Personne : Khandjian, Edward William
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Université Laval. Département de psychiatrie et de neurosciences
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- PublicationRestreintCumulus 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.
- PublicationRestreintThe 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.
- PublicationAccès libreDicer-derived microRNAs are utilized by the Fragile X mental retardation protein for assembly on target RNAs(2006-09-06) Tremblay, Sandra; Ouellet, Dominique; Khandjian, Edward William; Plante, Isabelle; Provost, Patrick; Davidovic, Laetitia; Gobeil, Lise-AndréeIn mammalian cells, fragile X mental retardation protein (FMRP) has been reported to be part of a microRNA (miRNA)-containing effector ribonucleoprotien (RNP) complex believed to mediate translational control of specific mRNAs. Here, using recombinant proteins, we demonstrate that human FMRP can act as a miRNA acceptor protein for the ribonuclease Dicer and facilitate the assembly of miRNAs on specific target RNA sequences. The miRNA assembler property of FMRP was abrogated upon deletion of its single-stranded (ss) RNA binding K-homology domains. The requirement of FMRP for efficient RNA interference (RNAi) in vivo was unveiled by reporter gene silencing assays using various small RNA inducers, which also supports its involvement in an ss small interfering RNA (siRNA)-containing RNP (siRNP) effector complex in mammalian cells. Our results define a possible role for FMRP in RNA silencing and may provide further insight into the molecular defects in patients with the fragile X syndrome.