The yin and yang of tenascin-R in CNS development and pathology

Developmental patterns of extracellular matrix molecules in the embryonic and postnatal mouse hindbrain

Normal brain development requires continuous communication between developing neurons and their environment filled by a complex network referred to as extracellular matrix (ECM). The ECM is divided into distinct families of molecules including hyaluronic acid, proteoglycans, glycoproteins such as tenascins, and link proteins. In this study, we characterize the temporal and spatial distribution of the extracellular matrix molecules in the embryonic and postnatal mouse hindbrain by using antibodies and lectin histochemistry. In the embryo, hyaluronan and neurocan were found in high amounts until the time of birth whereas versican and tenascin-R were detected in lower intensities during the whole embryonic period. After birth, both hyaluronic acid and neurocan still produced intense staining in almost all areas of the hindbrain, while tenascin-R labeling showed a continuous increase during postnatal development. The reaction with WFA and aggrecan was revealed first 4th postnatal day (P4) with low staining intensities, while HAPLN was detected two weeks after birth (P14). The perineuronal net appeared first around the facial and vestibular neurons at P4 with hyaluronic acid cytochemistry. One week after birth aggrecan, neurocan, tenascin-R, and WFA were also accumulated around the neurons located in several hindbrain nuclei, but HAPLN1 was detected on the second postnatal week. Our results provide further evidence that many extracellular macromolecules that will be incorporated into the perineuronal net are already expressed at embryonic and early postnatal stages of development to control differentiation, migration, and synaptogenesis of neurons. In late postnatal period, the experience-driven neuronal activity induces formation of perineuronal net to stabilize synaptic connections.

A Scd1-mediated metabolic alteration participates in liver responses to low-dose bavachin

Hepatotoxicity induced by bioactive constituents in traditional Chinese medicines or herbs, such as bavachin (BV) in Fructus Psoraleae, has a prolonged latency to overt drug-induced liver injury in the clinic. Several studies have described BV-induced liver damage and underlying toxicity mechanisms, but little attention has been paid to the deciphering of organisms or cellular responses to BV at no-observed-adverse-effect level, and the underlying molecular mechanisms and specific indicators are also lacking during the asymptomatic phase, making it much harder for early recognition of hepatotoxicity. Here, we treated mice with BV for 7 days and did not detect any abnormalities in biochemical tests, but found subtle steatosis in BV-treated hepatocytes. We then profiled the gene expression of hepatocytes and non-parenchymal cells at single-cell resolution and discovered three types of hepatocyte subsets in the BV-treated liver. Among these, the hepa3 subtype suffered from a vast alteration in lipid metabolism, which was characterized by enhanced expression of apolipoproteins, carboxylesterases, and stearoyl-CoA desaturase 1 (Scd1). In particular, increased Scd1 promoted monounsaturated fatty acids (MUFAs) synthesis and was considered to be related to BV-induced steatosis and polyunsaturated fatty acids (PUFAs) generation, which participates in the initiation of ferroptosis. Additionally, we demonstrated that multiple intrinsic transcription factors, including Srebf1 and Hnf4a, and extrinsic signals from niche cells may regulate the above-mentioned molecular events in BV-treated hepatocytes. Collectively, our study deciphered the features of hepatocytes in response to BV insult, decoded the underlying molecular mechanisms, and suggested that Scd1 could be a hub molecule for the prediction of hepatotoxicity at an early stage.

The Presence of Yin-Yang Effects in the Migration Pattern of Staurosporine-Treated Single versus Collective Breast Carcinoma Cells

BACKGROUND

Staurosporine-dependent single and collective cell migration patterns of breast carcinoma cells MDA-MB-231, MCF-7, and SK-BR-3 were analysed to characterise the presence of drug-dependent migration promoting and inhibiting yin-yang effects.

METHODS

Migration patterns of various breast cancer cells after staurosporine treatment were investigated using Western blot, cell toxicity assays, single and collective cell migration assays, and video time-lapse. Statistical analyses were performed with Kruskal-Wallis and Fligner-Killeen tests.

RESULTS

Application of staurosporine induced the migration of single MCF-7 cells but inhibited collective cell migration. With the exception of low-density SK-BR-3 cells, staurosporine induced the generation of immobile flattened giant cells. Video time-lapse analysis revealed that within the borderline of cell collectives, staurosporine reduced the velocity of individual MDA-MB-231 and SK-BR-3, but not of MCF-7 cells. In individual MCF-7 cells, mainly the directionality of migration became disturbed, which led to an increased migration rate parallel to the borderline, and hereby to an inhibition of the migration of the cell collective as a total. Moreover, the application of staurosporine led to a transient activation of ERK1/2 in all cell lines.

CONCLUSION

Dependent on the context (single versus collective cells), a drug may induce opposite effects in the same cell line.

One Raft to Guide Them All, and in Axon Regeneration Inhibit Them

Central nervous system damage caused by traumatic injuries, iatrogenicity due to surgical interventions, stroke and neurodegenerative diseases is one of the most prevalent reasons for physical disability worldwide. During development, axons must elongate from the neuronal cell body to contact their precise target cell and establish functional connections. However, the capacity of the adult nervous system to restore its functionality after injury is limited. Given the inefficacy of the nervous system to heal and regenerate after damage, new therapies are under investigation to enhance axonal regeneration. Axon guidance cues and receptors, as well as the molecular machinery activated after nervous system damage, are organized into lipid raft microdomains, a term typically used to describe nanoscale membrane domains enriched in cholesterol and glycosphingolipids that act as signaling platforms for certain transmembrane proteins. Here, we systematically review the most recent findings that link the stability of lipid rafts and their composition with the capacity of axons to regenerate and rebuild functional neural circuits after damage.

Extracellular matrix and traumatic brain injury

The brain extracellular matrix (ECM) plays a crucial role in both the developing and adult brain by providing structural support and mediating cell-cell interactions. In this review, we focus on the major constituents of the ECM and how they function in both normal and injured brain, and summarize the changes in the composition of the ECM as well as how these changes either promote or inhibit recovery of function following traumatic brain injury (TBI). Modulation of ECM composition to facilitates neuronal survival, regeneration and axonal outgrowth is a potential therapeutic target for TBI treatment.

Ischemic injury leads to extracellular matrix alterations in retina and optic nerve

Retinal ischemia occurs in a variety of eye diseases. Restrained blood flow induces retinal damage, which leads to progressive optic nerve degeneration and vision loss. Previous studies indicate that extracellular matrix (ECM) constituents play an important role in complex tissues, such as retina and optic nerve. They have great impact on de- and regeneration processes and represent major candidates of central nervous system glial scar formation. Nevertheless, the importance of the ECM during ischemic retina and optic nerve neurodegeneration is not fully understood yet. In this study, we analyzed remodeling of the extracellular glycoproteins fibronectin, laminin, tenascin-C and tenascin-R and the chondroitin sulfate proteoglycans (CSPGs) aggrecan, brevican and phosphacan/RPTPβ/ζ in retinae and optic nerves of an ischemia/reperfusion rat model via quantitative real-time PCR, immunohistochemistry and Western blot. A variety of ECM constituents were dysregulated in the retina and optic nerve after ischemia. Regarding fibronectin, significantly elevated mRNA and protein levels were observed in the retina following ischemia, while laminin and tenascin-C showed enhanced immunoreactivity in the optic nerve after ischemia. Interestingly, CSPGs displayed significantly increased expression levels in the optic nerve. Our study demonstrates a dynamic expression of ECM molecules following retinal ischemia, which strengthens their regulatory role during neurodegeneration.

