Hyperpolarization-activated and cyclic nucleotide-gated channels are differentially expressed in juxtaglomerular cells in the olfactory bulb of mice

In the olfactory bulb, input from olfactory receptor neurons is processed by neuronal networks before it is relayed to higher brain regions. In many neurons, hyperpolarization-activated and cyclic nucleotide-gated (HCN) channels generate and control oscillations of the membrane potential. Oscillations also appear crucial for information processing in the olfactory bulb. Four channel isoforms exist (HCN1–HCN4) that can form homo- or heteromers. Here, we describe the expression pattern of HCN isoforms in the olfactory bulb of mice by using a novel and comprehensive set of antibodies against all four isoforms. HCN isoforms are abundantly expressed in the olfactory bulb. HCN channels can be detected in most cell populations identified by commonly used marker antibodies. The combination of staining with marker and HCN antibodies has revealed at least 17 different staining patterns in juxtaglomerular cells. Furthermore, HCN isoforms give rise to an unexpected wealth of co-expression patterns but are rarely expressed in the same combination and at the same level in two given cell populations. Therefore, heteromeric HCN channels may exist in several cell populations in vivo. Our results suggest that HCN channels play an important role in olfactory information processing. The staining patterns are consistent with the possibility that both homomeric and heteromeric HCN channels are involved in oscillations of the membrane potential of juxtaglomerular cells

Doublecortin maintains bipolar shape and nuclear translocation during migration in the adult forebrain

The ability of the mature mammalian nervous system to continually produce neuronal precursors is of considerable importance, as manipulation of this process might one day permit the replacement of cells lost as a result of injury or disease. In mammals, the anterior subventricular zone (SVZa) region is one of the primary sites of adult neurogenesis. Here we show that doublecortin (DCX), a widely used marker for newly generated neurons, when deleted in mice results in a severe morphological defect in the rostral migratory stream and delayed neuronal migration that is independent of direction or responsiveness to Slit chemorepulsion. DCX is required for nuclear translocation and maintenance of bipolar morphology during migration of these cells. Our data identifies a critical function for DCX in the movement of newly generated neurons in the adult brain

BdR-repr\ue9sentations dans le cas relatif

-representations in the relative case In this work, we develop a relative analogue of Sen's theory for -representations. We give applications to the theory of -adic representations, linking it to the theory of relative -modules and to the theory of -adic Higgs modules, developed by G. Faltings

Surconvergence des repr\ue9sentations p-adiques : le cas relatif

We generalize Tate-Sen's formalism; this allows to extend Sen's theory and to prove the overconvergence of $p$-adic representations in the relative case

N003 Caractérisation électrophysiologique de progéniteurs cardiaques issus de cellules souches embryonnaires humaines

Les progéniteurs cardiaques issus de cellules souches embryonnaires humaines apparaissent comme de bons candidates dans la prévention et le traitement de la dysfonction cardiaque par thérapie cellulaire. Cependant, la greffe de cellules présentant des propriétés électriques indésirables pourrait prédisposer les patients à des arythmies. Il est donc important de caractériser les propriétés électrophysiologiques des progéniteurs cardiaques avant transplantation. Les cellules progénitrices cardiaques utilisées sont dérivées de la lignée HUES-24 et sélectionnées sur leur capacité à exprimer SSEA-1 après une induction de 4 jours par le BMP2. A l’aide de la technique de patch-clamp en configuration cellule entière, nous avons pu enregistrer des courants Ca2+ et K+, 24 à 48 H après la sélection. Les courants Ca2+ observés (2,22 ± 0.30 Pa/pF) sont de type L, aucun courant de type T n’ayant été détecté dans ces conditions. Ces courants sont insensibles à l’isoprotérénol (1μm) et à la forskoline (30μm) suggérant l’absence de regulation β-adrénergique. Des courants K+ activés par depolarization (6.79 ± 1.10 Pa/pF) sensibles au tétraéthylammonium (10 mM) et à la 4-aminopyridine (5 mM) ont été caractérisés. Ces courants rectifiants sortants ressemblent aux courants rectifiants sortants retardés (IKDR) déjà décrits sur des cellules souches embryonnaires murines. En revanche, aucun courant entrant activé par hyperpolarisation n’a été observé. Finalement, aucune conductance Na+ n’a pu être mise en évidence. Sur les cellules n’exprimant pas SSEA-1, utilisées comme contrôles négatifs, aucun courant Ca2+, K+ ou Na+ n’a été détecté. Le profil moléculaire des canaux ioniques exprimés par les cellules progénitrices est abordé parallèlement par une approche génomique à l’aide de la RT-PCR haut débit.En conclusion, les cellules souches embryonnaires humaines présentent les courants majeurs impliqués dans l’électrogenèse cardiaque dès 24 h après leur orientation cardiaque. Néanmoins, l’absence de régulation β-adrénergique et de courants Na+ souligne l’immaturité de ces cellules comparées aux cardiomyocytes matures. Le suivi de la genèse des propriétés électrophysiologiques de ces progéniteurs cardiaques, dans le contexte d’une thérapie cellulaire cardiovasculaire, devrait nous permettre d’explorer la capacité de ces cellules à exprimer un phénotype électrophysiologique mature et à établir des couplages excitation-contraction avec les cellules hôte

