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Maltby CJ, Krans A, Grudzien SJ, Palacios Y, Muiños J, Suárez A, Asher M, Khurana V, Barmada SJ, Dijkstra AA, Todd PK. AAGGG repeat expansions trigger RFC1-independent synaptic dysregulation in human CANVAS Neurons. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.12.13.571345. [PMID: 38168171 PMCID: PMC10760133 DOI: 10.1101/2023.12.13.571345] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2024]
Abstract
Cerebellar ataxia with neuropathy and vestibular areflexia syndrome (CANVAS) is a late onset, recessively inherited neurodegenerative disorder caused by biallelic, non-reference pentameric AAGGG(CCCTT) repeat expansions within the second intron of replication factor complex subunit 1 (RFC1). To investigate how these repeats cause disease, we generated CANVAS patient induced pluripotent stem cell (iPSC) derived neurons (iNeurons) and utilized calcium imaging and transcriptomic analysis to define repeat-elicited gain-of-function and loss-of-function contributions to neuronal toxicity. AAGGG repeat expansions do not alter neuronal RFC1 splicing, expression, or DNA repair pathway functions. In reporter assays, AAGGG repeats are translated into pentapeptide repeat proteins that selectively accumulate in CANVAS patient brains. However, neither these proteins nor repeat RNA foci were detected in iNeurons, and overexpression of these repeats in isolation did not induce neuronal toxicity. CANVAS iNeurons exhibit defects in neuronal development and diminished synaptic connectivity that is rescued by CRISPR deletion of a single expanded allele. These phenotypic deficits were not replicated by knockdown of RFC1 in control neurons and were not rescued by ectopic expression of RFC1. These findings support a repeat-dependent but RFC1-independent cause of neuronal dysfunction in CANVAS, with important implications for therapeutic development in this currently untreatable condition.
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Affiliation(s)
- Connor J. Maltby
- Department of Neurology, University of Michigan, Ann Arbor, MI, USA
| | - Amy Krans
- Department of Neurology, University of Michigan, Ann Arbor, MI, USA
- Ann Arbor Veterans Administration Healthcare, Ann Arbor, MI, USA
| | - Samantha J. Grudzien
- Department of Neurology, University of Michigan, Ann Arbor, MI, USA
- Neuroscience Graduate Program, University of Michigan, Ann Arbor, MI, USA
- Department of Computational Medicine and Bioinformatics, University of Michigan, Ann Arbor, MI, USA
| | - Yomira Palacios
- Department of Neurology, University of Michigan, Ann Arbor, MI, USA
- Postbaccalaureate Research Education Program, University of Michigan, Ann Arbor, MI, USA
| | - Jessica Muiños
- Department of Neurology, University of Michigan, Ann Arbor, MI, USA
- UM SMART Undergraduate Summer Program, University of Michigan, Ann Arbor, MI, USA
| | - Andrea Suárez
- Department of Neurology, University of Michigan, Ann Arbor, MI, USA
- Postbaccalaureate Research Education Program, University of Michigan, Ann Arbor, MI, USA
| | - Melissa Asher
- Department of Neurology, University of Michigan, Ann Arbor, MI, USA
| | - Vikram Khurana
- Department of Neurology, Brigham and Women’s Hospital and Harvard Medical School, Boston, MA, USA
- Broad Institute of MIT and Harvard, Cambridge, MA, USA
| | - Sami J. Barmada
- Department of Neurology, University of Michigan, Ann Arbor, MI, USA
| | - Anke A. Dijkstra
- Department of Pathology, Amsterdam UMC, Amsterdam Neuroscience, Amsterdam, The Netherlands
- Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, The Netherlands
| | - Peter K. Todd
- Department of Neurology, University of Michigan, Ann Arbor, MI, USA
- Ann Arbor Veterans Administration Healthcare, Ann Arbor, MI, USA
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Barsanti L, Birindelli L, Sbrana F, Lombardi G, Gualtieri P. Advanced Microscopy Techniques for Molecular Biophysics. Int J Mol Sci 2023; 24:9973. [PMID: 37373120 DOI: 10.3390/ijms24129973] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2023] [Revised: 05/31/2023] [Accepted: 06/05/2023] [Indexed: 06/29/2023] Open
Abstract
Though microscopy is most often intended as a technique for providing qualitative assessment of cellular and subcellular properties, when coupled with other instruments such as wavelength selectors, lasers, photoelectric devices and computers, it can perform a wide variety of quantitative measurements, which are demanding in establishing relationships between the properties and structures of biological material in all their spatial and temporal complexities. These combinations of instruments are a powerful approach to improve non-destructive investigations of cellular and subcellular properties (both physical and chemical) at a macromolecular scale resolution. Since many subcellular compartments in living cells are characterized by structurally organized molecules, this review deals with three advanced microscopy techniques well-suited for these kind of investigations, i.e., microspectrophotometry (MSP), super-resolution localization microscopy (SRLM) and holotomographic microscopy (HTM). These techniques can achieve an insight view into the role intracellular molecular organizations such as photoreceptive and photosynthetic structures and lipid bodies play in many cellular processes as well as their biophysical properties. Microspectrophotometry uses a set-up based on the combination of a wide-field microscope and a polychromator, which allows the measurement of spectroscopic features such as absorption spectra. Super resolution localization microscopy combines dedicated optics and sophisticated software algorithms to overcome the diffraction limit of light and allow the visualization of subcellular structures and dynamics in greater detail with respect to conventional optical microscopy. Holotomographic microscopy combines holography and tomography techniques into a single microscopy set-up, and allows 3D reconstruction by means of the phase separation of biomolecule condensates. This review is organized in sections, which for each technique describe some general aspects, a peculiar theoretical aspect, a specific experimental configuration and examples of applications (fish and algae photoreceptors, single labeled proteins and endocellular aggregates of lipids).
