Molecular and cellular neurosciences
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Mol. Cell. Neurosci. · Dec 2009
Axonal and neuromuscular synaptic phenotypes in Wld(S), SOD1(G93A) and ostes mutant mice identified by fiber-optic confocal microendoscopy.
We used live imaging by fiber-optic confocal microendoscopy (CME) of yellow fluorescent protein (YFP) expression in motor neurons to observe and monitor axonal and neuromuscular synaptic phenotypes in mutant mice. First, we visualized slow degeneration of axons and motor nerve terminals at neuromuscular junctions following sciatic nerve injury in Wld(S) mice with slow Wallerian degeneration. Protection of axotomized motor nerve terminals was much weaker in Wld(S) heterozygotes than in homozygotes. ⋯ We next applied CME repeatedly to living Wld(S) mice and to SOD1(G93A) mice, an animal model of motor neuron disease, and observed degeneration of identified neuromuscular synapses over a 1-4day period in both of these mutant lines. Finally, we used CME to observe slow axonal regeneration in the ENU-mutant ostes mouse strain. The data show that CME can be used to monitor covert axonal and neuromuscular synaptic pathology and, when combined with mutagenesis, to identify genetic modifiers of its progression in vivo.
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Mol. Cell. Neurosci. · Nov 2009
MeCP2 deficiency disrupts axonal guidance, fasciculation, and targeting by altering Semaphorin 3F function.
Rett syndrome (RTT) is an autism spectrum disorder that results from mutations in the transcriptional regulator methyl-CpG binding protein 2 (MECP2). In the present work, we demonstrate that MeCP2 deficiency disrupts the establishment of neural connections before synaptogenesis. Using both in vitro and in vivo approaches, we identify dynamic alterations in the expression of class 3 semaphorins that are accompanied by defects in axonal fasciculation, guidance, and targeting with MeCP2 deficiency. ⋯ This defect is restored when mutant olfactory axons are co-cultured with wild type olfactory bulbs. Thus, a non-cell autonomous mechanism involving Semaphorin 3F function may underlie abnormalities in the establishment of connectivity with Mecp2 mutation. These findings have broad implications for the role of MECP2 in neurodevelopment and RTT, given the critical role of the semaphorins in the formation of neural circuits.
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Mol. Cell. Neurosci. · Jul 2009
Isolation of neural stem/progenitor cells by using EGF/FGF1 and FGF1B promoter-driven green fluorescence from embryonic and adult mouse brains.
Fibroblast growth factor 1 (FGF1) and FGF2 have been shown to maintain the proliferation, self-renewal and multipotent capacities of neural stem/progenitor cells (NSPCs) in vitro. FGF1 is unique for binding to all known FGF receptors. In this study, we investigated if exogenous EGF and FGF1 could be used in the isolation of NSPCs from embryonic mouse brains. ⋯ Using F1BGFP reporter, we further demonstrated that F1BGFP+ cells showed similar multipotent capacities to CD133+ NSPCs, and could be induced more efficiently toward neuronal differentiation. Our results suggested that EGF/FGF1-responsive cells from E11.5 mouse brains could self-renew and have better multipotency than EGF/FGF2-responsive NSPCs. Further, CD133+ and F1BGFP+ NSPCs may also represent different subsets of NSPCs during neural development and adult neurogenesis.
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Mol. Cell. Neurosci. · Jun 2009
Chemokines direct neural progenitor cell migration following striatal cell loss.
In this study we demonstrate the chemokines MCP-1, MIP-1alpha and GRO-alpha play a role in directing adult subventricular zone (SVZ)-derived progenitor cell migration following striatal cell death. MCP-1, MIP-1alpha and GRO-alpha were significantly upregulated in the striatum 2-3 days following QA-induced lesioning, correlating with maximum SVZ-derived progenitor cell recruitment into the lesioned striatum. ⋯ Immunofluorescence revealed MCP-1, MIP-1alpha and GRO-alpha are predominantly expressed in the striatum by NG2-positive cells that appear to infiltrate from the bloodstream 6 h following QA lesioning. These results indicate that upregulation of MCP-1, MIP-1alpha and GRO-alpha following striatal cell death leads to chemoattraction of SVZ-derived progenitor cells into the damaged striatum and raises a potential role for blood-derived cells in directing the recruitment of SVZ-derived progenitors following brain injury.
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Mol. Cell. Neurosci. · Dec 2008
Opioids modulate pain facilitation from the dorsal reticular nucleus.
During chronic pain, the supraspinal pain modulatory system undergoes plastic changes with enhancement of facilitation transmission at the spinal cord. The changes induced by chronic pain at descending modulation often affect opioidergic modulation, and were never described for a key facilitatory component of the system, the dorsal reticular nucleus (DRt). Neurochemical characterization of the DRt-spinal pathway showed that delta-opioid receptors are positioned as to indirectly modulate the activity of non-projecting DRt neurons, whereas neurons expressing mu-opioid receptors project to the spinal dorsal horn or act as interneurons, the latter of which co-expressing GABA(B) receptors. ⋯ The opioid agonists [D-Ala(2), Glu(4)]-deltorphin (DELT) and [D-Ala(2), NMePhe(4)Gly-ol(5)]-enkephalin (DAMGO) induced thermal hyperalgesia in both non-inflamed and monoarthritic rats, but with lower doses in the latter group. The present study shows that opioidergic neurons at the DRt are modulated by GABAergic cells herein controlling the descending facilitation of pain transmission. The DRt exhibits plastic changes during chronic inflammatory pain, with decrease opioid receptor expression which may account for increased descending facilitation during chronic pain.