Expression of Semaphorins, Neuropilins, VEGF, and Tenascins in Rat and Human Primary Sensory Neurons after a Dorsal Root Injury

Dorsal root injury is a situation not expected to be followed by a strong regenerative growth, or growth of the injured axon into the central nervous system of the spinal cord, if the central axon of the dorsal root is injured but of strong regeneration if subjected to injury to the peripherally projecting axons. The clinical consequence of axonal injury is loss of sensation and may also lead to neuropathic pain. In this study, we have used in situ hybridization to examine the distribution of mRNAs for the neural guidance molecules semaphorin 3A (SEMA3A), semaphorin 3F (SEMA3F), and semaphorin 4F (SEMA4F), their receptors neuropilin 1 (NP1) and neuropilin 2 (NP2) but also for the neuropilin ligand vascular endothelial growth factor (VEGF) and Tenascin J1, an extracellular matrix molecule involved in axonal guidance, in rat dorsal root ganglia (DRG) after a unilateral dorsal rhizotomy (DRT) or sciatic nerve transcetion (SNT). The studied survival times were 1–365 days. The different forms of mRNAs were unevenly distributed between the different size classes of sensory nerve cells. The results show that mRNA for SEMA3A was diminished after trauma to the sensory nerve roots in rats. The SEMA3A receptor NP1, and SEMA3F receptor NP2, was significantly upregulated in the DRG neurons after DRT and SNT. SEMA4F was upregulated after a SNT. The expression of mRNA for VEGF in DRG neurons after DRT showed a significant upregulation that was high even a year after the injuries. These data suggest a role for the semaphorins, neuropilins, VEGF, and J1 in the reactions after dorsal root lesions.

Network-based characterization of the synaptic proteome reveals that removal of epigenetic regulator Prmt8 restricts proteins associated with synaptic maturation

The brain adapts to dynamic environmental conditions by altering its epigenetic state, thereby influencing neuronal transcriptional programs. An example of an epigenetic modification is protein methylation, catalyzed by protein arginine methyltransferases (PRMT). One member, Prmt8, is selectively expressed in the central nervous system during a crucial phase of early development, but little else is known regarding its function. We hypothesize Prmt8 plays a role in synaptic maturation during development. To evaluate this, we used a proteome-wide approach to characterize the synaptic proteome of Prmt8 knockout versus wild-type mice. Through comparative network-based analyses, proteins and functional clusters related to neurite development were identified to be differentially regulated between the two genotypes. One interesting protein that was differentially regulated was tenascin-R (TNR). Chromatin immunoprecipitation demonstrated binding of PRMT8 to the tenascin-r (Tnr) promoter. TNR, a component of perineuronal nets, preserves structural integrity of synaptic connections within neuronal networks during the development of visual-somatosensory cortices. On closer inspection, Prmt8 removal increased net formation and decreased inhibitory parvalbumin-positive (PV+) puncta on pyramidal neurons, thereby hindering the maturation of circuits. Consequently, visual acuity of the knockout mice was reduced. Our results demonstrated Prmt8's involvement in synaptic maturation and its prospect as an epigenetic modulator of developmental neuroplasticity by regulating structural elements such as the perineuronal nets.

The extracellular matrix glycoprotein tenascin-C and matrix metalloproteinases modify cerebellar structural plasticity by exposure to an enriched environment

The importance of the extracellular matrix (ECM) glycoprotein tenascin-C (TnC) and the ECM degrading enzymes, matrix metalloproteinases (MMPs) -2 and -9, in cerebellar histogenesis is well established. This study aimed to examine whether there is a functional relationship between these molecules in regulating structural plasticity of the lateral deep cerebellar nucleus. To this end, starting from postnatal day 21, TnC- or MMP-9-deficient mice were exposed to an enriched environment (EE). We show that 8 weeks of exposure to EE leads to reduced lectin-based staining of perineuronal nets (PNNs), reduction in the size of GABAergic and increase in the number and size of glutamatergic synaptic terminals in wild-type mice. Conversely, TnC-deficient mice showed reduced staining of PNNs compared to wild-type mice maintained under standard conditions, and exposure to EE did not further reduce, but even slightly increased PNN staining. EE did not affect the densities of the two types of synaptic terminals in TnC-deficient mice, while the size of inhibitory, but not excitatory synaptic terminals was increased. In the time frame of 4-8 weeks, MMP-9, but not MMP-2, was observed to influence PNN remodeling and cerebellar synaptic plasticity as revealed by measurement of MMP-9 activity and colocalization with PNNs and synaptic markers. These findings were supported by observations on MMP-9-deficient mice. The present study suggests that TnC contributes to the regulation of structural plasticity in the cerebellum and that interactions between TnC and MMP-9 are likely to be important for these processes to occur.

Near-future pH conditions severely impact calcification, metabolism and the nervous system in the pteropod Heliconoides inflatus

Shelled pteropods play key roles in the global carbon cycle and food webs of various ecosystems. Their thin external shell is sensitive to small changes in pH, and shell dissolution has already been observed in areas where aragonite saturation state is ~1. A decline in pteropod abundance has the potential to disrupt trophic networks and directly impact commercial fisheries. Therefore, it is crucial to understand how pteropods will be affected by global environmental change, particularly ocean acidification. In this study, physiological and molecular approaches were used to investigate the response of the Mediterranean pteropod, Heliconoides inflatus, to pH values projected for 2100 under a moderate emissions trajectory (RCP6.0). Pteropods were subjected to pH_T 7.9 for 3 days, and gene expression levels, calcification and respiration rates were measured relative to pH_T 8.1 controls. Gross calcification decreased markedly under low pH conditions, while genes potentially involved in calcification were up-regulated, reflecting the inability of pteropods to maintain calcification rates. Gene expression data imply that under low pH conditions, both metabolic processes and protein synthesis may be compromised, while genes involved in acid-base regulation were up-regulated. A large number of genes related to nervous system structure and function were also up-regulated in the low pH treatment, including a GABA_A receptor subunit. This observation is particularly interesting because GABA_A receptor disturbances, leading to altered behavior, have been documented in several other marine animals after exposure to elevated CO₂ . The up-regulation of many genes involved in nervous system function suggests that exposure to low pH could have major effects on pteropod behavior. This study illustrates the power of combining physiological and molecular approaches. It also reveals the importance of behavioral analyses in studies aimed at understanding the impacts of low pH on marine animals.

