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Dendrite Growth (dendrite + growth)
Selected AbstractsNormal dendrite growth in Drosophila motor neurons requires the AP-1 transcription factorDEVELOPMENTAL NEUROBIOLOGY, Issue 10 2008Cortnie L. Hartwig Abstract During learning and memory formation, information flow through networks is regulated significantly through structural alterations in neurons. Dendrites, sites of signal integration, are key targets of activity-mediated modifications. Although local mechanisms of dendritic growth ensure synapse-specific changes, global mechanisms linking neural activity to nuclear gene expression may have profound influences on neural function. Fos, being an immediate-early gene, is ideally suited to be an initial transducer of neural activity, but a precise role for the AP-1 transcription factor in dendrite growth remains to be elucidated. Here we measure changes in the dendritic fields of identified Drosophila motor neurons in vivo and in primary culture to investigate the role of the immediate-early transcription factor AP-1 in regulating endogenous and activity-induced dendrite growth. Our data indicate that (a) increased neural excitability or depolarization stimulates dendrite growth, (b) AP-1 (a Fos, Jun hetero-dimer) is required for normal motor neuron dendritic growth during development and in response to activity induction, and (c) neuronal Fos protein levels are rapidly but transiently induced in motor neurons following neural activity. Taken together, these results show that AP-1 mediated transcription is important for dendrite growth, and that neural activity influences global dendritic growth through a gene-expression dependent mechanism gated by AP-1. © 2008 Wiley Periodicals, Inc. Develop Neurobiol, 2008 [source] Laminin and fibronectin modulate inner ear spiral ganglion neurite outgrowth in an in vitro alternate choice assayDEVELOPMENTAL NEUROBIOLOGY, Issue 13 2007Amaretta R. Evans Abstract Extracellular matrix (ECM) molecules have been shown to function as cues for neurite guidance in various populations of neurons. Here we show that laminin (LN) and fibronectin (FN) presented in stripe micro-patterns can provide guidance cues to neonatal (P5) inner ear spiral ganglion (SG) neurites. The response to both ECM molecules was dose-dependent. In a LN versus poly- L -lysine (PLL) assay, neurites were more often observed on PLL at low coating concentrations (5 and 10 ,g/mL), while they were more often on LN at a high concentration (80 ,g/mL). In a FN versus PLL assay, neurites were more often on PLL than on FN stripes at high coating concentrations (40 and 80 ,g/mL). In a direct competition between LN and FN, neurites were observed on LN significantly more often than on FN at both 10 and 40 ,g/mL. The data suggest a preference by SG neurites for LN at high concentrations, as well as avoidance of both LN at low and FN at high concentrations. The results also support a potential model for neurite guidance in the developing inner ear in vivo. LN, in the SG and osseus spiral lamina may promote SG dendrite growth toward the organ of Corti. Within the organ of Corti, lower concentrations of LN may slow neurite growth, with FN beneath each row of hair cells providing a stop or avoidance signal. This could allow growth cone filopodia increased time to sample their cellular targets, or direct the fibers upward toward the hair cells. © 2007 Wiley Periodicals, Inc. Develop Neurobiol, 2007 [source] Differential roles of Rap1 and Rap2 small GTPases in neurite retraction and synapse elimination in hippocampal spiny neuronsJOURNAL OF NEUROCHEMISTRY, Issue 1 2007Zhanyan Fu Abstract The Rap family of small GTPases is implicated in the mechanisms of synaptic plasticity, particularly synaptic depression. Here we studied the role of Rap in neuronal morphogenesis and synaptic transmission in cultured neurons. Constitutively active Rap2 expressed in hippocampal pyramidal neurons caused decreased length and complexity of both axonal and dendritic branches. In addition, Rap2 caused loss of dendritic spines and spiny synapses, and an increase in filopodia-like protrusions and shaft synapses. These Rap2 morphological effects were absent in aspiny interneurons. In contrast, constitutively active Rap1 had no significant effect on axon or dendrite morphology. Dominant-negative Rap mutants increased dendrite length, indicating that endogenous Rap restrains dendritic outgrowth. The amplitude and frequency of ,-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA)-mediated miniature excitatory postsynaptic currents (mEPSCs) decreased in hippocampal neurons transfected with active Rap1 or Rap2, associated with reduced surface and total levels of AMPA receptor subunit GluR2. Finally, increasing synaptic activity with GABAA receptor antagonists counteracted Rap2's inhibitory effect on dendrite growth, and masked the effects of Rap1 and Rap2 on AMPA-mediated mEPSCs. Rap1 and Rap2 thus have overlapping but distinct actions that potentially link the inhibition of synaptic transmission with the retraction of axons and dendrites. [source] | ||||||||||