scholarly journals Glutathione S-transferase Pi (Gstp) Proteins Regulate Neuritogenesis in the Developing Cerebral Cortex

2020 ◽  
Author(s):  
Xiaonan Liu ◽  
Sara M. Blazejewski ◽  
Sarah A. Bennison ◽  
Kazuhito Toyo-oka
Keyword(s):  
Cortical Neurons ◽  
Cortical Development ◽  
Apical Dendrite ◽  
Autism Spectrum ◽  
Neuronal Morphology ◽  
Jnk Signaling ◽  
Neurite Elongation ◽  
Neurite Initiation ◽  
Neurite Formation

AbstractGSTP proteins are metabolic enzymes involved in removal of oxidative stress and intracellular signaling and also have inhibitory effects on JNK activity. However, the functions of Gstp proteins in the developing brain are unknown. In mice, there are three Gstp proteins, Gstp1, 2 and 3, while there is only one GSTP in humans. By RT-PCR analysis, we found that Gstp1 was expressed beginning at E15.5 in the cortex, but Gstp2 and 3 started expressing at E18.5. Gstp 1 and 2 knockdown caused decreased neurite number in cortical neurons, implicating them in neurite initiation. Using in utero electroporation to knockdown Gstp1 and 2 in layer 2/3 pyramidal neurons in vivo, we found abnormal swelling of the apical dendrite at P3 and reduced neurite number at P15. Using time-lapse live imaging, we found that the apical dendrite orientation was skewed compared to the control, but these defects were ameliorated. Overexpression of Gstp 1 or 2 resulted in changes in neurite length, suggesting a role in neurite elongation. We explored the molecular mechanism and found that JNK inhibition rescued reduced neurite number caused by Gstp knockdown, indicating that Gstp regulates neurite formation through JNK signaling. Thus, we found novel functions of Gstp proteins in neurite initiation during cortical development. Furthermore, the overexpression experiments suggest different functions of Gstp1 and 2 in neurite elongation. Since previous studies have shown the potential implication of Gstp in Autism Spectrum Disorder, our findings will attract more clinical interests in Gstp proteins in neurodevelopmental disorders.SignificanceNeurite formation, including neurite initiation and elongation, is the first step of generating polarized neuronal morphology in developing neurons, and thus is essential for establishing a neuronal network. Therefore, it is crucial to understand the mechanisms of neurite formation. Limited studies have been performed to clarify the mechanisms of neurite formation, especially neurite initiation. In this present study, we report a novel, essential role of Gstp in neurite initiation in mouse cortical neurons in vitro and in vivo. We also found that Gstp regulates neurite formation via JNK signaling pathways. These findings not only provide novel functions of Gstp proteins in neuritogenesis during cortical development but also help us to understand the complexity of neurite formation.

scholarly journals 14-3-3 shuttles Activity-dependent neuroprotective protein to the cytoplasm to promote appropriate neuronal morphogenesis, cortical connectivity and calcium signaling

2020 ◽  
Author(s):  
Sarah A. Bennison ◽  
Sara M. Blazejewski ◽  
Xiaonan Liu ◽  
Kazuhito Toyo-oka
Keyword(s):  
Calcium Signaling ◽  
Pyramidal Neurons ◽  
Autism Spectrum ◽  
Neuronal Morphology ◽  
Cortical Connectivity ◽  
Neuronal Morphogenesis ◽  
Layer 2 ◽  
Neurite Formation ◽  
Activity Dependent

