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Crosta CM, Hernandez K, Bhattiprolu AK, Fu AY, Moore JC, Clarke SG, Dudzinski NR, Brzustowicz LM, Paradiso KG, Firestein BL. Characterization hiPSC-derived neural progenitor cells and neurons to investigate the role of NOS1AP isoforms in human neuron dendritogenesis. Mol Cell Neurosci 2020; 109:103562. [PMID: 32987141 PMCID: PMC7736313 DOI: 10.1016/j.mcn.2020.103562] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2020] [Revised: 09/02/2020] [Accepted: 09/22/2020] [Indexed: 01/30/2023] Open
Abstract
Abnormal dendritic arbor development has been implicated in a number of neurodevelopmental disorders, such as autism and Rett syndrome, and the neuropsychiatric disorder schizophrenia. Postmortem brain samples from subjects with schizophrenia show elevated levels of NOS1AP in the dorsolateral prefrontal cortex, a region of the brain associated with cognitive function. We previously reported that the long isoform of NOS1AP (NOS1AP-L), but not the short isoform (NOS1AP-S), negatively regulates dendrite branching in rat hippocampal neurons. To investigate the role that NOS1AP isoforms play in human dendritic arbor development, we adapted methods to generate human neural progenitor cells and neurons using induced pluripotent stem cell (iPSC) technology. We found that increased protein levels of either NOS1AP-L or NOS1AP-S decrease dendrite branching in human neurons at the developmental time point when primary and secondary branching actively occurs. Next, we tested whether pharmacological agents can decrease the expression of NOS1AP isoforms. Treatment of human iPSC-derived neurons with d-serine, but not clozapine, haloperidol, fluphenazine, or GLYX-13, results in a reduction in endogenous NOS1AP-L, but not NOS1AP-S, protein expression; however, d-serine treatment does not reverse decreases in dendrite number mediated by overexpression of NOS1AP isoforms. In summary, we demonstrate how an in vitro model of human neuronal development can help in understanding the etiology of schizophrenia and can also be used as a platform to screen drugs for patients.
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Affiliation(s)
- Christen M Crosta
- Department of Cell Biology and Neuroscience, Rutgers, The State University of New Jersey, Piscataway, NJ, USA; Neurosciences Graduate Program, Rutgers, The State University of New Jersey, Piscataway, NJ, USA
| | - Kristina Hernandez
- Department of Cell Biology and Neuroscience, Rutgers, The State University of New Jersey, Piscataway, NJ, USA; Molecular Biosciences Graduate Program, Rutgers, The State University of New Jersey, Piscataway, NJ, USA
| | - Atul K Bhattiprolu
- Department of Cell Biology and Neuroscience, Rutgers, The State University of New Jersey, Piscataway, NJ, USA
| | - Allen Y Fu
- Department of Cell Biology and Neuroscience, Rutgers, The State University of New Jersey, Piscataway, NJ, USA
| | - Jennifer C Moore
- Department of Genetics, Rutgers, The State University of New Jersey, 604 Allison Road, Piscataway, NJ 08854-8082, USA
| | - Stephen G Clarke
- Department of Cell Biology and Neuroscience, Rutgers, The State University of New Jersey, Piscataway, NJ, USA
| | - Natasha R Dudzinski
- Department of Cell Biology and Neuroscience, Rutgers, The State University of New Jersey, Piscataway, NJ, USA
| | - Linda M Brzustowicz
- Department of Genetics, Rutgers, The State University of New Jersey, 604 Allison Road, Piscataway, NJ 08854-8082, USA
| | - Kenneth G Paradiso
- Department of Cell Biology and Neuroscience, Rutgers, The State University of New Jersey, Piscataway, NJ, USA
| | - Bonnie L Firestein
- Department of Cell Biology and Neuroscience, Rutgers, The State University of New Jersey, Piscataway, NJ, USA.
