Personne :
Gilbert, Isabelle

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Gilbert
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Isabelle
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Département des sciences animales, Faculté des sciences de l'agriculture et de l'alimentation, Université Laval
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2011 - 20177
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Voici les éléments 1 - 7 sur 7
  • Publication
    Accès libre
    Étude de l'expression génique dans les cellules de la granulosa bovine durant la période pré-ovulatoire
    (2011) Gilbert, Isabelle; Sirard, Marc-André; Blondin, Patrick.
    Dans cette étude, nous nous sommes principalement intéressés aux changements transcriptionnels des cellules de la granulosa (CG) durant la période pré-ovulatoire afin de mieux caractériser le rôle du pic de LH avant l'ovulation. Nous avons trouvé qu'avant le pic de LH, les CG exercent principalement des fonctions de division et de prolifération cellulaire, après le pic de LH, les CG sont impliquées dans la vascularisation et la synthèse de lipides, tandis que la réponse plus tardive suite au pic de LH, montrent des fonctions de localisation et de transport protéique. Ensuite, dans une optique plus appliquée à l'industrie bovine, nous avons investigué la présence de marqueurs moléculaires dans les CG associés à la compétence au développement embryonnaire de 1'ovocyte. Nous avons identifiés 18 transcrits sur-exprimés dans les CG associés aux ovocytes compétents. Plusieurs de ces marqueurs sont associés à la chromatine, au cycle cellulaire et à la stabilité de l'ADN. De plus, parmi les marqueurs trouvés, certaines séquences, malgré leur alignement sur le génome bovin, ne correspondent à aucun gène connu. Deux de ces nouvelles régions transcrites (NTR) se retrouvent près du gène de l'INHBA et pourraient constituer soit un variant d'épissage, soit un élément de régulation en 3'UTR. Les différents marqueurs trouvés dans les CG constituent un moyen non-invasif qui permettra de discriminer quels ovocytes ont le plus de potentiel à former un embryon sans que le gamète lui-même soit utilisé. Finalement, puisqu'il existe sur le marché plusieurs méthodes pour effectuer l'hybridation des biopuces, les cinq principales étapes de la préparation des échantillons et la validation post-hybridation par qRT-PCR ont été évalués. Dans l'ensemble, ces études ont permis de mettre en lumière les différentes étapes transcriptionnelles que les CG doivent compléter avant l'ovulation ainsi que quelques transcrits associés au statut de compétence de 1'ovocyte. Ultimement, une meilleure connaissance de la signature transcriptionnelle des CG à différentes étapes de la folliculogenèse permettra d'améliorer la stimulation ovarienne et la production embryonnaire subséquente.
  • Publication
    Accès libre
    Breed specific factors influence embryonic lipid composition : comparison between Jersey and Holstein
    (Commonwealth Scientific and Industrial Research Organization, 2015-01-15) Baldoceda Baldeon, Luis Manuel; Vigneault, Christian; Gilbert, Isabelle; Gagné, Dominic; Robert, Claude; Blondin, Patrick.; Ramires Ferreira, Christina
    Some embryos exhibit better survival potential to cryopreservation than others. The cause of such a phenotype is still unclear and may be due to cell damage during cryopreservation, resulting from overaccumulation and composition of lipids. In cattle embryos, in vitro culture conditions have been shown to impact the number of lipid droplets within blastomeres. Thus far, the impact of breed on embryonic lipid content has not been studied. In the present study were compared the colour, lipid droplet abundance, lipid composition, mitochondrial activity and gene expression of in vivo-collected Jersey breed embryos, which are known to display poor performance post-freezing, with those of in vivo Holstein embryos, which have good cryotolerance. Even when housed and fed under the same conditions, Jersey embryos were found to be darker and contain more lipid droplets than Holstein embryos, and this was correlated with lower mitochondrial activity. Differential expression of genes associated with lipid metabolism and differences in lipid composition were found. These results show genetic background can impact embryonic lipid metabolism and storage.
  • Publication
    Accès libre
    Exploring the function of long non-coding RNA in the development of bovine early embryos
    (CSIRO publishing, 2014-12-04) Gilbert, Isabelle; Caballero, Julieta; Fournier, Éric; Scantland, Sara; Gagné, Dominique; Robert, Claude; Macaulay, Angus
    Now recognised as part of the cellular transcriptome, the function of long non-coding (lnc) RNA remains unclear. Previously, we found that some lncRNA molecules in bovine embryos are highly responsive to culture conditions. In view of a recent demonstration that lncRNA may play a role in regulating important functions, such as maintenance of pluripotency, modification of epigenetic marks and activation of transcription, we sought evidence of its involvement in embryogenesis. Among the numerous catalogued lncRNA molecules found in oocytes and early embryos of cattle, three candidates chosen for further characterisation were found unexpectedly in the cytoplasmic compartment rather than in the nucleus. Transcriptomic survey of subcellular fractions found these candidates also associated with polyribosomes and one of them spanning transzonal projections between cumulus cells and the oocyte. Knocking down this transcript in matured oocytes increased developmental rates, leading to larger blastocysts. Transcriptome and methylome analyses of these blastocysts showed concordant data for a subset of four genes, including at least one known to be important for blastocyst survival. Functional characterisation of the roles played by lncRNA in supporting early development remains elusive. Our results suggest that some lncRNAs play a role in translation control of target mRNA. This would be important for managing the maternal reserves within which is embedded the embryonic program, especially before embryonic genome activation.
  • Publication
    Restreint
    Cumulus cell transcripts transit to the bovine oocyte in preparation for maturation
    (Society for the Study of Reproduction., 2015-11-13) Gilbert, Isabelle; Ettaoumi, Sara; Bastien, Alexandre; Gagné, Dominic; Ashkar, Fazl; Khandjian, Edward William; Macaulay, Angus; Shojaei Saadi, Habib Allah; Richard, François J.; Robert, Claude; Fournier, Éric; Sirard, Marc-André; Hyttel, P.
