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Personne :
Vigneault, Christian

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Vigneault

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Christian

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Département des sciences animales, Faculté des sciences de l'agriculture et de l'alimentation, Université Laval

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ncf11855439

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Voici les éléments 1 - 6 sur 6
  • PublicationAccès libre
    Étude de l'activation de la transcription chez le jeune embryon bovin
    (2008) Vigneault, Christian; Viger, Robert S.; Sirard, Marc-André
    Chez une multitude de métazoaires étudiés, une période de quiescence transcriptionnelle est observée chez le jeune embryon suite à la fécondation de l'ovocyte. La durée de cette période est spécifique à chaque espèce et chez le bovin, l'embryon n'active son propre génome qu'aux stades 8- à 16-cellules. Précédemment à cette activation de la transcription, l'embryon subsiste grâce à l'utilisation des ARNm et des protéines fournies par l'ovocyte. C'est également à partir de ces réserves que l'embryon doit puiser les différents facteurs impliqués dans l'activation de son génome au moment requis. Les expériences présentées dans cette thèse étaient destinées à améliorer nos connaissances de l'activation du génome embryonnaire chez le bovin. Dans un premier temps, la caractérisation de l'expression de plusieurs facteurs de transcription chez l'embryon a été effectuée et le rôle envisageable de ces facteurs dans l'activation du génome a aussi été démontré. Par la suite, nous avons établi une liste exhaustive de plus de 300 transcrits embryonnaires exprimés très tôt dès l'activation du génome. Cette étude du transcriptome a permis l'identification d'une multitude de gènes associés à la transcription et au maintient de la pluripotence que l'on retrouve chez les cellules embryonnaires. Afin de définir la fonction ou le rôle des différents joueurs identifiés lors de nos études, nous avons mis au point un procédé qui cible spécifiquement un transcrit donné et induit sa dégradation dans les ovocytes bovins sans toutefois induire des effets collatéraux dommageables sur la compétence au développement de ces ovocytes. Cette méthode utilise l'interférence ARN qui réduit à des niveaux très faibles la présence d'un transcrit ciblé, ce qui permet d'étudier les effets de sa perte de fonction. Cette méthode a permis d'établir le rôle crucial dans l'embryon d'un gène issu de nos premières études : MATRIN 3. La dégradation de l'ARN de MATRIN 3, une composante architecturale de la matrice nucléaire qui agit aussi au niveau de la transcription, s'est avérée avoir des effet néfastes sur la survie embryonnaire. Les informations fournies par la combinaison des études présentées dans cette thèse contribuent à dresser un portrait mieux défini de l'activation du génome chez le bovin.
  • PublicationRestreint
    Papaverine-sensitive phosphodiesterase activity is measured in bovine spermatozoa
    (Wiley, 2016-11-16) Vigneault, Christian; Poulin, Marie-Pier; Bergeron, Annick; Leclerc, Pierre; Richard, François J.; Sullivan, Robert; Hébert, Audrey; Guillemette, Christine; Aragon, Juan Pablo; Laroche, A.; Blondin, Patrick.
    Cyclic adenosine monophosphate (cAMP) plays a crucial role as a signaling molecule for capacitation, motility, and acrosome reaction in mammalian spermatozoa. It is well‐known that cAMP degradation by phosphodiesterase (PDE) enzyme has a major impact on sperm functions. This study was undertaken to characterize cAMP‐PDE activity in bovine spermatozoa. Total cAMP‐PDE activity in cauda epididymal and ejaculated spermatozoa was 543.2 ± 49.5 and 1252.6 ± 86.5 fmoles/min/106 spermatozoa, respectively. Using different family‐specific PDE inhibitors, we showed that in cauda epididymal and ejaculated spermatozoa, the major cAMP‐PDE activity was papaverine‐sensitive (44.5% and 57.5%, respectively, at 400 nm, papaverine is a specific inhibitor of the PDE10 family). These data are supporting the functional presence of PDE10 in bovine spermatozoa and were further confirmed by western blot to be PDE10A. Using immunocytochemistry, we showed immunoreactive signal for PDE10A present on the post‐acrosomal region of the head and on the flagella of ejaculated spermatozoa. Using papaverine, we showed that it promotes tyrosine phosphorylation of sperm proteins, phosphorylation of Erk1 and Erk2, and Ca²+ release from Ca²+ store. These results suggest that PDE10 is functionally present in bovine spermatozoa and is affecting different molecular events involved in capacitation, most probably by cAMP local regulation.
  • PublicationRestreint
    The use of adenosine to inhibit oocyte meiotic resumption in Bos taurus during pre-IVM and its potential to improve oocyte competence
    (Elsevier Inc., 2019-10-07) Vigneault, Christian; Caballero, Julieta; Richard, François J.; Sirard, Marc-André; Blondin, Patrick.
