The protein tyrosine phosphatase SHP-1 is a critical regulator of cytokine signaling and inflammation. Mice homozygous for a null allele at the SHP-1 locus have a phenotype of severe inflammation and are hyper-responsive to the TLR4 ligand LPS. TLR4 stimulation in the CNS has been linked to both neuropathic pain and sickness behaviors. To determine if reduction in SHP-1 expression affects LPS-induced behaviors, responses of heterozygous SHP-1-deficient (me/+) and wild-type (+/+) mice to LPS were measured. Chronic (4-week) treatment with LPS induced avoidant behaviors indicative of fear/anxiety in me/+, but not +/+, mice. These behaviors were correlated with a LPS-induced type 2 cytokine, cytokine receptor, and immune effector arginase profile in the brains of me/+ mice not found in +/+ mice. Me/+ mice also had a constitutively greater level of TLR4 in the CNS than +/+ mice. Additionally, me/+ mice displayed constitutively increased thermal sensitivity compared to +/+ mice, measured by the tail-flick test. Moreover, me/+ glial cultures were more responsive to LPS than +/+ glia. Therefore, the reduced expression of SHP-1 in me/+ imparts haploinsufficiency with respect to the control of CNS TLR4 and pain signaling. Furthermore, type 2 cytokines become prevalent during chronic TLR4 hyperstimulation in the CNS and are associated positively with behaviors that are usually linked to type 1 pro-inflammatory cytokines. These findings question the notion that type 2 immunity is solely anti-inflammatory in the CNS and indicate that type 2 immunity induces/potentiates CNS inflammatory processes.

Both neurons and glia of the PNS are derived from the neural crest. In this study, we have examined the potential function of lunatic fringe in neural tube and trunk neural crest development by gain-of-function analysis during early stages of nervous system formation. Normally lunatic fringe is expressed in three broad bands within the neural tube, and is most prominent in the dorsal neural tube containing neural crest precursors. Using retrovirally-mediated gene transfer, we find that excess lunatic fringe in the neural tube increases the numbers of neural crest cells in the migratory stream via an apparent increase in cell proliferation. In addition, lunatic fringe augments the numbers of neurons and upregulates Delta-1 expression. The results indicate that, by modulating Notch/Delta signaling, lunatic fringe not only increases cell division of neural crest precursors, but also increases the numbers of neurons in the trunk neural crest.

The assembly of photoreceptor outer segments into stacked discs is a complicated process, the precise regulation of which remains a mystery. It is known that the integrity of the outer segment is heavily dependent upon surrounding cell types including the retinal pigment epithelium and Müller cells; however the role played by Müller cells within this photoreceptor-specific process has not been fully explored. Using an RPE-deprived but otherwise intact Xenopus laevis eye rudiment preparation, we reveal that Müller cell involvement in outer segment assembly is dependent upon the stimulus provided to the retina. Pigment epithelium-derived factor is able to support proper membrane folding after inhibition of Müller cell metabolism by alpha-aminoadipic acid, while isopropyl beta-D-thiogalactoside, a permissive glycan, requires intact Müller cell function. These results demonstrate that both intrinsic and extrinsic redundant mechanisms exist to support the ability of photoreceptors to properly assemble their outer segments. Our study further suggests that the receptor for pigment epithelium-derived factor resides in photoreceptors themselves while that for permissive glycans is likely localized to Müller cells, which in turn communicate with photoreceptors to promote proper membrane assembly.

Malignant peripheral nerve sheath tumors (MPNSTs) are characteristic of Neurofibromatosis type 1 (NF1), a human genetic disorder affecting approximately 1 in 3000 individuals. The absence of neurofibromin in Schwann cells results in hyperactivation of Ras, which contributes to Schwann cell hyperplasia. However, additional intracellular abnormalities in Schwann cells might contribute to the malignancy. We now report that cell lines derived from MPNSTs secrete elevated levels of prostaglandin E2 (PGE2), express higher levels of phosphorylated mitogen-activated protein kinase (MAPK), phosphorylated cytosolic phospholipase A2 (cPLA2) and cyclooxygenase 2 (COX-2) when compared to normal adult human Schwann cells (nhSCs). PCR analysis reveals that NF1 MPNST cell lines express mRNA for both EP2 and EP4 prostaglandin E2 receptors, whereas nhSCs express only the EP4 receptor. COX-2 inhibitors and PGE2 receptor antagonists decrease the proliferation of MPNST cell lines. These results indicate that prostaglandin metabolism is activated in MPNSTs and might contribute to tumor growth in NF1.