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Dumoulin A, Ter-Avetisyan G, Schmidt H, Rathjen FG. Molecular Analysis of Sensory Axon Branching Unraveled a cGMP-Dependent Signaling Cascade. Int J Mol Sci 2018; 19:E1266. [PMID: 29695045 PMCID: PMC5983660 DOI: 10.3390/ijms19051266] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2018] [Revised: 04/15/2018] [Accepted: 04/20/2018] [Indexed: 01/11/2023] Open
Abstract
Axonal branching is a key process in the establishment of circuit connectivity within the nervous system. Molecular-genetic studies have shown that a specific form of axonal branching—the bifurcation of sensory neurons at the transition zone between the peripheral and the central nervous system—is regulated by a cyclic guanosine monophosphate (cGMP)-dependent signaling cascade which is composed of C-type natriuretic peptide (CNP), the receptor guanylyl cyclase Npr2, and cGMP-dependent protein kinase Iα (cGKIα). In the absence of any one of these components, neurons in dorsal root ganglia (DRG) and cranial sensory ganglia no longer bifurcate, and instead turn in either an ascending or a descending direction. In contrast, collateral axonal branch formation which represents a second type of axonal branch formation is not affected by inactivation of CNP, Npr2, or cGKI. Whereas axon bifurcation was lost in mouse mutants deficient for components of CNP-induced cGMP formation; the absence of the cGMP-degrading enzyme phosphodiesterase 2A had no effect on axon bifurcation. Adult mice that lack sensory axon bifurcation due to the conditional inactivation of Npr2-mediated cGMP signaling in DRG neurons demonstrated an altered shape of sensory axon terminal fields in the spinal cord, indicating that elaborate compensatory mechanisms reorganize neuronal circuits in the absence of bifurcation. On a functional level, these mice showed impaired heat sensation and nociception induced by chemical irritants, whereas responses to cold sensation, mechanical stimulation, and motor coordination are normal. These data point to a critical role of axon bifurcation for the processing of acute pain perception.
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Affiliation(s)
| | | | - Hannes Schmidt
- Interfaculty Institute of Biochemistry, University of Tübingen, Hoppe-Seyler-Str. 4, 72076 Tübingen, Germany.
| | - Fritz G Rathjen
- Max-Delbrück-Center, Robert-Rössle-Str. 10, 13092 Berlin, Germany.
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Xiong G, Metheny H, Johnson BN, Cohen AS. A Comparison of Different Slicing Planes in Preservation of Major Hippocampal Pathway Fibers in the Mouse. Front Neuroanat 2017; 11:107. [PMID: 29201002 PMCID: PMC5696601 DOI: 10.3389/fnana.2017.00107] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2017] [Accepted: 11/06/2017] [Indexed: 12/03/2022] Open
Abstract
The hippocampus plays a critical role in learning and memory and higher cognitive functions, and its dysfunction has been implicated in various neuropathological disorders. Electrophysiological recording undertaken in live brain slices is one of the most powerful tools for investigating hippocampal cellular and network activities. The plane for cutting the slices determines which afferent and/or efferent connections are best preserved, and there are three commonly used slices: hippocampal-entorhinal cortex (HEC), coronal and transverse. All three slices have been widely used for studying the major afferent hippocampal pathways including the perforant path (PP), the mossy fibers (MFs) and the Schaffer collaterals (SCs). Surprisingly, there has never been a systematic investigation of the anatomical and functional consequences of slicing at a particular angle. In the present study, we focused on how well fiber pathways are preserved from the entorhinal cortex (EC) to the hippocampus, and within the hippocampus, in slices generated by sectioning at different angles. The postmortem neural tract tracer 1,1′-dioctadecyl-3,3,3′3′-tetramethylindocarbocyanine perchlorate (DiI) was used to label afferent fibers to hippocampal principal neurons in fixed slices or whole brains. Laser scanning confocal microscopy was adopted for imaging DiI-labeled axons and terminals. We demonstrated that PP fibers were well preserved in HEC slices, MFs in both HEC and transverse slices and SCs in all three types of slices. Correspondingly, field excitatory postsynaptic potentials (fEPSPs) could be consistently evoked in HEC slices when stimulating PP fibers and recorded in stratum lacunosum-moleculare (sl-m) of area CA1, and when stimulating the dentate granule cell layer (gcl) and recording in stratum lucidum (sl) of area CA3. The MF evoked fEPSPs could not be recorded in CA3 from coronal slices. In contrast to our DiI-tracing data demonstrating severely truncated PP fibers in coronal slices, fEPSPs could still be recorded in CA1 sl-m in this plane, suggesting that an additional afferent fiber pathway other than PP might be involved. The present study increases our understanding of which hippocampal pathways are best preserved in the three most common brain slice preparations, and will help investigators determine the appropriate slices to use for physiological studies depending on the subregion of interest.
