NCAM expression induces neurogenesis in vivo

Post-translational modifications in prion diseases

More than 650 reversible and irreversible post-translational modifications (PTMs) of proteins have been listed so far. Canonical PTMs of proteins consist of the covalent addition of functional or chemical groups on target backbone amino-acids or the cleavage of the protein itself, giving rise to modified proteins with specific properties in terms of stability, solubility, cell distribution, activity, or interactions with other biomolecules. PTMs of protein contribute to cell homeostatic processes, enabling basal cell functions, allowing the cell to respond and adapt to variations of its environment, and globally maintaining the constancy of the milieu interieur (the body's inner environment) to sustain human health. Abnormal protein PTMs are, however, associated with several disease states, such as cancers, metabolic disorders, or neurodegenerative diseases. Abnormal PTMs alter the functional properties of the protein or even cause a loss of protein function. One example of dramatic PTMs concerns the cellular prion protein (PrPC), a GPI-anchored signaling molecule at the plasma membrane, whose irreversible post-translational conformational conversion (PTCC) into pathogenic prions (PrPSc) provokes neurodegeneration. PrPC PTCC into PrPSc is an additional type of PTM that affects the tridimensional structure and physiological function of PrPC and generates a protein conformer with neurotoxic properties. PrPC PTCC into PrPSc in neurons is the first step of a deleterious sequence of events at the root of a group of neurodegenerative disorders affecting both humans (Creutzfeldt-Jakob diseases for the most representative diseases) and animals (scrapie in sheep, bovine spongiform encephalopathy in cow, and chronic wasting disease in elk and deer). There are currently no therapies to block PrPC PTCC into PrPSc and stop neurodegeneration in prion diseases. Here, we review known PrPC PTMs that influence PrPC conversion into PrPSc. We summarized how PrPC PTCC into PrPSc impacts the PrPC interactome at the plasma membrane and the downstream intracellular controlled protein effectors, whose abnormal activation or trafficking caused by altered PTMs promotes neurodegeneration. We discussed these effectors as candidate drug targets for prion diseases and possibly other neurodegenerative diseases.

Regulation of young-adult neurogenesis and neuronal differentiation by neural cell adhesion molecule 2 (NCAM2)

Adult neurogenesis persists in mammals in the neurogenic zones, where newborn neurons are incorporated into preexisting circuits to preserve and improve learning and memory tasks. Relevant structural elements of the neurogenic niches include the family of cell adhesion molecules (CAMs), which participate in signal transduction and regulate the survival, division, and differentiation of radial glial progenitors (RGPs). Here we analyzed the functions of neural cell adhesion molecule 2 (NCAM2) in the regulation of RGPs in adult neurogenesis and during corticogenesis. We characterized the presence of NCAM2 across the main cell types of the neurogenic process in the dentate gyrus, revealing different levels of NCAM2 amid the progression of RGPs and the formation of neurons. We showed that Ncam2 overexpression in adult mice arrested progenitors in an RGP-like state, affecting the normal course of young-adult neurogenesis. Furthermore, changes in Ncam2 levels during corticogenesis led to transient migratory deficits but did not affect the survival and proliferation of RGPs, suggesting a differential role of NCAM2 in adult and embryonic stages. Our data reinforce the relevance of CAMs in the neurogenic process by revealing a significant role of Ncam2 levels in the regulation of RGPs during young-adult neurogenesis in the hippocampus.

Zika Virus Neuropathogenesis: The Different Brain Cells, Host Factors and Mechanisms Involved

Zika virus (ZIKV), despite being discovered six decades earlier, became a major health concern only after an epidemic in French Polynesia and an increase in the number of microcephaly cases in Brazil. Substantial evidence has been found to support the link between ZIKV and neurological complications in infants. The virus targets various cells in the brain, including radial glial cells, neural progenitor cells (NPCs), astrocytes, microglial and glioblastoma stem cells. It affects the brain cells by exploiting different mechanisms, mainly through apoptosis and cell cycle dysregulation. The modulation of host immune response and the inflammatory process has also been demonstrated to play a critical role in ZIKV induced neurological complications. In addition to that, different ZIKV strains have exhibited specific neurotropism and unique molecular mechanisms. This review provides a comprehensive and up-to-date overview of ZIKV-induced neuroimmunopathogenesis by dissecting its main target cells in the brain, and the underlying cellular and molecular mechanisms. We highlighted the roles of the different ZIKV host factors and how they exploit specific host factors through various mechanisms. Overall, it covers key components for understanding the crosstalk between ZIKV and the brain.

