Prox1 Is Required for Oligodendrocyte Cell Identity in Adult Neural Stem Cells of the Subventricular Zone.

Adult neural stem cells with the ability to generate neurons and glia cells are active throughout life in both the dentate gyrus (DG) and the subventricular zone (SVZ). Differentiation of adult neural stem cells is induced by cell fate determinants like the transcription factor Prox1. Evidence has been provided for a function of Prox1 as an inducer of neuronal differentiation within the DG. We now show that within the SVZ Prox1 induces differentiation into oligodendrocytes. Moreover, we find that loss of Prox1 expression in vivo reduces cell migration into the corpus callosum, where the few Prox1 deficient SVZ-derived remaining cells fail to differentiate into oligodendrocytes. Thus, our work uncovers a novel function of Prox1 as a fate determinant for oligodendrocytes in the adult mammalian brain. These data indicate that the neurogenic and oligodendrogliogenic lineages in the two adult neurogenic niches exhibit a distinct requirement for Prox1, being important for neurogenesis in the DG but being indispensable for oligodendrogliogenesis in the SVZ. Stem Cells 2016;34:2115-2129.

Protoporphyrin IX (PpIX) Fluorescence during Meningioma Surgery: Correlations with Histological Findings and Expression of Heme Pathway Molecules.

Background: The usefulness of 5-ALA-mediated fluorescence-guided resection (FGR) in meningiomas is controversial, and information on the molecular background of fluorescence is sparse. Methods: Specimens obtained during 44 FGRs of intracranial meningiomas were analyzed for the presence of tumor tissue and fluorescence. Protein/mRNA expression of key transmembrane transporters/enzymes involved in PpIX metabolism (ABCB6, ABCG2, FECH, CPOX) were investigated using immunohistochemistry/qPCR. Results: Intraoperative fluorescence was observed in 70 of 111 specimens (63%). No correlation was found between fluorescence and the WHO grade (p = 0.403). FGR enabled the identification of neoplastic tissue (sensitivity 84%, specificity 67%, positive and negative predictive value of 86% and 63%, respectively, AUC: 0.75, p < 0.001), and was improved in subgroup analyses excluding dura specimens (86%, 88%, 96%, 63% and 0.87, respectively; p < 0.001). No correlation was found between cortical fluorescence and tumor invasion (p = 0.351). Protein expression of ABCB6, ABCG2, FECH and CPOX was found in meningioma tissue and was correlated with fluorescence (p < 0.05, each), whereas this was not confirmed for mRNA expression. Aberrant expression was observed in the CNS. Conclusion: FGR enables the intraoperative identification of meningioma tissue with limitations concerning dura invasion and due to ectopic expression in the CNS. ABCB6, ABCG2, FECH and CPOX are expressed in meningioma tissue and are related to fluorescence.

The E3-ubiquitin ligase TRIM2 regulates neuronal polarization.

The establishment of a polarized morphology with a single axon and multiple dendrites is an essential step during neuronal differentiation. This cellular polarization is largely depending on changes in the dynamics of the neuronal cytoskeleton. Here, we show that the tripartite motif (TRIM)-NHL protein TRIM2 is regulating axon specification in cultured mouse hippocampal neurons, where one of several initially indistinguishable neurites is selected to become the axon. Suppression of TRIM2 by RNA interference results in the loss of neuronal polarity while over-expression of TRIM2 induces the specification of multiple axons. TRIM2 conducts its function during neuronal polarization by ubiquitination of the neurofilament light chain. Together, our results imply an important function of TRIM2 for axon outgrowth during development.

p53 upregulated mediator of apoptosis (Puma) deficiency increases survival of adult neural stem cells generated physiologically in the hippocampus, but does not protect stem cells generated in surplus after an excitotoxic lesion.

OBJECTIVES: Neurogenesis occurs in the mammalian brain throughout adulthood and increases in response to metabolic, toxic or traumatic insults. To remove potentially superfluous or unwanted neural stem cells/neuronal progenitors, their rate of proliferation and differentiation is fine-tuned against their rate of apoptosis. Apoptosis requires the transcriptional and posttranslational activation of Bcl-2-homolgy domain 3 (BH3)-only proteins. Previously, we demonstrated that the BH3-only protein p53-upregulated mediator of apoptosis (Puma) controls the physiological rate of apoptosis of neural precursor cells in the adult mouse hippocampus. Puma's role in controlling a lesion-induced increase in neural stem cells is currently not known. METHODS: We employed a model of local, N-methyl-D-asparte (NMDA)-induced excitotoxic injury to the CA1 hippocampal subfield and immunofluorescence labelling to produce increased neural stem cell proliferation/ neurogenesis in the dentate gyrus at two survival times following the excitotoxic lesion. RESULTS: Deletion of puma failed to rescue any NMDA-induced increase in adult born cells as assessed by BrdU or Doublecortin labelling in the long-term. No difference in the proportion of BrdU/NeuN-positive cells comparing the different genotypes and treatments suggested that the phenotypic fate of the cells was preserved regardless of the genotype and the treatment. CONCLUSIONS: While neurogenesis is up-regulated in puma-deficient animals following NMDA-induced excitotoxicity to the hippocampal CA1 subfield, puma deficiency could not protect this surplus of newly generated cells from apoptotic cell death.

