Neurons derived from P19 embryonal carcinoma cells develop responses to excitatory and inhibitory neurotransmitters

Murine teratocarcinoma-derived neuronal cultures

This chapter describes the culture and propagation of murine embryonic stem cells, F9 and P19 and strategies for differentiation of these stem cells into neurons. Protocols focus on maintenance and propagation of these cells and routine procedures employed for differentiation into neuronal cells. Additional protocols are also described for obtaining enriched populations of mature neurons from P19 cells and differentiation of F9 cells into serotonergic or catecholaminergic neurons.The protocols described herein can be employed for dissection of the pathways such as gliogenesis and neurogenesis that are involved in differentiation of pluripotent stem cells such as F9 and P19 into glial cells or terminally differentiated neurons.

Expression of functional CB1 cannabinoid receptors in retinoic acid-differentiated P19 embryonal carcinoma cells

Although primary neuronal cell cultures, usually obtained from embryonic or early postnatal rodents, have been used in vitro to study the neural cannabinoid signalling system, development of cell lines with neural properties exhibiting native expression of cannabinoid receptors is desirable. This study was undertaken to investigate the expression of CB1 and CB2 cannabinoid receptors in neurons that develop from retinoic acid (RA)-primed mouse P19 embryonal carcinoma cells. Both undifferentiated P19 cells and RA-treated P19 neurons were positive, by using reverse transcription-polymerase chain reaction (RT-PCR), for CB1 (but not CB2) mRNA. Neuronal differentiation increased the CB1 mRNA expression, and Western blotting with a CB1 receptor antibody showed a strong immunoreactive band at approximately 62 kDa in membranes from P19-derived neurons. The cannabinoid receptor agonists CP 55,940 and HU-210 produced concentration-dependent inhibition of forskolin-induced (3 microM) cyclic AMP production in the P19-derived neurons (29% at 1 microM CP 55,940 and 34% at 1 microM HU-210), which could be blocked by the CB1-selective receptor antagonist AM251, but not by the CB2-selective antagonist AM630. Furthermore, glutamate (100 microM) induced a sustained increase in [Ca2+]i in P19-derived neurons that could be concentration-dependently blocked by the cannabinoid receptor agonists WIN 55,212-2. Thus, the protocol used provides an in vitro model system expressing CB1 cannabinoid receptors at the level of mRNA, protein, and AM251-sensitive agonist-induced inhibition of intracellular cyclic AMP accumulation, which may be useful to investigate the developmental regulation, expression and function of neuronal cannabinoid receptors.

Laminin activates CaMK-II to stabilize nascent embryonic axons

In neurons, the interaction of laminin with its receptor, beta1 integrin, is accompanied by an increase in cytosolic Ca2+. Neuronal behavior is influenced by CaMK-II, the type II Ca2+/calmodulin-dependent protein kinase, which is enriched in axons of mouse embryonic neurons. In this study, we sought to determine whether CaMK-II is activated by laminin, and if so, how CaMK-II influences axonal growth and stability. Axons grew up to 200 microm within 1 day of plating P19 embryoid bodies on laminin-1 (EHS laminin). Activated CaMK-II was found enriched along the axon and in the growth cone as detected using a phospho-Thr(287) specific CaMK-II antibody. beta1 integrin was found in a similar pattern along the axon and in the growth cone. Direct inhibition of CaMK-II in 1-day-old neurons immediately froze growth cone dynamics, disorganized F-actin and ultimately led to axon retraction. Collapsed axonal remnants exhibited diminished phospho-CaMK-II levels. Treatment of 1-day neurons with a beta1 integrin-blocking antibody (CD29) also reduced axon length and phospho-CaMK-II levels and, like CaMK-II inhibitors, decreased CaMK-II activation. Among several CaMK-II variants detected in these cultures, the 52-kDa delta variant preferentially associated with actin and beta 3 tubulin as determined by reciprocal immunoprecipitation. Our findings indicate that persistent activation of delta CaMK-II by laminin stabilizes nascent embryonic axons through its influence on the actin cytoskeleton.