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Affiliation(s)
- Laura Barsanti
- Istituto di Biofisica, CNR, Via Moruzzi 1, 56124 Pisa, Italy
| | | | | | - Giovanni Lombardi
- Istituto di Scienza e Tecnologia dell'Informazione, CNR, Via Moruzzi 1, 56124 Pisa, Italy
| | - Paolo Gualtieri
- Istituto di Biofisica, CNR, Via Moruzzi 1, 56124 Pisa, Italy
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3
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Petrozziello T, Huntress SS, Castillo-Torres AL, Quinn JP, Connors TR, Auger CA, Mills AN, Kim SE, Liu S, Mahmood F, Boudi A, Wu M, Sapp E, Kivisäkk P, Sunderesh SR, Pouladi MA, Arnold SE, Hyman BT, Rosas HD, DiFiglia M, Pinto RM, Kegel-Gleason K, Sadri-Vakili G. Age-dependent increase in tau phosphorylation at serine 396 in Huntington's disease pre-frontal cortex. MEDRXIV : THE PREPRINT SERVER FOR HEALTH SCIENCES 2023:2023.06.03.23290851. [PMID: 37333415 PMCID: PMC10274990 DOI: 10.1101/2023.06.03.23290851] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/20/2023]
Abstract
Background To date, it is still controversial whether tau phosphorylation plays a role in Huntington's disease (HD), as previous studies demonstrated either no alterations or increases in phosphorylated tau (pTau) in HD post-mortem brain and mouse models. Objectives The goal of this study was to determine whether total tau and pTau levels are altered in HD. Methods Immunohistochemistry, cellular fractionations, and western blots were used to measure tau and pTau levels in a large cohort of HD and control post-mortem prefrontal cortex (PFC). Furthermore, western blots were performed to assess tau, and pTau levels in HD and control isogenic embryonic stem cell (ESC)-derived cortical neurons and neuronal stem cells (NSCs). Similarly, western blots were used to assess tau and pTau in Htt Q111 and transgenic R6/2 mice. Lastly, total tau levels were assessed in HD and healthy control plasma using Quanterix Simoa assay. Results Our results revealed that, while there was no difference in tau or pTau levels in HD PFC compared to controls, tau phosphorylated at S396 levels were increased in PFC samples from HD patients 60 years or older at time of death. Additionally, tau and pTau levels were not changed in HD ESC-derived cortical neurons and NSCs. Similarly, tau or pTau levels were not altered in Htt Q111 and transgenic R6/2 mice compared to wild-type littermates. Lastly, tau levels were not changed in plasma from a small cohort of HD patients compared to controls. Conclusion Together these findings demonstrate that pTau-S396 levels increase significantly with age in HD PFC.