AbstractNeurite formation is the earliest stage of neuronal morphogenesis, where primitive dendrites and the primitive axon emerge from a spherical neuron and begin to elongate. Defective neuritogenesis is a contributing pathogenic mechanism behind a variety of neurodevelopmental disorders. Activity-dependent neuroprotective protein (Adnp) is essential to embryonic and postnatal brain development, and mutations in ADNP are among the most frequent underlying autism spectrum disorder (ASD). We found that knockdown of Adnp in vitro and in vivo in mouse layer 2/3 pyramidal neurons leads to increased neurite initiation and defective neurite elongation, suggesting that Adnp has distinct roles in each. In vivo analysis revealed that deficits begin at P0 and are sustained throughout development, the most notable of which include increased neurite stabilization, disrupted angle of the apical dendrite, increased basal dendrite number, and increased axon length. Because small changes in neuronal morphology can have large-scale effects on neuronal function and connectivity, we performed ex vivo calcium imaging to assess spontaneous function of layer 2/3 pyramidal neurons deficient in Adnp. This revealed that Adnp deficient neurons had a greater spontaneous calcium influx and a higher proportion of cells firing action potentials. Next, we utilized GRAPHIC, a novel synaptic tracing technology, to assess interhemispheric cortical connectivity. We found increased interhemispheric excitatory connectivity between Adnp deficient layer 2/3 pyramidal neurons. Because Adnp is a multifunctional protein with both transcription factor and cytoskeletal activity, we performed localization analysis of Adnp as neurons underwent neurite formation to probe the mechanism of our morphological defects. We found that Adnp is shuttled from the nucleus to the cytoplasm upon differentiation and this shuttling can be blocked via application of a global 14-3-3 inhibitor, difopein. Furthermore, we found that Adnp binds nuclear-cytoplasmic shuttle 14-3-3ε. We conclude that Adnp is shuttled from the nucleus to the cytoplasm by 14-3-3ε, where it regulates neuronal morphology, maturation, cortical connectivity, and calcium signaling.

scholarly journals Gene Deletion Mutants Reveal a Role for Semaphorin Receptors of the Plexin-B Family in Mechanisms Underlying Corticogenesis

2009 ◽  
Vol 30 (3) ◽  
pp. 764-780 ◽  
Author(s):  
A. Hirschberg ◽  
S. Deng ◽  
A. Korostylev ◽  
E. Paldy ◽  
M. R. Costa ◽  
...  
Keyword(s):  
Cortical Neurons ◽  
Ex Vivo ◽  
Time Windows ◽  
Expression Patterns ◽  
Cortical Development ◽  
Critical Time ◽  
Dependent Manner ◽  
Semaphorin 4D ◽  
Developing Neurons

ABSTRACT Semaphorins and their receptors, plexins, are emerging as key regulators of various aspects of neural and nonneural development. Semaphorin 4D (Sema4D) and B-type plexins demonstrate distinct expression patterns over critical time windows during the development of the murine neocortex. Here, analysis of mice genetically lacking plexin-B1 or plexin-B2 revealed the significance of Sema4D-plexin-B signaling in cortical development. Deficiency of plexin-B2 resulted in abnormal cortical layering and defective migration and differentiation of several subtypes of cortical neurons, including Cajal-Retzius cells, GABAergic interneurons, and principal cells in vivo. In contrast, a lack of plexin-B1 did not impact on cortical development in vivo. In various ex vivo assays on embryonic forebrain, Sema4D enhanced the radial and tangential migration of developing neurons in a plexin-B2-dependent manner. These results suggest that Sema4D-plexin-B2 interactions regulate mechanisms underlying cell specification, differentiation, and migration during corticogenesis.

scholarly journals Loss of EPAC2 results in altered synaptic composition of dendritic spines and excitatory and inhibitory balance

2019 ◽  
Author(s):  
Kelly A Jones ◽  
Michiko Sumiya ◽  
Kevin M Woolfrey ◽  
Deepak P Srivastava ◽  
Peter Penzes
Keyword(s):  
Ampa Receptors ◽  
Cortical Neurons ◽  
Glutamate Transporter ◽  
Autism Spectrum ◽  
Small Gtpase ◽  
Anterior Cingulate ◽  
Synaptic Proteins ◽  
Inhibitory Synapses ◽  
Nucleotide Exchange