Anti-inflammatory treatment induced regenerative oligodendrogenesis in parkinsonian mice.

INTRODUCTION: The adult mammalian brain retains niches for neural stem cells (NSCs), which can generate glial and neuronal components of the brain tissue. However, it is barely established how chronic neuroinflammation, as it occurs in neurodegenerative diseases, such as Alzheimer's and Parkinson's disease, affects adult neurogenesis and, therefore, modulates the brain's potential for self-regeneration. METHODS: Neural stem cell culture techniques, intraventricular tumor necrosis factor (TNF)-α infusion and the 6-hydroxydopamine mouse model were used to investigate the influence of neuroinflammation on adult neurogenesis in the Parkinson's disease background. Microscopic methods and behavioral tests were used to analyze samples. RESULTS: Here, we demonstrate that differences in the chronicity of TNF-α application to cultured NSCs result in opposed effects on their proliferation. However, chronic TNF-α treatment, mimicking Parkinson's disease associated neuroinflammation, shows detrimental effects on neural progenitor cell activity. Inversely, pharmacological inhibition of neuroinflammation in a 6-hydroxydopamine mouse model led to increased neural progenitor cell proliferation in the subventricular zone and neuroblast migration into the lesioned striatum. Four months after surgery, we measured improved Parkinson's disease-associated behavior, which was correlated with long-term anti-inflammatory treatment. But surprisingly, instead of newly generated striatal neurons, oligodendrogenesis in the striatum of treated mice was enhanced. CONCLUSIONS: We conclude that anti-inflammatory treatment, in a 6-hydroxydopamine mouse model for Parkinson's disease, leads to activation of adult neural stem cells. These adult neural stem cells generate striatal oligodendrocytes. The higher numbers of newborn oligodendrocytes possibly contribute to axonal stability and function in this mouse model of Parkinson's disease and thereby attenuate dysfunctions of basalganglian motor-control.

JAM-C is an apical surface marker for neural stem cells.

Junctional adhesion molecule-C (JAM-C) is an adhesive cell surface protein expressed in various cell types. JAM-C localizes to the apically localized tight junctions (TJs) between contacting endothelial and epithelial cells, where it contributes to cell-cell adhesions. Just as those epithelial cells, also neural stem cells are highly polarized along their apical-basal axis. The defining feature of all stem cells, including neural stem cells (NSCs) is their ability to self renew. This self-renewal depends on the tight control of symmetric and asymmetric cell divisions. In NSCs, the decision whether a division is symmetric or asymmetric largely depends on the distribution of the apical membrane and cell fate determinants on the basal pole of the cell. In this study we demonstrate that JAM-C is expressed on neural progenitor cells and neural stem cells in the embryonic as well as the adult mouse brain. Furthermore, we demonstrate that in vivo JAM-C shows enrichment at the apical surface and therefore is asymmetrically distributed during cell divisions. These results define JAM-C as a novel surface marker for neural stem cells.

Cellular organization of adult neurogenesis in the Common Marmoset.

Adult neurogenesis within the subgranular zone (SGZ) of the hippocampal dentate gyrus and the subventricular zone (SVZ) of the lateral ventricle (LV) has been most intensely studied within the brains of rodents such as mice and rats. However, little is known about the cell types and processes involved in adult neurogenesis within primates such as the common marmoset (Callithrix jacchus). Moreover, substantial differences seem to exist between the neurogenic niche of the LV between rodents and humans. Here, we set out to use immunohistochemical and autogradiographic analysis to characterize the anatomy of the neurogenic niches and the expression of cell type-specific markers in those niches in the adult common marmoset brain. Moreover, we demonstrate significant differences in the activity of neurogenesis in the adult marmoset brain compared to the adult mouse brain. Finally, we provide evidence for ongoing proliferation of neuroblasts within both the SGZ and SVZ of the adult brain and further show that the age-dependent decline of neurogenesis in the hippocampus is associated with a decrease in neuroblast cells.

NMDA-induced injury of mouse organotypic hippocampal slice cultures triggers delayed neuroblast proliferation in the dentate gyrus: an in vitro model for the study of neural precursor cell proliferation.

We present a model for the study of injury-induced neurogenesis in the dentate gyrus (DG) in murine organotypic hippocampal slice cultures (OHCs). A brief exposure of 8-day-old hippocampal slice cultures to the glutamate receptor agonist N-methyl-d-aspartate (NMDA; 20-50µM for 30 min) caused a selective excitotoxic injury in the CA1 subfield of the hippocampus that matured over a period of 24h. The insult resulted in a prominent up-regulation of proliferating nuclei within the OHC dentate gyrus (DG), and a corresponding increase in Ki67/doublecortin double-positive cells in the SGZ of the dentate gyrus. 5-bromo-2-deoxyuridine (BrdU)-labelling of the OHCs for three days subsequent to the NMDA exposure revealed significantly increased BrdU incorporation within the DG (SGZ and GCL) of the hippocampus. Doublecortin immunofluorescence indicated a concurrent up-regulation of neuronal precursor cells specifically in the SGZ and GCL. Significantly increased BrdU incorporation could be detected up to 6-9 days after termination of the NMDA exposure. The model presented here enables easy manipulation and follow-up of injury-induced neuroblast proliferation in the DG that is amenable to the study of transgenic mice.