Cell contact-dependent signaling is a major regulatory mechanism in the organization of developing tissues and in the reorganization (post-injury responses) of specialized tissues in multicellular organisms. In this review we contribute to the further understanding of post-injury recovery processes in adult nervous tissue. We emphasize evidence that supports the involvement of cell contact-inhibition signaling in the cell proliferation, growth and differentiation that occurs during healing and neural reorganization after brain damage.

The co-ordinate functioning of neurons and glia is required for glutamate-mediated neurotransmission. In this study, we show by immunocytochemical detection of D-aspartate uptake, that functional glutamate transporters are present in the developing CNS of fetal and neonatal rats, including forebrain, midbrain and hindbrain, at least as early as embryonic day 12 (E12). Use of the transport inhibitor dihydrokainic acid revealed a significant role for GLT-1 in the uptake process. Immunolabelling for the glutamate transporters GLAST, GLT-1α and GLT-1v showed that each of these proteins are expressed early in development and appear to be restricted to glial-like cells throughout the development period examined (except in the retina, where neuronal elements were also labelled). Our capacity to detect very early expression of the variant forms of GLT-1 contrasts with other studies, a feature that we attribute to the use of antigen-recovery techniques that unmask protein epitopes that are otherwise undetectable. These studies illustrate the widespread presence of functional glutamate transporters in the developing CNS, in many cases before the onset of periods of synaptogenesis and indicate that regulation of extracellular glutamate by multiple excitatory amino acid transporters might be crucial in early CNS development.

In the present paper, we have further developed an in vitro model to study neuronal–glial interaction at trigeminal level by characterizing the effects of conditioned medium (CM) collected from activated primary cultures of satellite glial cells (SGCs) on calcitonin gene-related peptide (CGRP) release from rat trigeminal neurons. Moreover, we investigated whether such release is inhibited by a clinically relevant anti-migraine drug, sumatriptan. CM effects were tested on trigeminal neuronal cultures in different conditions of activation and at different time points. Long-term exposures of trigeminal neurons to CM increased directly neuronal CGRP release, which was further enhanced by the exposure to capsaicin. In this framework, the anti-migraine drug sumatriptan was able to inhibit the evoked CGRP release from naïve trigeminal neuron cultures, as well as from trigeminal cultures pre-exposed for 30 min to CM. On the contrary, sumatriptan failed to inhibit evoked CGRP release from trigeminal neurons after prolonged (4 and 8 h) pre-exposures to CM. These findings were confirmed in co-culture experiments (neurons and SGCs), where activation of SGCs or a bradykinin priming were used. Our data demonstrate that SGCs activation could influence neuronal excitability, and that this event affects the neuronal responses to triptans.

“Of what use a newborn babe?” was Oersted's response to a question from the audience as to the value of electromagnetism following his demonstration that a compass needle could be deflected by passing current through a nearby wire. Such is the immediate reaction anytime something new is encountered: What is it, and why do we need it? This perplexity arises from the certain conclusion of a proof derived from the objective facts: we seem to have managed quite well up to now without it. But as functional as a world before cell phones and email seemed, how dysfunctional would the world now appear without them? Time changes, and Science is change. Scientific journals track and pioneer those changes.

Modulation of astroglial components involved in reactive postlesional responses in the rat cerebral cortex was analyzed following exposure to environmental enrichment (EE) condition prior to injury. For this purpose, changes in % immunoreactive (IR) area of GFAP, vimentin, EAAT1 and ezrin were evaluated in the perilesional zone after placing a cortical stab wound in the visual cerebral cortex of adult rats. GFAP-IR postlesional reactive astrocytosis in the perilesional cortex was significantly lower in the animal group exposed to EE during postnatal development. This GFAP-IR reaction seems to be associated with existing astroglia, because neither BrdU- nor endogenous Ki-67-labeled nuclei were found in the perilesional cortex analyzed. Increased ezrin-IR area in the visual cortex of rats exposed to EE condition suggests the formation of new synapses or the enhancement of astroglial involvement in the existing ones. No effects of EE were found on either EAAT1- or vimentin-IR area. Results suggest that exposure to EE conditions prior to injury attenuates the postlesional astroglia GFAP-response in the perilesional cortex of rats. Whether this attenuated postlesional astroglia GFAP-response promotes or not protective effects on the cortical neuropil remains to be explored in futures studies.