EPAC2 is a guanine nucleotide exchange factor that regulates GTPase activity of the small GTPase Rap and Ras) and is highly enriched at synapses. Activation of EPAC2 has been shown to induce dendritic spine shrinkage and increase spine motility, effects that are necessary for synaptic plasticity. These morphological effects are dysregulated by rare mutations of EPAC2 associated with autism spectrum disorders. In addition, EPAC2 destabilizes synapses through the removal of synaptic GluA2/3-containing AMPA receptors. Previous work has shown that Epac2 knockout mice (Epac2-/-) display abnormal social interactions, as well as gross disorganization of the frontal cortex and abnormal spine motility in vivo. In this study we sought to further understand the cellular consequences of knocking out Epac2 on the development of neuronal and synaptic structure and organization of cortical neurons. Using primary cortical neurons generated from Epac2+/+ or Epac2-/- mice, we confirm that EPAC2 is required for cAMP-dependent spine shrinkage. Neurons from Epac2-/- mice also displayed increased synaptic expression of GluA2/3-containing AMPA receptors, as well as of the adhesion protein N-cadherin. Intriguingly, analysis of excitatory and inhibitory synaptic proteins revealed that loss of EPAC2 resulted in altered of expression of vesicular glutamate transporter 1 (VGluT1) and vesicular GABA transporter (VGAT), indicating a potential imbalance in excitatory/inhibitory inputs onto neurons. Finally, examination of cortical neurons located within the anterior cingulate cortex further revealed subtle deficits in the establishment of dendritic arborization in vivo. These data provide evidence that EPAC2 is required for the correct composition of synapses and that loss of this protein could result in an imbalance of excitatory and inhibitory synapses.

scholarly journals Dynein activating adaptor BICD2 controls radial migration of upper-layer cortical neurons in vivo

2019 ◽  
Vol 7 (1) ◽  
Author(s):  
Lena Will ◽  
Sybren Portegies ◽  
Jasper van Schelt ◽  
Merel van Luyk ◽  
Dick Jaarsma ◽  
...  
Keyword(s):  
Cortical Neuron ◽  
Cortical Neurons ◽  
Cortical Development ◽  
Adaptor Protein ◽  
Cortical Plate ◽  
Neuron Migration ◽  
Knock Out ◽  
Radial Migration

Abstract For the proper organization of the six-layered mammalian neocortex it is required that neurons migrate radially from their place of birth towards their designated destination. The molecular machinery underlying this neuronal migration is still poorly understood. The dynein-adaptor protein BICD2 is associated with a spectrum of human neurological diseases, including malformations of cortical development. Previous studies have shown that knockdown of BICD2 interferes with interkinetic nuclear migration in radial glial progenitor cells, and that Bicd2-deficient mice display an altered laminar organization of the cerebellum and the neocortex. However, the precise in vivo role of BICD2 in neocortical development remains unclear. By comparing cell-type specific conditional Bicd2 knock-out mice, we found that radial migration in the cortex predominantly depends on BICD2 function in post-mitotic neurons. Neuron-specific Bicd2 cKO mice showed severely impaired radial migration of late-born upper-layer neurons. BICD2 depletion in cortical neurons interfered with proper Golgi organization, and neuronal maturation and survival of cortical plate neurons. Single-neuron labeling revealed a specific role of BICD2 in bipolar locomotion. Rescue experiments with wildtype and disease-related mutant BICD2 constructs revealed that a point-mutation in the RAB6/RANBP2-binding-domain, associated with cortical malformation in patients, fails to restore proper cortical neuron migration. Together, these findings demonstrate a novel, cell-intrinsic role of BICD2 in cortical neuron migration in vivo and provide new insights into BICD2-dependent dynein-mediated functions during cortical development.

scholarly journals High-throughput kinase inhibitor screening reveals roles for Aurora and Nuak kinases in neurite initiation and dendritic branching

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Sara M. Blazejewski ◽  
Sarah A. Bennison ◽  
Xiaonan Liu ◽  
Kazuhito Toyo-oka
Keyword(s):  
High Throughput ◽  
Cortical Neurons ◽  
High Throughput Screening ◽  
Kinase Inhibitors ◽  
Kinase Inhibitor ◽  
Traumatic Injury ◽  
Aurora Kinases ◽  
Neurite Initiation ◽  
Dendritic Branching ◽  
Neurite Formation