Poly(d,l lactic-co-glycolic acid) microspheres as biodegradable microcarriers for pluripotent stem cells

The pluripotent nature and proliferative capacity of embryonic stem cells makes them an attractive cell source for tissue engineering and regeneration. In our study we investigated the use of poly(D,L-lactic-co-glycolic acid) (PLGA) microspheres as biodegradable microcarriers of pluripotent cells and as delivery systems of bioactive factors, which influence cell differentiation. The pluripotent P19 embryonal carcinoma cell line was used as a model to study cell attachment, growth and differentiation of pluripotent stem cells on PLGA microspheres. Retinoic acid (RA) was encapsulated in the PLGA microcarriers to influence cell differentiation-more specifically, to induce P19 cell differentiation into neurons. The results revealed that P19 cells attach and grow on the surface of the RA loaded PLGA microspheres. Moreover, the RA loaded PLGA microspheres were shown to be as effective as soluble RA at inducing P19 cell differentiation into neurons. Hence, the results of these ex vivo studies clearly demonstrate the capacity of PLGA microspheres to serve a dual role as both delivery systems of bioactive factors and as scaffolds for pluripotent cells. More importantly, our study demonstrates the potential use of PLGA microspheres as transplantation matrices of pluripotent stem cells for tissue engineering and regeneration.

Gene structure and alternative splicing of the mouse glycine transporter type-2

The type-2 glycine transporter GLYT2 is expressed in glycinergic neurons and is involved in the termination of inhibitory neurotransmission at strychnine-sensitive glycinergic synapses. We isolated cDNA of a GLYT2 isoform, GLYT2a, from mouse brain, and found that it contains a coding sequence of 798 amino acids. We also isolated and characterized the mouse GLYT2 (mGLYT2) gene, which was found to be divided into 18 exons and spread over 55 kb. 5'-rapid amplification of cDNA ends analyses demonstrated the existence of another two isoforms, mGLYT2b and mGLYT2c, in addition to mGLYT2a. Both mGLYT2b and mGLYT2c would produce a protein eight amino acids shorter than mGLYT2a. Analysis of the genomic clones encompassing the 5'-exons revealed that the three transcripts arose from a single gene by alternative splicing. RT-PCR analysis indicated that all three mGLYT2 isoforms were expressed at high levels in brain stem and spinal cord. These data will be useful for investigating the function of GLYT2 proteins and glycinergic neurons by gene targeting experiments.

Roles of ionotropic glutamate receptors in early developing neurons derived from the P19 mouse cell line

We cultured a P19 mouse teratocarcinoma cell line and induced its neuronal differentiation to study the function of ionotropic glutamate receptors (GluRs) in early neuronal development. Immunocytochemical studies showed 85% neuronal population at 5 days in vitro (DIV) with microtubule-associated protein 2-positive staining. Thirty percent and 50% of the cells expressed the alpha-amino-3-hydroxy-5-methyl-4-isopropinonate (AMPA) receptor subunit, GluR2/3, and the kainate (kainic acid; KA) receptor subunit, GluR5/6/7, respectively. In Western blot analysis, the temporal expression of GluR2/3 began to appear at 3 DIV, whereas GluR5/6/7 was already expressed in the undifferentiated cells. P19-derived neurons began to respond to glutamate, AMPA and KA, but not to the metabotropic GluR agonist trans-1-aminocyclopentane-1,3-decarboxylic acid, by 5 DIV in terms of increases in intracellular calcium and phospholipase C-mediated poly-phosphoinositide turnover. Furthermore, KA reduced cell death of P19-derived neurons in both atmospheric and hypobaric conditions in a phospholipase C-dependent manner. The common AMPA/KA receptor antagonist, 6-cyano-7-nitroquinoxaline-2,3-dione, but not the AMPA receptor antagonist, 1,2,3,4-tetrahydro-6-nitro-2,3-dioxo-benzo[f]quinoxaline-7-sulfonamide disodium, profoundly increased hypobaric insult-induced neurotoxicity. In a flow cytometry study, the nerve growth factor-mediated antiapoptotic effect was facilitated by AMPA, with an induction of TrkA, but not p75(NTR) expression. Therefore, AMPA and KA receptors might mediate neurotrophic functions to facilitate neurotrophic factor signaling to protect neurons against hypoxic insult in early neuronal development.