In adult olfactory nerves of mammals and moths, a network of glial cells ensheathes small bundles of olfactory receptor axons. In the developing antennal nerve (AN) of the moth Manduca sexta, the axons of olfactory receptor neurons (ORNs) migrate from the olfactory sensory epithelium toward the antennal lobe. Here we explore developmental interactions between ORN axons and AN glial cells. During early stages in AN glial-cell migration, glial cells are highly dye coupled, dividing glia are readily found in the nerve and AN glial cells label strongly for glutamine synthetase. By the end of this period, dye-coupling is rare, glial proliferation has ceased, glutamine synthetase labeling is absent, and glial processes have begun to extend to enwrap bundles of axons, a process that continues throughout the remainder of metamorphic development. Whole-cell and perforated-patch recordings in vivo from AN glia at different stages of network formation revealed two potassium currents and an R-like calcium current. Chronic in vivo exposure to the R-type channel blocker SNX-482 halted or greatly reduced AN glial migration. Chronically blocking spontaneous Na-dependent activity by injection of tetrodotoxin reduced the glial calcium current implicating an activity-dependent interaction between ORNs and glial cells in the development of glial calcium currents.

The aim of this study was to investigate the developmental expression of major histocompatibility complex class II (MHCII) by microglia and macrophages and their relationship to blood vessels in the retina, a representative tissue of the central nervous system. Such information is crucial to understanding the role of these cells in immune surveillance. Wholemount preparations of retinas from late embryonic, postnatal and adult rabbits were subjected to three-colour fluorescence microscopy using β2 integrin (CD18) and MHCII antibodies and biotinylated Griffonia simplicifolia B4 isolectin labelling of blood vessels. CD18+ cells consistently exhibited characteristics of macrophages or microglia in the vascularized and non-vascularized regions of the retina, respectively. At all ages, MHCII was expressed by a high proportion of cells in the vascularized region, which contained macrophage-like ‘parenchymal cells’ as well as typical perivascular macrophages. MHCII expression by ramified microglia, first detected on postnatal day 30, was lower in the peripheral retina and intermediate in the avascular region of the myelinated streak. The observed localization of MHCII+ cells in relation to blood vessels and location-dependent differences in MHCII expression point to the possibility that these cells may be distributed strategically within the retina to provide multiple lines of defence against immune challenge arriving via the retinal vasculature.

Neurostatin, a modified ganglioside in mammalian brain, is highly immunogenic. Fusion of spleen cells of Balb/C mice immunized with bovine neurostatin with SP2O myeloma cells, led to hybridoma producers of anti-neurostatin antibodies. Two, monoclonal, IgG secreters were selected that recognized the inhibitor in blots and tissue of cow, rat and pig. The lack of species specificity indicated that the molecular structure of the inhibitory epitope is similar in these mammals. That epitope was also present in other gangliosides of the b series, defining a new regulatory system of glial-cell proliferation and apoptosis. The antibodies further revealed the neuronal origin of neurostatin.

Glutamate toxicity from hypoxia-ischaemia during the perinatal period causes white matter injury that can result in long-term motor and intellectual disability. Blocking ionotropic glutamate receptors (GluRs) has been shown to inhibit oligodendrocyte injury in vitro, but GluR antagonists have not yet proven helpful in clinical studies. The opposite approach of activating GluRs on developing oligodendrocytes shows promise in experimental studies on rodents as reported by Jartzie et al., in this issue. Group I metabotropic glutamate receptors (mGluRs) are expressed transiently on developing oligodendrocytes in humans during the perinatal period, and the blood–brain-barrier permeable agonist of group I mGluRs, 1-aminocyclopentane-trans-1,3-dicarboxylic acid (ACPD), reduces white matter damage significantly in a rat model of perinatal hypoxia-ischaemia. The results suggest drugs activating this class of GluRs could provide a new therapeutic approach for preventing cerebral palsy and other neurological consequences of diffuse white matter injury in premature infants.

