Necdin蛋白与神经元的生长分化

在神经系统,Necdin只在成熟神经元的细胞核中表达,可能与成熟神经元分裂静止状态的保持有关.近年的研究表明,Necdin是一种生长抑制蛋白,能与多种因子如SV40大T抗原,腺病毒E1A,转录因子E2F1以及肿瘤抑制蛋白p53等结合,在功能上类似于成视网膜瘤蛋白Rb.necdin基因缺陷时,会引起脑内,特别是下丘脑神经元分化障碍.人类necdin基因位于PWS综合征的基因缺失区,可能与PWS的一些症状有关.本文从Necdin蛋白的基本概况,生物功能以及Necdin与疾病三个方面进行了综述.     

Necdin蛋白与神经元的生长分化

在神经系统 ,Necdin只在成熟神经元的细胞核中表达 ,可能与成熟神经元分裂静止状态的保持有关。近年的研究表明 ,Necdin是一种生长抑制蛋白 ,能与多种因子如SV4 0大T抗原 ,腺病毒E1A ,转录因子E2F1以及肿瘤抑制蛋白p5 3等结合 ,在功能上类似于成视网膜瘤蛋白Rb。necdin基因缺陷时 ,会引起脑内 ,特别是下丘脑神经元分化障碍。人类necdin基因位于PWS综合征的基因缺失区 ,可能与PWS的一些症状有关。本文从Necdin蛋白的基本概况 ,生物功能以及Necdin与疾病三个方面进行了综述     

Pleiotrophin fights Brd2 for neuronal differentiation

<正>Bromodomain containing 2(Brd2)protein belongs to the Bromodomains and Extra Terminal domain(BET)family of chromatin adaptors characterized by the presence of two N-terminal tandem bromodomains and an exclusive C-terminal extra terminal domain(ET)(Belkina and Denis,2012;Shi and Vakoc,2014).Bromodomains are involved     

Extracellular matrix and biomimetic engineering microenvironment for neuronal differentiation

Extracellular matrix(ECM)influences cell differentiation through its structural and biochemical properties.In nervous system,neuronal behavior is influenced by these ECMs structures which are present in a meshwork,fibrous,or tubular forms encompassing specific molecular compositions.In addition to contact guidance,ECM composition and structures also exert its effect on neuronal differentiation.This short report reviewed the native ECM structure and composition in central nervous system and peripheral nervous system,and their impact on neural regeneration and neuronal differentiation.Using topographies,stem cells have been differentiated to neurons.Further,focussing on engineered biomimicking topographies,we highlighted the role of anisotropic topographies in stem cell differentiation to neurons and its recent temporal application for efficient neuronal differentiation.     

Cerebellar medullomyoblastoma with advanced neuronal differentiation and hamartomatous component

Summary This report describes an unusual medullo-myoblastoma which developed in the cerebellar vermis of a 6-year-old girl. Histological investigation showed a highly cellular and predominantly undifferentiated tumor. Myogenic differentiation was prominent in clusters of large tumor cells with eosinophilic cytoplasm and immunoreactivity for desmin and myoglobin. Electron microscopy revealed the presence of immature Z-bands. Immunohistochemically, numerous cells showed incipient expression of myoblastic marker antigens, supporting the view that medulloblastomas and related primitive neuroectodermal tumors possess the potential for non-neural differentiation. In addition, there was evidence of advanced neuronal differentiation, with expression of neuron-specific enolase, synaptophysin, retinal S-antigen, and the formation of ganglioid tumor cells. Occassional neoplastic cells expressed glial fibrillary acidic protein without morphologically detectable astrocytic differentiation. Associated with the neoplasm was brain tissue containing clusters of neuronal cells and focal accumulations of immature oligodendroglia-like cells which expressed neuronal marker antigens. This unusual component resembled a hamartomatous lesion and would support the hypothesis that the cerebellar medullomyoblastoma originated from a teratomatous or malformative lesion. Alternatively, this component may constitute the end stage of advanced neuronal differentiation of a primitive neuroectodermal tumor.     