AbstractKinases are essential regulators of a variety of cellular signaling processes, including neurite formation—a foundational step in neurodevelopment. Aberrant axonal sprouting and failed regeneration of injured axons are associated with conditions like traumatic injury, neurodegenerative disease, and seizures. Investigating the mechanisms underlying neurite formation will allow for identification of potential therapeutics. We used a kinase inhibitor library to screen 493 kinase inhibitors and observed that 45% impacted neuritogenesis in Neuro2a (N-2a) cells. Based on the screening, we further investigated the roles of Aurora kinases A, B, and C and Nuak kinases 1 and 2. The roles of Aurora and Nuak kinases have not been thoroughly studied in the nervous system. Inhibition or overexpression of Aurora and Nuak kinases in primary cortical neurons resulted in various neuromorphological defects, with Aurora A regulating neurite initiation, Aurora B and C regulating neurite initiation and elongation, all Aurora kinases regulating arborization, and all Nuak kinases regulating neurite initiation and elongation and arborization. Our high-throughput screening and analysis of Aurora and Nuak kinases revealed their functions and may contribute to the identification of therapeutics.

scholarly journals Long-Lasting Changes in Glial Cells Isolated From Rats Subjected to the Valproic Acid Model of Autism Spectrum Disorder

2021 ◽  
Vol 12 ◽  
Author(s):  
Marianela Evelyn Traetta ◽  
Nonthué Alejandra Uccelli ◽  
Sandra Cristina Zárate ◽  
Dante Gómez Cuautle ◽  
Alberto Javier Ramos ◽  
...  
Keyword(s):  
Autism Spectrum Disorder ◽  
Valproic Acid ◽  
Cortical Neurons ◽  
Primary Cultures ◽  
Autism Spectrum ◽  
Spectrum Disorder ◽  
Saline Control ◽  
Synaptic Changes

Synaptic alterations concomitant with neuroinflammation have been described in patients and experimental models of autism spectrum disorder (ASD). However, the role of microglia and astroglia in relation to synaptic changes is poorly understood. Male Wistar rats prenatally exposed to valproic acid (VPA, 450 mg/kg, i.p.) or saline (control) at embryonic day 10.5 were used to study synapses, microglia, and astroglia in the prefrontal cortex (PFC) at postnatal days 3 and 35 (PND3 and PND35). Primary cultures of cortical neurons, microglia, and astroglia isolated from control and VPA animals were used to study each cell type individually, neuron-microglia and microglia-astroglia crosstalk. In the PFC of VPA rats, synaptic changes characterized by an increase in the number of excitatory synapses were evidenced at PND3 and persisted until PND35. At PND3, microglia and astroglia from VPA animals were morphologically similar to those of age-matched controls, whereas at PND35, reactive microgliosis and astrogliosis were observed in the PFC of VPA animals. Cortical neurons isolated from VPA rats mimicked in vitro the synaptic pattern seen in vivo. Cortical microglia and astroglia isolated from VPA animals exhibited reactive morphology, increased pro-inflammatory cytokines, and a compromised miRNA processing machinery. Microglia from VPA animals also showed resistance to a phagocytic challenge. In the presence of neurons from VPA animals, microglia isolated from VPA rats revealed a non-reactive morphology and promoted neurite outgrowth, while microglia from control animals displayed a reactive profile and promoted dendritic retraction. In microglia-astroglia co-cultures, microglia from VPA animals displayed a reactive profile and exacerbated astrocyte reactivity. Our study indicates that cortical microglia from VPA animals are insensitive or adapted to neuronal cues expressed by neurons from VPA animals. Further, long-term in vivo microgliosis could be the result of altered microglia-astroglia crosstalk in VPA animals. Thus, our study highlights cortical microglia-astroglia communication as a new mechanism implicated in neuroinflammation in ASD; consequently, we propose that this crosstalk is a potential target for interventions in this disorder.