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Affiliation(s)
- Guoxiang Xiong
- Department of Anesthesiology and Critical Care Medicine, Children's Hospital of Philadelphia, Philadelphia, PA, United States
| | - Hannah Metheny
- Department of Anesthesiology and Critical Care Medicine, Children's Hospital of Philadelphia, Philadelphia, PA, United States
| | - Brian N Johnson
- Department of Anesthesiology and Critical Care Medicine, Children's Hospital of Philadelphia, Philadelphia, PA, United States
| | - Akiva S Cohen
- Department of Anesthesiology and Critical Care Medicine, Children's Hospital of Philadelphia, Philadelphia, PA, United States.,Department of Anesthesiology and Critical Care Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States
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Sugahara Y, Kawaguchi M, Itoyama T, Kurokawa D, Tosa Y, Kitamura SI, Handoh IC, Nakayama K, Murakami Y. Pyrene induces a reduction in midbrain size and abnormal swimming behavior in early-hatched pufferfish larvae. MARINE POLLUTION BULLETIN 2014; 85:479-486. [PMID: 24793779 DOI: 10.1016/j.marpolbul.2014.04.022] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/06/2013] [Revised: 04/01/2014] [Accepted: 04/08/2014] [Indexed: 06/03/2023]
Abstract
Spills of heavy oil (HO) have an adverse effect on marine life. We have demonstrated previously that exposure to HO by fertilized eggs of the pufferfish (Takifugu rubripes) induces neural disruption and behavioral abnormality in early-hatched larvae. Here, two kinds of polycyclic aromatic hydrocarbons, pyrene and phenanthrene, were selected to examine their toxic effects on larval behavior of another pufferfish species (T. niphobles). Larvae exposed to pyrene or phenanthrene exhibited no abnormalities in morphology. However, those exposed to pyrene but not phenanthrene swam in an uncoordinated manner, although their swimming distance and speed were normal. The optic tectum, a part of the midbrain, of pyrene-exposed larvae did not grow to full size. Thus, these findings are indicated that pyrene might be a contributor to the behavioral and neuro-developmental toxicity, although there is no indication that it is the only compound participating in the toxicity of the heavy oil mixture.
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Affiliation(s)
- Yuki Sugahara
- Graduate School of Science and Engineering, Ehime University, 2-5 Bunkyo-cho, Matsuyama, Japan
| | - Masahumi Kawaguchi
- Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, 2630 Sugitani, Toyama, Japan
| | - Tatsuya Itoyama
- Graduate School of Science and Engineering, Ehime University, 2-5 Bunkyo-cho, Matsuyama, Japan
| | - Daisuke Kurokawa
- Misaki Marine Biological Station, The University of Tokyo, 1024 Koajiro, Misaki, Miura, Japan
| | - Yasuhiko Tosa
- Graduate School of Science and Engineering, Ehime University, 2-5 Bunkyo-cho, Matsuyama, Japan
| | - Shin-Ichi Kitamura
- Center for Marine Environmental Studies (CMES), Ehime University, 2-5 Bunkyo-cho, Matsuyama, Japan
| | - Itsuki C Handoh
- The Futurability Initiatives, Research Institute for Humanity and Nature, 457-4 Motoyama, Kamigamo, Kita-ku, Kyoto, Japan
| | - Kei Nakayama
- Center for Marine Environmental Studies (CMES), Ehime University, 2-5 Bunkyo-cho, Matsuyama, Japan.
| | - Yasunori Murakami
- Graduate School of Science and Engineering, Ehime University, 2-5 Bunkyo-cho, Matsuyama, Japan.
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Nitric oxide synthesis and cGMP production is important for neurite growth and synapse remodeling after axotomy. J Neurosci 2013; 33:5626-37. [PMID: 23536077 DOI: 10.1523/jneurosci.3659-12.2013] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Nitric oxide (NO) is an important signaling molecule with a variety of functions in the CNS, including a potential role in modulating neuronal growth and synapse formation. In the present study, we used tractable, identified neurons in the CNS of the pond snail Lymnaea stagnalis to study the role of endogenous NO signaling in neuronal growth and synaptic remodeling after nerve injury. Axonal damage of L. stagnalis neurons B1 and B2 induces extensive central growth of neurites that is accompanied by changes in existing electrical connections, the transient formation of novel electrical connections, and the formation of a novel excitatory chemical synapse from B2 to B1 neurons. Partial chronic inhibition of endogenous NO synthesis reduces neurite growth in NO-synthase-expressing B2, but has only minor effects on NOS-negative B1 neurons. Chronic application of an NO donor while inhibiting endogenous NO synthesis rescues neurite extension in B2 neurons and boosts growth of B1 neurons. Blocking soluble guanylate cyclase activity completely suppresses neurite extension and synaptic remodeling after nerve crush, demonstrating the importance of cGMP in these processes. Interestingly, inhibition of cGMP-dependent protein kinase only suppresses chemical synapse formation without effects on neuronal growth and electrical synapse remodeling. We conclude that NO signaling via cGMP is an important modulator of both neurite growth and synaptic remodeling after nerve crush. However, differential effects of cGMP-dependent protein kinase inhibition on neurite growth and synaptic remodeling suggest that these effects are mediated by separate signaling pathways.