Re-Expression of Poly/Oligo-Sialylated Adhesion Molecules on the Surface of Tumor Cells Disrupts Their Interaction with Immune-Effector Cells and Contributes to Pathophysiological Immune Escape

Glycans linked to surface proteins are the most complex biological macromolecules that play an active role in various cellular mechanisms. This diversity is the basis of cell-cell interaction and communication, cell growth, cell migration, as well as co-stimulatory or inhibitory signaling. Our review describes the importance of neuraminic acid and its derivatives as recognition elements, which are located at the outermost positions of carbohydrate chains linked to specific glycoproteins or glycolipids. Tumor cells, especially from solid tumors, mask themselves by re-expression of hypersialylated neural cell adhesion molecule (NCAM), neuropilin-2 (NRP-2), or synaptic cell adhesion molecule 1 (SynCAM 1) in order to protect themselves against the cytotoxic attack of the also highly sialylated immune effector cells. More particularly, we focus on α-2,8-linked polysialic acid chains, which characterize carrier glycoproteins such as NCAM, NRP-2, or SynCam-1. This characteristic property correlates with an aggressive clinical phenotype and endows them with multiple roles in biological processes that underlie all steps of cancer progression, including regulation of cell-cell and/or cell-extracellular matrix interactions, as well as increased proliferation, migration, reduced apoptosis rate of tumor cells, angiogenesis, and metastasis. Specifically, re-expression of poly/oligo-sialylated adhesion molecules on the surface of tumor cells disrupts their interaction with immune-effector cells and contributes to pathophysiological immune escape. Further, sialylated glycoproteins induce immunoregulatory cytokines and growth factors through interactions with sialic acid-binding immunoglobulin-like lectins. We describe the processes, which modulate the interaction between sialylated carrier glycoproteins and their ligands, and illustrate that sialic acids could be targets of novel therapeutic strategies for treatment of cancer and immune diseases.

NCAM regulates temporal specification of neural progenitor cells via profilin2 during corticogenesis

The development of cerebral cortex requires spatially and temporally orchestrated proliferation, migration, and differentiation of neural progenitor cells (NPCs). The molecular mechanisms underlying cortical development are, however, not fully understood. The neural cell adhesion molecule (NCAM) has been suggested to play a role in corticogenesis. Here we show that NCAM is dynamically expressed in the developing cortex. NCAM expression in NPCs is highest in the neurogenic period and declines during the gliogenic period. In mice bearing an NPC-specific NCAM deletion, proliferation of NPCs is reduced, and production of cortical neurons is delayed, while formation of cortical glia is advanced. Mechanistically, NCAM enhances actin polymerization in NPCs by interacting with actin-associated protein profilin2. NCAM-dependent regulation of NPCs is blocked by mutations in the profilin2 binding site. Thus, NCAM plays an essential role in NPC proliferation and fate decision during cortical development by regulating profilin2-dependent actin polymerization.

Molecular Mechanisms of Bortezomib Action: Novel Evidence for the miRNA-mRNA Interaction Involvement