In vitro neuronal differentiation of Drosophila embryo cells

Early gastrula-stage Drosophila embryo cells will differentiate in vitro to form several cell types, including neurons. We report here the morphological appearance of cultured embryo cells, the pattern of DNA synthesis, and the expression of neurotransmitter-metabolizing macromolecules. The cells initially exhibit no overt morphological differentiation, and all cells incorporate 3H-thymidine following a 1 hr pulse-labeling period. As cells undergo morphological differentiation, fewer total cells as well as qualitatively different cell types incorporate label. By the time cells are 8 or 9 hr old, no myocytes or myotubes are labeled. In contrast, some neurons are labeled with a thymidine pulse as late as 18 hr. We have also stained cultured cells of various developmental ages with the insect neuron-specific antibody: anti-HRP. Some positive cells can be detected as early as 5 hr, when no overt morphological differentiation is apparent. As the cells differentiate, the staining is limited to the small, round neuronal type and its processes. These findings suggest that this neuron-specific cell marker is expressed very early in cultured gastrula-stage cells and may be used to identify neuronal precursor cells. We have studied the patterns of expression of several macromolecules involved in acetylcholine metabolism using these cultures. The appearance of choline acetyltransferase (ChAT), the biosynthetic enzyme for ACh production, is first detected in 5-hr-old cells. There is an initial phase of low-level expression, followed by a rapid rise in activity shortly after the differentiating neuron clusters make contact with one another. ChAT activity reaches a plateau in 36-48-hr-old cells. Acetylcholinesterase activity can be detected several hours before ChAT and also shows a period of low-level expression followed by a rapidly increasing phase, reaching a plateau at around 36-48 hr. 125I-alpha-bungarotoxin binding appears in cells about 4 hr old and rapidly approaches maximum levels by about 36 hr. The in vitro expression pattern for ChAT and AChE is similar to that seen in vivo. AChE activity has been localized histochemically to the neurons and their processes in vitro. The normal in vitro expression pattern for ChAT and AChE can be altered by adding various cholinergic drugs to the culture medium during cell differentiation. Medium conditioned by older cultures can also result in lower levels of ChAT and AChE expression.(ABSTRACT TRUNCATED AT 250 WORDS)     

Function-blocking antibodies against cholinergic neuronal differentiation factor.

Cholinergic neuronal differentiation factor, CDF, causes a transition from noradrenergic to cholinergic phenotype in cultured sympathetic neurons. Moreover, its identification with leukemia inhibitory factor has shown that CDF is a multifunctional cytokine. To examine the physiological role of CDF and to further elucidate the as yet unknown effects of CDF on the nervous system, two kinds of function-blocking antibodies were generated. One type, raised against whole native CDF, completely blocks CDF activity, whereas the other type, raised against a synthetic peptide corresponding to the N-terminal amino acid region of CDF, blocks activity partially. All three anti-CDF and two antipeptide polyclonal antibodies tested in this study significantly inhibit CDF function.     

Enhanced neuronal differentiation in a three-dimensional collagen-hyaluronan matrix

Efficient 3D cell systems for neuronal induction are needed for future use in tissue regeneration. In this study, we have characterized the ability of neural stem/progenitor cells (NS/PC) to survive, proliferate, and differentiate in a collagen type I-hyaluronan scaffold. Embryonic, postnatal, and adult NS/PC were seeded in the present 3D scaffold and cultured in medium containing epidermal growth factor and fibroblast growth factor-2, a condition that stimulates NS/PC proliferation. Progenitor cells from the embryonic brain had the highest proliferation rate, and adult cells the lowest, indicating a difference in mitogenic responsiveness. NS/PC from postnatal stages down-regulated nestin expression more rapidly than both embryonic and adult NS/PC, indicating a faster differentiation process. After 6 days of differentiation in the 3D scaffold, NS/PC from the postnatal brain had generated up to 70% neurons, compared with 14% in 2D. NS/PC from other ages gave rise to approximately the same proportion of neurons in 3D as in 2D (9-26% depending on the source for NS/PC). In the postnatal NS/PC cultures, the majority of betaIII-tubulin-positive cells expressed glutamate, gamma-aminobutyric acid, and synapsin I after 11 days of differentiation, indicating differentiation to mature neurons. Here we report that postnatal NS/PC survive, proliferate, and efficiently form synapsin I-positive neurons in a biocompatible hydrogel.     

Induced neuronal differentiation of human embryonic stem cells

Human embryonic stem (ES) cells are pluripotent cells capable of forming differentiated embryoid bodies (EBs) in culture. We examined the ability of growth factors under controlled conditions to increase the number of human ES cell-derived neurons. Retinoic acid (RA) and nerve growth factor (betaNGF) were found to be potent enhancers of neuronal differentiation, eliciting extensive outgrowth of processes and the expression of neuron-specific molecules. Our findings show that human ES cells have great potential to become an unlimited cell source for neurons in culture. These cells may then be used in transplantation therapies for neural pathologies.     