scholarly journals Regulation of Dendritic Synaptic Morphology and Transcription by the SRF Cofactor MKL/MRTF

2021 ◽  
Vol 14 ◽  
Author(s):  
Akiko Tabuchi ◽  
Daisuke Ihara
Keyword(s):  
Nervous System ◽  
Transcriptional Activation ◽  
Cortical Neurons ◽  
Serum Response Factor ◽  
Autism Spectrum ◽  
Neuronal Morphology ◽  
Fine Tuning ◽  
Actin Binding ◽  
Special Focus ◽  
Dendritic Complexity

Accumulating evidence suggests that the serum response factor (SRF) cofactor megakaryoblastic leukemia (MKL)/myocardin-related transcription factor (MRTF) has critical roles in many physiological and pathological processes in various cell types. MKL/MRTF molecules comprise MKL1/MRTFA and MKL2/MRTFB, which possess actin-binding motifs at the N-terminus, and SRF-binding domains and a transcriptional activation domain (TAD) at the C-terminus. Several studies have reported that, in association with actin rearrangement, MKL/MRTF translocates from the cytoplasm to the nucleus, where it regulates SRF-mediated gene expression and controls cell motility. Therefore, it is important to elucidate the roles of MKL/MRTF in the nervous system with regard to its structural and functional regulation by extracellular stimuli. We demonstrated that MKL/MRTF is highly expressed in the brain, especially the synapses, and is involved in dendritic complexity and dendritic spine maturation. In addition to the positive regulation of dendritic complexity, we identified several MKL/MRTF isoforms that negatively regulate dendritic complexity in cortical neurons. We found that the MKL/MRTF isoforms were expressed differentially during brain development and the impacts of these isoforms on the immediate early genes including Arc/Arg3.1, were different. Here, we review the roles of MKL/MRTF in the nervous system, with a special focus on the MKL/MRTF-mediated fine-tuning of neuronal morphology and gene transcription. In the concluding remarks, we briefly discuss the future perspectives and the possible involvement of MKL/MRTF in neurological disorders such as schizophrenia and autism spectrum disorder.

scholarly journals Homeostatic Plasticity Requires Remodeling of the Homer-Shank Interactome

2020 ◽  
Author(s):  
Whitney E. Heavner ◽  
Haley Speed ◽  
Jonathan D. Lautz ◽  
Edward P. Gniffke ◽  
Karen B. Immendorf ◽  
...  
Keyword(s):  
Protein Interactions ◽  
Cortical Neurons ◽  
Barrel Cortex ◽  
Protein Complexes ◽  
Sensory Deprivation ◽  
Interaction Network ◽  
Autism Spectrum ◽  
Homeostatic Plasticity

AbstractNeurons maintain constant levels of excitability using homeostatic scaling, which adjusts relative synaptic strength in response to large changes in overall activity. It is still unknown how homeostatic scaling affects network-level protein interactions in the synapse despite extensive reporting of individual scaling-associated transcriptomic and proteomic changes. Here, we assessed a glutamatergic synapse protein interaction network (PIN) composed of 380 binary interactions among 21 protein members to identify protein complexes altered by synaptic scaling in vitro and in vivo. In cultured cortical neurons, we observed widespread bidirectional PIN alterations during up- and downscaling that reflected rapid glutamate receptor shuttling via synaptic scaffold remodeling. Sensory deprivation of the barrel cortex caused a PIN response that reflected changes in mGluR tone and NMDAR-dependent metaplasticity, consistent with emerging models of homeostatic plasticity in the barrel cortex that restore excitatory/inhibitory balance. Mice lacking Homer1 or Shank3B did not undergo normal PIN rearrangements, suggesting that these Autism Spectrum Disorder (ASD)-linked proteins serve as structural hubs for synaptic homeostasis. Our approach demonstrates how changes in the protein content of synapses during homeostatic plasticity translate into functional PIN alterations that mediate changes in neuron excitability.

