Sixty years elapsed since Chang (Hsiang-Tung Chang, Xiang-Tong Zhang) presented his seminal report "Cortical neurons with particular reference to the apical dendrite" at the Cold Spring Harbor Symposium. Thanks to the development of elaborated techniques through the 6 decades, our understanding of the dendrite has been pushed forward greatly: the backward and forward conductions during excitation, sodium and calcium conductances, chemical excitation by uncaging glutamate at a dimension of micrometer, and the quantitative study of chemical organization of postsynaptic density (PSD), etc. Though the progression is great, there are still tough problems in dendritic research, especially the integration through dendritic spine.
Calcium Signaling ; Dendrites ; physiology ; Glutamic Acid ; metabolism

Secretion of neurotransmitters is initiated by voltagegated calcium influx through presynaptic, voltage- gated N-type calcium channels. However, little is known about their cellular distribution in the mouse cerebellum. In the cerebellum, alpha1B immunoreactivity is found mainly on the cell bodies of all Purkinje cells. In addition, the immunoreactivity was detected on a subset of Purkinje cell dendrites, clustered to form a parasagittal array of bands. In the anterior lobe vermis, immunoreactive Purkinje cell dendrites form narrow stripes separated by broad bands of unstained dendrites. Moving caudally through the vermis, these stripes become thicker as a larger fraction of the Purkinje cell dendrites become immunoreactive. This localization study of the alpha1B pore-forming subunits in mouse cerebellum may guide future investigations of the role of calcium channels in neurological pathways.
Animals ; Calcium Channels, N-Type/*metabolism ; Cerebellum/cytology/*metabolism ; Dendrites/metabolism ; Immunohistochemistry ; Mice ; Mice, Inbred BALB C ; Purkinje Cells/metabolism

Neurons are the structural and functional unit of the nervous system. Precisely regulated dendrite morphogenesis is the basis of neural circuit assembly. Numerous studies have been conducted to explore the regulatory mechanisms of dendritic morphogenesis. According to their action regions, we divide them into two categories: the intrinsic and extrinsic regulators of neuronal dendritic morphogenesis. Intrinsic factors are cell type-specific transcription factors, actin polymerization or depolymerization regulators and regulators of the secretion or endocytic pathways. These intrinsic factors are produced by neuron itself and play an important role in regulating the development of dendrites. The extrinsic regulators are either secreted proteins or transmembrane domain containing cell adhesion molecules. They often form receptor-ligand pairs to mediate attractive or repulsive dendritic guidance. In this review, we summarize recent findings on the intrinsic and external molecular mechanisms of dendrite morphogenesis from multiple model organisms, including , and mice. These studies will provide a better understanding on how defective dendrite development and maintenance are associated with neurological diseases.
Animals ; Caenorhabditis elegans ; cytology ; Dendrites ; Mice ; Morphogenesis ; Nervous System Diseases ; physiopathology ; Neurons ; cytology ; Transcription Factors ; metabolism

BACKGROUNDWallerian degeneration is a self-destructive process of axonal degeneration that occurs after an axonal injury or during neurodegenerative disorders such as Parkinson's or Alzheimer's disease. Recent studies have found that the activity of the nicotinamide adenine dinucleotide (NAD) synthase enzyme, nicotinamide mononucleotide adenylyltransferase 1 (NMNAT1) can affect the rate of Wallerian degeneration in mice and drosophila. NMNAT1 protects neurons and axons from degeneration. However, the role of NMNAT1 in neurons of central nervous system is still not well understood.

METHODSWe set up the culture of primary mouse neurons in vitro and manipulated the expression level of NMNAT1 by RNA interference and gene overexpression methods. Using electroporation transfection we can up-regulate or down-regulate NMNAT1 in cultured mouse dendrites and axons and study the neuronal morphogenesis by immunocytochemistry. In all functional assays, FK-866 (CAS 658084-64-1), a highly specific non-competitive inhibitor of nicotinamide phosphoribosyltransferase was used as a pharmacological and positive control.

