP, Ki-67 e OCT4) de neoplasias mamárias foi descritas. Foi observada marcação positiva para o OCT4, porém não se observou associação com fatores prognósticos clínicos. Assim como a marcação de RE, PR e Ki-67 foram observados. Houve uma forte associação entre graduação histopatológica de malignidade e tipo histológico. / Mammary neoplasms are the most common neoplasm in female dogs. The clinical features of canine mammary gland tumors and their relation to prognosis were discussed, including age, breed, staging, histopathological diagnosis, hormones, cell proliferation. Additional clinical prognostic factors including tumor size, and lymph node status are discussed in relation to graduation histopathological and OCT4 expression (cancer stem cell marker). Immunohistochemical evaluation of the markers (ER, PR, KI-67, OCT4) of the neoplastic canine mammary gland is described. We observed positive staining for OCT4, but was not associated with clinical prognostic factors. And the marking of ER, PR and Ki-67 was observed. There was a strong association between histopathological grade and histological type of malignancy.

Regeneration is a process that renews damaged or lost cells, tissues, or even of entire body structures, and is a phenomenon which is widespread in the animal kingdom. Urodeles such as newts and salamanders have a remarkable regeneration ability. They can regenerate organs such as gills, lower jaws, retina, appendages like fore- and hind limbs, and also the tail including the spinal cord. The regeneration process requires the use of resident stem cells or somatic cells, which have to be reprogrammed. In both cases the reprogrammed cells are less differentiated, meaning the cell would have the ability to form any kind of fetal or adult cell which rose from the three different germ layers, the ectoderm, mesoderm and endoderm. Artificial reprogramming of differentiated mammalian somatic cell had been reported previously. It was shown that four pluripotency factors, OCT4 (also called POU5f1), SOX2, c-MYC and KLF4 are sufficient to generate an induced pluripotent stem (iPS) cell. It has been shown that some of these factors are also involved in regenerating processes. In newt limb and lens tissue, Sox2, c-Myc and Klf4 mRNA levels were upregulated in the beginning of blastema formation when compared to non-amputated tissue. Oct4 mRNA however, was not detected. During xenopus tail regeneration, Sox2 and c-Myc were expressed, while the xenopus Pou homologs Pou25, Pou60, Pou79, Pou91 were not detected. In regenerating zebrafish fin tissue, Sox2, Pou2, c-Myc and Klf4 mRNA were not upregulated. The mammalian transcription factor OCT4, a class V POU protein, is responsible in maintaining pluripotency in gastrula stage embryos. It was reported that mouse OCT4 is also expressed in the caudal node of embryos having 16 somites. It is further known that progenitors exist in mouse tailbud, which give rise to neural and mesodermal cell lineage. This suggests that the OCT4 expressing cells in caudal node might be a stem cell reservoir. Oct4 was detected in axolotl during embryonic development, and prior to my work we found Oct4 when screening the axolotl blastema cDNA library. In addition, we also identified Pou2, another class V POU gene. Phylogenetic analysis showed a clear distinction of both genes in the axolotl. We determined the mRNA pattern of Pou2 during embryogenesis and compared it to Oct4 mRNA and protein. Both genes are expressed in the primordial germ cells and the pluripotent animal cap region of the embryo. Apart from this similarity, both genes have a different expression pattern in the embryo. We are interested in the involvement of OCT4, POU2, as well as the transcription factor SOX2 in regenerating axolotl spinal cord. We asked whether the cellular pluripotent character conferred by POU factors is limited to mammals or if it is an ancient characteristic of lower vertebrates. To answer the question we performed in vitro and in vivo studies. Hence this thesis is separated into two chapter. By in vitro studies we investigated the pluripotent PouV orthologs from different species. Therefore, we performed reprogramming experiments using mouse or human fibroblasts and transduced them with axolotl Oct4 or Pou2, in combination with human or axolotl Sox2, c-Myc and/or Klf4. The generated iPS cells with the different sets of factors had similar endogenous pluripotency gene expression profiles to embryonic stem cells. Further, iPS cells expressed the pluripotency markers like OCT4, NANOG, SSEA4, TRA1-60 and TRA1-81. Another evaluation of the iPS cells was the formation of embryoid bodies. Immunouorescence staining showed that tissue from all three germ layers was formed after induction. We observed a positive staining for the endoderm marker !-FEROPROTEIN, the mesoderm marker !