Heterogeneous expression of extracellular matrix molecules in the red nucleus of the rat

Previous studies in our laboratory showed that the organization and heterogeneous molecular composition of extracellular matrix is associated with the variable cytoarchitecture, connections and specific functions of the vestibular nuclei and two related areas of the vestibular neural circuits, the inferior olive and prepositus hypoglossi nucleus. The aim of the present study is to reveal the organization and distribution of various molecular components of extracellular matrix in the red nucleus, a midbrain premotor center. Morphologically and functionally the red nucleus is comprised of the magno- and parvocellular parts, with overlapping neuronal population. By using histochemical and immunohistochemical methods, the extracellular matrix appeared as perineuronal net, axonal coat, perisynaptic matrix or diffuse network in the neuropil. In both parts of the red nucleus we have observed positive hyaluronan, tenascin-R, link protein, and lectican (aggrecan, brevican, versican, neurocan) reactions. Perineuronal nets were detected with each of the reactions and the aggrecan showed the most intense staining in the pericellular area. The two parts were clearly distinguished on the basis of neurocan and HAPLN1 expression as they have lower intensity in the perineuronal nets of large cells and in the neuropil of the magnocellular part. Additionally, in contrast to this pattern, the aggrecan was heavily labeled in the magnocellular region sharply delineating from the faintly stained parvocellular area. The most characteristic finding was that the appearance of perineuronal nets was related with the neuronal size independently from its position within the two subdivisions of red nucleus. In line with these statements none of the extracellular matrix molecules were restricted exclusively to the magno- or parvocellular division. The chemical heterogeneity of the perineuronal nets may support the recently accepted view that the red nucleus comprises more different populations of neurons than previously reported.

Transcriptional regulation of tenascin genes

Extracellular matrix proteins of the tenascin family resemble each other in their domain structure, and also share functions in modulating cell adhesion and cellular responses to growth factors. Despite these common features, the 4 vertebrate tenascins exhibit vastly different expression patterns. Tenascin-R is specific to the central nervous system. Tenascin-C is an “oncofetal” protein controlled by many stimuli (growth factors, cytokines, mechanical stress), but with restricted occurrence in space and time. In contrast, tenascin-X is a constituitive component of connective tissues, and its level is barely affected by external factors. Finally, the expression of tenascin-W is similar to that of tenascin-C but even more limited. In accordance with their highly regulated expression, the promoters of the tenascin-C and -W genes contain TATA boxes, whereas those of the other 2 tenascins do not. This article summarizes what is currently known about the complex transcriptional regulation of the 4 tenascin genes in development and disease.

Role of tenascins in the ECM of gliomas

Tenascins are a family of extracellular matrix molecules that are mainly expressed in embryonic development and down-regulated in adulthood. A re-expression in the adult occurs under pathological conditions such as inflammation, regeneration or neoplasia. As the most prominent member of the tenascin family, TN-C, is highly expressed in glioma tissue and rising evidence suggests that TN-C plays a crucial role in cell migration or invasion - the most fatal characteristics of glioma - also the other members of this protein family have been investigated with regard to their impact on glioma biology. For all tenascins correlations between the expression levels of the different family members and the degree of malignancy and invasiveness of glial tumors could be detected. Overall, the former and recent results in the research on glioma and tenascins point at distinct roles of each of the molecules in glioma biology and the devastating properties of these tumors.

Modification of tenascin-R expression following unilateral labyrinthectomy in rats indicates its possible role in neural plasticity of the vestibular neural circuit

We have previously found that unilateral labyrinthectomy is accompanied by modification of hyaluronan and chondroitin sulfate proteoglycan staining in the lateral vestibular nucleus of rats and the time course of subsequent reorganization of extracellular matrix assembly correlates to the restoration of impaired vestibular function. The tenascin-R has repelling effect on pathfinding during axonal growth/regrowth, and thus inhibits neural circuit repair. By using immunohistochemical method, we studied the modification of tenascin-R expression in the superior, medial, lateral, and descending vestibular nuclei of the rat following unilateral labyrinthectomy. On postoperative day 1, tenascin-R reaction in the perineuronal nets disappeared on the side of labyrinthectomy in the superior, lateral, medial, and rostral part of the descending vestibular nuclei. On survival day 3, the staining intensity of tenascin-R reaction in perineuronal nets recovered on the operated side of the medial vestibular nucleus, whereas it was restored by the time of postoperative day 7 in the superior, lateral and rostral part of the descending vestibular nuclei. The staining intensity of tenascin-R reaction remained unchanged in the caudal part of the descending vestibular nucleus bilaterally. Regional differences in the modification of tenascin-R expression presented here may be associated with different roles of individual vestibular nuclei in the compensatory processes. The decreased expression of the tenascin-R may suggest the extracellular facilitation of plastic modifications in the vestibular neural circuit after lesion of the labyrinthine receptors.

Different forms of tenascin-C with tenascin-R regulate neural differentiation in bone marrow-derived human mesenchymal stem cells

Mesenchymal stem cells (MSCs) are currently thought to transdifferentiate into neural lineages under specific microenvironments. Studies have reported that the tenascin family members, tenascin-C (TnC) and tenascin-R (TnR), regulate differentiation and migration, in addition to neurite outgrowth and survival in numerous types of neurons and mesenchymal progenitor cells. However, the mechanisms by which TnC and TnR affect neuronal differentiation are not well understood. In this study, we hypothesized that different forms of tenascin might regulate the neural transdifferentiation of human bone marrow-derived mesenchymal stem cells. Human MSCs were cultured in media incorporated with soluble tenascins, or on precoated tenascins. In a qualitative polymerase chain reaction analysis, adding a soluble TnC and TnR mixture to the medium significantly enhanced the expression of neuronal and glial markers, whereas no synaptic markers were expressed. Conversely, in groups of cells treated with coated TnC, hMSCs showed neurite outgrowth and synaptic marker expression. After being treated with coated TnR, hMSCs exhibited neuronal differentiation; however, it inhibited neurite outgrowth and synaptic marker expression. A combination of TnC and TnR significantly promoted hMSC differentiation in neurons or oligodendrocytes, induced neurite formation, and inhibited differentiation into astrocytes. Furthermore, the effect of the tenascin mixture showed dose-dependent effects, and a mixture ratio of 1:1 to 1:2 (TnC:TnR) provided the most obvious differentiation of neurons and oligodendrocytes. In a functional blocking study, integrin α7 and α9β1-blocking antibodies inhibited, respectively, 80% and 20% of mRNA expression by hMSCs in the coated tenascin mixture. In summary, the coated combination of TnC and TnR appeared to regulate neural differentiation signaling through integrin α7 and α9β1 in bone marrow-derived hMSCs. Our findings demonstrate novel mechanisms by which tenascin regulates neural differentiation, and enable the use of cell therapy to treat neurodegenerative diseases.