RESULTSOur results showed that knocking down NMNAT1 by RNA interference led to a marked decrease in dendrite outgrowth and branching and a significant decrease in axon growth and branching in developing cortical neurons in vitro.

CONCLUSIONSThese findings reveal a novel role for NMNAT1 in the morphogenesis of developing cortical neurons, which indicate that the loss of function of NMNAT1 may contribute to different neurodegenerative disorders in central nervous system.

Animals ; Axons ; metabolism ; Blotting, Western ; Cells, Cultured ; Dendrites ; metabolism ; Immunohistochemistry ; Mice ; Morphogenesis ; genetics ; physiology ; Neurons ; cytology ; metabolism ; Nicotinamide-Nucleotide Adenylyltransferase ; genetics ; metabolism

MicroRNAs (miRNAs) are critical for both development and function of the central nervous system. Significant evidence suggests that abnormal expression of miRNAs is associated with neurodevelopmental disorders. MeCP2 protein is an epigenetic regulator repressing or activating gene transcription by binding to methylated DNA. Both loss-of-function and gain-of-function mutations in the MECP2 gene lead to neurodevelopmental disorders such as Rett syndrome, autism and MECP2 duplication syndrome. In this study, we demonstrate that miR-130a inhibits neurite outgrowth and reduces dendritic spine density as well as dendritic complexity. Bioinformatics analyses, cell cultures and biochemical experiments indicate that miR-130a targets MECP2 and down-regulates MeCP2 protein expression. Furthermore, expression of the wild-type MeCP2, but not a loss-of-function mutant, rescues the miR-130a-induced phenotype. Our study uncovers the MECP2 gene as a previous unknown target for miR-130a, supporting that miR-130a may play a role in neurodevelopment by regulating MeCP2. Together with data from other groups, our work suggests that a feedback regulatory mechanism involving both miR-130a and MeCP2 may serve to ensure their appropriate expression and function in neural development.
Animals ; Dendrites ; genetics ; metabolism ; Dendritic Spines ; genetics ; metabolism ; Down-Regulation ; physiology ; Methyl-CpG-Binding Protein 2 ; biosynthesis ; genetics ; MicroRNAs ; genetics ; metabolism ; Rats

To study the relationship between tau hyperphosphorylation and the function of glutamate transporter okadaic acid (OA), a protein phosphatase inhibitor, 20 ng in a 0.5 microl volume, was injected into the frontal cortex of rat brain and immunostaining was used to observe the phosphorylation of tau protein and the expression of excitatory amino acid transporter 1 (EAAT1) in the brain following the injection. The results showed that (1) the neurons in the center of the injection region displayed cytoplasmic shrinkage, swelling, nuclear pyknosis, and dislocation at the early stage, and necrosis appeared 3 d after the injection. However, most neurons in the peri-injected areas showed normal morphological characters with immuno positive reaction for AT8, a tau phosphorylated marker; (2) morphological analysis showed that tau hyperphosphorylation caused by OA treatment was mainly observed in the axons and dendrites of neuronal cells at 6 h in the cell body at 1 d, which brought about dystrophic neurites and neurofibrillary tangle (NFT)-like pathological changes; (3) the induction of glutamate transporter EAAT1 was observed in the involved areas corresponding to that with AT8 immunopositive staining, and the number of EAAT1-positive staining cells markedly increased at 12 h (P<0.01), peaked at 1 d (P<0.001), then decreased at 3 d following the injection. Combined with a confocal laser scanning microscopic analysis, double fluorescent immunostaining showed that EAAT1 positive staining appeared in neurons as well as astrocytes in the peri-injected areas of the frontal cortex. These results demonstrate that OA increases glutamate transporter EAAT1 expression in neurons while it induces tau hyperphosphorylation. However, the mechanism and significance of the induction of glutamate transporter EAAT1 expression remain to be further elucidated.
Animals ; Astrocytes ; drug effects ; metabolism ; Axons ; drug effects ; metabolism ; Brain ; cytology ; Dendrites ; drug effects ; metabolism ; Excitatory Amino Acid Transporter 1 ; metabolism ; Neurofibrillary Tangles ; pathology ; Neurons ; drug effects ; metabolism ; Okadaic Acid ; pharmacology ; Phosphorylation ; Rats ; tau Proteins ; metabolism