Bortezomib is an anti-tumor agent, which inhibits 26S proteasome degrading ubiquitinated proteins. While apoptotic transcription-associated activation in response to bortezomib has been suggested, mechanisms related to its influence on post-transcriptional gene silencing mediated regulation by non-coding RNAs remain not fully elucidated. In the present study, we examined changes in global gene and miRNA expression and analyzed the identified miRNA-mRNA interactions after bortezomib exposure in human neuroblastoma cells to define pathways affected by this agent in this type of cells. Cell viability assays were performed to assess cytotoxicity of bortezomib. Global gene and miRNA expression profiles of neuroblastoma cells after 24-h incubation with bortezomib were determined using genome-wide RNA and miRNA microarray technology. Obtained results were then confirmed by qRT-PCR and Western blot. Further bioinformatical analysis was performed to identify affected biological processes and pathways. In total, 719 genes and 28 miRNAs were downregulated, and 319 genes and 61 miRNAs were upregulated in neuroblastoma cells treated with bortezomib. Possible interactions between dysregulated miRNA/mRNA, which could be linked to bortezomib-induced neurotoxicity, affect neurogenesis, cellular calcium transport, and neuron death. Bortezomib might exert toxic effects on neuroblastoma cells and regulate miRNA-mRNA interactions influencing vital cellular functions. Further studies on the role of specific miRNA-mRNA interactions are needed to elucidate mechanisms of bortezomib action.

Heterocellular molecular contacts in the mammalian stem cell niche

Adult tissue homeostasis and repair relies on prompt and appropriate intervention by tissue-specific adult stem cells (SCs). SCs have the ability to self-renew; upon appropriate stimulation, they proliferate and give rise to specialized cells. An array of environmental signals is important for maintenance of the SC pool and SC survival, behavior, and fate. Within this special microenvironment, commonly known as the stem cell niche (SCN), SC behavior and fate are regulated by soluble molecules and direct molecular contacts via adhesion molecules providing connections to local supporting cells and the extracellular matrix. Besides the extensively discussed array of soluble molecules, the expression of adhesion molecules and molecular contacts is another fundamental mechanism regulating niche occupancy and SC mobilization upon activation. Some adhesion molecules are differentially expressed and have tissue-specific consequences, likely reflecting the structural differences in niche composition and design, especially the presence or absence of a stromal counterpart. However, the distribution and identity of intercellular molecular contacts for adhesion and adhesion-mediated signaling within stromal and non-stromal SCN have not been thoroughly studied. This review highlights common details or significant differences in cell-to-cell contacts within representative stromal and non-stromal niches that could unveil new standpoints for stem cell biology and therapy.

Nuclear fragments of the neural cell adhesion molecule NCAM with or without polysialic acid differentially regulate gene expression

The neural cell adhesion molecule (NCAM) is the major carrier of polysialic acid (PSA) which modulates NCAM functions of neural cells at the cell surface. In previous studies, we have shown that stimulation of cultured neurons with surrogate NCAM ligands leads to the generation and nuclear import of PSA-lacking and -carrying NCAM fragments. Here, we show that the nuclear import of the PSA-carrying NCAM fragment is mediated by positive cofactor 4 and cofilin, which we identified as novel PSA-binding proteins. In the nucleus, the PSA-carrying NCAM fragment interacts via PSA with PC4 and cofilin, which are involved in RNA polymerase II-dependent transcription. Microarray analysis revealed that the nuclear PSA-carrying and -lacking NCAM fragments affect expression of different genes. By qPCR and immunoblot analysis we verified that the nuclear PSA-carrying NCAM fragment increases mRNA and protein expression of nuclear receptor subfamily 2 group F member 6, whereas the PSA-lacking NCAM fragment increases mRNA and protein expression of low density lipoprotein receptor-related protein 2 and α-synuclein. Differential gene expression evoked by nuclear NCAM fragments without and with PSA indicates that PSA-carrying and -lacking NCAM play different functional roles in the nervous system.

Role of the adhesion molecule F3/Contactin in synaptic plasticity and memory

Cell adhesion molecules (CAMs) have a pivotal role in building and maintaining synaptic structures during brain development participating in axonal elongation and pathfinding, glial guidance of neuronal migration, as well as myelination. CAMs expression persists in the adult brain particularly in structures undergoing postnatal neurogenesis and involved in synaptic plasticity and memory as the hippocampus. Among the neural CAMs, we have recently focused on F3/Contactin, a glycosylphosphatidyl inositol-anchored glycoprotein belonging to the immunoglobulin superfamily, involved in neuronal development, synaptic maintenance and organization of neuronal networks. Here, we discuss our recent data suggesting that F3/Contactin exerts a role in hippocampal synaptic plasticity and memory in adult and aged mice. In particular, we have studied long-term potentiation (LTP), spatial and object recognition memory, and phosphorylation of the transcription factor cAMP-Responsive-Element Binding protein (CREB) in a transgenic mouse model of F3/Contactin overexpression. We also investigated whether F3/Contactin might influence neuronal apoptosis and the production of amyloid-beta peptide (Aβ), known to be one of the main pathogenetic hallmarks of Alzheimer's disease (AD). In conclusion, a further understanding of F3/Contactin role in synaptic plasticity and memory might have interesting clinical outcomes in cognitive disorders, such as aging and AD, offering innovative therapeutic opportunities.