Extracellular matrix regulation of inflammation in the healthy and injured spinal cord

Throughout the body, the extracellular matrix (ECM) provides structure and organization to tissues and also helps regulate cell migration and intercellular communication. In the injured spinal cord (or brain), changes in the composition and structure of the ECM undoubtedly contribute to regeneration failure. Less appreciated is how the native and injured ECM influences intraspinal inflammation and, conversely, how neuroinflammation affects the synthesis and deposition of ECM after CNS injury. In all tissues, inflammation can be initiated and propagated by ECM disruption. Molecules of ECM newly liberated by injury or inflammation include hyaluronan fragments, tenascins, and sulfated proteoglycans. These act as "damage-associated molecular patterns" or "alarmins", i.e., endogenous proteins that trigger and subsequently amplify inflammation. Activated inflammatory cells, in turn, further damage the ECM by releasing degradative enzymes including matrix metalloproteinases (MMPs). After spinal cord injury (SCI), destabilization or alteration of the structural and chemical compositions of the ECM affects migration, communication, and survival of all cells - neural and non-neural - that are critical for spinal cord repair. By stabilizing ECM structure or modifying their ability to trigger the degradative effects of inflammation, it may be possible to create an environment that is more conducive to tissue repair and axon plasticity after SCI.

Inhibitors of myelination: ECM changes, CSPGs and PTPs

After inflammation-induced demyelination, such as in the disease multiple sclerosis, endogenous remyelination often fails. However, in animal models of demyelination induced with toxins, remyelination can be quite robust. A significant difference between inflammation-induced and toxin-induced demyelination is the response of local cells within the lesion, including astrocytes, oligodendrocytes, microglia/macrophages, and NG2+ cells, which respond to inflammatory stimuli with increased extracellular matrix (ECM) protein and chondroitin sulfate proteoglycan (CSPG) production and deposition. Here, we summarize current knowledge of ECM changes in demyelinating lesions, as well as oligodendrocyte responses to aberrant ECM proteins and CSPGs after various types of demyelinating insults. The discovery that CSPGs act through the receptor protein tyrosine phosphatase sigma (PTPσ) and the Rho-ROCK pathway to inhibit oligodendrocyte process extension and myelination, but not oligodendrocyte differentiation (Pendleton et al., Experimental Neurology (2013) vol. 247, pp. 113-121), highlights the need to better understand the ECM changes that accompany demyelination and their influence on oligodendrocytes and effective remyelination.

Prediction and analysis of higher-order coiled-coils: insights from proteins of the extracellular matrix, tenascins and thrombospondins

α-Helical coiled-coil domains (CCDs) direct protein oligomerisation in many biological processes and are of great interest as tools in protein engineering. Although CCDs are recognizable from protein sequences, prediction of oligomer state remains challenging especially for trimeric states and above. Here we evaluate LOGICOIL, a new multi-state predictor for CCDs, with regard to families of extracellular matrix proteins. Tenascins, which are known to assemble as trimers, were the first test case. LOGICOIL out-performed other algorithms in predicting trimerisation of these proteins and sequence analyses identified features associated with many other trimerising CCDs. The thrombospondins are a larger and more ancient family that includes sub-groups that assemble as trimers or pentamers. LOGICOIL predicted the pentamerising CCDs accurately. However, prediction of TSP trimerisation was relatively poor, although accuracy was improved by analyzing only the central regions of the CCDs. Sequence clustering and phylogenetic analyses grouped the TSP CCDs into three clades comprising trimers and pentamers from vertebrates, and TSPs from invertebrates. Sequence analyses revealed distinctive, conserved features that distinguish trimerising and pentamerising CCDs. Together, these analyses provide insight into the specification of higher-order CCDs that should direct improved CCD predictions and future experimental investigations of sequence-to-structure functional relationships.

Identifying SNP targeted pathways in partial epilepsies with genome-wide association study data

PURPOSE

In a recent genome-wide association study for partial epilepsies in the European population, a common genetic variation has been reported to affect partial epilepsy only modestly. However, in complex diseases such as partial epilepsy, multiple factors (e.g. single nucleotide polymorphisms, microRNAs, metabolic and epigenetic factors) may target different sets of genes in the same pathway, affecting its function and thus causing the disease development. In this regard, we hypothesize that the pathways are critical for elucidating the mechanisms underlying partial epilepsy.

METHODS

Previously we had developed a novel methodology with the aim of identifying the disease-related pathways. We had combined evidence of genetic association with current knowledge of (i) biochemical pathways, (ii) protein-protein interaction networks, and (iii) the functional information of selected single nucleotide polymorphisms. In our present study, we apply this methodology to a data set on partial epilepsy, including 3445 cases and 6935 controls of European ancestry.

RESULTS

We have identified 30 overrepresented pathways with corrected p-values smaller than 10(-12). These pathways include complement and coagulation cascades, cell cycle, focal adhesion, extra cellular matrix-receptor interaction, JAK-STAT signaling pathway, MAPK signaling pathway, proteasome, ribosome, calcium signaling and regulation of actin cytoskeleton pathways. Most of these pathways have growing scientific support in the literature as being associated with partial epilepsy. We also demonstrate that different factors affect distinct parts of the pathways, as shown here on complement and coagulation cascades pathway with a comparison of gene expression vs. genome-wide association study.

CONCLUSIONS

Traditional studies on genome-wide association have not revealed strong associations in epilepsies, since these single nucleotide polymorphisms are not shared by most of the patients. Our results suggest that it is more effective to incorporate the functional effect of a single nucleotide polymorphism on the gene product, protein-protein interaction networks and functional enrichment tools into genome-wide association studies. These can then be used to determine leading molecular pathways, which cannot be detected through traditional analyses. We hope that this type of analysis brings the research community one step closer to unraveling the complex genetic structure of epilepsies.

The extracellular matrix glycoprotein tenascin-R regulates neurogenesis during development and in the adult dentate gyrus of mice

Abnormal generation of inhibitory γ-aminobutyric acid synthesizing (GABAergic) neurons is characteristic of neuropsychological disorders. We provide evidence that the extracellular matrix molecule tenascin-R (TNR) – being predominantly expressed, among neurons, by subpopulation of interneurons - plays a role in the generation of GABAergic and granule neurons in the murine dentate gyrus by regulating fate determination of neural stem/progenitor cells (NSCs). During development, absence of TNR in constitutively TNR-deficient (TNR−/−) mice results in increased numbers of dentate gyrus GABAergic neurons, being associated with decreased expression of its receptor β1 integrin, increased activation of p38 MAPK, and increased expression of the GABAergic specification gene ASCL1. Postnatally, increased GABAergic input to adult hippocampal NSCs in TNR−/− mice is associated not only with increased numbers of GABAergic and, particularly, parvalbumin-immunoreactive neurons, as seen during development, but also with increased numbers of granule neurons, thus contributing to the increased differentiation of NSCs into granule cells. These findings indicate the importance of TNR in the regulation of hippocampal neurogenesis and suggest that TNR acts through distinct direct and indirect mechanisms during development and in the adult.