-SMOOTH MUSCLE ACTIN and the ectoderm marker \"III TUBULIN in the generated cells. This indicated that the iPS cells generated using axolotl Oct4 and Sox2 in combination with mammalian Klf4 and with or without c-Myc, as well as iPS cell generated with axolotl Pou2 and mammalian Sox2 and Klf4 and with or without c-Myc have a pluripotent potential. In addition, the axolotl factors are able to form heterodimers with the mammalian proteins. Furthermore, we compared the reprogramming ability with POU factors from mouse, human, zebrash, medaka and xenopus. We showed that xenopus Pou91, as the only non-mammalian example, is nearly as efficient as mouse and human Oct4 cDNAs in inducing GFP expressing cells. Also axolotl Pou2, axolotl Oct4 and medaka Pou2 showed reprogramming character however at a much lower efficiency. In contrast, zebrash Pou2 is not able to establish iPS cells. This indicates that a reprogramming ability to a pluripotent cell state is an ancient trait of Pou2 and Oct4 homologs. By in vivo studies we investigated the role of Oct4, Pou2 and Sox2 gene expression in regenerating spinal cord tissue. Performed in situ hybridizations and antibody staining studies in the regenerating spinal cord showed that Oct4, Pou2 and Sox2 were expressed during spinal cord regeneration. Knockdown experiments in regenerating spinal cord using morpholino showed that Pou2-morpholino does not have an effect. In contrast, SOX2 was required for spinal cord regeneration but to a lesser extent, than OCT4, which decreased the regenerated length signicantly compared to control. Even though, with Sox2-morpholino we did not observe the phenotype as a significantly shorter regenerated spinal cord, about 45% of SOX2 knocked down cells were not cycling and proliferating anymore. This indicates that axolotl SOX2 has an effect in regeneration. Therefore we wanted to know whether spinal cord cells would also have a pluripotent character in vivo and form other tissue types. Regenerating cells of the spinal cord are only able to form the same cell type and thus they keep their cell memory. However, when we performed transplantations of OCT4/SOX2 expressing spinal cord cells into somite stage embryos, we could show the formation of muscle cells. This shows that the spinal cord cells have the potential to change their fate in an embryonic context, where the normal environment of spinal cord has changed. However, our data do not indicate whether muscle is formed directly from the spinal cord or whether spinal cord cells fuse to developmental myoblasts, a cell type of embryonic progenitors, which give rise to muscle cells. To clearly state whether regenerating OCT4/SOX2 expressing spinal cord cells are pluripotent we have to perform OCT4 knock down in spinal cord and transplant these less proliferating cells into embryos, observing their cell fate.

Les cellules souches cancéreuses (CSC) sont les cellules responsables du pouvoir tumoral et/ou métastasique, et résistent à la plus part des molécules anticancéreuses. L’expression de facteurs de transcription impliqués dans l’auto-renouvellement des cellules souches embryonnaires tels que Oct4 ou Nanog, indique toujours un mauvais pronostic quelle que soit l’origine de la tumeur. Ne pouvant pas isoler ces CSC à signature embryonnaire à l’aide des marqueurs de surface « traditionnels », le laboratoire a créé un modèle murin qui permet de sélectionner les cellules exprimant Oct4 à partir de tumeurs se développant spontanément dans différents tissus. A partir de ce modèle, nous avons cherché une classe de molécule pouvant cibler ces cellules. Nous montrons que les inhibiteurs de la protéase du VIH et principalement le Lopinavir, ciblent spécifiquement les CSC murines exprimant une signature embryonnaire. Ces cellules expriment aussi CXCR4, un récepteur au facteur chimiotactique CXCL12, impliqué dans la migration des cellules tumorales. Bien que préliminaires, nos résultats indiquent que CXCR4 joue un rôle tout comme Oct4 dans le maintien de l’auto-renouvellement des CSC exprimant une signature embryonnaire. De plus, nous proposons un mécanisme pour expliquer l’inter-dépendance entre ces deux facteurs dans le maintien des propriétés souches de ces CSC. Des travaux sur la transposition de ce modèle murin à un modèle humain sont actuellement en cours. / Cancer Stem Cells (CSC) bear the tumorigenic and/or metastatic potential and are resistant to most of the chemotherapeutic drugs. CSC expressing embryonic transcription factors such as Oct4 or Nanog are always associated to tumours with poor prognosis. As it is not possible to isolate them based on the expression of common cell surface markers, our lab has developed a mouse model selecting Oct4 expressing cells from tumours of diverse origins. Based on this model, we looked for a class of molecules that were able to target these cells. Here we show that HIV protease inhibitors, especially Lopinavir, specifically target CSC expressing an embryonic signature. These cells also express CXCR4, which is a receptor for the CXCL12 chemotactic factor implicated in cell migration including tumour cells. Although preliminary, our results indicate an unexpected role of CXCR4 in maintaining self-renewal of CSCs expressing an embryonic signature. We propose a model to explain the inter-dependence between Oct4 and CXCR4 to maintain stem cell properties in this population of CSC. We are now trying to transpose our mouse model to a human model.