The N Terminus of the Prion Protein Mediates Functional Interactions with the Neuronal Cell Adhesion Molecule (NCAM) Fibronectin Domain

The cellular form of the prion protein (PrP^C) is a highly conserved glycoprotein mostly expressed in the central and peripheral nervous systems by different cell types in mammals. A misfolded, pathogenic isoform, denoted as prion, is related to a class of neurodegenerative diseases known as transmissible spongiform encephalopathy. PrP^C function has not been unequivocally clarified, and it is rather defined as a pleiotropic protein likely acting as a dynamic cell surface scaffolding protein for the assembly of different signaling modules. Among the variety of PrP^C protein interactors, the neuronal cell adhesion molecule (NCAM) has been studied in vivo, but the structural basis of this functional interaction is still a matter of debate. Here we focused on the structural determinants responsible for human PrP^C (HuPrP) and NCAM interaction using stimulated emission depletion (STED) nanoscopy, SPR, and NMR spectroscopy approaches. PrP^C co-localizes with NCAM in mouse hippocampal neurons, and this interaction is mainly mediated by the intrinsically disordered PrP^C N-terminal tail, which binds with high affinity to the NCAM fibronectin type-3 domain. NMR structural investigations revealed surface-interacting epitopes governing the interaction between HuPrP N terminus and the second module of the NCAM fibronectin type-3 domain. Our data provided molecular details about the interaction between HuPrP and the NCAM fibronectin domain, and revealed a new role of PrP^C N terminus as a dynamic and functional element responsible for protein-protein interaction.

Kinesin-1 promotes post-Golgi trafficking of NCAM140 and NCAM180 to the cell surface

The neural cell adhesion molecule (NCAM, also known as NCAM1) is important during neural development, because it contributes to neurite outgrowth in response to its ligands at the cell surface. In the adult brain, NCAM is involved in regulating synaptic plasticity. The molecular mechanisms underlying delivery of NCAM to the neuronal cell surface remain poorly understood. We used a protein macroarray and identified the kinesin light chain 1 (KLC1), a component of the kinesin-1 motor protein, as a binding partner of the intracellular domains of the two transmembrane isoforms of NCAM, NCAM140 and NCAM180. KLC1 binds to amino acids CGKAGPGA within the intracellular domain of NCAM and colocalizes with kinesin-1 in the Golgi compartment. Delivery of NCAM180 to the cell surface is increased in CHO cells and neurons co-transfected with kinesin-1. We further demonstrate that the p21-activated kinase 1 (PAK1) competes with KLC1 for binding to the intracellular domain of NCAM and contributes to the regulation of the membrane insertion of NCAM. Our results indicate that NCAM is delivered to the cell surface through a kinesin-1-mediated transport mechanism in a PAK1-dependent manner.

Improvement in the neural stem cell proliferation in rats treated with modified "Shengyu" decoction may contribute to the neurorestoration

ETHNOPHARMACOLOGICAL RELEVANCE

"Shengyu" decoction, a traditional Chinese medicine, has been used to treat diseases with deficit in "qi" and "blood". The modified "Shengyu" decoction (MSD) used in the present study was designed to treat traumatic brain injury (TBI) on the basis of the "Shengyu" decoction, in which additional four herbs were added. Many ingredients in these herbs have been demonstrated to be effective for the treatment of brain injury. The present study was performed to evaluate the neurorestorative effect and the underlying mechanisms of MSD on the rat brain after a TBI.