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He C, Wang C, Zhou Y, Li J, Zuo Z. Embryonic exposure to benzo(a)pyrene influences neural development and function in rockfish (Sebastiscus marmoratus). Neurotoxicology 2012; 33:758-62. [DOI: 10.1016/j.neuro.2012.01.002] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2011] [Revised: 11/20/2011] [Accepted: 01/06/2012] [Indexed: 12/27/2022]
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He C, Wang C, Li B, Wu M, Geng H, Chen Y, Zuo Z. Exposure of Sebastiscus marmoratus embryos to pyrene results in neurodevelopmental defects and disturbs related mechanisms. AQUATIC TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2012; 116-117:109-115. [PMID: 22487263 DOI: 10.1016/j.aquatox.2012.03.009] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2011] [Revised: 03/13/2012] [Accepted: 03/13/2012] [Indexed: 05/31/2023]
Abstract
Polycyclic aromatic hydrocarbons (PAHs) are widespread environmental contaminants, which are known to be carcinogenic and teratogenic. These compounds cause a range of macroscopic malformations, particularly to the craniofacial apparatus and cardiovascular system during vertebrate development. However, little is known concerning microscopic effects, especially on the sensitive early life stages or on the molecular basis of developmental neurotoxicity. Using the rockfish (Sebastiscus marmoratus), we explored the neurodevelopmental defects caused by early-life exposure to environmentally relevant concentrations of pyrene, a 4-ring PAH. The results showed that pyrene substantially disrupted the cranial innervation pattern and caused deficiency of motor nerves. The expression of a protein associated with axon growth, growth associated protein 43, was decreased in the central nervous system after treatment with pyrene. N-methyl-D-aspartate receptor (NMDAR) plays a vital role in a variety of processes, including neuronal development, synaptic plasticity, and neuronal survival and death. Our results showed that the expression of Ca²⁺/calmodulin dependent kinase II and cAMP-response element-binding, which belong to the NMDAR pathway, were increased in a dose-dependent manner after exposure to pyrene. Acetylcholine, an important neurotransmitter which is known to suppress retinal cells neurite outgrowth, was increased by pyrene exposure. Nitric oxide (NO) acts as an activity-dependent retrograde signal that can coordinate axonal targeting and synaptogenesis during development. The level of NO was decreased in a dose-dependent manner following exposure to pyrene. Taken together, the defects in neurodevelopment and the damage to related mechanisms provided the basis for a better understanding of the neurotoxic effects of pyrene.
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Affiliation(s)
- Chengyong He
- Key Laboratory of Ministry of Education for Subtropical Wetland Ecosystem Research, School of Life Sciences, Xiamen University, Xiamen, China
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8
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Abstract
Nitric oxide (NO) is a signaling molecule that is synthesized in a range of tissues by the NO synthases (NOSs). In the immature nervous system, the neuronal isoform of NOS (NOS1) is often expressed during periods of axon outgrowth and elaboration. However, there is little direct molecular evidence to suggest that NOS1 influences these processes. Here we address the functional role of NOS1 during in vivo zebrafish locomotor circuit development. We show that NOS1 is expressed in a population of interneurons that lie close to nascent motoneurons of the spinal cord. To determine how this protein regulates spinal network assembly, we perturbed NOS1 expression in vivo with antisense morpholino oligonucleotides. This treatment dramatically increased the number of axon collaterals formed by motoneuron axons, an effect mimicked by pharmacological inhibition of the NO/cGMP signaling pathway. In contrast, exogenous elevation of NO/cGMP levels suppressed motor axon branching. These effects were not accompanied by a change in motoneuron number, suggesting that NOS1 does not regulate motoneuron differentiation. Finally we show that perturbation of NO signaling affects the ontogeny of locomotor performance. Our findings provide evidence that NOS1 is a key regulator of motor axon ontogeny in the developing vertebrate spinal cord.