Neurons from stem cells: Implications for understanding nervous system development and repair

Neurodegenerative diseases cost the economies of the developed world billions of dollars per annum. Given ageing population profiles and the increasing extent of this problem, there has been a surge of interest in neural stem cells and in neural differentiation protocols that yield neural cells for therapeutic transplantation. Due to the oncogenic potential of stem cells a better characterisation of neural differentiation, including the identification of new neurotrophic factors, is required. Stem cell cultures undergoing synchronous in vitro neural differentiation provide a valuable resource for gene discovery. Novel tools such as microarrays promise to yield information regarding gene expression in stem cells. With the completion of the yeast, C. elegans, Drosophila, human, and mouse genome projects, the functional characterisation of genes using genetic and bioinformatic tools will aid in the identification of important regulators of neural differentiation.Key words: neural differentiation, neural precursor cell, brain repair, central nervous system repair, CNS.

Culturing neuronal cells on surfaces coated by a novel polyethyleneimine-based polymer

Maintaining cells in culture is essential for studying many aspects of cell biology and physiology. Cell culturing is dependent on proper anchorage of cells to the growth surfaces. For most cell lines, and especially for post-mitotic neurons, coated tissue culture plates are prerequisite for seeding. The most commonly used coating reagents are positively charged polymers such as poly-L-lysine or biologically purified adhesive molecules such as collagen. In this report, we present a simple procedure for synthesizing and for coating cell culture surfaces. The reagent is a biologically inert hydrophobized polyethyleneimine (PEI), which provides adequate adhesive properties for cultured cell lines including those of neuronal lineage. The hydrophobized PEI is branched PEI modified by octadecanyl groups bound to 2 mol% of the amino groups of the PEI. Unlike the native PEI that is water soluble, the modified PEI is soluble in ethanol, and thus resistant to solubilization in biological media. The protocol of coating was optimized for tissue culture plates as well as glass surfaces and in many respects this polymer outperformed other routinely used coating reagents. Neuronal cell lines, plated on the polymer-treated surfaces are resistant to manipulations including repeated media changes and extensive washing. The advantage of coating surfaces with the developed PEI-based polymer compared to other commonly used coating reagents is discussed.

Early expression of the BM88 antigen during neuronal differentiation of P19 embryonal carcinoma cells

Previous studies have shown that the BM88 antigen, a neuron-specific molecule, promotes the differentiation of mouse neuroblastoma cells [23] (Mamalaki A., Boutou E., Hurel C., Patsavoudi E., Tzartos S. and Matsas R. (1995) The BM88 antigen, a novel neuron-specific molecule, enhances the differentiation of mouse neuroblastoma cells. J. Biol. Chem. 270, 14201-14208). In particular, stably transfected with the BM88 cDNA, Neuro 2a cells over-expressing the BM88 antigen are morphologically distinct from their non-transfected counterparts; they exhibit enhanced process outgrowth and a slower rate of division. Moreover, they respond differentially to growth factors [10] (Gomez J., Boutou E., Hurel C., Mamalaki A., Kentroti S. , Vernadakis A. and Matsas R. (1998) Overexpression of the neuron-specific molecule BM88 in mouse neuroblastoma cells: Altered responsiveness to growth factors. J. Neurosci. Res. 51, 119-128). In order to further elucidate the role of the BM88 antigen in the differentiation of developing neurons we used the in vitro system of differentiating P19 cells which closely resembles early murine development in vivo. In this study, P19 cells were driven to the neuronal pathway with retinoic acid. We examined by immunofluorescence studies the expression of the BM88 antigen in these cells and we found that it correlates well with the expression of the polysialylated form of the neural cell adhesion molecule (PSA-NCAM) which characterizes early differentiating post-mitotic neurons. In contrast, very few of the BM88 antigen-positive/PSA-NCAM-positive cells expressed neurofilament protein, a marker of more mature neurons. Our findings, in accordance with previously reported data, strongly suggest that the BM88 antigen is involved in the early stages of differentiation of neuronal cells.