    One of the major challenges of artificial reproductive technologies is to develop new methods for pro-ducing greater numbers of embryos. An oocyte fosters the ability to develop into an embryo beforeoocyte meiotic resumption. The aim of the present study was to assess the effect of adenosine (ADO), apurine nucleoside found in follicularfluid, on the inhibition of oocyte meiotic resumption and theproduction of blastocysts. The results showed the efficacy of ADO to inhibit oocyte meiotic resumption.The use of ADO (3 mM) during a pre-in vitro maturation (pre-IVM) culture period of 6 h resulted in asignificant increase (p<0.05) of blastocysts compared to control conditions with no pre-IVM cultureperiod. No effect on the percentage of cleavage was observed. The effect of adenosine on blastocyst yieldwas time- and concentration-dependent with an optimum effect at 3 mM for 6 h. Supplementing theADO pre-IVM culture medium with estradiol, follicle-stimulating hormone, progesterone, epidermalgrowth factor, insulin-like growth factor-2 or reelin did not improve the blastocyst yield. Transcriptionalanalyses of ADO-treated cumulus cells revealed that NRP1, RELN, MAN1A1, THRA and GATM were up-regulated. Finally, bioinformatic analysis identified mitochondrial function as the top canonicalpathway affected by ADO. This opens up new opportunities for further investigations.
  • PublicationRestreint
    Cumulus cell gene expression associated with pre-ovulatory acquisition of developmental competence in bovine oocytes
    (Commonwealth Scientific and Industrial Research Organization, 2013-07-05) Vigneault, Christian; Bunel, Audrey; Nivet, Anne-Laure; Richard, François J.; Sirard, Marc-André; Blondin, Patrick.
    The final days before ovulation impact significantly on follicular function and oocyte quality. This study investigated the cumulus cell (CC) transcriptomic changes during the oocyte developmental competence acquisition period. Six dairy cows were used for 24 oocyte collections and received FSH twice daily over 3 days, followed by FSH withdrawal for 20, 44, 68 and 92 h in four different oestrous cycles for each of the six cows. Half of the cumulus–oocyte complexes were subjected to in vitro maturation, fertilisation and culture to assess blastocyst rate. The other half of the CC underwent microarray analysis (n = 3 cows, 12 oocyte collections) and qRT-PCR (n = 3 other cows, 12 oocyte collections). According to blastocyst rates, 20 h of FSH withdrawal led to under-differentiated follicles (49%), 44 and 68 h to the most competent follicles (71% and 61%) and 92 h to over-differentiated ones (51%). Ten genes, from the gene lists corresponding to the three different follicular states, were subjected to qRT-PCR. Interestingly, CYP11A1 and NSDHL gene expression profiles reflected the blastocyst rate. However most genes were associated with the over-differentiated status: GATM, MAN1A1, VNN1 and NRP1. The early period of FSH withdrawal has a minimal effect on cumulus gene expression, whereas the longest period has a very significant one and indicates the beginning of the atresia process.
  • PublicationAccès 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.
  • PublicationRestreint
    Changes in granulosa cells' gene expression associated with increased oocyte competence in bovine.
    (Journals of Reproduction and Fertility, 2013-05-01) Nivet, Anne-Laure; Vigneault, Christian; Sirard, Marc-André; Blondin, Patrick.
    One of the challenges in mammalian reproduction is to understand the basic physiology of oocyte quality. It is believed that the follicle status is linked to developmental competence of the enclosed oocyte. To explore the link between follicles and competence in cows, previous research at our laboratory has developed an ovarian stimulation protocol that increases and then decreases oocyte quality according to the timing of oocyte recovery post-FSH withdrawal (coasting). Using this protocol, we have obtained the granulosa cells associated with oocytes of different qualities at selected times of coasting. Transcriptome analysis was done with Embryogene microarray slides and validation was performed by real-time PCR. Results show that the major changes in gene expression occurred from 20 to 44 h of coasting, when oocyte quality increases. Secondly, among upregulated genes (20-44 h), 25% were extracellular molecules, highlighting potential granulosa signaling cascades. Principal component analysis identified two patterns: one resembling the competence profile and another associated with follicle growth and atresia. Additionally, three major functional changes were identified: (i) the end of follicle growth (BMPR1B, IGF2, and RELN), involving interactions with the extracellular matrix (TFPI2); angiogenesis (NRP1), including early hypoxia, and potentially oxidative stress (GFPT2, TF, and VNN1) and (ii) apoptosis (KCNJ8) followed by iii) inflammation (ANKRD1). This unique window of analysis indicates a progressive hypoxia during coasting mixed with an increase in apoptosis and inflammation. Potential signaling pathways leading to competence have been identified and will require downstream testing. This preliminary analysis supports the potential role of the follicular differentiation in oocyte quality both during competence increase and decrease phases.