Glia are required for axon pathfinding along longitudinal trajectories, but it is unknown how this relates to the molecular paradigm of axon guidance across the midline. Most interneuron axons in bilateral organisms cross the midline only once. Preventing them from recrossing the midline requires the expression of Robo receptors on the axons. These sense the repulsive signal Slit, which is produced by the midline. The lateral positioning of longitudinal axons depends on the response to Slit by the combination of Robo receptors expressed by the axons, on selective fasciculation, and on longitudinal (lateral) glia. Here, we analyse how longitudinal glia influence reading of the ‘Robo code’ by axons. We show that whereas loss of robo1 alone only affects the most medial axons, loss of both glial cells missing (gcm) and robo1 causes a severe midline collapse of longitudinal axons, similar to that caused by the loss of multiple Robo receptors. Furthermore, whereas ectopic expression of robo2 is sufficient to displace the medial MP2 axons along a more lateral trajectory, this does not occur in gcm–robo1 double-mutant embryos, where axons either do not extend at all or they misroute exiting the CNS. Hence, lateral neuron–glia interactions steer the response of axons to the Robo code.

Although Na+,K+-ATPase-mediated K+ uptake into astrocytes plays a major role in re-establishing resting extracellular K+ following neuronal excitation little information is available about astrocytic Na+,K+-ATPase function, let alone mechanisms returning K+ to neurons. The catalytic units of the Na+,K+-ATPase are the astrocyte-specific α2, the neuron-specific α3 and the ubiquitously expressed α1. In the present work, Bmax and KD values for α1, α2 and α3 subunits were computed in cultured cerebro-cortical mouse astrocytes and cerebellar granule neurons by non-linear regression as high-affinity (α2, α3) and low-affinity (α1) [3H]ouabain binding sites, which stoichiometrically equal transporter sites. Cellular expression was also determined of the brain- and α1-β1 isoform-specific FDYX7, regulating Na+,K+-ATPase efficiency and K+-sensitivity. From ouabain-sensitive K+ uptake rates published by ourselves (Walz and Hertz, 1982) or others (Atterwill et al., 1985), Na+,K+-ATPase turnover was determined. Subunits α2 and α3 showed Bmax of 15–30 pmol/mg protein, with maximum turnover rates of 70–80/s. Bmax of the α1 subunit was low in neurons but very high in astrocytes (645 pmol/mg protein), where turnover rate was slow, reflecting expression of selectively expressed FXYD7, and binding was increased by K+. The role of these characteristics for K+ homeostasis are discussed.

Vertebrate myelin membranes are compacted and held in close apposition by three structural proteins of myelin, myelin basic protein, myelin protein zero (MPZ) and myelin proteolipid protein (PLP1/DMalpha). PLP1/DMalpha is considered to function as a scaffolding protein and play a role in intracellular trafficking in oligodendrocytes. In humans, point mutations, duplications or deletions of PLP1 are associated with Pelizaeus–Merzbacher disease and spastic paraplegia Type 2. PLP1 is highly conserved between mammals, but less so in lower vertebrates. This has led some researchers to question whether certain fish species express PLP1 orthologues at all, and to suggest that the function of PLP1/DMalpha in the central nervous system (CNS) may have been taken over by MPZ. Here, we review the evidence for the conservation of orthologues of PLP1/DMalpha in actinopterygian fishes and provide a comparison of currently available sequence data across 17 fish species. Our analysis demonstrates that orthologues of PLP1/DMalpha have been retained and are functionally expressed in many, if not all, extant species of bony fish. Many of the amino acids that, when mutated, are associated with severe CNS pathology are conserved in teleosts, demonstrating conservation of essential functions and justifying the development of novel disease models in species such as the zebrafish.

Dominant mutations in GJA1, the gene encoding the gap junction protein connexin43 (Cx43), cause oculodentodigital dysplasia (ODDD), a syndrome affecting multiple tissues, including the central nervous system (CNS). We investigated the effects of the G60S mutant, which causes a similar, dominant phenotype in mice (Gja1Jrt/+). Astrocytes in acute brain slices from Gja1Jrt/+ mice transfer sulforhodamine-B comparably to that in their wild-type (WT) littermates. Further, astrocytes and cardiomyocytes cultured from Gja1Jrt/+ mice showed a comparable transfer of lucifer yellow to those from WT mice. In transfected cells, the G60S mutant formed gap junction (GJ) plaques but not functional channels. In co-transfected cells, the G60S mutant co-immunoprecipitated with WT Cx43, but did not diminish GJ coupling as measured by dual patch clamp. Thus, whereas G60S has dominant effects, it did not appreciably reduce GJ coupling.