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S Boisseau

Publications and source records attributed to S Boisseau.

15 recordsLinked to original sources
PubMed2005

Na+ channel-mediated Ca2+ entry leads to glutamate secretion in mouse neocortical preplate.

Before synaptogenesis, early excitability implicating voltage-dependent and transmitter-activated channels is known to be crucial for neuronal development. We previously showed that preplate (PP) neurons of the mouse neocortex express functional Na(+) channels as early as embryonic day 12. In this study, we investigated the role of these Na(+) channels in signaling during early development. In the neocortex of embryonic-day-13 mice, activation of Na(+) channels with veratridine induced a large Ca(2+) response throughout the neocortex, even in cell populations that lack the Na(+) channel. This Na(+)-dependent Ca(2+) activity requires external Ca(2+) and is completely blocked by inhibitors of Na(+)/Ca(2+) exchangers. Moreover, veratridine-induced Ca(2+) increase coincides with a burst of exocytosis in the PP. In parallel, we show that Na(+) channel stimulation enhances glutamate secretion in the neocortical wall. Released glutamate triggers further Ca(2+) response in PP and ventricular zone, as indicated by the decreased response to veratridine in the presence of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor and NMDA-receptor inhibitors. Therefore, the combined activation of the Na(+) channel and the Na(+)/Ca(2+) exchanger triggers Ca(2+) signaling in the PP neurons, leading to glutamate secretion, which amplifies the signal and serves as an autocrine/paracrine transmitter before functional synapses are formed in the neocortex. Membrane depolarization induced by glycine receptors activation could be one physiological activator of this Na(+) channel-dependent pathway.

Animals↗
PubMed2001

The bacterial nucleoside N(6)-methyldeoxyadenosine induces the differentiation of mammalian tumor cells.

Contrary to bacterial DNA, mammalian DNA contains very little if any N(6)-methyldeoxyadenosine (MDA). The possible biological effect of this nucleoside on eukaryotic cells has been studied on different tumor cell lines. Addition of MDA to C6.9 glioma cells triggers a differentiation process and the expression of the oligodendroglial marker 2',3'-cyclic nucleotide 3'phosphorylase (CNP). The biological effects of N(6)-methyldeoxyadenosine were not restricted to C6.9 glioma cells since differentiation was also observed on pheochromocytoma and teratocarcinoma cell lines and on dysembryoplastic neuroepithelial tumor cells. The precise mechanism by which MDA induces cell differentiation remains unclear, but is related to cell cycle modifications. These data point out the potential interest of N(6)-methyldeoxyadenosine as a novel antitumoral and differentiation agent. They also raise the intriguing question of the loss of adenine methylation in mammalian DNA. Furthermore, the finding that a methylated nucleoside found in bacterial DNA induces a biological process might have implications in gene therapy approaches when plasmid DNAs are injected into humans.

2',3'-Cyclic Nucleotide 3'-Phosphodiesterase↗
PubMed2000

Muscle transfection by electroporation with high-voltage and short-pulse currents provides high-level and long-lasting gene expression.

Gene transfer into muscle by electroporation with low-voltage and long-pulse (LV/LP, 100 V/50 msec) currents was shown to be more efficient than simple intramuscular DNA injection. Nevertheless, transgene expression declined from day 7 and only reached 10% of the maximum 3 weeks after electroporation. We have optimized electroporation conditions including voltage, pulse number, and the amount of injected luciferase-encoding plasmid DNA in the tibialis anterior muscle. Using high-voltage and short-pulse (HV/SP, 900 V/100 microsec) currents, we observed an average 500-fold increase in luciferase expression, in comparison with nonelectroporated muscle. Moreover, sustained and long-lasting gene expression was observed for at least 6 months. When we compared HV/SP currents with LV/LP currents, luciferase expression was similar 24 hr after electroporation. One month later, whereas luciferase expression was stable in muscle electroporated with HV/SP currents, it decreased 600-fold in muscle electroporated with LV/LP currents. In conclusion, electroporation with high-voltage and short-pulse currents provides high-level and long-lasting gene expression in muscle.

Animals↗
PubMed1999

Therapeutic efficacy of the thymidine kinase/ganciclovir system on large experimental gliomas: a nuclear magnetic resonance imaging study.