Passive immunization with tenascin-R (TN-R) polyclonal antibody promotes axonal regeneration and functional recovery after spinal cord injury in rats

Tenascin-R (TN-R) is a neural specific protein and an important molecule involved in inhibition of axonal regeneration after spinal cord injury (SCI). Here we report on rabbit-derived TN-R polyclonal antibody, which acts as a TN-R antagonist with high titer and high specificity, promoted neurite outgrowth and sprouting of rat cortical neurons cultured on the inhibitory TN-R substrate in vitro. When locally administered into the lesion sites of rats received spinal cord dorsal hemisection, these TN-R antibodies could significantly decrease RhoA activation and improve functional recovery from corticospinal tract (CST) transection. Thus, passive immunotherapy with specific TN-R antagonist may represent a promising repair strategy following acute SCI.

KIAA0510, the 3'-untranslated region of the tenascin-R gene, and tenascin-R are overexpressed in pilocytic astrocytomas

AIMS

Studying the molecules and signalling pathways regulating glioma invasiveness is a major challenge because these processes determine malignancy, progression, relapse and prognosis. We took advantage of our previous study focused on genes that were critical in tumour invasion to further study here an unknown sequence, referred to as KIAA0510, the chromosomal location of which was 1q25, described as a 5596-bp long mRNA and that we found to be significantly overexpressed in pilocytic astrocytomas compared with glioblastomas.

METHODS AND RESULTS

Using in silico analysis as well as Polymerase chain reaction techniques, we decipher the full genomic characterization of the KIAA0510 sequence and demonstrate that KIAA0510 constitutes the 3'-untranslated region of tenascin-R gene. We have clearly confirmed the overexpression of tenascin-R in pilocytic astrocytomas vs. glioblastomas at mRNA and protein levels. We also analysed a large series of various brain tumours and found that in the group of astrocytic tumours, tenascin-R expression decreased with malignancy, whereas oligodendrogliomas sometimes retained a high level of tenascin-R even in high-grade tumours. Gangliogliomas strongly expressed tenascin-R too. In contrast, ependymomas and meningiomas were negative. In normal brain, tenascin-R was exclusively expressed by normal oligodendrocytes and subsets of neurones during post-natal development and in adulthood, where it could differentially affect cellular adhesiveness and/or differentiation.

CONCLUSION

KIAA0510, the 3'-untranslated region of the tenascin-R gene, and tenascin-R are overexpressed in pilocytic astrocytomas. Gangliogliomas shared with pilocytic astrocytomas strong tenascin-R expression. Whether tenascin-R overexpression negatively influences brain invasion remains to be determined.

Short DNA sequences inserted for gene targeting can accidentally interfere with off-target gene expression

Targeting of genes in mice, a key approach to study development and disease, often leaves a neo cassette, loxP, or FRT sites inserted in the mouse genome. Insertion of neo can influence the expression of neighboring genes, but similar effects have not been reported for loxP sites. We therefore performed microarray analyses of mice in which the Ncam or the Tnr gene were targeted either by insertion of neo or loxP/FRT sites. In the case of Ncam, neo, but not loxP/FRT insertion, led to a 2-fold reduction in mRNA levels of 3 genes located at distances between 0.2 and 3.1 Mb from the target. In contrast, after introduction of loxP/FRT sites into introns of Tnr, we observed a 2.5- to 4-fold reduction in the transcript level of the Gas5 gene, 1.1 Mb away from Tnr, most probably due to disruption of a conserved regulatory element in Tnr. Insertion of short DNA sequences such as loxP/FRT can thus influence off-target mRNA levels if these sites are accidentally placed into regulatory elements. Our results imply that conditional knockout mice should be analyzed for genomic positional side effects that may influence the animals' phenotypes.

Distribution and synthesis of extracellular matrix proteoglycans, hyaluronan, link proteins and tenascin-R in the rat spinal cord

Perineuronal nets (PNNs) are dense extracellular matrix (ECM) structures that form around many neuronal cell bodies and dendrites late in development. They contain several chondroitin sulphate proteoglycans (CSPGs), hyaluronan, link proteins and tenascin-R. Their time of appearance correlates with the ending of the critical period for plasticity, and they have been implicated in this process. The distribution of PNNs in the spinal cord was examined using Wisteria floribunda agglutinin lectin and staining for chondroitin sulphate stubs after chondroitinase digestion. Double labelling with the neuronal marker, NeuN, showed that PNNs were present surrounding approximately 30% of motoneurons in the ventral horn, 50% of large interneurons in the intermediate grey and 20% of neurons in the dorsal horn. These PNNs formed in the second week of postnatal development. Immunohistochemical staining demonstrated that the PNNs contain a mixture of CSPGs, hyaluronan, link proteins and tenascin-R. Of the CSPGs, aggrecan was present in all PNNs while neurocan, versican and phosphacan/RPTPbeta were present in some but not all PNNs. In situ hybridization showed that aggrecan and cartilage link protein (CRTL 1) and brain link protein-2 (BRAL 2) are produced by neurons. PNN-bearing neurons express hyaluronan synthase, and this enzyme and phosphacan/RPTPbeta may attach PNNs to the cell surface. During postnatal development the expression of link protein and aggrecan mRNA is up-regulated at the time of PNN formation, and these molecules may therefore trigger their formation.

Functional delay of myelination of auditory delay lines in the nucleus laminaris of the barn owl

In the barn owl, maps of interaural time difference (ITD) are created in the nucleus laminaris (NL) by interdigitating axons that act as delay lines. Adult delay line axons are myelinated, and this myelination is timely, coinciding with the attainment of adult head size, and stable ITD cues. The proximal portions of the axons become myelinated in late embryonic life, but the delay line portions of the axon in NL remain unmyelinated until the first postnatal week. Myelination of the delay lines peaks at the third week posthatch, and myelinating oligodendrocyte density approaches adult levels by one month, when the head reaches its adult width. Migration of oligodendrocyte progenitors into NL and the subsequent onset of myelination may be restricted by a glial barrier in late embryonic stages and the first posthatch week, since the loss of tenascin-C immunoreactivity in NL is correlated with oligodendrocyte progenitor migration into NL.

