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Gordon A, Geschwind DH. Human in vitro models for understanding mechanisms of autism spectrum disorder. Mol Autism 2020; 11:26. [PMID: 32299488 PMCID: PMC7164291 DOI: 10.1186/s13229-020-00332-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2019] [Accepted: 04/01/2020] [Indexed: 02/06/2023] Open
Abstract
Early brain development is a critical epoch for the development of autism spectrum disorder (ASD). In vivo animal models have, until recently, been the principal tool used to study early brain development and the changes occurring in neurodevelopmental disorders such as ASD. In vitro models of brain development represent a significant advance in the field. Here, we review the main methods available to study human brain development in vitro and the applications of these models for studying ASD and other psychiatric disorders. We discuss the main findings from stem cell models to date focusing on cell cycle and proliferation, cell death, cell differentiation and maturation, and neuronal signaling and synaptic stimuli. To be able to generalize the results from these studies, we propose a framework of experimental design and power considerations for using in vitro models to study ASD. These include both technical issues such as reproducibility and power analysis and conceptual issues such as the brain region and cell types being modeled.
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Affiliation(s)
- Aaron Gordon
- Department of Neurology, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA, USA
| | - Daniel H Geschwind
- Department of Neurology, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA, USA.
- Program in Neurobehavioral Genetics, Semel Institute, David Geffen School of Medicine, University of California, Los Angeles, CA, USA.
- Center for Autism Research and Treatment, Semel Institute, David Geffen School of Medicine, University of California, Los Angeles, CA, USA.
- Department of Human Genetics, David Geffen School of Medicine, University of California, Los Angeles, CA, USA.
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102
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Beckner ME. A roadmap for potassium buffering/dispersion via the glial network of the CNS. Neurochem Int 2020; 136:104727. [PMID: 32194142 DOI: 10.1016/j.neuint.2020.104727] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2019] [Revised: 03/08/2020] [Accepted: 03/09/2020] [Indexed: 12/19/2022]
Abstract
Glia use multiple mechanisms to mediate potassium fluxes that support neuronal function. In addition to changes in potassium levels within synapses, these ions are dynamically dispersed through the interstitial parenchyma, perivascular spaces, leptomeninges, cerebrospinal fluid, choroid plexus, blood, vitreous, and endolymph. Neural circuits drive diversity in the glia that buffer potassium and this is reciprocal. Glia mediate buffering of potassium locally at glial-neuronal interfaces and via widespread networked connections. Control of potassium levels in the central nervous system is mediated by mechanisms operating at various loci with complexity that is difficult to model. However, major components of networked glial buffering are known. The role that potassium buffering plays in homeostasis of the CNS underlies some pathologic phenomena. An overview of potassium fluxes in the CNS is relevant for understanding consequences of pathogenic sequence variants in genes that encode potassium buffering proteins. Potassium flows in the CNS are described as follows: K1, the coordinated potassium fluxes within the astrocytic cradle around the synapse; K2, temporary storage of potassium within astrocytic processes in proposed microdomains; K3, potassium fluxes between oligodendrocytes and astrocytes; K4, potassium fluxes between astrocytes; K5, astrocytic potassium flux mediation of neurovasular coupling; K6, CSF delivery of potassium to perivascular spaces with dispersion to interstitial fluid between astrocytic endfeet; K7, astrocytic delivery of potassium to CSF and K8, choroid plexus (modified glia) regulation of potassium at the blood-CSF barrier. Components, mainly potassium channels, transporters, connexins and modulators, and the pathogenic sequence variants of their genes with the associated diseases are described.
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Affiliation(s)
- Marie E Beckner
- School of Biomedical Sciences, Kent State University, Kent, OH, USA.
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103
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Guet-McCreight A, Skinner FK. Computationally going where experiments cannot: a dynamical assessment of dendritic ion channel currents during in vivo-like states. F1000Res 2020; 9:180. [PMID: 32595950 PMCID: PMC7309567 DOI: 10.12688/f1000research.22584.2] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 06/08/2020] [Indexed: 12/21/2022] Open
Abstract
Background: Despite technological advances, how specific cell types are involved in brain function remains shrouded in mystery. Further, little is known about the contribution of different ion channel currents to cell excitability across different neuronal subtypes and their dendritic compartments
in vivo. The picture that we do have is largely based on somatic recordings performed
in vitro. Uncovering
dendritic ion channel current contributions in neuron subtypes that represent a minority of the neuronal population is not currently a feasible task using purely experimental means. Methods: We employ two morphologically-detailed multi-compartment models of a specific type of inhibitory interneuron, the oriens lacunosum moleculare (OLM) cell. The OLM cell is a well-studied cell type in CA1 hippocampus that is important in gating sensory and contextual information. We create
in vivo-like states for these cellular models by including levels of synaptic bombardment that would occur
in vivo. Using visualization tools and analyses we assess the ion channel current contribution profile across the different somatic and dendritic compartments of the models. Results: We identify changes in dendritic excitability, ion channel current contributions and co-activation patterns between
in vitro and
in vivo-like states. Primarily, we find that the relative timing between ion channel currents are mostly invariant between states, but exhibit changes in magnitudes and decreased propagation across dendritic compartments. We also find enhanced dendritic hyperpolarization-activated cyclic nucleotide-gated channel (h-channel) activation during
in vivo-like states, which suggests that dendritically located h-channels are functionally important in altering signal propagation in the behaving animal. Conclusions: Overall, we have demonstrated, using computational modelling, the dynamical changes that can occur to ion channel mechanisms governing neuronal spiking. Simultaneous access to dendritic compartments during simulated
in vivo states shows that the magnitudes of some ion channel current contributions are differentially altered during
in vivo-like states relative to
in vitro.
