Platelet-derived growth factor receptor (PDGFRA)/NG2-expressing glia are distributed throughout the adult CNS. They are descended from oligodendrocyte precursors (OLPs) in the perinatal CNS, but it is not clear whether they continue to generate myelinating oligodendrocytes or other differentiated cells during normal adult life. We followed the fates of adult OLPs in Pdgfra-creER T2 /Rosa26-YFP double-transgenic mice and found that they generated many myelinating oligodendrocytes during adulthood; >20% of all oligodendrocytes in the adult mouse corpus callosum were generated after 7 weeks of age, raising questions about the function of the late-myelinating axons. OLPs also produced some myelinating cells in the cortex, but the majority of adult-born cortical cells did not appear to myelinate. We found no evidence for astrocyte production in gray or white matter. However, small numbers of projection neurons were generated in the forebrain, especially in the piriform cortex, which is the main target of the olfactory bulb.Oligodendrocytes, the myelin-forming cells of the CNS, are mostly generated during the first few postnatal weeks in rodents, peaking in the second week (postnatal day 7-14, P7-P14). They differentiate from proliferative, migratory OLPs that originate in the ventricular zones of the developing spinal cord and brain. OLPs express a characteristic set of markers, including PDGFRA and the NG2 proteoglycan, allowing OLP development to be followed in situ. Both PDGFRA and NG2 are rapidly downregulated when OLPs differentiate into oligodendrocytes 1-3 , unlike other lineage markers (for example, transcription factors SOX10 and OLIG2), which are expressed in both OLPs and oligodendrocytes. By the time of birth, OLPs are more or less evenly distributed throughout the brain, both in gray matter and developing white matter, and remain so during the early postnatal period, when oligodendrocyte production is in full swing. The size of the OLP population remains relatively stable throughout this time, presumably because, although OLPs continue to proliferate, half of the daughter cells either differentiate or die. To determine the behavior and fates of adult OLPs in vivo, we generated a transgenic mouse line that expresses a tamoxifen-inducible form of the Cre recombinase (CreER T2 ) under PDGFRA transcriptional control in a phage artificial chromosome (PAC). The PAC transgene was faithfully expressed by OLPs in the postnatal CNS. By combining PdgfracreER T2 mice with the Rosa26-YFP reporter line, we were able to induce expression of yellow fluorescent protein (YFP) de novo in adult OLPs and identify their differentiated progeny. We found that OLPs generated mature, myelinating oligodendrocytes in adult mice until at least 8 months of age, raising questions about the function of the newly myelinated axons. We were unable to find any evidence for astrocyte production from adult OLPs in either gray or white matter. Notably, we found small numbers of YFP-labeled neurons in the forebrain, particularly in th...

Glioblastoma (GBM), a malignant brain cancer, is characterized by abnormal activation of receptor tyrosine kinase (RTK) signaling pathways and poor prognosis. Extracellular proteoglycans, including heparan sulfate and chondroitin sulfate, play critical roles in the regulation of cell signaling and migration via interactions with extracellular ligands, growth factor receptors, extracellular matrix components, and intracellular enzymes and structural proteins. In cancer, proteoglycans help drive multiple oncogenic pathways in tumor cells and promote critical tumor-microenvironment interactions. In this review, we summarize the evidence for proteoglycan function in gliomagenesis and we examine the expression of proteoglycans and their modifying enzymes in human GBM using data from The Cancer Genome Atlas (TCGA). Furthermore, we demonstrate an association between specific proteoglycan alterations and changes in RTKs. Based on these data we propose a model in which proteoglycans and their modifying enzymes promote RTK signaling and progression in GBM, and we suggest cancer associated proteoglycans are promising biomarkers for disease and therapeutic targets.

SUMMARYsE-selectin, sICAM-1, sVCAM-1 and von Willebrand factor (vWF) were assayed in 238 samples in a longitudinal study of 81 normal children from 9 . 5 to 15 . 5 years old. Multilevel modelling was used to quantify changes with age. sE-selectin, sICAM-1 and sVCAM-1 all fell significantly over the age range (by 17%, 16%, and 10%, respectively). In contrast, levels of vWF were not age-dependent. Our findings highlight the need for age-matched controls when studying cell surface adhesion molecules in disease groups, and may imply developmental changes in expression of these molecules and their shedding from the cell surface.

Elevations of the levels of N-acetyl-aspartyl-glutamate (NAAG) and N-acetyl-aspartate (NAA) are associated with myelin loss in the leucodystrophies Canavan's disease and Pelizaeus-Merzbacher-like disease. NAAG and NAA can activate and antagonize neuronal N-methyl-D-aspartate (NMDA) receptors, and also act on group II metabotropic glutamate receptors. Oligodendrocytes and their precursors have recently been shown to express NMDA receptors, and activation of these receptors in ischaemia leads to the death of oligodendrocyte precursors and the loss of myelin. This raises the possibility that the failure to develop myelin, or demyelination, occurring in the leucodystrophies could reflect an action of NAAG or NAA on oligodendrocyte NMDA receptors. However, since the putative subunit composition of NMDA receptors on oligodendrocytes differs from that of neuronal NMDA receptors, the effects of NAAG and NAA on them are unknown. We show that NAAG, but not NAA, evokes an inward membrane current in cerebellar white matter oligodendrocytes, which is reduced by NMDA receptor block (but not by block of metabotropic glutamate receptors). The size of the current evoked by NAAG, relative to that evoked by NMDA, was much smaller in oligodendrocytes than in neurons, and NAAG induced a rise in [Ca2+]i in neurons but not in oligodendrocytes. These differences in the effect of NAAG on oligodendrocytes and neurons may reflect the aforementioned difference in receptor subunit composition. In addition, as a major part of the response in oligodendrocytes was blocked by tetrodotoxin (TTX), much of the NAAG-evoked current in oligodendrocytes is a secondary consequence of activating neuronal NMDA receptors. Six hours exposure to 1 mM NAAG did not lead to the death of cells in the white matter. We conclude that an action of NAAG on oligodendrocyte NMDA receptors is unlikely to be a major contributor to white matter damage in the leucodystrophies.