    So far, the characteristics of a good quality egg have been elusive, similar to the nature of the physiological, cellular, and molecular cues leading to its production both in vivo and in vitro. Current understanding highlights a strong and complex interdependence between the follicular cells and the gamete. Secreted factors induce cellular responses in the follicular cells, and direct exchange of small molecules from the cumulus cells to the oocyte through gap junctions controls meiotic arrest. Studying the interconnection between the cumulus cells and the oocyte, we previously demonstrated that the somatic cells also contribute transcripts to the gamete. Here, we show that these transcripts can be visualized moving down the transzonal projections (TZPs) to the oocyte, and that a time course analysis revealed progressive RNA accumulation in the TZPs, indicating that RNA transfer occurs before the initiation of meiosis resumption under a timetable fitting with the acquisition of developmental competence. A comparison of the identity of the nascent transcripts trafficking in the TZPs, with those in the oocyte increasing in abundance during maturation, and that are present on the oocyte's polyribosomes, revealed transcripts common to all three fractions, suggesting the use of transferred transcripts for translation. Furthermore, the removal of potential RNA trafficking by stripping the cumulus cells caused a significant reduction in maturation rates, indicating the need for the cumulus cell RNA transfer to the oocyte. These results offer a new perspective to the determinants of oocyte quality and female fertility, as well as provide insight that may eventually be used to improve in vitro maturation conditions.
  • Publication
    Accès libre
    Quantitative profiling of the UGT transcriptome in human drug metabolizing tissues
    (Nature Publishing Group., 2017-04-25) Rouleau, Michèle; Gilbert, Isabelle; Droit, Arnaud; Tourancheau, Alan; Guillemette, Chantal; Guauque-Olarte, Sandra; Villeneuve, Lyne
    Alternative splicing as a mean to control gene expression and diversify function is suspected to considerably influence drug response and clearance. We report the quantitative expression profiles of the human UGT genes including alternatively spliced variants not previously annotated established by deep RNA-sequencing in tissues of pharmacological importance. We reveal a comprehensive quantification of the alternative UGT transcriptome that differ across tissues and among individuals. Alternative transcripts that comprise novel in-frame sequences associated or not with truncations of the 5′- and/or 3′- termini, significantly contribute to the total expression levels of each UGT1 and UGT2 gene averaging 21% in normal tissues, with expression of UGT2 variants surpassing those of UGT1. Quantitative data expose preferential tissue expression patterns and remodeling in favor of alternative variants upon tumorigenesis. These complex alternative splicing programs have the strong potential to contribute to interindividual variability in drug metabolism in addition to diversify the UGT proteome.
  • Publication
    Accès libre
    Unravelling the transcriptomic landscape of the major phase II UDP-glucuronosyltransferase drug metabolizing pathway using targeted RNA sequencing
    (Nature, 2015-04-14) Lévesque, Éric; Margaillan, Guillaume; Rouleau, Michèle; Gilbert, Isabelle; Droit, Arnaud; Tourancheau, Alan; Guillemette, Chantal; Villeneuve, Lyne
    A comprehensive view of the human UDP-glucuronosyltransferase (UGT) transcriptome is a prerequisite to the establishment of an individual's UGT metabolic glucuronidation signature. Here, we uncover the transcriptome landscape of the 10 human UGT gene loci in normal and tumoral metabolic tissues by targeted RNA next-generation sequencing. Alignment on the human hg19 reference genome identifies 234 novel exon-exon junctions. We recover all previously known UGT1 and UGT2 enzyme-coding transcripts and identify over 130 structurally and functionally diverse novel UGT variants. We further expose a revised genomic structure of UGT loci and provide a comprehensive repertoire of transcripts for each UGT gene. Data also uncover a remodelling of the UGT transcriptome occurring in a tissue- and tumor-specific manner. The complex alternative splicing program regulating UGT expression and protein functions is likely critical in determining detoxification capacity of an organ and stress-related responses, with significant impact on drug responses and diseases.
  • Publication
    Restreint
    The gametic synapse : RNA transfer to the bovine oocyte
    (Oxford University Press, 2014-10-01) Gilbert, Isabelle; Caballero, Julieta; Tossou, Prudencio; Khandjian, Edward William; Macaulay, Angus; Richard, François J.; Barreto, Rodrigo; Clarke, Hugh James; Robert, Claude; Fournier, Éric; Sirard, Marc-André; Hyttel, P.
    Even after several decades of quiescent storage in the ovary, the female germ cell is capable of reinitiating transcription to build the reserves that are essential to support early embryonic development. In the current model of mammalian oogenesis, there exists bilateral communication between the gamete and the surrounding cells that is limited to paracrine signaling and direct transfer of small molecules via gap junctions existing at the end of the somatic cells' projections that are in contact with the oolemma. The purpose of this work was to explore the role of cumulus cell projections as a means of conductance of large molecules, including RNA, to the mammalian oocyte. By studying nascent RNA with confocal and transmission electron microscopy in combination with transcript detection, we show that the somatic cells surrounding the fully grown bovine oocyte contribute to the maternal reserves by actively transferring large cargo, including mRNA and long noncoding RNA. This occurrence was further demonstrated by the reconstruction of cumulus-oocyte complexes with transfected cumulus cells transferring a synthetic transcript. We propose selective transfer of transcripts occurs, the delivery of which is supported by a remarkable synapselike vesicular trafficking connection between the cumulus cells and the gamete. This unexpected exogenous contribution to the maternal stores offers a new perspective on the determinants of female fertility.