title: Undifferentiated embryonic stem cells express ionotropic glutamate receptor mRNAs.
abstract: Ionotropic glutamate receptors (iGluRs) do not only mediate the majority of excitatory neurotransmission in the vertebrate CNS, but also modulate pre- and postnatal neurogenesis. Most of the studies on the developmental role of iGluRs are performed on neural progenitors and neural stem cells (NSCs). We took a step back in our study by examining the role of iGluRs in the earliest possible cell type, embryonic stem cells (ESCs), by looking at the mRNA expression of the major iGluR subfamilies in undifferentiated mouse ESCs. For that, we used two distinct murine ES cell lines, 46C ESCs and J1 ESCs. Regarding 46C ESCs, we found transcripts of kainate receptors (KARs) (GluK2 to GluK5), AMPA receptors (AMPARs) (GluA1, GluA3, and GluA4), and NMDA receptors (NMDARs) (GluN1, and GluN2A to GluN2D). Analysis of 46C-derived cells of later developmental stages, namely neuroepithelial precursor cells (NEPs) and NSCs, revealed that the mRNA expression of KARs is significantly upregulated in NEPs and, subsequently, downregulated in NSCs. However, we could not detect any protein expression of any of the KAR subunits present on the mRNA level either in ESCs, NEPs, or NSCs. Regarding AMPARs and NMDARs, GluN2A is weakly expressed at the protein level only in NSCs. Matching our findings for iGluRs, all three cell types were found to weakly express pre- and postsynaptic markers of glutamatergic synapses only at the mRNA level. Finally, we performed patch-clamp recordings of 46C ESCs and could not detect any current upon iGluR agonist application. Similar to 46C ESCs, J1 ESCs express KARs (GluK2 to GluK5), AMPARs (GluA3), and NMDARs (GluN1, and GluN2A to GluN2D) at the mRNA level, but these transcripts are not translated into receptor proteins either. Thus, we conclude that ESCs do not contain functional iGluRs, although they do express an almost complete set of iGluR subunit mRNAs.
authors.affiliation: Department of Biochemistry I - Receptor Biochemistry, Ruhr University Bochum Bochum, Germany ; International Graduate School of Neuroscience, Ruhr University Bochum Bochum, Germany ; Ruhr University Research School, Ruhr University Bochum Bochum, Germany.
authors.forename: Svenja
authors.initials: S
authors.lastname: Pachernegg
authors.affiliation: Department of Biochemistry I - Receptor Biochemistry, Ruhr University Bochum Bochum, Germany ; International Graduate School of Neuroscience, Ruhr University Bochum Bochum, Germany ; DFG Graduate School 736, Ruhr University Bochum Bochum, Germany.
authors.forename: Illah
authors.initials: I
authors.lastname: Joshi
authors.affiliation: Department of Biochemistry I - Receptor Biochemistry, Ruhr University Bochum Bochum, Germany ; International Graduate School of Neuroscience, Ruhr University Bochum Bochum, Germany ; Ruhr University Research School, Ruhr University Bochum Bochum, Germany.
authors.forename: Elke
authors.initials: E
authors.lastname: Muth-Köhne
authors.affiliation: Department of Biochemistry I - Receptor Biochemistry, Ruhr University Bochum Bochum, Germany ; International Graduate School of Neuroscience, Ruhr University Bochum Bochum, Germany ; Ruhr University Research School, Ruhr University Bochum Bochum, Germany.
authors.forename: Steffen
authors.initials: S
authors.lastname: Pahl
authors.affiliation: Department of Biochemistry I - Receptor Biochemistry, Ruhr University Bochum Bochum, Germany.
authors.forename: Yvonne
authors.initials: Y
authors.lastname: Münster
authors.affiliation: Department of Biochemistry I - Receptor Biochemistry, Ruhr University Bochum Bochum, Germany ; Ruhr University Research School, Ruhr University Bochum Bochum, Germany ; DFG Graduate School 736, Ruhr University Bochum Bochum, Germany.
authors.forename: Jan
authors.initials: J
authors.lastname: Terhag
authors.affiliation: International Graduate School of Neuroscience, Ruhr University Bochum Bochum, Germany ; Ruhr University Research School, Ruhr University Bochum Bochum, Germany ; Department of Cell Morphology and Molecular Neurobiology, Ruhr University Bochum Bochum, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Karus
authors.affiliation: Department of Biochemistry I - Receptor Biochemistry, Ruhr University Bochum Bochum, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Werner
authors.affiliation: Department of Biochemistry I - Receptor Biochemistry, Ruhr University Bochum Bochum, Germany ; International Graduate School of Neuroscience, Ruhr University Bochum Bochum, Germany.
authors.forename: Zhan-Lu
authors.initials: ZL
authors.lastname: Ma-Högemeier
authors.affiliation: Department of Biochemistry I - Receptor Biochemistry, Ruhr University Bochum Bochum, Germany.
authors.forename: Christoph
authors.initials: C
authors.lastname: Körber
authors.affiliation: Department of Molecular and Medical Virology, Ruhr University Bochum Bochum, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Grunwald
authors.affiliation: Department of Cell Morphology and Molecular Neurobiology, Ruhr University Bochum Bochum, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Faissner
authors.affiliation: Group for Molecular Cell Biology, Department of Cell Morphology and Molecular Neurobiology, Ruhr University Bochum Bochum, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Wiese
authors.affiliation: Department of Biochemistry I - Receptor Biochemistry, Ruhr University Bochum Bochum, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Hollmann
keywords: ESCs; neural stem cells; neuroepithelial cells; patch-clamp recordings; qRT-PCR; synaptic markers