MATERIALS AND METHODS

TBI was induced in the right cerebral cortex of adult rats using Feeney's weight-drop method. Intragastrical administration of MSD (1.0 ml/200 g) was begun 6h after TBI. The neurological functions and neuronal loss in the cortex and hippocampus were determined. The levels of nerve growth-related factors GDNF, NGF, NCAM, TN-C, and Nogo-A and the number of GFAP(+)/GDNF(+), BrdU(+)/nestin(+), BrdU(+)/NeuN(+) immunoreactive cells in the brain ipsilateral to TBI were also measured. Moreover, the influences of MSD on these variables were observed at the same time.

RESULTS

We found that treatment with MSD in TBI rats ameliorated the neurological functions and alleviated neuronal loss. MSD treatment elevated the expression of GDNF, NGF, NCAM, and TN-C, and inhibited the expression of Nogo-A. Moreover, MSD treatment increased the number of GFAP(+)/GDNF(+), BrdU(+)/nestin(+), and BrdU(+)/NeuN(+) immunoreactive cells in the cortex and hippocampus.

CONCLUSION

The present results suggest that MSD treatment in TBI rats could improve the proliferation of neural stem/progenitor cells and differentiation into neurons, which may facilitate neural regeneration and tissue repair and thus contribute to the recovery of neurological functions. These effects of modified "Shengyu" decoction may provide a foundation for the use of MSD as a prescription of medicinal herbs in the traditional medicine to treat brain injuries in order to improve the neurorestoration.

Neural Progenitor Cells Derived from Human Embryonic Stem Cells as an Origin of Dopaminergic Neurons

Human embryonic stem cells (hESCs) are able to proliferate in vitro indefinitely without losing their ability to differentiate into multiple cell types upon exposure to appropriate signals. Particularly, the ability of hESCs to differentiate into neuronal subtypes is fundamental to develop cell-based therapies for several neurodegenerative disorders, such as Alzheimer's disease, Huntington's disease, and Parkinson's disease. In this study, we differentiated hESCs to dopaminergic neurons via an intermediate stage, neural progenitor cells (NPCs). hESCs were induced to neural progenitor cells by Dorsomorphin, a small molecule that inhibits BMP signalling. The resulting neural progenitor cells exhibited neural bipolarity with high expression of neural progenitor genes and possessed multipotential differentiation ability. CBF1 and bFGF responsiveness of these hES-NP cells suggested their similarity to embryonic neural progenitor cells. A substantial number of dopaminergic neurons were derived from hES-NP cells upon supplementation of FGF8 and SHH, key dopaminergic neuron inducers. Importantly, multiple markers of midbrain neurons were detected, including NURR1, PITX3, and EN1, suggesting that hESC-derived dopaminergic neurons attained the midbrain identity. Altogether, this work underscored the generation of neural progenitor cells that retain the properties of embryonic neural progenitor cells. These cells will serve as an unlimited source for the derivation of dopaminergic neurons, which might be applicable for treating patients with Parkinson's disease.

Role of F3/contactin expression profile in synaptic plasticity and memory in aged mice

We have recently shown that overexpression of the F3/contactin adhesive glycoprotein (also known as Contactin-1) promotes neurogenesis in adult hippocampus, which correlates with improved synaptic plasticity and memory. Because F3/contactin levels physiologically decrease with age, here, we aim at investigating whether its overexpression might counteract the cognitive decline in aged animals. For this we use 20- to 24-month-old TAG/F3 transgenic mice in which F3/contactin overexpression is driven by regulatory sequences from the gene encoding the transient axonal glycoprotein TAG-1 throughout development. We show that aged TAG/F3 mice display improved hippocampal long-term potentiation and memory compared with wild-type littermates. The same mice undergo a decrease of neuronal apoptosis at the hippocampal level, which correlated to a decrease of active caspase-3; by contrast, procaspase-3 and Bax as well as the anti-apoptotic and plasticity-related pathway BDNF/CREB/Bcl-2 were rather increased. Interestingly, amyloid-precursor protein processing was shifted toward sAPPα generation, with a decrease of sAPPβ and amyloid-beta levels. Our data confirm that F3/contactin plays a role in hippocampal synaptic plasticity and memory also in aged mice, suggesting that it acts on molecular pathways related to apoptosis and amyloid-beta production.