Regeneration is a process that renews damaged or lost cells, tissues, or even of entire body structures, and is a phenomenon which is widespread in the animal kingdom. Urodeles such as newts and salamanders have a remarkable regeneration ability. They can regenerate organs such as gills, lower jaws, retina, appendages like fore- and hind limbs, and also the tail including the spinal cord. The regeneration process requires the use of resident stem cells or somatic cells, which have to be reprogrammed. In both cases the reprogrammed cells are less differentiated, meaning the cell would have the ability to form any kind of fetal or adult cell which rose from the three different germ layers, the ectoderm, mesoderm and endoderm. Artificial reprogramming of differentiated mammalian somatic cell had been reported previously. It was shown that four pluripotency factors, OCT4 (also called POU5f1), SOX2, c-MYC and KLF4 are sufficient to generate an induced pluripotent stem (iPS) cell. It has been shown that some of these factors are also involved in regenerating processes. In newt limb and lens tissue, Sox2, c-Myc and Klf4 mRNA levels were upregulated in the beginning of blastema formation when compared to non-amputated tissue. Oct4 mRNA however, was not detected. During xenopus tail regeneration, Sox2 and c-Myc were expressed, while the xenopus Pou homologs Pou25, Pou60, Pou79, Pou91 were not detected. In regenerating zebrafish fin tissue, Sox2, Pou2, c-Myc and Klf4 mRNA were not upregulated. The mammalian transcription factor OCT4, a class V POU protein, is responsible in maintaining pluripotency in gastrula stage embryos. It was reported that mouse OCT4 is also expressed in the caudal node of embryos having 16 somites. It is further known that progenitors exist in mouse tailbud, which give rise to neural and mesodermal cell lineage. This suggests that the OCT4 expressing cells in caudal node might be a stem cell reservoir. Oct4 was detected in axolotl during embryonic development, and prior to my work we found Oct4 when screening the axolotl blastema cDNA library. In addition, we also identified Pou2, another class V POU gene. Phylogenetic analysis showed a clear distinction of both genes in the axolotl. We determined the mRNA pattern of Pou2 during embryogenesis and compared it to Oct4 mRNA and protein. Both genes are expressed in the primordial germ cells and the pluripotent animal cap region of the embryo. Apart from this similarity, both genes have a different expression pattern in the embryo. We are interested in the involvement of OCT4, POU2, as well as the transcription factor SOX2 in regenerating axolotl spinal cord. We asked whether the cellular pluripotent character conferred by POU factors is limited to mammals or if it is an ancient characteristic of lower vertebrates. To answer the question we performed in vitro and in vivo studies. Hence this thesis is separated into two chapter. By in vitro studies we investigated the pluripotent PouV orthologs from different species. Therefore, we performed reprogramming experiments using mouse or human fibroblasts and transduced them with axolotl Oct4 or Pou2, in combination with human or axolotl Sox2, c-Myc and/or Klf4. The generated iPS cells with the different sets of factors had similar endogenous pluripotency gene expression profiles to embryonic stem cells. Further, iPS cells expressed the pluripotency markers like OCT4, NANOG, SSEA4, TRA1-60 and TRA1-81. Another evaluation of the iPS cells was the formation of embryoid bodies. Immunouorescence staining showed that tissue from all three germ layers was formed after induction. We observed a positive staining for the endoderm marker !-FEROPROTEIN, the mesoderm marker !-SMOOTH MUSCLE ACTIN and the ectoderm marker \"III TUBULIN in the generated cells. This indicated that the iPS cells generated using axolotl Oct4 and Sox2 in combination with mammalian Klf4 and with or without c-Myc, as well as iPS cell generated with axolotl Pou2 and mammalian Sox2 and Klf4 and with or without c-Myc have a pluripotent potential. In addition, the axolotl factors are able to form heterodimers with the mammalian proteins. Furthermore, we compared the reprogramming ability with POU factors from mouse, human, zebrash, medaka and xenopus. We showed that xenopus Pou91, as the only non-mammalian example, is nearly as efficient as mouse and human Oct4 cDNAs in inducing GFP expressing cells. Also axolotl Pou2, axolotl Oct4 and medaka Pou2 showed reprogramming character however at a much lower efficiency. In