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Neurite Development (neurite + development)
Selected AbstractsThe type 1 cannabinoid receptor is highly expressed in embryonic cortical projection neurons and negatively regulates neurite growth in vitroEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 9 2008Tania Vitalis Abstract In the rodent and human embryonic brains, the cerebral cortex and hippocampus transiently express high levels of type 1 cannabinoid receptors (CB1Rs), at a developmental stage when these areas are composed mainly of glutamatergic neurons. However, the precise cellular and subcellular localization of CB1R expression as well as effects of CB1R modulation in this cell population remain largely unknown. We report that, starting from embryonic day 12.5, CB1Rs are strongly expressed in both reelin-expressing Cajal-Retzius cells and newly differentiated postmitotic glutamatergic neurons of the mouse telencephalon. CB1R protein is localized first to somato-dendritic endosomes and at later developmental stages it localizes mostly to developing axons. In young axons, CB1Rs are localized both to the axolemma and to large, often multivesicular endosomes. Acute maternal injection of agonist CP-55940 results in the relocation of receptors from axons to somato-dendritic endosomes, indicating the functional competence of embryonic CB1Rs. The adult phenotype of CB1R expression is established around postnatal day 5. By using pharmacological and mutational modulation of CB1R activity in isolated cultured rat hippocampal neurons, we also show that basal activation of CB1R acts as a negative regulatory signal for dendritogenesis, dendritic and axonal outgrowth, and branching. Together, the overall negative regulatory role in neurite development suggests that embryonic CB1R signaling may participate in the correct establishment of neuronal connectivity and suggests a possible mechanism for the development of reported glutamatergic dysfunction in the offspring following maternal cannabis consumption. [source] Signaling mechanisms that regulate actin-based motility processes in the nervous systemJOURNAL OF NEUROCHEMISTRY, Issue 3 2002Gary Meyer Abstract Actin-based motility is critical for nervous system development. Both the migration of neurons and the extension of neurites require organized actin polymerization to push the cell membrane forward. Numerous extracellular stimulants of motility and axon guidance cues regulate actin-based motility through the rho GTPases (rho, rac, and cdc42). The rho GTPases reorganize the actin cytoskeleton, leading to stress fiber, filopodium, or lamellipodium formation. The activity of the rho GTPases is regulated by a variety of proteins that either stimulate GTP uptake (activation) or hydrolysis (inactivation). These proteins potentially link extracellular signals to the activation state of rho GTPases. Effectors downstream of the rho GTPases that directly influence actin polymerization have been identified and are involved in neurite development. The Arp2/3 complex nucleates the formation of new actin branches that extend the membrane forward. Ena/VASP proteins can cause the formation of longer actin filaments, characteristic of growth cone actin morphology, by preventing the capping of barbed ends. Actin-depolymerizing factor (ADF)/cofilin depolymerizes and severs actin branches in older parts of the actin meshwork, freeing monomers to be re-incorporated into actively growing filaments. The signaling mechanisms by which extracellular cues that guide axons to their targets lead to direct effects on actin filament dynamics are becoming better understood. [source] GAP43 overexpression and enhanced neurite outgrowth in mucopolysaccharidosis type IIIB cortical neuron culturesJOURNAL OF NEUROSCIENCE RESEARCH, Issue 1 2010Michaël Hocquemiller Abstract Behavioral manifestations mark the onset of disease expression in children with mucopolysaccharidosis type III (MPSIII, Sanfilippo syndrome), a genetic disorder resulting from interruption of the lysosomal degradation of heparan sulfate. In the mouse model of MPSIII type B (MPSIIIB), cortical neuron pathology and dysfunction occur several months before neuronal loss and are primarily cell autonomous. The gene coding for GAP43, a neurite growth potentiator, is overexpressed in the MPSIIIB mouse cortex, and neurite dystrophy was reported in other types of lysosomal storage diseases. We therefore examined the development of the neuritic trees in pure populations of MPSIIIB mouse embryo cortical neurons grown for up to 12 days in primary culture. Dynamic observation of living neurons and quantification of neurite growth parameters indicated more frequent neurite elongation and branching and less frequent neurite retraction, resulting in a relative overgrowth of MPSIIIB neuron neuritic trees, involving both dendrites and axons, compared with normal controls. Neurite overgrowth was concomitant with more than twofold increased expression of GAP43 mRNAs and proteins. Correction of the genetic defect leads to expression of the missing lysosomal enzyme, normal GAP43 mRNA expression, and reduced neurite outgrowth. These results indicate that heparan sulfate oligosaccharide storage modifies GAP43 expression in MPSIIIB cortical neurons with potential consequences for neurite development and neuronal functions that may be relevant to clinical manifestations. © 2009 Wiley-Liss, Inc. [source] Developmental regulation of neuron-specific P2X3 receptor expression in the rat cochleaTHE JOURNAL OF COMPARATIVE NEUROLOGY, Issue 2 2005Lin-Chien Huang Abstract ATP-gated ion channels assembled from P2X3 receptor (P2X3R) subunits contribute to neurotransmission and neurotrophic signaling, associated with neurite development and synaptogenesis, particularly in peripheral sensory neurons. Here, P2X3R expression was characterized in the rat cochlea from embryonic day 16 (E16) to adult (P49,56), using RT-PCR and immunohistochemistry. P2X3R mRNA was strongly expressed in the cochlea prior to birth, declined to a minimal level at P14, and was absent in adult tissue. P2X3R protein expression was confined to spiral ganglion neurons (SGN) within Rosenthal's canal of the cochlea. At E16, immunolabeling was detected in the SGN neurites, but not the distal neurite projection within the developing sensory epithelium (greater epithelial ridge). From E18, the immunolabeling was observed in the peripheral neurites innervating the inner hair cells but was reduced by P6. However, from P2,8, immunolabeling of the SGN neurites extended to include the outer spiral bundle fiber tract beneath the outer hair cells. This labeling of type II SGN afferent fiber declined after P8. By P14, all synaptic terminal immunolabeling in the organ of Corti was absent, and SGN cell body labeling was minimal. In adult cochlear tissue, P2X3R immunolabeling was not detected. Noise exposure did not induce P2X3R expression in the adult cochlea. These data indicate that ATP-gated ion channels incorporating P2X3R subunit expression are specifically targeted to the afferent terminals just prior to the onset of hearing, and likely contribute to the neurotrophic signaling which establishes functional auditory neurotransmission. J. Comp. Neurol. 484:133,143, 2005. © 2005 Wiley-Liss, Inc. [source] | ||||||||||