Guanine derivatives modulate extracellular matrix proteins organization and improve neuron-astrocyte co-culture

Guanine derivatives (GD) have been shown to exert relevant extracellular effects as intercellular messengers, neuromodulators in the central nervous system, and trophic effects on astrocytes and neurons. Astrocytes have been pointed out as the major source of trophic factors in the nervous system, however, several trophic effects of astrocytic-released soluble factors are mediated through modulation of extracellular matrix (ECM) proteins. In this study, we investigated the effects of guanosine-5'-monophosphate (GMP) and guanosine (GUO) on the expression and organization of ECM proteins in cerebellar astrocytes. Moreover, to evaluate the effects of astrocytes pre-treated with GMP or GUO on cerebellar neurons we used a neuron-astrocyte coculture model. GMP or GUO alters laminin and fibronectin organization from a punctate to a fibrillar pattern, however, the expression levels of the ECM proteins were not altered. Guanine derivatives-induced alteration of ECM proteins organization is mediated by activation of mitogen activated protein kinases (MAPK), CA(2+)-calmodulin-dependent protein kinase II (CaMK-II), protein kinase C (PKC), and protein kinase A (PKA) pathways. Furthermore, astrocytes treated with GMP or GUO promoted an increased number of cerebellar neurons in coculture, without altering the neuritogenesis pattern. No proliferation of neurons or astrocytes was observed due to GMP or GUO treatment. Our results show that guanine derivatives promote a reorganization of the ECM proteins produced by astrocytes, which might be responsible for a better interaction with neurons in cocultures.

Therapeutic vaccination for central nervous system repair

1. Vaccination against infectious agents has been heralded as a triumph in modern medicine and, more recently, cancer vaccines have risen in prominence. The present review looks towards the use of vaccine therapy to attenuate damage after injury to the central nervous system (CNS). 2. Significant debility is associated with brain injury, most commonly occurring as a result of physical trauma or stroke. This end result reflects the inability of neurons and axons to regenerate following injury to the CNS. This unconductive environment is due, in large part, to the presence of myelin and oligodendrocyte-related inhibitors of neurite outgrowth. 3. We review how a vaccine-based approach has been variably used to circumvent this issue and promote axonal regeneration and repair following traumatic injury and other neurodegenerative disorders. In addition, emerging evidence suggests that the immune response to injury in the CNS may be manipulated so as to reduce cellular damage. Vaccine-directed approaches using this concept are also outlined.

A review and re-evaluation of an association between the NOTCH4 locus and schizophrenia

This work reviewed all the reports on the NOTCH4 gene in schizophrenia, which have been published since the gene was found to be associated with illness among a British population in 2000. The results from independent studies were inconsistent. Allelic heterogeneity, clinical diagnosis, ethnical backgrounds, and linkage disequilibrium (LD) structures in the human genome may be major reasons for poor replication. A couple of studies suggested that the NOTCH4 gene could play a role in a subgroup of the disease, such as early-onset schizophrenia and negative symptoms. A single study revealed a weak association of the NOTCH4 gene with frontal lobe brain volumes and a strong association with frontal lobe cognitive performance. A meta-analysis showed stronger evidence of the NOTCH4 association in family-based studies than in case-control studies. In a previous study, we found that rs520692, a single nucleotide polymorphism (SNP) at the NOTCH4 locus, was associated with schizophrenia in a Chinese population. In the present study, we applied a large sample size to re-evaluate our initial findings and then confirmed the rs520692 association with illness. The pairwise measures did not show strong LD between paired SNPs although the SNPs tested are located within a 34-kb region, suggesting that LD within the NOTCH4 gene has been broken rapidly by historical recombination in the Chinese population. Taken together, the NOTCH4 gene may be associated with schizophrenia but how the gene contributes to the etiology of the illness needs a further investigation.

Tenascin-R restricts posttraumatic remodeling of motoneuron innervation and functional recovery after spinal cord injury in adult mice

Tenascin-R (TNR) is an extracellular glycoprotein in the CNS implicated in neural development and plasticity. Its repellent properties for growing axons in a choice situation with a conducive substrate in vitro have indicated that TNR may impede regeneration in the adult mammalian CNS. Here we tested whether constitutive lack of TNR has beneficial impacts on recovery from spinal cord injury in adult mice. Using the Basso, Beattie, Bresnahan (BBB) locomotor rating scale, we found that open-field locomotion in TNR-deficient (TNR-/-) mice recovered better that in wild-type (TNR+/+) littermates after compression of the thoracic spinal cord. We also designed, validated, and applied a motion analysis approach allowing numerical assessment of motor functions. We found, in agreement with the BBB score, that functions requiring low levels of supraspinal control such as plantar stepping improved more in TNR-/- mice. This was not the case for motor tasks demanding precision such as ladder climbing. Morphological analyses revealed no evidence that improved recovery of some functions in the mutant mice were attributable to enhanced tissue sparing or axonal regrowth. Estimates of perisomatic puncta revealed reduced innervation by cholinergic and GABAergic terminals around motoneurons in intact TNR-/- compared with TNR+/+ mice. Relative to nonlesioned animals, spinal cord repair was associated with increase in GABAergic and decrease of glutamatergic puncta in TNR-/- but not in TNR+/+ mice. Our results suggest that TNR restricts functional recovery by limiting posttraumatic remodeling of synapses around motoneuronal cell bodies where TNR is normally expressed in perineuronal nets.

Early coevolution of adhesive but not antiadhesive tenascin-R ligand-receptor pairs in vertebrates: A phylogenetic study

Axon growth inhibitory CNS matrix proteins, such as tenascin-R (TN-R), have been supposed to contribute to the poor regenerative capacity of adult mammalian CNS. With regard to TN-R function in low vertebrates capable of CNS regeneration, questions of particular interest concern the (co)evolution of ligand-receptor pairs and cellular response mechanisms associated with axon growth inhibition and oligodendrocyte differentiation. We address here these questions in a series of comparative in vivo and in vitro analyses using TN-R proteins purified from different vertebrates (from fish to human). Our studies provide strong evidence that unlike TN-R of higher vertebrates, fish TN-R proteins are not repellent for fish and less repellent for mammalian neurons and do not interfere with F3/contactin- and fibronectin-mediated mammalian cell adhesion and axon growth. However, axonal repulsion is induced in fish neurons by mammalian TN-R proteins, suggesting that the intracellular inhibitory machinery induced by TN-R-F3 interactions is already present during early vertebrate evolution. In contrast to TN-R-F3, TN-R-sulfatide interactions, mediating oligodendrocyte adhesion and differentiation, are highly conserved during vertebrate evolution. Our findings thus indicate the necessity of being cautious about extrapolations of the function of ligand-receptor pairs beyond a species border and, therefore, about the phylogenetic conservation of a molecular function at the cellular/tissue level.

Opposite impacts of tenascin-C and tenascin-R deficiency in mice on the functional outcome of facial nerve repair

The glycoproteins tenascin-C (TNC) and tenascin-R (TNR) are extracellular matrix proteins involved in the development, plasticity and repair of the nervous system. Altered expression patterns after nerve lesions in adult animals have suggested that these molecules influence axonal regeneration. To test this hypothesis, we investigated adult mice constitutively deficient in the expression of TNC, TNR or both, using the facial nerve injury paradigm. Quantitative analysis of vibrissal movements prior to nerve transection and repair (facial-facial anastomosis) did not reveal genotype-specific differences, and thus impacts of the mutations on motor function in intact animals. Two months after nerve repair, recovery of vibrissal whisking was poor in wild-type mice, a typical finding after facial-facial anastomosis in rodents. Differential effects of the mutations on whisking were found: recovery of function was worse in TNC-deficient and better in TNR null mice compared with wild-type littermates. In double-knockout animals, vibrissal performance was insufficient, but to a lesser extent compared with TNC null mutant mice. Retrograde labelling of motoneurons in the same animals showed that similar numbers of motoneurons had reinnervated the whisker pads in all experimental groups precluding varying extents of motoneuron death and/or axon regeneration failures as causes for the different outcomes of nerve repair. Our results provide strong evidence that TNC promotes and TNR impedes recovery after nerve lesion. These findings are of particular interest with regard to the scanty knowledge about factors determining success of regeneration in the peripheral nervous system of mammals.