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9
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Stern M, Bicker G. Nitric oxide as a regulator of neuronal motility and regeneration in the locust embryo. JOURNAL OF INSECT PHYSIOLOGY 2010; 56:958-965. [PMID: 20361970 DOI: 10.1016/j.jinsphys.2010.03.031] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/23/2010] [Revised: 03/18/2010] [Accepted: 03/19/2010] [Indexed: 05/29/2023]
Abstract
Nitric oxide (NO) is known as a gaseous messenger in the nervous system. It plays a role in synaptic plasticity, but also in development and regeneration of nervous systems. We have studied the function of NO and its signaling cascade via cyclic GMP in the locust embryo. Its developing nervous system is well suited for pharmacological manipulations in tissue culture. The components of this signaling pathway are localized by histochemical and immunofluorescence techniques. We have analyzed cellular mechanisms of NO action in three examples: 1. in the peripheral nervous system during antennal pioneer axon outgrowth, 2. in the enteric nervous system during migration of neurons forming the midgut nerve plexus, and 3. in the central nervous system during axonal regeneration of serotonergic neurons after axotomy. In each case, internally released NO or NO-induced cGMP synthesis act as permissive signals for the developmental process. Carbon monoxide (CO), as a second gaseous messenger, modulates enteric neuron migration antagonistic to NO.
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Affiliation(s)
- Michael Stern
- Division of Cell Biology, Institute of Physiology, University of Veterinary Medicine Hannover, D-30173 Hannover, Germany.
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Currie DA, Corlew R, de Vente J, Moody WJ. Elevated glutamate and NMDA disrupt production of the second messenger cyclic GMP in the early postnatal mouse cortex. Dev Neurobiol 2009; 69:255-66. [PMID: 19172658 DOI: 10.1002/dneu.20697] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The second messenger cyclic guanosine monophosphate (cGMP) plays many roles during nervous system development. Consequently, cGMP production shows complex patterns of regulation throughout early development. Elevated glutamate levels are known to increase cGMP levels in the mature nervous system. A number of clinical conditions including ischemia and perinatal asphyxia can result in elevated glutamate levels in the developing brain. To investigate the effects of elevated glutamate levels on cGMP in the developing cortex we exposed mouse brain slices to glutamate or N-methyl D-aspartate (NMDA). We find that at early postnatal stages when the endogenous production of cGMP is high, glutamate or NMDA exposure results in a significant lowering of the overall production of cGMP in the cortex, unlike the situation in the mature brain. However, this response pattern is complex with regional and cell-type specific exceptions to the overall lowered cGMP production. These data emphasize that the response of the developing brain to physiological disturbances can be different from that of the mature brain, and must be considered in the context of the developmental events occurring at the time of disturbance.
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Affiliation(s)
- Douglas A Currie
- Department of Biology, University of Washington, Seattle, Washington 98195, USA.
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Regulate axon branching by the cyclic GMP pathway via inhibition of glycogen synthase kinase 3 in dorsal root ganglion sensory neurons. J Neurosci 2009; 29:1350-60. [PMID: 19193882 DOI: 10.1523/jneurosci.3770-08.2009] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Cyclic GMP has been proposed to regulate axonal development, but the molecular and cellular mechanisms underlying the formation of axon branches are not well understood. Here, we report the use of rodent embryonic sensory neurons from the dorsal root ganglion (DRG) to demonstrate the role of cGMP signaling in axon branching and to identify the downstream molecular pathway mediating this novel regulation. Pharmacologically, a specific cGMP analog promotes DRG axon branching in culture, and this activity can be achieved by activating the endogenous soluble guanylyl cyclase that produces cGMP. At the molecular level, the cGMP-dependent protein kinase 1 (PrkG1) mediates this activity, as DRG neurons isolated from the kinase-deficient mouse fail to respond to cGMP activation to make branches, whereas overexpression of a PrkG1 mutant with a higher-than-normal basal kinase activity is sufficient to induce branching. In addition, cGMP activation in DRG neurons leads to phosphorylation of glycogen synthase kinase 3 (GSK3), a protein that normally suppresses branching. This interaction is direct, because PrkG1 binds GSK3 in heterologous cells and the purified kinase can phosphorylate GSK3 in vitro. More importantly, overexpression of a dominant active form of GSK3 suppresses cGMP-dependent branching in DRG neurons. Thus, our study establishes an intrinsic signaling cascade that links cGMP activation to GSK3 inhibition in controlling axon branching during sensory axon development.