Contradictory experimental results and human trials have questioned the clinical relevance of the HSVtk/ganciclovir system. To bypass the problem of transfection efficiency, we used a glioma cell line stably expressing the HSVtk gene, which was also fully characterized from gene to protein. We also designed a more clinically relevant experimental protocol, consisting of late GCV delivery on large tumor formations. In short-term studies, histological examination revealed a significant decrease in tumor volume in GCV-treated animals from day 1 or from day 10 after cell inoculation. We observed that late GCV delivery is as efficient as early delivery, probably because GCV can reach tumor cells more easily when neoangiogenesis occurs. In long-term experiments, the survival of treated rats bearing 15-day tumors was improved by 60% compared with C6 control animals. Surprisingly, a 30% survival rate was observed in C6TK control animals. Nuclear magnetic resonance imaging demonstrated, in all surviving animals, a complete regression of tumors without mass effect. These results clearly demonstrate that the HSVtk/GCV system remains a potent therapeutic strategy, even when tested in large tumors, in contrast with the microscopic tumor formations previously reported.

Animals↗
PubMed1994

Environmental signals and neural crest cells.

Cell lineage analysis in both the central and peripheral nervous system of vertebrates has revealed that many neural progenitor cells are multipotent. These observations have raised the general issue of when and how such multipotent progenitors generate their various differentiated progeny. The environment of these progenitors controls the cell lineage decisions in the neural crest. This review considers the roles of the environmental signals in the context of the development of several different neural crest-derived lineages.

Animals↗
PubMed1993

Alginate immobilized mammalian neurons: a potential tool to isolate new neuronal ligands.

We developed improved immobilization conditions which permitted (i) to immobilize neuroblastoma cells (N18) in calcium-alginate gel beads, (ii) to test the function of ionic channels using patch-clamp electrophysiological techniques and (iii) to quantitatively analyze ligand interactions with voltage-dependent sodium channels in neurons inside the beads. These results qualify this immobilization technique for the isolation and/or purification of ligands specific for neuronal cells.

Alginates↗
PubMed1991

Analysis of high PSA N-CAM expression during mammalian spinal cord and peripheral nervous system development.

Using a monoclonal antibody that recognizes specifically a high polysialylated form of N-CAM (high PSA N-CAM), the temporal and spatial expression of this molecule was studied in developing spinal cord and neural crest derivatives of mouse truncal region. Temporal expression was analyzed on immunoblots of spinal cord and dorsal root ganglia (DRGs) extracts microdissected at different developmental stages. Analysis of the ratio of high PSA N-CAM to total N-CAM indicated that sialylation and desialylation are independently regulated from the expression of polypeptide chains of N-CAM. Motoneurons, dorsal root ganglia cells and commissural neurons present a homogeneous distribution of high PSA N-CAMs on both their cell bodies and their neurites. Sialylation of N-CAM can occur in neurons after their aggregation in peripheral ganglia as demonstrated for dorsal root ganglia at E12. Furthermore, peripheral ganglia express different levels of high PSA N-CAM. With in vitro models using mouse neural crest cells, we found that expression of high PSA N-CAM was restricted to cells presenting an early neuronal phenotype, suggesting a common regulation for the expression of high PSA N-CAM molecules, neurofilament proteins and sodium channels. Using perturbation experiments with endoneuraminidase, we confirmed that high PSA N-CAM molecules are involved in fasciculation and neuritic growth when neurons derived from neural crest grow on collagen substrata. However, we demonstrated that these two parameters do not appear to depend on high PSA N-CAM molecules when cells were grown on a fibronectin substratum, indicating the existence of a hierarchy among adhesion molecules.

Animals↗
PubMed1991

A mammalian in vitro model to study gangliogenesis from neural crest cells.

In spite of considerable advances towards understanding lineages derived from neural crest cells using amphibian and avian embryos, the molecular mechanisms involved in the formation of mammalian peripheral ganglia remain largely unknown, mainly because of the lack of experimental systems that will allow their in vitro manipulation. Here, we present a novel mammalian in vitro model permitting to study gangliogenesis from neural crest cells. This model allowed us to manipulate molecules involved in cell-cell interactions. Our data are in favour of the existence of a hierarchy among adhesion molecules.

Animals↗
PubMed1990

Storage and growth of neuroblastoma cells immobilized in calcium-alginate beads.

