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Personne :
Khan, Daulat Raheem

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Khan

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Daulat Raheem

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

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ncf11892089

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  • PublicationRestreint
    Transcriptomic analysis of cyclic AMP response in bovine cumulus cells
    (American Physiological Society, 2015-09-01) Khan, Daulat Raheem; Richard, François J.; Guillemette, Chantal; Sirard, Marc-André
    Acquisition of oocyte developmental competence needs to be understood to improve clinical outcomes of assisted reproduction. The stimulation of cumulus cell concentration of cyclic adenosine 3′5′-monophosphate (cAMP) by pharmacological agents during in vitro maturation (IVM) participates in improvement of oocyte quality. However, precise coordination and downstream targets of cAMP signaling in cumulus cells are largely unknown. We have previously demonstrated better embryo development after cAMP stimulation for first 6 h during IVM. Using this model, we investigated cAMP signaling in cumulus cells through in vitro culture of cumulus-oocyte complexes (COCs) in the presence of cAMP raising agents: forskolin, IBMX, and dipyridamole (here called FID treatment). Transcriptomic analysis of cumulus cells indicated that FID-induced differentially expressed transcripts were implicated in cumulus expansion, steroidogenesis, cell metabolism, and oocyte competence. Functional genomic analysis revealed that protein kinase-A (PKA), extracellular signal regulated kinases (ERK1/2), and calcium (Ca2+) pathways as key regulators of FID signaling. Inhibition of PKA (H89) in FID-supplemented COCs or substitution of FID with calcium ionophore (A23187) demonstrated that FID activated primarily the PKA pathway which inhibited ERK1/2 phosphorylation and was upstream of calcium signaling. Furthermore, inhibition of ERK1/2 phosphorylation by FID supported a regulation by dual specific phosphatase (DUSP1) via PKA. Our findings imply that cAMP (FID) regulates cell metabolism, steroidogenesis, intracellular signaling and cumulus expansion through PKA which modulates these functions through optimization of ERK1/2 phosphorylation and coordination of calcium signaling. These findings have implications for development of new strategies for improving oocyte in vitro maturation leading to better developmental competence.
  • PublicationRestreint
    Characterization of FSH signalling networks in bovine cumulus cells : a perspective on oocyte competence acquisition
    (Oxford University Press, 2015-06-24) Khan, Daulat Raheem; Richard, François J.; Guillemette, Christine; Sirard, Marc-André
    Understanding the mechanisms regulating oocyte developmental competence is essential to enhance the clinical efficiency of assisted reproduction. FSH orchestrates the acquisition of oocyte competence, both in vivo and in vitro. Multiple pathways are implicated in FSH signalling; however, their precise coordination remains unresolved. A robust system to investigate FSH signalling is oocyte in vitro maturation (IVM) and we have previously demonstrated better bovine embryo development after FSH addition for the first 6 h during IVM. Using this model, we investigated FSH signalling in cumulus through transcriptomic and pharmacological tools. We demonstrate modulation of cumulus transcriptome by FSH mainly through protein kinase A (PKA) and epidermal growth factor (EGF) pathways. Differentially expressed transcripts were implicated in cumulus expansion, steroidogenesis, cell metabolism and oocyte competence. FSH required rouse-sarcoma oncogene (SRC) for EGF receptor transactivation. PKA and EGF pathway crosstalk was investigated using extracellular signal-regulated kinases (ERK1/2) phosphorylation as the functional end-point. FSH enhanced ERK1/2 activation by the EGF pathway with a simultaneous diminution through PKA. More specifically, FSH increased dual specific phosphatase (DUSP1) transcripts via PKA although DUSP1 protein did not change since EGF was required to prevent degradation. Our findings implicate FSH in PKA and EGF pathway activation, which interact to maintain appropriate levels of ERK1/2 phosphorylation and eventually cumulus expansion, metabolism and steroidogenesis. Moreover, considering the implication of the EGF pathway in GDF9 and BMP15 actions, our findings suggest that FSH may have a role in modulation of the cumulus response to oocyte-secreted factors. This information has implications for improvement of IVM and hence oocyte developmental competence.