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van Zundert B, Peuscher MH, Hynynen M, Chen A, Neve RL, Brown RH, Constantine-Paton M, Bellingham MC. Neonatal neuronal circuitry shows hyperexcitable disturbance in a mouse model of the adult-onset neurodegenerative disease amyotrophic lateral sclerosis. J Neurosci 2008; 28:10864-74. [PMID: 18945894 PMCID: PMC3844745 DOI: 10.1523/jneurosci.1340-08.2008] [Citation(s) in RCA: 186] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2008] [Revised: 08/07/2008] [Accepted: 09/02/2008] [Indexed: 12/13/2022] Open
Abstract
Distinguishing the primary from secondary effects and compensatory mechanisms is of crucial importance in understanding adult-onset neurodegenerative diseases such as amyotrophic lateral sclerosis (ALS). Transgenic mice that overexpress the G93A mutation of the human Cu-Zn superoxide dismutase 1 gene (hSOD1(G93A) mice) are a commonly used animal model of ALS. Whole-cell patch-clamp recordings from neurons in acute slice preparations from neonatal wild-type and hSOD1(G93A) mice were made to characterize functional changes in neuronal activity. Hypoglossal motoneurons (HMs) in postnatal day 4 (P4)-P10 hSOD1(G93A) mice displayed hyperexcitability, increased persistent Na(+) current (PC(Na)), and enhanced frequency of spontaneous excitatory and inhibitory transmission, compared with wild-type mice. These functional changes in neuronal activity are the earliest yet reported for the hSOD1(G93A) mouse, and are present 2-3 months before motoneuron degeneration and clinical symptoms appear in these mice. Changes in neuronal activity were not restricted to motoneurons: superior colliculus interneurons also displayed hyperexcitability and synaptic changes (P10-P12). Furthermore, in vivo viral-mediated GFP (green fluorescent protein) overexpression in hSOD1(G93A) HMs revealed precocious dendritic remodeling, and behavioral assays revealed transient neonatal neuromotor deficits compared with controls. These findings underscore the widespread and early onset of abnormal neural activity in this mouse model of the adult neurodegenerative disease ALS, and suggest that suppression of PC(Na) and hyperexcitability early in life might be one way to mitigate or prevent cell death in the adult CNS.
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Affiliation(s)
- Brigitte van Zundert
- McGovern Institute for Brain Research, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
- Day Laboratory for Neuromuscular Research, Department of Neurology, Massachusetts General Hospital, Charlestown, Massachusetts 02429
| | - Marieke H. Peuscher
- McGovern Institute for Brain Research, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
| | - Meri Hynynen
- Day Laboratory for Neuromuscular Research, Department of Neurology, Massachusetts General Hospital, Charlestown, Massachusetts 02429
| | - Adam Chen
- Day Laboratory for Neuromuscular Research, Department of Neurology, Massachusetts General Hospital, Charlestown, Massachusetts 02429
| | - Rachael L. Neve
- Department of Psychiatry, Harvard Medical School, McLean Hospital, Belmont, Massachusetts 02178, and
| | - Robert H. Brown
- Day Laboratory for Neuromuscular Research, Department of Neurology, Massachusetts General Hospital, Charlestown, Massachusetts 02429
| | - Martha Constantine-Paton
- McGovern Institute for Brain Research, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
| | - Mark C. Bellingham
- McGovern Institute for Brain Research, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
- School of Biomedical Sciences, University of Queensland, Brisbane, Queensland 4072, Australia
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13
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Abstract
Activity-dependent specification of neuronal architecture during early postnatal life is essential for refining the precision of communication between neurons. In the spinal cord under normal circumstances, the AMPA receptor subunit GluR1 is expressed at high levels by motor neurons and surrounding interneurons during this critical developmental period, although the role it plays in circuit formation and locomotor behavior is unknown. Here, we show that GluR1 promotes dendrite growth in a non-cell-autonomous manner in vitro and in vivo. The mal-development of motor neuron dendrites is associated with changes in the pattern of interneuronal connectivity within the segmental spinal cord and defects in strength and endurance. Transgenic expression of GluR1 in adult motor neurons leads to dendrite remodeling and supernormal locomotor function. GluR1 expression by neurons within the segmental spinal cord plays an essential role in formation of the neural network that underlies normal motor behavior.
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