Treatment with ginseng total saponins improves the neurorestoration of rat after traumatic brain injury

ETHNOPHARMACOLOGICAL RELEVANCE

Ginseng, the root of Panax ginseng C.A. Meyer, is a traditional medicinal herb that has been widely used in Asia for the treatment of many diseases through its effects of reinforcing vitality, strengthening the bodily resistance to pathogenic factors, engendering body liquids and allaying thirst, relieving uneasiness of the body and mind and benefiting intelligence, reducing body weight and prolonging life. Ginsenosides are the most important biologically active substances in ginseng. Many reports have suggested that ginsenosides could exert prominent neuroprotective and neurotrophic effects, promote neural stem/progenitor cell (NSC) proliferation and promote neurite outgrowth and neuronal network formation. The present study aimed to investigate whether treatment with ginsenosides could facilitate NSC proliferation in the hippocampal formation after traumatic brain injury (TBI) and contribute to the recovery of neurological functions including learning and memory.

MATERIALS AND METHODS

The modified Feeney׳s method was used to induce a TBI in rats. Ginseng total saponins (GTS) were treated intraperitoneally twice a day for 1 week after the TBI. The neurological functions, morphology of the hippocampus, expression of nerve growth-related factors and number of NSCs in the hippocampal formation ipsilateral to the trauma were determined.

RESULTS

We determined 1) GTS (5-80 mg/kg) treatment after a TBI improved the recovery of neurological functions, including learning and memory, and reduced cell loss in the hippocampal area. The effects of GTS at 20, 40, 60, and 80 mg/kg were better than the effects of GTS at 5 and 10 mg/kg. 2) GTS treatment (20 mg/kg) after a TBI increased the expression of NGF, GDNF and NCAM, inhibited the expression of Nogo-A, Nogo-B, TN-C, and increased the number of BrdU/nestin positive NSCs in the hippocampal formation.

CONCLUSIONS

GTS treatment in rats after a TBI alleviated the secondary brain injury and ameliorated the neurological functions with an effective dose limit of 5-80 mg/kg. GTS regulated the expression of nerve growth-related factors and improved the proliferation of neural stem/progenitor cells, which might facilitate neural regeneration and tissue repair, and might contribute to the recovery of neurological functions, including learning and memory. These effects of GTS might provide a foundation for the use of ginseng as a medicinal herb to enhance intelligence, reduce the aging process and prolong life in the traditional medicine.

Imaging proteomics for diagnosis, monitoring and prediction of Alzheimer's disease

Proteomic and imaging markers have been widely studied as potential biomarkers for diagnosis, monitoring and prognosis of Alzheimer's disease. In this study, we used Alzheimer Disease Neuroimaging Initiative dataset and performed parallel independent component analysis on cross sectional and longitudinal proteomic and imaging data in order to identify the best proteomic model for diagnosis, monitoring and prediction of Alzheimer disease (AD). We used plasma proteins measurement and imaging data from AD and healthy controls (HC) at the baseline and 1 year follow-up. Group comparisons at baseline and changes over 1 year were calculated for proteomic and imaging data. The results were fed into parallel independent component analysis in order to identify proteins that were associated with structural brain changes cross sectionally and longitudinally. Regression model was used to find the best model that can discriminate AD from HC, monitor AD and to predict MCI converters from non-converters. We showed that five proteins are associated with structural brain changes in the brain. These proteins could discriminate AD from HC with 57% specificity and 89% sensitivity. Four proteins whose change over 1 year were associated with brain structural changes could discriminate AD from HC with sensitivity of 93%, and specificity of 92%. This model predicted MCI conversion to AD in 2 years with 94% accuracy. This model has the highest accuracy in prediction of MCI conversion to AD within the ADNI-1 dataset. This study shows that combination of selected plasma protein levels and MR imaging is a useful method in identifying potential biomarker.