contrast, zebrash Pou2 is not able to establish iPS cells. This indicates that a reprogramming ability to a pluripotent cell state is an ancient trait of Pou2 and Oct4 homologs. By in vivo studies we investigated the role of Oct4, Pou2 and Sox2 gene expression in regenerating spinal cord tissue. Performed in situ hybridizations and antibody staining studies in the regenerating spinal cord showed that Oct4, Pou2 and Sox2 were expressed during spinal cord regeneration. Knockdown experiments in regenerating spinal cord using morpholino showed that Pou2-morpholino does not have an effect. In contrast, SOX2 was required for spinal cord regeneration but to a lesser extent, than OCT4, which decreased the regenerated length signicantly compared to control. Even though, with Sox2-morpholino we did not observe the phenotype as a significantly shorter regenerated spinal cord, about 45% of SOX2 knocked down cells were not cycling and proliferating anymore. This indicates that axolotl SOX2 has an effect in regeneration. Therefore we wanted to know whether spinal cord cells would also have a pluripotent character in vivo and form other tissue types. Regenerating cells of the spinal cord are only able to form the same cell type and thus they keep their cell memory. However, when we performed transplantations of OCT4/SOX2 expressing spinal cord cells into somite stage embryos, we could show the formation of muscle cells. This shows that the spinal cord cells have the potential to change their fate in an embryonic context, where the normal environment of spinal cord has changed. However, our data do not indicate whether muscle is formed directly from the spinal cord or whether spinal cord cells fuse to developmental myoblasts, a cell type of embryonic progenitors, which give rise to muscle cells. To clearly state whether regenerating OCT4/SOX2 expressing spinal cord cells are pluripotent we have to perform OCT4 knock down in spinal cord and transplant these less proliferating cells into embryos, observing their cell fate.

Oct4, a transcription factor belonging to the fifth class of POU proteins (POUV), plays essential roles in the maintenance of pluripotency, differentiation and the generation of induced pluripotent stem cells (iPSCs). Oct4 regulates two levels of pluripotency, which are distinguished by their gene expression profiles and epigenetic status, namely the naïve and primed state of pluripotency. Embryonic stem cells (ESCs) and embryonic germ cells (EGCs), which are isolated from inner cell mass and primordial germ cells in the embryo, respectively, are in vitro models in which the naïve state is propagated through self-renewal. Epiblast stem cells (EpiSCs) and traditional human ESCs have gene expression profiles that are closest to the post-implantation epiblast, which is closer to embryonic differentiation, and exhibit a primed state of pluripotency. As Oct4 is important for pluripotency in all these cell types, where it regulates different targets, it appears to have two distinct sets of functions, namely germ cell/naïve ESC-like activity and epiblast/primed pluripotency-like activity. Based on protein sequences and syntenic gene analysis, Oct4/POUV homologs of jawed vertebrates can be classified into two subfamilies: POU5F1 and POU5F3, which are thought to originate from a genome duplication event that occurred in a common ancestor. Most extant vertebrates have lost one of these paralogs, while a small fraction, including coelacanths, axolotls, turtles, and marsupials, retains both POUV forms. In my thesis, I investigated the gene duplication event that underlies divergence of POU5F1 and POU5F3 in both expression pattern and specialised function. In particular, I focused on species that have retained both genes and asked whether POUV functional divergence correlates with ancestral origin. To test the function of POU5F1 and POU5F3, I substituted endogenous mouse Oct4/Pou5f1 with different POUV proteins using a cell line in which endogenous Oct4 expression can be silenced with tetracycline (ZHBTc4). Results showed that POU5F1 proteins had a greater capacity to support naïve ESC pluripotency and self-renewal than POU5F3 proteins. Global transcriptome analysis of the POUV-rescued ESC lines revealed that coelacanth POU5F1 protein regulates gene expression in a similar manner to mouse Oct4, in that genes involved in stem cell maintenance, reproduction and development are upregulated in ESCs rescued by POU5F1, but not POU5F3. Coelacanth POU5F3 rescued lines, however, expressed genes involved in various