OBJECTIVETo measure mobility of dendritic filopodia, complexity of dendritic arborization using method of live imaging in cultured rat hippocampal neurons and to analyze their morphological characters quantitatively.

METHODSVectors expressing Green Fluorescent Protein- Fibrous Actin (GFP-F-Actin) and F-GFP were co-transfected into cultured rat hippocampal neurons at 5 d in vitro (DIV 5). Neurons expressing GFP were photographed and analyzed with Metamorph software.

RESULTDendritic filopodia was observed to move actively from DIV 7 to DIV 9. The mean density of filopodia was (10.78 +/-3.78)/100 microm, (10.68 +/-2.96)/100 microm and (9.99 +/-3.67)/100 microm (P >0.05), and there were (30.18 +/-14.03)% to (87.36 +/-20.88)% filopodia were mobile (P <0.001). During DIV 7-DIV 14, the total length of dendritic branches grew from (410.74 +/-185.98) microm to (1238.21 +/-418.32)microm (P <0.001) and the number of dendritic branches increased from 18.93 +/-7.23 to 33.60 +/-10.46 (P<0.001). The density of spine was (37.17 +/-6.46)/100 microm at DIV 14.

CONCLUSIONThe combination of live imaging with quantitative analysis is a useful method to study dendritic morphological development in vitro, including indicators of dendritic filopodia, dendritic arborization and spines.

Actins ; genetics ; metabolism ; Animals ; Animals, Newborn ; Cells, Cultured ; Dendrites ; metabolism ; Green Fluorescent Proteins ; genetics ; metabolism ; Hippocampus ; cytology ; Microscopy, Fluorescence ; Neurons ; cytology ; metabolism ; Rats ; Rats, Sprague-Dawley ; Recombinant Fusion Proteins ; genetics ; metabolism ; Transfection

N-acetylglucosamine kinase (GlcNAc kinase or NAGK) is a ubiquitously expressed enzyme in mammalian cells. Recent studies have shown that NAGK has an essential structural, non-enzymatic role in the upregulation of dendritogenesis. In this study, we conducted yeast two-hybrid screening to search for NAGK-binding proteins and found a specific interaction between NAGK and dynein light-chain roadblock type 1 (DYNLRB1). Immunocytochemistry (ICC) on hippocampal neurons using antibodies against NAGK and DYNLRB1 or dynein heavy chain showed some colocalization, which was increased by treating the live cells with a crosslinker. A proximity ligation assay (PLA) of NAGK-dynein followed by tubulin ICC showed the localization of PLA signals on microtubule fibers at dendritic branch points. NAGK-dynein PLA combined with Golgi ICC showed the colocalization of PLA signals with somal Golgi facing the apical dendrite and with Golgi outposts in dendritic branch points and distensions. NAGK-Golgi PLA followed by tubulin or DYNLRB1 ICC showed that PLA signals colocalize with DYNLRB1 at dendritic branch points and at somal Golgi, indicating a tripartite interaction between NAGK, dynein and Golgi. Finally, the ectopic introduction of a small peptide derived from the C-terminal amino acids 74-96 of DYNLRB1 resulted in the stunting of hippocampal neuron dendrites in culture. Our data indicate that the NAGK-dynein-Golgi tripartite interaction at dendritic branch points functions to regulate dendritic growth and/or branching.
Amino Acid Sequence ; Animals ; Cells, Cultured ; Cytoplasmic Dyneins/chemistry/*metabolism ; Dendrites/metabolism ; Golgi Apparatus/metabolism ; HEK293 Cells ; Hippocampus ; Humans ; Molecular Sequence Data ; Neurons/*metabolism ; Phosphotransferases (Alcohol Group Acceptor)/*metabolism ; Protein Interaction Maps ; Rats, Sprague-Dawley ; Tubulin