scholarly journals P.135 Autism-associated mutations in SHANK2 increase synaptic connectivity and dendrite complexity in human neurons

2018 ◽  
Vol 45 (s2) ◽  
pp. S52-S52
Author(s):  
K Zaslavsky ◽  
W Zhang ◽  
E Deneault ◽  
M Zhao ◽  
DC Rodrigues ◽  
...  
Keyword(s):  
Cortical Neurons ◽  
Autism Spectrum ◽  
Dermal Fibroblasts ◽  
Neuronal Morphology ◽  
Synaptic Connectivity ◽  
Loss Of Function ◽  
Knock Out ◽  
Electrophysiological Properties ◽  
Dendrite Length ◽  
Human Neurons

Background: Heterozygous loss-of-function mutations in the synaptic scaffolding gene SHANK2 are strongly associated with autism spectrum disorder (ASD). However, their impact on the function of human neurons is unknown. Derivation of induced pluripotent stem cells (iPSC) from affected individuals permits generation of live neurons to answer this question. Methods: We generated iPSCs by reprogramming dermal fibroblasts of neurotypic and ASD-affected donors. To isolate the effect of SHANK2, we used CRISPR/Cas9 to knock out SHANK2 in control iPSCs and correct a heterozygous nonsense mutation in ASD-affected donor iPSCs. We then derived cortical neurons from SOX1+ neural precursor cells differentiated from these iPSCs. Using a novel assay that overcomes line-to-line variability, we compared neuronal morphology, total synapse number, and electrophysiological properties between SHANK2 mutants and controls. Results: Relative to controls, SHANK2 mutant neurons have increased dendrite complexity, dendrite length, total synapse number (1.5-2-fold), and spontaneous excitatory postsynaptic current (sEPSC) frequency (3-7.6-fold). Conclusions: ASD-associated heterozygous loss-of-function mutations in SHANK2 increase synaptic connectivity among human neurons by increasing synapse number and sEPSC frequency. This is partially supported by increased dendrite length and complexity, providing evidence that SHANK2 functions as a suppressor of dendrite branching during neurodevelopment.

scholarly journals High-Throughput Kinase Inhibitor Screening Reveals Roles for Aurora and Nuak Kinases in Neurite Initiation and Dendritic Branching

2020 ◽  
Author(s):  
Sara M. Blazejewski ◽  
Sarah A. Bennison ◽  
Xiaonan Liu ◽  
Kazuhito Toyo-oka
Keyword(s):  
High Throughput ◽  
Cortical Neurons ◽  
High Throughput Screening ◽  
Kinase Inhibitors ◽  
Kinase Inhibitor ◽  
Traumatic Injury ◽  
Aurora Kinases ◽  
Neurite Initiation ◽  
Dendritic Branching ◽  
Neurite Formation

AbstractKinases are essential regulators of a variety of cellular signaling processes, including neurite formation – a foundational step in neurodevelopment. Aberrant axonal sprouting and failed regeneration of injured axons are associated with conditions like traumatic injury, neurodegenerative disease, and seizures. Investigating the mechanisms underlying neurite formation will allow for identification of potential therapeutics. We used a kinase inhibitor library to screen 493 kinase inhibitors and observed that 45% impacted neuritogenesis in Neuro2a (N-2a) cells. Based on the screening, we further investigated the roles of Aurora kinases A, B, and C and Nuak kinases 1 and 2. The roles of Aurora and Nuak kinases have not been thoroughly studied in the nervous system. Inhibition or overexpression of Aurora and Nuak kinases in primary cortical neurons resulted in various neuromorphological defects, with Aurora A regulating neurite initiation, Aurora B and C regulating neurite initiation and elongation, all Aurora kinases regulating arborization, and all Nuak kinases regulating neurite initiation and elongation and arborization. Our high-throughput screening and analysis of Aurora and Nuak kinases revealed their functions and may contribute to the identification of therapeutics.

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