cell differentiation programs, including cell adhesion (e.g. E-cadherin and N-cadherin). This suggests that POU5F3 plays a role in primed pluripotency, while POU5F1 regulates naïve pluripotency. However, there is one POU5F3 factor that rescues ESCs like Oct4, the Xenopus gene Xlpou91 (Pou5f3.1). In Xenopus, a further duplication of POU5F3 gene enabled specialization, and Xlpou91 is expressed specifically in the primordial germ cells. Xlpou25 (Pou5f3.2) exhibits epiblast-specific activities and lacks the capacity to maintain naïve ESC pluripotency, similar to other POU5F3 proteins. This functional distinction between the different Xenopus POUV paralogs enabled us to address how specific Oct4 functions (germ cell-like versus epiblast-like activity) are related to the induction of pluripotency. To address this question, mouse Oct4 was replaced by either Xlpou91 or Xlpou25 in murine cellular reprogramming using a Nanog-GFP reporter line to monitor iPSC generation. Results showed that Xlpou91 and mouse Oct4 were required at similar levels to reprogram somatic cells toward iPSCs and reprogrammed cells emerged with similar kinetics. Conversely, Xlpou25 was required at higher expression levels and the resulting iPSCs appeared at a later timepoint, while the pluripotent population in these cultures appeared to be less stable and more prone to differentiate. I found that this phenotype of enhanced differentiation in Xlpou25 reprogrammed cultures may be a product of a different set of immediate early genes induced at the first stages of differentiation. Global transcriptome analysis of the naïve ESC-like pluripotent subpopulation of these iPSC lines confirmed the capacity of all Xenopus POUVs to drive reprogramming towards the pluripotent state. However, the gene sets induced by both Xlpou91 and mouse Oct4, but not Xlpou25, were somewhat enriched for genes involved in reproduction, emphasizing the segregated role of Xlpou91 as a germ cell specific POUV protein. Lastly, I explored the evolutionary origin of these two POUV paralogs and attempted to identify a POUV-related gene in jawless vertebrate (cyclostomes). Based on in silico analysis of genomic and transcriptome databases, my collaborators and I were able to identify a single POUV gene in the Japanese/arctic lamprey, thus providing the first insight into the origin of gnathosome POUV genes.

Doctor of Philosophy / Department of Animal Sciences and Industry / David M. Grieger / Early in embryonic development a series of events occur whereby pluripotent cells undergo differentiation to give rise to the three germ layers and extraembryonic tissues of the developing conceptus. Nanog, Sox-2, and Oct-4 genes have been identified as having key roles in maintaining pluripotency in undifferentiated human and mouse cells but recent evidence suggests they may have different roles in farm animals. We cloned the coding sequence for porcine Nanog including 452 base pairs of the Nanog promoter, and partial coding sequences of Oct-4 and Sox-2. Embryos were flushed from sows 10, 12, 15, and 17 days post insemination. RNA was isolated from whole d-10 and -12 conceptuses, d-15 embryonic disk, distal and proximal extraembryonic tissue, and d-17 embryonic disk, distal and proximal extraembryonic tissue, and allantois for real-time PCR. RNA from d-40 maternal myometrium and endometrium, fetal placenta, and liver were also used in real-time PCR. The homeodomain and c-terminal tryptophan repeats are highly conserved in porcine Nanog compared to the mouse, human and bovine. In the promoter, the highly conserved Octamer and Sox binding sequences are also present. The Nanog expression pattern was different when compared to Oct-4 and Sox-2. Day-40 tissues demonstrated the highest expression including endometrium (7 fold) fetal liver (27 fold), placenta (40 fold) and myometrium (72 fold) when compared to day 15 distal extraembryonic tissue. Oct-4 and Sox-2 expression was lowest in d-40 tissues except for fetal liver which was 20 and 71 fold, respectively, higher than endometrium. Oct-4 levels were consistent in d-10, -12, and -15 conceptuses and disk but dropped 3 fold in d-17 disk. On the other hand, Sox-2 was upregulated a 1000 fold in the d-15 disk and 2000 fold in the d-17 disk when compared to the d-12 conceptus. Nanog may have other roles in than maintenance of pluripotency including a possible role in multipotent or progenitor stem cells. Expression of all 3 markers in fetal liver suggests a more primitive cell type is present such as hematopoietic stem cells.