The role of metallothionein II in neuronal differentiation and survival

Metallothionein I and II (MT-I+II) are antioxidant and tissue protective factors. We have previously shown that MT-I+II prevent oxidative stress and apoptotic cell death and are of therapeutic value in brain inflammation. However, MT-I+II are expressed in glia and it remains to be elucidated if MT-I+II can affect neurons directly. It is likely that MT isoforms could be beneficial also during neurodegenerative disorders. In this study, we have examined if MT-II affects survival and neurite extension of dopaminergic and hippocampal neurons. We show for the first time that MT-II treatment can significantly stimulate neurite extension from both dopaminergic and hippocampal neurons. Moreover, MT-II treatment significantly increases survival of dopaminergic neurons exposed to 6-hydroxydopamine (6-OHDA) and protects significantly hippocampal neurons from amyloid beta-peptide-induced neurotoxicity. Accordingly, treatment with MT-II may be of therapeutic value in neurodegenerative disorders.     

Immunoaffinity purification and dose-response of cholinergic neuronal differentiation factor.

A glycoprotein from heart cell-conditioned medium, cholinergic neuronal differentiation factor (CDF), causes a transition from noradrenergic to cholinergic phenotype in cultured rat sympathetic neurons. Although the transition has been known to occur in a dose-dependent manner and CDF has been purified, the examination of a complete dose-response of neurons to CDF has not been possible because sufficient quantities of pure CDF have not been available. A complete dose-response curve is essential for evaluating the biological response of the neurons, for assessing the physiological role of CDF and for understanding the mechanism of action of CDF. We report here an immunoaffinity-purification procedure for CDF with a 73.1% recovery using antibodies raised against a synthetic peptide homologous with the N-terminal region of CDF. This method produced pure CDF in quantities sufficient for examination of the full dose-response range of the neurons. Our main findings are the following. The dose-responses of acetylcholine and catecholamine metabolisms to CDF are different, although the same molecule affects both transmitters. While the half-maximal concentrations for acetylcholine induction (0.20 nM) and for catecholamine suppression (0.28 nM) are similar, the response of catecholamine metabolism begins slowly and saturates at a CDF concentration (5-20 nM) considerably higher than that of acetylcholine (0.6 nM). This may indicate that CDF affects multiple processes in catecholamine metabolism.     

Ablation of neuronal ADAM17 impairs oligodendrocyte differentiation and myelination

Myelin, one of the most important adaptations of vertebrates, is essential to ensure efficient propagation of the electric impulse in the nervous system and to maintain neuronal integrity. In the central nervous system (CNS), the development of oligodendrocytes and the process of myelination are regulated by the coordinated action of several positive and negative cell-extrinsic factors. We and others previously showed that secretases regulate the activity of proteins essential for myelination. We now report that the neuronal α-secretase ADAM17 controls oligodendrocyte differentiation and myelin formation in the CNS. Ablation of Adam17 in neurons impairs in vivo and in vitro oligodendrocyte differentiation, delays myelin formation throughout development and results in hypomyelination. Furthermore, we show that this developmental defect is, in part, the result of altered Notch/Jagged 1 signaling. Surprisingly, in vivo conditional loss of Adam17 in immature oligodendrocytes has no effect on myelin formation. Collectively, our data indicate that the neuronal α-secretase ADAM17 is required for proper CNS myelination. Further, our studies confirm that secretases are important post-translational regulators of myelination although the mechanisms controlling CNS and peripheral nervous system (PNS) myelination are distinct.     

Retinoids increase perinatal spinal cord neuronal survival and astroglial differentiation

In this report we demonstrate that retinol and retinoic acid (RA) increase the survival and morphological differentiation of rat spinal cord neurons in vitro. Micromolar amounts of retinol and RA increased the number of surviving neurons by 2- to 3-fold and affected neuritic density resulting in increased secondary and tertiary processes compared to untreated sister cultures. A marked morphological differentiation of the astrocyte population in conjunction with an antiproliferative effect in the presence of retinoids were apparent. These trophic effects occurred mainly after 5 days in vitro, a time that corresponds to the time of birth in vivo. Retinoic acid exerted a direct trophic effect on spinal cord neurons in the absence of glial cells while retinol lost its effectiveness. Metabolic labeling suggested that retinol is converted to the biologically active RA within astrocytes but not in neurons. Taken together, our results have demonstrated direct trophic effects of RA on spinal cord neurons and have suggested another role for astrocytes in the maintenance of normal neural physiology by regulating RA concentrations through the oxidation of retinol.     