Electrophysiological properties of mitogen-expanded adult rat spinal cord and subventricular zone neural precursor cells

Growth factor-expanded neural precursor cells isolated from the mammalian central nervous system can differentiate into neurons and glia. Although the morphological and neurochemical development of these neural precursor cells has been investigated, little attention has been paid to their electrophysiology. This study examined the electrophysiological properties of neurons and glia derived from neural precursor cells isolated from the adult rat spinal cord (SC) and subventricular zone (SVZ). Cells were cultured in medium containing epidermal growth factor and/or fibroblast growth factor-2. After at least two passages, spheres of neural precursor cells were plated on coated coverslips and maintained in culture for up to 6 weeks. Whole-cell patch recordings were made using standard current clamp techniques. Immature action potentials were observed within hours of plating for both SC and SVZ cells. Input resistance and time constants decreased over the first week after plating and no further changes were found at later times. At similar times following plating, however, SVZ cells had a lower input resistance and shorter time constant compared to SC cells. SVZ cells also had higher resting membrane potentials and smaller after hyperpolarizations than those of SC cells, despite no significant difference in the amplitude of action potentials. Neither the SC nor the SVZ cells were capable of eliciting more than a single action potential in response to injected current. While all SC cells tested were depolarized by glutamate, the response of SVZ cells to glutamate varied considerably. This study revealed that neural precursor cells from SC and SVZ differ in both active and passive membrane properties. It appears also that the electrophysiological development of SC and SVZ precursor-derived neurons is incomplete under the conditions used. These observations suggest that the neural precursor cells from different anatomical locations may be physiologically diverse and may exhibit some differences in commitment toward neuronal or glial phenotypes.

P19 cells differentiate into glutamatergic and glutamate-responsive neurons in vitro

The neurotransmitter L-glutamate has been associated with a number of developmental events within the central nervous system including synaptogenesis and the refinement of topographically ordered neural maps. As a model for studying such events at the molecular level, we have examined the expression of glutamate and glutamate receptors in neurons that develop from P19 cells in response to retinoids. We report here that many P19-derived neurons do contain glutamate in secretory vesicles and that this glutamate appears to function as a neurotransmitter. The neurotransmitter GABA is also present in these cultures and both glutamate and GABA appeared to co-localize in some neuronal processes. Both neurotransmitters were released from the neurons in response to membrane depolarization. These neurons also express various glutamate receptor subunits including GluR1, GluR4 and NMDAR1 as detected by immunological methods. Using whole-cell patch-clamping, we have recorded spontaneous postsynaptic potentials which increase in both amplitude and frequency with time in culture and which are sensitive to the glutamate antagonist kynurenic acid Thus, P19-derived neurons mature in culture and form electrically active neural networks involving glutamate and glutamate receptors.

Expression and mRNA splicing of glycine receptor subunits and gephyrin during neuronal differentiation of P19 cells in vitro, studied by RT-PCR and immunocytochemistry

The mouse EC cell line P19, differentiating in vitro into neural cell types under the influence of retinoic acid, represents a well established model system for neurogenesis. In this system the expression of the alpha (alpha 1-alpha 3) and beta subunits of the inhibitory glycine receptor (GlyR) and of gephyrin as well as their mRNA splice variants was analyzed by RT-PCR and by immunocytochemistry. In the course of neuronal differentiation of P19 cells mRNA of GlyR beta is constitutively expressed, GlyR alpha 1 and alpha 2 are induced and GlyR alpha 3 was not detected. From the three gephyrin transcripts known to be differently spliced in the C3/C4 cassette region, the C3 transcript was found at all stages while the C4 transcript was not detectable. The insert-free form was measurable in P19 cells only 3-4 days post induction by retinoic acid. In addition a GlyR beta splice variant and a fourth gephyrin transcript were detected. Primary glial cells do not contain significant amounts of GlyR alpha subunits while in primary neuronal cells transcripts of GlyR alpha 2 were found as well as the mRNA of the GlyR beta subunit and of gephyrin. PC12 cells do not express glycine receptor genes but do express gephyrin. Immunocytochemistry confirmed the constitutive expression of gephyrin at the protein level, whereas GlyR antigens could only be detected in islets of the 'P19 neurons'. In conclusion, P19 and primary neuronal cells but not PC12 cells express the transcripts of glycine receptor components, necessary to generate functional receptors.