F3/Contactin promotes hippocampal neurogenesis, synaptic plasticity, and memory in adult mice

F3/contactin, a cell-adhesion molecule belonging to the immunoglobulin supergene family, is involved in several aspects of neural development including synapse building, maintenance and functioning. Here, we examine F3/contactin function in adult hippocampal neurogenesis, synaptic plasticity, and memory, using as a model TAG/F3 transgenic mice, where F3/contactin overexpression was induced under control of regulatory sequences from the human TAG-1 (TAX-1) gene. Transgenic mice aged 5 (M5) and 12 (M12) months exhibited an increase in hippocampal size, which correlated with positive effects on precursor proliferation and NeuN expression, these data suggesting a possible role for F3/contactin in promoting adult hippocampal neurogenesis. On the functional level, TAG/F3 mice exhibited increased CA1 long-term potentiation and improved spatial and object recognition memory, notably at 12 months of age. Interestingly, these mice showed an increased expression of the phosphorylated transcription factor CREB, which may represent the main molecular correlate of the observed morphological and functional effects. Altogether, these findings indicate for the first time that F3/contactin plays a role in promoting adult hippocampal neurogenesis and that this effect correlates with improved synaptic function and memory.

The novel protein MANI modulates neurogenesis and neurite-cone growth

Neuronal regeneration and axonal re-growth in the injured mammalian central nervous system remains an unsolved field. To date, three myelin-associated proteins [Nogo or reticulon 4 (RTN4), myelin-associated glycoprotein (MAG) and oligodendrocyte myelin glycoprotein (OMG)] are known to inhibit axonal regeneration via activation of the neuronal glycosylphosphatidylinositol-anchored Nogo receptor [NgR, together with p75 neurotrophin receptor (p75NTR) and Lingo-1]. In the present study we describe the novel protein MANI (myelin-associated neurite-outgrowth inhibitor) that localizes to neural membranes. Functional characterization of MANI overexpressing neural stem cells (NSCs) revealed that the protein promotes differentiation into catecholaminergic neurons. Yeast two-hybrid screening and co-immunoprecipitation experiments confirmed the cell division cycle protein 27 (Cdc27) as an interacting partner of Mani. The analyses of Mani-overexpressing PC12 cells demonstrated that Mani retards neuronal axonal growth as a positive effector of Cdc27 expression and activity. We show that knockdown of Cdc27, a component of the anaphase-promoting complex (APC), leads to enhanced neurite outgrowth. Our finding describes the novel MANI-Cdc27-APC pathway as an important cascade that prevents neurons from extending axons, thus providing implications for the potential treatment of neurodegenerative diseases.

Control of neuronal migration through rostral migration stream in mice

During the nervous system development, immature neuroblasts have a strong potential to migrate toward their destination. In the adult brain, new neurons are continuously generated in the neurogenic niche located near the ventricle, and the newly generated cells actively migrate toward their destination, olfactory bulb, via highly specialized migratory route called rostral migratory stream (RMS). Neuroblasts in the RMS form chains by their homophilic interactions, and the neuroblasts in chains continually migrate through the tunnels formed by meshwork of astrocytes, glial tube. This review focuses on the development and structure of RMS and the regulation of neuroblast migration in the RMS. Better understanding of RMS migration may be crucial for improving functional replacement therapy by supplying endogenous neuronal cells to the injury sites more efficiently.

Coupling between hydrodynamic forces and planar cell polarity orients mammalian motile cilia

In mammals, motile cilia cover many organs, such as fallopian tubes, respiratory tracts and brain ventricles. The development and function of these organs critically depend on efficient directional fluid flow ensured by the alignment of ciliary beating. To identify the mechanisms involved in this process, we analysed motile cilia of mouse brain ventricles, using biophysical and molecular approaches. Our results highlight an original orientation mechanism for ependymal cilia whereby basal bodies first dock apically with random orientations, and then reorient in a common direction through a coupling between hydrodynamic forces and the planar cell polarity (PCP) protein Vangl2, within a limited time-frame. This identifies a direct link between external hydrodynamic cues and intracellular PCP signalling. Our findings extend known PCP mechanisms by integrating hydrodynamic forces as long-range polarity signals, argue for a possible sensory role of ependymal cilia, and will be of interest for the study of fluid flow-mediated morphogenesis.