Extracellular matrix glycoproteins inhibit neurite outgrowth of different types of identified leech neurons in culture

We explored the contribution of inhibitory peanut-binding extracellular matrix glycoproteins to the regeneration of characteristic outgrowth patterns by different types of identified neurons. Adult leech neurons were isolated one by one and plated in culture on a substrate that consisted of the capsules that encase the CNS ganglia. On the inside surface of this substrate, a combination of growth-promoting and -inhibiting extracellular matrix glycoproteins regulates the regeneration of distinctive outgrowth patterns by different neuron types. The role of inhibitory glycoproteins that bind to peanut lectin was studied by perturbation experiments in which peanut lectin was added to the culture medium. The effects of peanut lectin on the outgrowth patterns depended on the specific cell type that was tested. Anterior pagoda neurons, which on capsules produce a bipolar outgrowth pattern, in the presence of the lectin multiplied the number of primary neurites and the total neurite length and also lost their bipolarity. Annulus erector motoneurons, which on capsules grow poorly, in the presence of peanut lectin sprouted 70% more neurites and duplicated their total neurite length. By contrast, Retzius neurons which grow profusely on ganglion capsules, in the presence of peanut lectin increased the number of primary neurites without increasing their total neurite length or branch points. When neurons were plated on plastic, peanut lectin added to the culture medium did not affect the growth of neurons, thus showing that the effects of peanut lectin were induced by blocking the binding of neurons to inhibitory glycoproteins on the capsules. These results show that regeneration of different neuron types has different regulation by inhibitory extracellular matrix molecules.

Reduced extracellular space in the brain of tenascin-R- and HNK-1-sulphotransferase deficient mice

Tenascin-R (TN-R), a large extracellular glycoprotein, is an important component of the adult brain's extracellular matrix (ECM); tenascin-C (TN-C) is expressed mainly during early development, while human natural killer 1 (HNK-1) is a sulphated carbohydrate epitope that attaches to these molecules, modifying their adhesive properties. To assess their influence on extracellular space (ECS) volume and geometry, we used the real-time iontophoretic method to measure ECS volume fraction alpha and tortuosity lambda, and diffusion-weighted magnetic resonance imaging (MRI) to measure the apparent diffusion coefficient of water (ADC(W)). Measurements were performed in vivo in the cortex and CA1 hippocampal region of TN-R-, TN-C- and HNK-1 sulphotransferase (ST)-deficient adult mice and their wild-type littermate controls. In both cortex and hippocampus, the lack of TN-R or HNK-1 sulphotransferase resulted in a significant decrease in alpha and lambda. Compared with controls, alpha in TN-R-/- and ST-/- mice decreased by 22-26% and 9-15%, respectively. MRI measurements revealed a decreased ADC(W) in the cortex, hippocampus and thalamus. ADC(W) reflected the changes in alpha; the decrease in lambda indicated fewer diffusion obstacles in the ECS, presumably due to a decreased macromolecular content. No significant changes were found in TN-C-/- animals. We conclude that in TN-R-/- and ST-/- mice, which show morphological, electrophysiological and behavioural abnormalities, the ECS is reduced and its geometry altered. TN-R, as an important component of the ECM, appears to maintain an optimal distance between cells. The altered diffusion of neuroactive substances in the brain will inevitably affect extrasynaptic transmission, neuron-glia interactions and synaptic efficacy.

Expression of netrin-1, slit-1 and slit-3 but not of slit-2 after cerebellar and spinal cord lesions

To determine whether members of the Netrin-1 and Slit families and their receptors are expressed after central nervous system (CNS) injury, we performed in situ hybridization for netrin-1, slit-1, 2 and 3, and their receptors (dcc, unc5h-1, 2 and 3, robo-1, 2 and 3) 8 days, 2-3 months and 12-18 months after traumatic lesions of rat cerebellum. The expression pattern of these molecules was unchanged in axotomized Purkinje cells, whereas unc5h3 expression was upregulated in deafferented granule cells. Cells expressing slit-2 or dcc were never detected at the lesion site. By contrast, cells expressing netrin-1, slit-1 and slit-3, unc5h-1, 2 and 3, and robo-1, 2 and 3 (rig-1) could be detected at the cerebellar lesion site as soon as 8 days after injury. Expression of unc5h-2, robo-1, robo-2, slit-1 and slit-3 at the lesion site was maintained until 3 months, and up to 12-18 months for unc5h-1 and 3 and robo-3. Likewise, in the mouse spinal cord, netrin-1, slit-1 and slit-3 were also expressed at the lesion site 8 days after injury. Most of the cells expressing these mRNAs were located at the centre of the lesions, suggesting that they are macrophages/activated microglial cells (macrophagic cells) or meningeal fibroblastic cells. The macrophagic nature of most Netrin-1-positive cells and the macrophagic or fibroblastic nature of Robo-1-positive cells were corroborated by double staining. Thus, Netrin-1, Slits and their receptors may contribute to the regenerative failure of axons in the adult CNS by inhibiting axon outgrowth or by participating in the formation of the CNS scar.

Cell death and axon regeneration of Purkinje cells after axotomy: challenges of classical hypotheses of axon regeneration

Although adult mammalian neurons are able to regenerate their axons in the peripheral nervous system under certain conditions, they are not able to do it in the central nervous system. The environment surrounding the severed axons appears to be a key factor for axon regeneration. Many studies aiming to enhance axon regeneration in the CNS of adult mammals have successfully manipulated this environment by adding growth permissive molecules and/or neutralizing growth inhibitory molecules. In both cases, the number of axons able to regenerate was low and the different neuronal populations were not equal in their regenerative response, suggesting that manipulation of the environment is not always sufficient. This is particularly well illustrated in the cerebellar system, in which axotomized inferior olivary neurons regenerate when confronted with a permissive environment, whereas mature Purkinje cells do not. The intrinsic ability of a neuron to regenerate its axon is generally correlated with the intensity of its reaction to axotomy (expression of molecules, probability to die). Furthermore, molecules such as GAP-43 (growth-associated molecule) and c-Jun are involved in both axon regeneration and cell death suggesting that these two processes are linked. Surprisingly, Purkinje cells lose their capacity to regenerate their axon (even in the absence of myelin) during development before losing their capacity to react to an axotomy by cell death. These results emphasize the different reactions to axotomy between neuron types and underline that in Purkinje cells, the two cell decisions (axon regeneration and cell death) are differently regulated and therefore not part of the same signaling pathway.