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Zarate N, Gundry K, Yu D, Casby J, Eberly LE, Öz G, Gomez-Pastor R. Neurochemical correlates of synapse density in a Huntington's disease mouse model. J Neurochem 2023; 164:226-241. [PMID: 36272099 PMCID: PMC9892354 DOI: 10.1111/jnc.15714] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2022] [Revised: 10/01/2022] [Accepted: 10/18/2022] [Indexed: 02/04/2023]
Abstract
Striatal medium spiny neurons are highly susceptible in Huntington's disease (HD), resulting in progressive synaptic perturbations that lead to neuronal dysfunction and death. Non-invasive imaging techniques, such as proton magnetic resonance spectroscopy (1 H-MRS), are used in HD mouse models and patients with HD to monitor neurochemical changes associated with neuronal health. However, the association between brain neurochemical alterations and synaptic dysregulation remains unknown, limiting our ability to monitor potential treatments that may affect synapse function. We conducted in vivo longitudinal 1 H-MRS in the striatum followed by ex vivo analyses of excitatory synapse density of two synaptic circuits disrupted in HD, thalamo-striatal (T-S), and cortico-striatal (C-S) pathways, to assess the relationship between neurochemical alterations and changes in synapse density. We used the zQ175(Tg/0) HD mouse model as well as zQ175 mice lacking one allele of CK2α'(zQ175(Tg/0) :CK2α'(+/-) ), a kinase previously shown to regulate synapse function in HD. Longitudinal analyses of excitatory synapse density showed early and sustained reduction in T-S synapses in zQ175 mice, preceding C-S synapse depletion, which was rescued in zQ175:CK2α'(+/-) . Changes in T-S and C-S synapses were accompanied by progressive alterations in numerous neurochemicals between WT and HD mice. Linear regression analyses showed C-S synapse number positively correlated with 1 H-MRS-measured levels of GABA, while T-S synapse number positively correlated with levels of phosphoethanolamine and negatively correlated with total creatine levels. These associations suggest that these neurochemical concentrations measured by 1 H-MRS may facilitate monitoring circuit-specific synaptic dysfunction in the zQ175 mouse model and in other HD pre-clinical studies.
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Affiliation(s)
- Nicole Zarate
- Department of Neuroscience, Medical School, University of Minnesota, Minneapolis, MN, United States
| | - Katherine Gundry
- Center for Magnetic Resonance Research, Department of Radiology, Medical School, University of Minnesota, Minneapolis, MN, United States
| | - Dahyun Yu
- Department of Neuroscience, Medical School, University of Minnesota, Minneapolis, MN, United States
| | - Jordan Casby
- Department of Pharmacology, Medical School, University of Minnesota, Minneapolis, MN, United States
| | - Lynn E Eberly
- Center for Magnetic Resonance Research, Department of Radiology, Medical School, University of Minnesota, Minneapolis, MN, United States.,Division of Biostatistics, School of Public Health, University of Minnesota, Minneapolis, Minnesota
| | - Gülin Öz
- Center for Magnetic Resonance Research, Department of Radiology, Medical School, University of Minnesota, Minneapolis, MN, United States
| | - Rocio Gomez-Pastor
- Department of Neuroscience, Medical School, University of Minnesota, Minneapolis, MN, United States
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Farzana F, McConville MJ, Renoir T, Li S, Nie S, Tran H, Hannan AJ, Hatters DM, Boughton BA. Longitudinal spatial mapping of lipid metabolites reveals pre-symptomatic changes in the hippocampi of Huntington's disease transgenic mice. Neurobiol Dis 2023; 176:105933. [PMID: 36436748 DOI: 10.1016/j.nbd.2022.105933] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2022] [Revised: 11/16/2022] [Accepted: 11/23/2022] [Indexed: 11/26/2022] Open
Abstract
In Huntington's disease (HD), a key pathological feature includes the development of inclusion-bodies of fragments of the mutant huntingtin protein in the neurons of the striatum and hippocampus. To examine the molecular changes associated with inclusion-body formation, we applied MALDI-mass spectrometry imaging and deuterium pulse labelling to determine lipid levels and synthesis rates in the hippocampus of a transgenic mouse model of HD (R6/1 line). The R6/1 HD mice lacked inclusions in the hippocampus at 6 weeks of age (pre-symptomatic), whereas inclusions were pervasive by 16 weeks of age (symptomatic). Hippocampal subfields (CA1, CA3 and DG), which formed the highest density of inclusion formation in the mouse brain showed a reduction in the relative abundance of neuron-enriched lipids that have roles in neurotransmission, synaptic plasticity, neurogenesis, and ER-stress protection. Lipids involved in the adaptive response to ER stress (phosphatidylinositol, phosphatidic acid, and ganglioside classes) displayed increased rates of synthesis in HD mice relative to WT mice at all the ages examined, including prior to the formation of the inclusion bodies. Our findings, therefore, support a role for ER stress occurring pre-symptomatically and potentially contributing to pathological mechanisms underlying HD.