Biotecnologias reprodutivas como a produção in vitro de embriões e a transferência de núcleo apresentam grande potencial de aplicação na medicina veterinária seja para a correção de infertilidades, para o aumento na eficiência da produção animal ou mesmo para um melhor entendimento sobre os mecanismos envolvidos no desenvolvimento embrionário inicial. Porém, manipulações in vitro de gametas ou embriões levam a alterações na regulação epigenética, podendo causar altas taxas de anormalidades no desenvolvimento e no nascimento de indivíduos derivados. A geração de um modelo de indução da pluripotência in vitro, ou seja, a geração de células iPS (do inglês induced pluripotent stem cells) possibilitou estudar o processo de reprogramação in vitro de maneira robusta e precisa. Os genes OCT4 e SOX2 são fundamentais no processo de aquisição e manutenção da pluripotência celular, e recentemente foi reportado que a ação destes dois fatores exerce grande influência sobre a regulação de alguns genes imprinted, em especial, no locus H19/IGF2, sabidamente importantes para o desenvolvimento normal do embrião e de sua placenta. Este estudo propõe a geração de um modelo experimental in vitro onde os fatores em questão sejam estudados, juntos ou em combinação, quanto à sua influência na regulação do imprinting genômico. Para tal, três linhagens de fibroblastos fetais bovinos (bFF1, bFF2 e bFF3) foram transduzidas com vetores lentivirais contendo cDNAs de OCT4 ou SOX2 humanos. Os fibroblastos foram analisados através de citometria e as células positivas foram separadas e recuperadas (sorted). Os fibroblastos expressando OCT4, SOX2, ambos (OCT4 + SOX2), nenhum (controle) juntamente com um controle recuperado (não sorted) não transgênico (total de cinco tratamentos) foram investigados quanto à expressão de genes relacionados à pluripotência e expressão de genes imprinted, bem como a manutenção dos padrões de metilação do DNA no locus H19/IGF2. Além disso, estas células foram submetidas à reprogramação in vitro e produção de células iPS. A indução à pluripotência foi realizada através da transdução dos fibroblastos com o vetor policistrônico contendo o cDNAs murino ou humano dos fatores de transcrição OCT4, SOX2, c-MYC e KLF4 (OSMK, vetor STEMCCA). Os resultados da análise de fluorescência por citometria de fluxo foram, em média, de 40,4% para OCT4, 6,1% para SOX2 e 0,63% para OCT4 + SOX2. A bFF1 foi a única linhagem a apresentar uma recuperação pós-sorting, o que possibilitou sua utilização para a indução da pluripotência. De maneira interessante, as células que não passaram pela citometria geraram colónias de células iPS, enquanto que os demais grupos não. A quantificação de transcritos por qRT-PCR mostrou que a expressão de OCT4 e de SOX2 estava aumentada nos respectivos grupos, a expressão do gene H19 mostrou-se aumentada no grupo controle que passou pelo procedimento de sorting e a expressão do gene imprinted IGF2R não variou entre os grupos. Já a análise preliminar da manutenção do padrão de metilação de DNA na DMR do locus H19/IGF2 mostrou que o grupo controle sorted apresentou uma leve diferença no padrão de metilação quando comparada aos outros grupos. Neste estudo, portanto, o procedimento de separação e recuperação celular por citometria de fluxo celular, aliado ao elevado número de repiques celulares durante o cultivo prolongado pode ter levado a um efeito prejudicial sobre a eficiência de reprogramação in vitro / Reproductive biotechniques such as in vitro embryo production and somatic cell nuclear transfer may greatly contribute for fertility improvements, to enhance animal production or else to contribute to a better understanding of the underlying mechanism involved during initial embryonic development. However, in vitro manipulation of gametes or embryos may lead to possible disruptions on epigenetic regulation, causing high developmental abnormalities and decreased healthy calves born at term. The generation of induced pluripotency models (induced pluripotent stem cells, or iPS) made it possible to study the process of in vitro reprogramming in a more solid and precise manner. OCT4 and SOX2 are fundamental genes for the acquisition and maintenance process of cellular pluripotency. Recently, it has been reported that both factors may have a huge influence on the regulation of some imprinted genes, specially at locus H19/IGF2, known to be important for the normal development of