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Affiliation(s)
- Alexandre Guet-McCreight
- Krembil Research Institute, University Health Network, Toronto, ON, M5T 0S8, Canada.,Department of Physiology, University of Toronto, Toronto, ON, Canada
| | - Frances K Skinner
- Krembil Research Institute, University Health Network, Toronto, ON, M5T 0S8, Canada.,Departments of Medicine (Neurology) and Physiology, University of Toronto, Toronto, ON, Canada
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104
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Buel GR, Chen X, Chari R, O'Neill MJ, Ebelle DL, Jenkins C, Sridharan V, Tarasov SG, Tarasova NI, Andresson T, Walters KJ. Structure of E3 ligase E6AP with a proteasome-binding site provided by substrate receptor hRpn10. Nat Commun 2020; 11:1291. [PMID: 32157086 PMCID: PMC7064531 DOI: 10.1038/s41467-020-15073-7] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2019] [Accepted: 02/15/2020] [Indexed: 12/16/2022] Open
Abstract
Regulated proteolysis by proteasomes involves ~800 enzymes for substrate modification with ubiquitin, including ~600 E3 ligases. We report here that E6AP/UBE3A is distinguished from other E3 ligases by having a 12 nM binding site at the proteasome contributed by substrate receptor hRpn10/PSMD4/S5a. Intrinsically disordered by itself, and previously uncharacterized, the E6AP-binding domain in hRpn10 locks into a well-defined helical structure to form an intermolecular 4-helix bundle with the E6AP AZUL, which is unique to this E3. We thus name the hRpn10 AZUL-binding domain RAZUL. We further find in human cells that loss of RAZUL by CRISPR-based gene editing leads to loss of E6AP at proteasomes. Moreover, proteasome-associated ubiquitin is reduced following E6AP knockdown or displacement from proteasomes, suggesting that E6AP ubiquitinates substrates at or for the proteasome. Altogether, our findings indicate E6AP to be a privileged E3 for the proteasome, with a dedicated, high affinity binding site contributed by hRpn10.
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Affiliation(s)
- Gwen R Buel
- Protein Processing Section, Structural Biophysics Laboratory, Center for Cancer Research, National Cancer Institute, Frederick, MD, 21702, USA
| | - Xiang Chen
- Protein Processing Section, Structural Biophysics Laboratory, Center for Cancer Research, National Cancer Institute, Frederick, MD, 21702, USA.
| | - Raj Chari
- Genome Modification Core, Frederick National Laboratory for Cancer Research, Frederick, MD, 21702, USA
| | - Maura J O'Neill
- Protein Characterization Laboratory, Frederick National Laboratory for Cancer Research, Frederick, MD, 21702, USA
| | - Danielle L Ebelle
- Protein Processing Section, Structural Biophysics Laboratory, Center for Cancer Research, National Cancer Institute, Frederick, MD, 21702, USA
| | - Conor Jenkins
- Protein Characterization Laboratory, Frederick National Laboratory for Cancer Research, Frederick, MD, 21702, USA
| | - Vinidhra Sridharan
- Protein Processing Section, Structural Biophysics Laboratory, Center for Cancer Research, National Cancer Institute, Frederick, MD, 21702, USA
| | - Sergey G Tarasov
- Biophysics Resource, Structural Biophysics Laboratory, Center for Cancer Research, National Cancer Institute, Frederick, MD, 21702, USA
| | - Nadya I Tarasova
- Laboratory of Cancer Immunometabolism, Center for Cancer Research, National Cancer Institute, Frederick, MD, 21702, USA
| | - Thorkell Andresson
- Protein Characterization Laboratory, Frederick National Laboratory for Cancer Research, Frederick, MD, 21702, USA
| | - Kylie J Walters
- Protein Processing Section, Structural Biophysics Laboratory, Center for Cancer Research, National Cancer Institute, Frederick, MD, 21702, USA.
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