Activity-dependent dendritic translation in CNS neurons is important for the synapse-specific provision of proteins that may be necessary for strengthening of synaptic connections. A major rate-limiting factor during protein synthesis is the availability of eukaryotic translation initiation factor 4E (eIF4E), an mRNA 5'-cap-binding protein. In this study we show by fluorescence in situ hybridization (FISH) that the mRNA for eIF4E is present in the dendrites of cultured rat hippocampal neurons. Under basal culture conditions, 58.7 +/- 11.6% of the eIF4E mRNA clusters localize with or immediately adjacent to PSD-95 clusters. Neuronal activation with KCl (60 mM, 10 min) very significantly increases the number of eIF4E mRNA clusters in dendrites by 50.1 and 74.5% at 2 and 6 h after treatment, respectively. In addition, the proportion of eIF4E mRNA clusters that localize with PSD-95 increases to 74.4 +/- 7.7% and 77.8 +/- 7.6% of the eIF4E clusters at 2 and 6 h after KCl treatment, respectively. Our results demonstrate the presence of eIF4E mRNA in dendrites and an activity-dependent increase of these clusters at synaptic sites. This provides a potential mechanism by which protein translation at synapses may be enhanced in response to synaptic stimulation.
Animals ; Cells, Cultured ; Dendrites/*metabolism ; Eukaryotic Initiation Factor-4E/genetics/*metabolism ; Hippocampus/*cytology ; Immunohistochemistry ; In Situ Hybridization, Fluorescence ; Microscopy, Confocal ; Neurons/cytology/*physiology ; Potassium Chloride/pharmacology ; Protein Biosynthesis ; RNA, Messenger/genetics/*metabolism ; Rats ; Rats, Sprague-Dawley ; Synapses ; *Up-Regulation

OBJECTIVETo investigate the effects of mobile phone 1800 MHz electromagnetic fields (EMF) on the surface markers and the functions of human dendritic cells (DC).

METHODSHuman DCs were exposed to intermittent 5 min on/10 min off EMF with specific absorption rates (SAR) 4 W/kg for 0 h, 1 h, 12 h or 24 h, respectively. FACS analysis was used to detect the positive percentage of DC surface markers including HLA-DR and co-stimulatory molecules such as CD80, CD86, CD40 and CD11c. CCK-8 kit was adopted to examine the function of allo-mixed lymphocyte reaction (allo-MLR) of DC, and enzyme linked immunosorbent assay (ELISA) to identify the levels of IL-12p70 and TNF-alpha secreted by DC.

RESULTCompared with the sham radiation group, after exposure to the electromagnetic fields for 1 h, 12 h, or 24 h, HLA-DR, CD80,CD86 and CD40 were all declined except CD11c. The ability of DC allo-MLR in each exposure group was decreased significantly (P<0.05), especially in the 24 h exposure group. However, the secreted levels of IL-12p70 and TNF-alpha of DC in each exposure group remained no changed.

CONCLUSIONThe study showed that EMF exposure could down-regulate the surface molecules and stimulation ability of human DC.

B7-1 Antigen ; B7-2 Antigen ; immunology ; Biomarkers ; analysis ; CD11c Antigen ; immunology ; Cell Phone ; Cells, Cultured ; Dendrites ; pathology ; Dendritic Cells ; metabolism ; physiology ; radiation effects ; Electromagnetic Fields ; HLA-DR Antigens ; analysis ; Humans ; Interleukin-12 ; immunology