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Presynaptic Differentiation (presynaptic + differentiation)
Selected AbstractsMitochondrial clustering at the vertebrate neuromuscular junction during presynaptic differentiationDEVELOPMENTAL NEUROBIOLOGY, Issue 6 2006Chi Wai Lee Abstract During vertebrate neuromuscular junction (NMJ) development, presynaptic motor axons differentiate into nerve termini enriched in synaptic vesicles (SVs). At the nerve terminal, mitochondria are also concentrated, but how mitochondria become localized at these specialized domains is poorly understood. This process was studied in cultured Xenopus spinal neurons with mitochondrion-specific probe MitoTracker and SV markers. In nerve-muscle cocultures, mitochondria were concentrated stably at sites where neurites and muscle cells formed NMJs, and mitochondria coclustered with SVs where neurites were focally stimulated by beads coated with growth factors. Labeling with a mitochondrial membrane potential-dependent probe JC-1 revealed that these synaptic mitochondria were with higher membrane potential than the extrasynaptic ones. At early stages of bead-stimulation, actin-based protrusions and microtubule fragmentation were observed in neurites at bead contact sites, suggesting the involvement of cytoskeletal dynamics and rearrangement during presynaptic differentiation. Treating the cultures with an actin polymerization blocker, latrunculin A (Ltn A), almost completely abolished the formation of actin-based protrusions and partially inhibited bead-induced mitochondrial and SV clustering, whereas the microtubule disrupting agent nocodazole was ineffective in inhibiting the clustering of mitochondria and SVs. Lastly, in contrast to Ltn A, which blocked bead-induced clustering of both mitochondria and SVs, the ser/thr phosphatase inhibitor okadaic acid inhibited SV clustering but not mitochondrial clustering. These results suggest that at developing NMJs, synaptogenic stimuli induce the clustering of mitochondria together with SVs at presynaptic terminals in an actin cytoskeleton-dependent manner and involving different intracellular signaling molecules. © 2006 Wiley Periodicals, Inc. J Neurobiol, 2006 [source] Seeking long-term relationship: axon and target communicate to organize synaptic differentiationJOURNAL OF NEUROCHEMISTRY, Issue 5 2006Michael A. Fox Abstract Synapses form after growing axons recognize their appropriate targets. The subsequent assembly of aligned pre and postsynaptic specializations is critical for synaptic function. This highly precise apposition of presynaptic elements (i.e. active zones) to postsynaptic specializations (i.e. neurotransmitter receptor clusters) strongly suggests that communication between the axon and target is required for synaptic differentiation. What trans-synaptic factors drive such differentiation at vertebrate synapses? First insights into the answers to this question came from studies at the neuromuscular junction (NMJ), where axon-derived agrin and muscle-derived laminin ,2 induce post and presynaptic differentiation, respectively. Recent work has suggested that axon- and target-derived factors similarly drive synaptic differentiation at central synapses. Specifically, WNT-7a, neuroligin, synaptic cell adhesion molecule (SynCAM) and fibroblast growth factor-22 (FGF-22) have all been identified as target-derived presynaptic organizers, whereas axon-derived neuronal activity regulated pentraxin (Narp), ephrinB and neurexin reciprocally co-ordinate postsynaptic differentiation. In addition to these axon- and target-derived inducers of synaptic differentiation, factors released from glial cells have also been implicated in regulating synapse assembly. Together, these recent findings have profoundly advanced our understanding of how precise appositions are established during vertebrate nervous system development. [source] Cysteine-string protein in inner hair cells of the organ of Corti: synaptic expression and upregulation at the onset of hearingEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 9 2002Michel Eybalin Abstract Cysteine-string protein is a vesicle-associated protein that plays a vital function in neurotransmitter release. We have studied its expression and regulation during cochlear maturation. Both the mRNA and the protein were found in primary auditory neurons and the sensory inner hair cells. More importantly, cysteine-string protein was localized on synaptic vesicles associated with the synaptic ribbon in inner hair cells and with presynaptic differentiations in lateral and medial olivocochlear terminals , the cell bodies of which lie in the auditory brainstem. No cysteine-string protein was expressed by the sensory outer hair cells suggesting that the distinct functions of the two cochlear hair cell types imply different mechanisms of neurotransmitter release. In developmental studies in the rat, we observed that cysteine-string protein was present beneath the inner hair cells at birth and beneath outer hair cells by postnatal day 2 only. We found no expression in the inner hair cells before about postnatal day 12, which corresponds to the period during which the first cochlear action potentials could be recorded. In conclusion, the close association of cysteine-string protein with synaptic vesicles tethered to synaptic ribbons in inner hair cells and its synchronized expression with the appearance and maturation of the cochlear potentials strongly suggest that this protein plays a fundamental role in sound-evoked glutamate release by inner hair cells. This also suggests that this role may be common to ribbon synapses and conventional central nervous system synapses. [source] | ||||||||||