Glioblastoma (GBM) is the most common primary malignant brain tumor of adults and confers a poor prognosis due, in part, to diffuse invasion of tumor cells. Heparan sulfate (HS) glycosaminoglycans, present on the cell surface and in the extracellular matrix, regulate cell signaling pathways and cell-microenvironment interactions. In GBM, the expression of HS glycosaminoglycans and the enzymes that regulate their function are altered but the actual HS content and structure are unknown. However, inhibition of HS glycosaminoglycan function is emerging as a promising therapeutic strategy for some cancers. In this study, we use liquid chromatography-mass spectrometry (LC/MS) analysis to demonstrate differences in HS disaccharide content and structure across four patient-derived tumorsphere lines (GBM1, 5, 6, 43) and between two murine tumorsphere lines derived from murine GBM with enrichment of mesenchymal and proneural gene expression (mMES and mPN, respectively) markers. In GBM, the heterogeneous HS content and structure across patient-derived tumorsphere lines suggested diverse functions in the GBM tumor microenvironment (TME). In GBM5 and mPN, elevated expression of sulfatase 2 (SULF2), an extracellular enzyme that alters ligand binding to HS, was associated with low trisulfated HS disaccharides, a substrate of SULF2. In contrast, other primary tumorsphere lines had elevated expression of the HS-modifying enzyme heparanase (HPSE). Using gene editing strategies to inhibit HPSE a role for HPSE in promoting tumor cell adhesion and invasion was identified. These studies characterize the heterogeneity in HS glycosaminoglycan content and structure across GBM and reveal their role in tumor cell invasion.

Background Neural stem/progenitor cells (NSPCs) reside within a complex and dynamic extracellular microenvironment, or niche. This niche regulates fundamental aspects of their behavior during normal neural development and repair. Precise yet dynamic regulation of NSPC self-renewal, migration, and differentiation is critical and must persist over the life of an organism. Scope of Review In this review, we summarize some of the major components of the NSPC niche and provide examples of how cues from the extracellular matrix regulate NSPC behaviors. We use proteoglycans to illustrate the many diverse roles of the niche in providing temporal and spatial regulation of cellular behavior. Major Conclusions The NSPC niche is comprised of multiple components that include; soluble ligands, such as growth factors, morphogens, chemokines, and neurotransmitters, the extracellular matrix, and cellular components. As illustrated by proteoglycans, a major component of the extracellular matrix, the NSPC niche provides temporal and spatial regulation of NSPC behaviors. General Significance The factors that control NSPC behavior are vital to understand as we attempt to modulate normal neural development and repair. Furthermore, an improved understanding of how these factors regulate cell proliferation, migration, and differentiation, crucial for malignancy, may reveal novel anti-tumor strategies.

Development of the nervous system requires differentiating neurons to grow axons over great distances following long-and short-range signals that are controlled by distinct guidance systems. In general, long-distance acting molecules, such as growth factors, are soluble and bind receptors on the neuronal surface. In contrast, short-range membrane-associated molecules interact with surrounding cells and extracellular matrix, allowing for growth through diverse and changing environments. However, the boundaries between long-range diffusible ligands and short-range contact-mediated factors have blurred. Abbreviations used: ALCAM, activated leukocyte cell adhesion molecule; BSA, bovine serum albumin; CAM, cell adhesion molecule; DMEM, Dulbecco's minimum essential medium; EDL, extensor digitorum longus; GDNF, glial cell-derived neurotrophic factor; H C, carboxy-terminal fragment of tetanus toxin; Ig, immunoglobulin; LAL, levator auris longus; MION, monocrystalline iron oxide nanoparticles; NGF, nerve growth factor; NMJ, neuromuscular junction; p75 NTR, p75 neurotrophin receptor; PBS, phosphate-buffered saline; pERK1/2, phosphorylation of ERK1/2; pTrkA, phosphorylation of TrkA; SDS, sodium dodecyl sulfate; Trk, tropomyosin-receptor-kinase. Abstract Cell adhesion molecules of the immunoglobulin superfamily (IgCAMs) have been shown to modulate growth factor signaling and follow complex trafficking pathways in neurons. Similarly, several growth factors, including members of the neurotrophin family, undergo axonal retrograde transport that is required to elicit their full signaling potential in neurons. We sought to determine whether IgCAMs that enter the axonal retrograde transport route co-operate with neurotrophin signaling. We identified activated leukocyte cell adhesion molecule (ALCAM), a protein involved in axon pathfinding and development of the neuromuscular junction, to be associated with an axonal endocytic compartment that contains neurotrophins and their receptors. Although ALCAM enters carriers that are transported bidirectionally in motor neuron axons, it is predominantly co-transported with the neurotrophin receptor p75 NTR toward the cell body. ALCAM was found to specifically potentiate nerve growth factor (NGF)-induced differentiation and signaling. The extracellular domain of ALCAM is both necessary and sufficient to potentiate NGF-induced neurite outgrowth, and its homodimerization is required for this novel role. Our findings indicate that ALCAM synergizes with NGF to induce neuronal differentiation, raising the possibility that it functions not only as an adhesion molecule but also in the modulation of growth factor signaling in the nervous system.

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