Mouse neuroblastoma cells (N18) were immobilized in calcium-alginate gel beads. Under standard culture conditions (37 degrees C; 5% CO2), cell growth was observed inside the beads. The number of cells increased threefold during 7 days of culture with cell division and differentiation visualized by electron microscopy. Cell properties maintained after short-term storage (2-3 days at 4 degrees C) included: (i) properties of voltage-dependent ionic channels tested by patch-clamp electrophysiological techniques; (ii) expression of cell-adhesion membrane proteins tested by immunohistochemistry (iii) morphological differentiation obtained by depletion of foetal calf serum in culture medium. The advantages of such an immobilization technique as applied to neurone cells are discussed.

Alginates↗
PubMed1990

Advantages of mouse models to study early steps of peripheral nervous system development.

The molecular mechanisms involved in the formation of mammalian peripheral nervous system remain largely unknown. Here we describe the new possibilities offered by mouse mutant analysis, new mouse in vitro models and the recent development of molecular genetic techniques which may permit analysis of the peripheral nervous system development at a level that was heretofore restricted to lower vertebrates.

Animals↗
PubMed1989

Expression of voltage-dependent sodium and transient potassium currents in an identified sub-population of dorsal root ganglion cells acutely isolated from 12-day-old mouse embryos.

The electrophysiological properties of a subset of dorsal root ganglion (DRG) neurons microdissected from 12-day-old (E12) mouse embryos and acutely isolated were analyzed as soon as 3 h after their isolation. Two classes of neurons were defined according to their mean diameter. The larger diameter class was examined in this study. They display uniform cytoskeletal properties with co-expression of vimentin and neurofilament triplet proteins. Patch-clamp methods also revealed a homogeneous and limited repertoire of ionic channels that included (1) a TTX-sensitive Na+ current whose properties are similar to that reported in mature mammalian neurons, and (2) two types of K+ currents that can be compared with the delayed rectifier (Ik) and the transient (IA) potassium currents found in other mammalian preparations. It may be possible to use this in vitro model to examine the development of new types of currents, such as Ca2+ currents during neuronal growth and differentiation.

Animals↗
PubMed1989

Mammalian neuronal differentiation: early expression of a neuronal phenotype from mouse neural crest cells in a chemically defined culture medium.

We show that mouse neural crest cells cultured in a serum-deprived chemically defined medium on appropriate culture substrata can be induced to express a neuronal phenotype. The uncommitted neural crest cells express a mesenchymal intermediate filament protein such as vimentin, but not the usual neuronal markers such as receptor sites for tetanus toxin or neurofilaments. In the chemically defined medium, receptor sites for tetanus toxin or neurofilaments can be characterized after a few hours in culture. Furthermore, these cells acquire tetrodotoxin-sensitive voltage-dependent Na+ channels and can generate action potentials. Such an in vitro system should allow us to analyze and manipulate early stages of neuronal differentiation in a mammalian embryo, at a level so far restricted to lower vertebrate embryos.

Action Potentials↗
PubMedDate not supplied

Both upstream and intragenic sequences of the human neurofilament light gene direct expression of lacZ in neurons of transgenic mouse embryos.

Initial expression of the neurofilament light gene coincides with the appearance of postmitotic neurons. To investigate the molecular mechanisms involved in neuron-specific gene expression during embryogenesis, we generated transgenic mice carrying various regions of the human neurofilament light gene (hNF-L) fused to the lacZ reporter gene. We found that 2.3 or 0.3 kb of the hNF-L promoter region directs expression of lacZ in neurons of transgenic embryos. Addition of 1.8 kb hNF-L intragenic sequences (IS) enlarges the neuronal pattern of transgene expression. The 2.3-kb hNF-L promote lacZ-IS construct contains all regulatory elements essential for both spatial and temporal expression of the hNF-L gene during embryogenesis and in the adult. The use of a heterologous promoter demonstrated that the 1.8-kb hNF-L intragenic sequences are sufficient to direct the expression of lacZ in a NF-L-specific manner both temporally and spatially during development and in the adult. We conclude that these hNF-L intragenic sequences contain cis-acting DNA regulatory elements that specify neuronal expression. Taken together, these results show that the neurofilament light gene contains separate upstream and intragenic elements, each of which directs lacZ expression in embryonic neurons.

Animals↗