Effects of MSC Coadministration and Route of Delivery on Cord Blood Hematopoietic Stem Cell Engraftment

Hematopoietic stem cell transplantation (HSCT) using umbilical cord blood (UCB) progenitors is increasingly being used. One of the problems that may arise after UCB transplantation is an impaired engraftment. Either intrabone (IB) injection of hematopoietic progenitors or mesenchymal stem cell (MSC) coadministration has been proposed among the strategies to improve engraftment. In the current study, we have assessed the effects of both approaches. Thus, NOD/SCID recipients were transplanted with human UCB CD34+ cells administered either intravenously (IV) or IB, receiving or not bone marrow (BM)-derived MSCs also IV or IB (in the right femur). Human HSC engraftment was measured 3 and 6 weeks after transplantation. Injected MSCs were tracked weekly by bioluminescence. Also, lodgment within the BM niche was assessed at the latter time point by immunofluorescence. Our study shows regarding HSC engraftment that the number of BM human CD45+ cells detected 3 weeks after transplantation was significantly higher in mice cotransplanted with human MSCs. Moreover, these mice had a higher myeloid (CD13+) engraftment and a faster B-cell (CD19+) chimerism. At the late time point evaluated (6 weeks), human engraftment was higher in the group in which both strategies were employed (IB injection of HSC and MSC coadministration). When assessing human MSC administration route, we were able to track MSCs only in the injected femurs, whereas they lost their signal in the contralateral bones. These human MSCs were mainly located around blood vessels in the subendosteal region. In summary, our study shows that MSC coadministration can enhance HSC engraftment in our xenogenic transplantation model, as well as IB administration of the CD34+ cells does. The combination of both strategies seems to be synergistic. Interestingly, MSCs were detected only where they were IB injected contributing to the vascular niche

High throughput screening for inhibitors of REST in neural derivatives of human embryonic stem cells reveals a chemical compound that promotes expression of neuronal genes

Decreased expression of neuronal genes such as brain-derived neurotrophic factor (BDNF) is associated with several neurological disorders. One molecular mechanism associated with Huntington disease (HD) is a discrete increase in the nuclear activity of the transcriptional repressor REST/NRSF binding to repressor element-1 (RE1) sequences. High-throughput screening of a library of 6,984 compounds with luciferase-assay measuring REST activity in neural derivatives of human embryonic stem cells led to identify two benzoimidazole-5-carboxamide derivatives that inhibited REST silencing in a RE1-dependent manner. The most potent compound, X5050, targeted REST degradation, but neither REST expression, RNA splicing nor binding to RE1 sequence. Differential transcriptomic analysis revealed the upregulation of neuronal genes targeted by REST in wild-type neural cells treated with X5050. This activity was confirmed in neural cells produced from human induced pluripotent stem cells derived from a HD patient. Acute intraventricular delivery of X5050 increased the expressions of BDNF and several other REST-regulated genes in the prefrontal cortex of mice with quinolinate-induced striatal lesions. This study demonstrates that the use of pluripotent stem cell derivatives can represent a crucial step toward the identification of pharmacological compounds with therapeutic potential in neurological affections involving decreased expression of neuronal genes associated to increased REST activity, such as Huntington disease