Glycosylation-related Gene Expression in Prion Diseases

Several lines of evidence indicate that some glycoconjugates are efficient effectors of the cellular prion protein (PrP(C)) conversion into its pathogenic (PrP(Sc)) isoform. To assess how glycoconjugate glycan moieties participate in the biogenesis of PrP(Sc), an exhaustive comparative analysis of the expression of about 200 glycosylation-related genes was performed on prion-infected or not, hypothalamus-derived GT1 cells by hybridization of DNA microarrays, semiquantitative RT-PCR, and biochemical assays. A significant up- (30-fold) and down- (17-fold) regulation of the expression of the ChGn1 and Chst8 genes, respectively, was observed in prion-infected cells. ChGn1 and Chst8 are involved in the initiation of the synthesis of chondroitin sulfate and in the 4-O-sulfation of non-reducing N-acetylgalactosamine residues, respectively. A possible role for a hyposulfated chondroitin in PrP(Sc) accumulation was evidenced at the protein level and by determination of chondroitin and heparan sulfate amounts. Treatment of Sc-GT1 cells with a heparan mimetic (HM2602) induced an important reduction of the amount of PrP(Sc), associated with a total reversion of the transcription pattern of the N-acetylgalactosamine-4-O-sulfotransferase 8. It suggests a link between the genetic control of 4-O-sulfation and PrP(Sc) accumulation.

Destruction of extracellular matrix proteoglycans is pervasive in simian retroviral neuroinfection

Disruption of the perineuronal matrix has been reported in human immunodeficiency virus (HIV) encephalitis. To better understand the extent of matrix disruption during lentiviral encephalitis, we characterized the extracellular matrix (ECM) damage in brains of 12 macaques infected with simian immunodeficiency virus (SIV). Matrix integrity was assessed by Wisteria floribunda lectin histochemistry. Confocal microscopy was used to quantify matrix loss, macrophage infiltration, and synaptic damage. Disruption of brain ECM was present shortly after retroviral infection, preceding parenchymal macrophage infiltration. In agreement with previous observations, reduced staining of presynaptic and postsynaptic proteins in SIV encephalitis occurred concurrently with matrix abnormalities. Lentiviral infection induced microglial and macrophage expression of two disintegrins and metalloproteinases with thrombospondin motifs (ADAMTS-1 and ADAMTS-4), with high substrate specificity for matrix proteoglycans. Matrix damage is pervasive during SIV neuroinfection, which suggests interventions to conserve brain matrix proteoglycans might avert or delay retroviral-induced neurodegeneration.

Myelin-, reactive glia-, and scar-derived CNS axon growth inhibitors: expression, receptor signaling, and correlation with axon regeneration

Axon regeneration is arrested in the injured central nervous system (CNS) by axon growth-inhibitory ligands expressed in oligodendrocytes/myelin, NG2-glia, and reactive astrocytes in the lesion and degenerating tracts, and by fibroblasts in scar tissue. Growth cone receptors (Rc) bind inhibitory ligands, activating a Rho-family GTPase intracellular signaling pathway that disrupts the actin cytoskeleton inducing growth cone collapse/repulsion. The known inhibitory ligands include the chondroitin sulfate proteoglycans (CSPG) Neurocan, Brevican, Phosphacan, Tenascin, and NG2, as either membrane-bound or secreted molecules; Ephrins expressed on astrocyte/fibroblast membranes; the myelin/oligodendrocyte-derived growth inhibitors Nogo, MAG, and OMgp; and membrane-bound semaphorins (Sema) produced by meningeal fibroblasts invading the scar. No definitive CSPG Rc have been identified, although intracellular signaling through the Rho family of G-proteins is probably common to all the inhibitory ligands. Ephrins bind to signalling Ephs. The ligand-binding Rc for all the myelin inhibitors is NgR and requires p75(NTR) for transmembrane signaling. The neuropilin (NP)/plexin (Plex) Rc complex binds Sema. Strategies for promoting axon growth after CNS injury are thwarted by the plethora of inhibitory ligands and the ligand promiscuity of some of their Rc. There is also paradoxical reciprocal expression of many of the inhibitory ligands/Rc in normal and damaged neurons, and NgR expression is restricted to a limited number of neuronal populations. All these factors, together with an incomplete understanding of the normal functions of many of these molecules in the intact CNS, presently confound interpretive acumen in regenerative studies.

Tenascin-R mediates activity-dependent recruitment of neuroblasts in the adult mouse forebrain

Neuroblasts arising in the adult forebrain that travel to the olfactory bulb use two modes of migration: tangentially, along the rostral migratory stream, and radially, in the core of the olfactory bulb where they start to ascend to the outer layers. Although the mechanisms of tangential migration have been extensively studied, the factors controlling radial migration remain unexplored. Here we report that the extracellular matrix glycoprotein tenascin-R, expressed in the adult mouse olfactory bulb, initiates both the detachment of neuroblasts from chains and their radial migration. Expression of tenascin-R is activity dependent, as it is markedly reduced by odor deprivation. Furthermore, grafting of tenascin-R-transfected cells into non-neurogenic regions reroutes migrating neuroblasts toward these regions. The identification of an extracellular microenvironment capable of directing migrating neuroblasts provides insights into the mechanisms regulating radial migration in the adult olfactory bulb and offers promising therapeutic venues for brain repair.

TNXB locus may be a candidate gene predisposing to schizophrenia

We report here on the detection of nine single nucleotide polymorphisms (SNPs) near to the NOTCH4 locus in the search for schizophrenia susceptibility genes in the class III region of the human major histocompatibility complex (MHC). We totally analyzed 122 family trios recruited in the UK. The TDT analysis demonstrated that of the nine SNPs, three were associated with schizophrenia, including rs1009382 (P = 0.00047), rs204887 (P = 0.007), and rs8283 (P = 0.015). Both rs1009382 and rs204887 are present in the TNXB locus. The rs1009382 is a non-synonymous SNP located in exon 23 of the gene and its A to G base change causes a Glu2578Gly substitution. The goodness-of-fit test showed that genotypic distribution of rs1009382 was deviated from Hardy-Weinberg equilibrium due to homozygote excess in the patient group (P = 0.01), suggesting that a double dose of a genetic risk may be involved. Possibly, rs1009382 is a candidate SNP predisposing to a schizophrenic illness. Moreover, the test for linkage disequilibrium (LD) between paired SNPs showed that the nine SNPs studied may be in the same LD block with an unexpected pattern as the strength of LD was not correlated with the distance between paired SNPs. The haplotype analysis suggested that there might be more than one disease-related allele located in the class III region of the MHC, and that these alleles possibly confer either susceptibility or resistance to schizophrenia.