Ependymomas with neuronal differentiation: a morphologic and immunohistochemical spectrum

The category of mixed glioneuronal tumors of the CNS is rapidly losing its definition as encompassing tumors composed of histologically distinct neuron variants and glia. We encountered five ependymomas with neuronal differentiation seen in two by histology, in two by immunohistochemistry alone, and in one by electron microscopy. Antibodies against GFAP, S-100 protein, neurofilament protein, chromogranin, synaptophysin, Neu-N, and EMA were applied. Ultrastructural studies were also performed. In addition, 33 randomly selected ependymomas of various histologic types were screened for these same antigens. Cases 1 and 2 were anaplastic and showed clearly defined neuropil islands or pale islands as in nodular desmoplastic medulloblastoma, respectively. The tumors affected a 16-year-old male and a 5-year-old female and involved the right frontoparietal lobe and fourth ventricle, respectively. The islands were positive for synaptophysin and Neu-N (cases 1 and 2), and chromogranin (case 1). Cases 3–5, as well as 7 of the 33 screened ependymomas, showed a suggestion of neuronal differentiation by immunohistochemistry alone, including immunoreactivity for Neu-N (n = 8), synaptophysin (n = 4), neurofilament protein (n = 4), and chromogranin (n = 2). Five tumors each were WHO grade II and III. Electron microscopy performed on the two cases with neuronal islands demonstrated microtubule bundles and dense core granules (case 1) and poorly differentiated cells with high nuclear/cytoplasmic ratios, with intermediate filament accumulation and rare cilia (case 2). Cases identified by immunohistochemistry or electron microscopy demonstrated dense core granules (n = 5) and aligned microtubules (n = 3). Neuronal differentiation occurs in ependymomas but is less frequently definitive (histologic, ultrastructural) than merely a limited immunohistochemical finding. The clinical significance of these observations is unknown but deserves further exploration.     

Ensheathing cells utilize dynamic tiling of neuronal somas in development and injury as early as neuronal differentiation

Background

Glial cell ensheathment of specific components of neuronal circuits is essential for nervous system function. Although ensheathment of axonal segments of differentiated neurons has been investigated, ensheathment of neuronal cell somas, especially during early development when neurons are extending processes and progenitor populations are expanding, is still largely unknown.

Methods

To address this, we used time-lapse imaging in zebrafish during the initial formation of the dorsal root ganglia (DRG).

Results

Our results show that DRG neurons are ensheathed throughout their entire lifespan by a progenitor population. These ensheathing cells dynamically remodel during development to ensure axons can extend away from the neuronal cell soma into the CNS and out to the skin. As a population, ensheathing cells tile each DRG neuron to ensure neurons are tightly encased. In development and in experimental cell ablation paradigms, the oval shape of DRG neurons dynamically changes during partial unensheathment. During longer extended unensheathment neuronal soma shifting is observed. We further show the intimate relationship of these ensheathing cells with the neurons leads to immediate and choreographed responses to distal axonal damage to the neuron.

Conclusion

We propose that the ensheathing cells dynamically contribute to the shape and position of neurons in the DRG by their remodeling activity during development and are primed to dynamically respond to injury of the neuron.

     

Dysregulation of neuronal differentiation and cell cycle control in Alzheimer's disease

Degeneration in Alzheimer's disease primarily occurs in those neurons that in the adult brain retain, a high degree of structural plasticity and, is associated with the activation of mitogenic signaling and cell cycle activation. Brain areas affected by neurofibrillary degeneration in Alzheimer's disease are structures involved in the regulation of "higher brain functions" that become increasingly predominant as the evolutionary process of encephalization progresses. The functions these areas subserve require a life-long adaptive reorganization of neuronal connectivity. With the increasing need during evolution to organize brain structures of increasing complexity, these processes of dynamic stabilization and de-stabilization become more and more important but might also provide the basis for an increasing rate of failure. The hypothesis is put forward that it is the labile state of differentiation of a subset of neurons in the adult brain that allows for ongoing morphoregulatory processes after development is completed but at the same time renders these neurons particularly vulnerable. Interferring with neuronal differentiation control might, thus, be a potential strategy to prevent neurodegeneration in Alzheimer's disease and related disorders.