embryo and placenta. Therefore, this study aimed to generate an in vitro experimental model where the above transcription factors will be studied together or separately regarding their influence on genomic imprinting regulation. For that, three bovine fetal fibroblasts cell lines (bFF1, bFF2 and bFF3) were transduced with lentiviral vectors containing human OCT4 or SOX2 cDNAs. The fibroblasts were analyzed trough cell cytometry and positive cells were sorted. Fibroblasts expressing OCT4, SOX2, both (OCT4+SOX2), none (control) together with a non-sorted and non-transgenic control (five treatments) were investigated regarding pluripotency and imprinted gene expression, as well maintenance of DNA methylation patterns at H19/IGF2 locus. Further, these cells were also submitted to in vitro induced reprogramming and production of iPS cell colonies. Induction into pluripotency was realized by transducing fibroblasts with polycistronic excisable vector containing the murine or human cDNA of OCT4, SOX2, c-MYC and KLF4 transcription factors (OSMK, STEMCCA vector). The results of fluorescence analysis by flow cytometry were, on average, 40.4% for OCT4, 6.1% for SOX2 and 0,63% for OCT4+SOX2 groups. bFF1 was the only lineage presenting a post-sorting recovery that enabled its use for pluripotency induction. Interestingly, non-sorted cells generated biPS colonies whereas sorted cells (control non transgenic, OCT4, SOX2 and OCT4+SOX2 expressing cells) did not generate biPS cells. The transcript quantification by qRT-PCR showed that OCT4 and SOX2 expression were increased in the respective groups, the expression of H19 gene was increased in the control sorted group and IGF2R expression was not different between groups. Preliminary results of imprinting pattern methylation at H19/IGF2 locus showed that sorted group was slightly different from others. In this study, therefore, analysis and sorting procedure by flow citometry, together with an extended period in culture may have lead to a detrimental effect on in vitro reprogramming efficiency

Lors de la fécondation, le sperme et l'ovule s'unissent pour former un zygote totipotent. Initialement, le zygote est transcriptionnellement inactif. Au cours des premiers clivages a lieu la mise en route du génome embryonnaire (EGA) et le développement passe alors sous le contrôle de l’information embryonnaire (au stade 8-16-cellules chez le bovin). Cette transition d’un contrôle maternel à un contrôle embryonnaire est appelée « maternal to embryonic transition (MET) ». De la même façon, lors du transfert nucléaire (clonage), un noyau de cellule somatique placé dans un ovocyte énucléé devient totipotent. Ce processus est appelé «reprogrammation nucléaire somatique?». En fait, la reprogrammation nucléaire lors du clonage est équivalente à la MET, toutefois, le clonage est très peu efficace. Les objectifs de cette étude chez les bovins sont a) d'explorer le processus de reprogrammation lors de la MET dans des embryons fécondés in vitro (FIV) et b) d’estimer l'efficacité de la reprogrammation génique après le transfert nucléaire lors du clonage. Nous émettons l'hypothèse que l'acquisition d'un profil d'expression génique correct pourrait être prédictif d’un potentiel de développement à terme de l'embryon, et pourrait être évalué dès juste après l'activation du génome embryonnaire (EGA) chez les bovins. Nous avons développé notre travail selon deux axes a) des analyses globales d'expression génique utilisant une puce dédiée à l’EGA et b) l’analyse du profil d'expression de gènes candidats par qRT-PCR dans les embryons fécondés et clonés. Dans un premier temps nous avons optimisé le protocole d'amplification d'ARNm pour l'analyse du transcriptome de matériels rares. Puis nous avons fait l'analyse du transcriptome avant et après EGA d’embryons issus d’ovocytes prélevés sur des vaches phénotypées comme « bonnes » ou « mauvaises » donneuses d’embryons. En outre, ces ovocytes ont été maturés soit in vivo soit in vitro. Nos analyses montrent que l'effet individuel est plus important que l'effet « bonne ou mauvaise donneuse » ou même que l’effet « conditions de maturation ». Nous avons ensuite analysé les expressions géniques de 5 types d'embryons clonés ayant différents potentiels de développement à terme en fonction de la lignée cellulaire utilisée comme source de cellules donneuses. Globalement, leur expression génique est proche de celle de morulae FIV, mais quelques gènes présentent une expression différente. Ces gènes varient avec la lignée de cellules donneuses et leur nombre n’est pas lié à l’aptitude au développement à terme. L’analyse d’un lien éventuel entre leur nature et cette aptitude devra être poursuivie. Dans un deuxième temps, nous avons analysé les profils d'expression spatio-temporelle des transcrits et des protéines des gènes de pluripotence (OCT4, SOX2 et NANOG) et les niveaux d'ARNm de certains de leurs cibles dans les ovocytes et les embryons précoces chez le bovin. Les profils d'expression de ces gènes ont aussi été analysés dans des embryons clonés présentant différents potentiels de développement à terme. Nos résultats montrent que (1) la triade de gènes de pluripotence n'est probablement pas impliquée dans l’EGA bovine. (2) les transcrits et protéines de SOX2 et de NANOG sont restreints au lignage pluripotent plus tôt que ceux de OCT4, (3) les embryons à faible taux de développement à terme ont un taux de transcription plus élevé, néanmoins, l’équilibre précaire entre les gènes de pluripotence est maintenue. Cet équilibre pourrait permettre un développement normal in vitro, mais le taux de transcription plus élevé pourrait avoir des conséquences délétères sur le développement ultérieur. / In natural fertilization, sperm and ovum unite to form a totipotent zygote. Initially, the zygote is transcriptionally inactive and after few cleavages (8-16-cell stage in bovine) embryonic genome activation (EGA) takes place and embryo shifts from maternal to embryonic control, the process called maternal to embryonic transition (MET). Likewise, in nuclear transplantation (cloning) a somatic cell nucleus achieves totipotency when placed in an enucleated oocyte, the process called “nuclear reprogramming”. In fact, nuclear reprogramming in cloning experiments is equivalent to MET; however, this process is afflicted with low efficiency. The objectives of this study in bovine were a) to explore the process of MET reprogramming of in vitro fertilized (IVF) embryos and b) to estimate the efficiency of gene reprogramming after nuclear transfer in animal cloning. We hypothesized that the acquisition of a proper gene expression pattern could herald development potential of the embryos, which could be assessed as early as morula stage or after embryonic genome activation (EGA) in bovine. Here, we opted for a study plan consisting of two axes a) global gene expression analysis using an EGA-dedicated microarray and b) candidate gene expression profiling through qRT-PCR in the fertilized and cloned bovine embryos. Firstly, we optimized the protocol of mRNA amplification for transcriptome analysis which generates antisens-RNA (aRNA). Then we did transcriptomic analysis of the 4-cell and morulae derived from two genotypes having better and two genotypes having poorer in vitro embryonic development potentials. In addition, these oocytes were either matured in vivo or in vitro. We observed that the effect of individual genotype was more important than the effect of the phenotypic category (poorer or better) or conditions of oocyte maturation. Furthermore, we explored the expression patterns of 5 types of cloned embryos having different full term developmental potentials depending upon the donor cell line used. Their genes expression patterns closely resembled to the IVF morulae, except for few genes which present differences. These genes vary with the cell line used as somatic cell donor for SCNT and the number of these deregulated genes did not increase with the poorer developmental potential of the cloned embryos. The analysis of an eventual correlation between the potential for embryonic development to term and nature of the deregulated genes should be addressed. Secondly, 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, instead of gene ablation, having similar in vitro but different full term development rates. We chose these genes to be analysed since 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. Our findings affirm: first, the core triad of pluripotency genes probably is not implicated in bovine EGA since their proteins were not detected during pre-EGA phase, despite the transcripts for OCT4 and SOX2 were present. Second, an earlier ICM specification of SOX2 and NANOG makes them better candidates of bovine pluripotent lineage specification than OCT4. Third, 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.