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Affiliation(s)
- Farheen Farzana
- Florey Institute of Neuroscience & Mental Health, The University of Melbourne, Victoria 3010, Australia; Department of Biochemistry and Pharmacology, Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Victoria 3010, Australia
| | - Malcolm J McConville
- Department of Biochemistry and Pharmacology, Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Victoria 3010, Australia; Metabolomics Australia, The University of Melbourne, Victoria 3010, Australia
| | - Thibault Renoir
- Florey Institute of Neuroscience & Mental Health, The University of Melbourne, Victoria 3010, Australia
| | - Shanshan Li
- Florey Institute of Neuroscience & Mental Health, The University of Melbourne, Victoria 3010, Australia
| | - Shuai Nie
- Melbourne Mass Spectrometry and Proteomics Facility, Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Victoria 3010, Australia
| | - Harvey Tran
- Florey Institute of Neuroscience & Mental Health, The University of Melbourne, Victoria 3010, Australia
| | - Anthony J Hannan
- Florey Institute of Neuroscience & Mental Health, The University of Melbourne, Victoria 3010, Australia.
| | - Danny M Hatters
- Department of Biochemistry and Pharmacology, Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Victoria 3010, Australia.
| | - Berin A Boughton
- School of Biosciences, The University of Melbourne, Victoria 3010, Australia; Australian National Phenome Centre, Murdoch University, Murdoch 6150, Western Australia, Australia.
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Simmons DA, Belichenko NP, Longo FM. Pharmacological Co-Activation of TrkB and TrkC Receptor Signaling Ameliorates Striatal Neuropathology and Motor Deficits in Mouse Models of Huntington's Disease. J Huntingtons Dis 2023; 12:215-239. [PMID: 37638447 DOI: 10.3233/jhd-230589] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/29/2023]
Abstract
BACKGROUND Loss of neurotrophic support in the striatum, particularly reduced brain-derived neurotrophic factor (BDNF) levels, contributes importantly to Huntington's disease (HD) pathogenesis. Another neurotrophin (NT), NT-3, is reduced in the cortex of HD patients; however, its role in HD is unknown. BDNF and NT-3 bind with high affinity to the tropomyosin receptor-kinases (Trk) B and TrkC, respectively. Targeting TrkB/TrkC may be an effective HD therapeutic strategy, as multiple links exist between their signaling pathways and HD degenerative mechanisms. We developed a small molecule ligand, LM22B-10, that activates TrkB and TrkC to promote cell survival. OBJECTIVE This study aimed to determine if upregulating TrkB/TrkC signaling with LM22B-10 would alleviate the HD phenotype in R6/2 and Q140 mice. METHODS LM22B-10 was delivered by concomitant intranasal-intraperitoneal routes to R6/2 and Q140 mice and then motor performance and striatal pathology were evaluated. RESULTS NT-3 levels, TrkB/TrkC phosphorylation, and AKT signaling were reduced in the R6/2 striatum; LM22B-10 counteracted these deficits. LM22B-10 also reduced intranuclear huntingtin aggregates, dendritic spine loss, microglial activation, and degeneration of dopamine- and cyclic AMP-regulated phosphoprotein with a molecular weight of 32 kDa (DARPP-32) and parvalbumin-containing neurons in the R6/2 and/or Q140 striatum. Moreover, both HD mouse models showed improved motor performance after LM22B-10 treatment. CONCLUSIONS These results reveal an NT-3/TrkC signaling deficiency in the striatum of R6/2 mice, support the idea that targeting TrkB/TrkC alleviates HD-related neurodegeneration and motor dysfunction, and suggest a novel, disease-modifying, multi-target strategy for treating HD.
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Affiliation(s)
- Danielle A Simmons
- Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, CA, USA
| | - Nadia P Belichenko
- Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, CA, USA
| | - Frank M Longo
- Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, CA, USA
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7
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Petrozziello T, Huntress SS, Castillo-Torres AL, Quinn JP, Connors TR, Auger CA, Mills AN, Kim SE, Liu S, Mahmood F, Boudi A, Wu M, Sapp E, Kivisäkk P, Sunderesh SR, Pouladi MA, Arnold SE, Hyman BT, Rosas HD, DiFiglia M, Mouro Pinto R, Kegel-Gleason K, Sadri-Vakili G. Age-Dependent Increase in Tau Phosphorylation at Serine 396 in Huntington's Disease Prefrontal Cortex. J Huntingtons Dis 2023; 12:267-281. [PMID: 37694372 DOI: 10.3233/jhd-230588] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/12/2023]
Abstract
BACKGROUND To date, it is still controversial whether tau phosphorylation plays a role in Huntington's disease (HD), as previous studies demonstrated either no alterations or increases in phosphorylated tau (pTau) in HD postmortem brain and mouse models. OBJECTIVE The goal of this study was to determine whether total tau and pTau levels are altered in HD. METHODS Immunohistochemistry, cellular fractionations, and western blots were used to measure total tau and pTau levels in a large cohort of HD and control postmortem prefrontal cortex (PFC). Furthermore, western blots were performed to assess tau, and pTau levels in HD and control isogenic embryonic stem cell (ESC)-derived cortical neurons and neuronal stem cells (NSCs). Similarly, western blots were used to assess tau and pTau levels in HttQ111 and transgenic R6/2 mice. Lastly, total tau levels were assessed in HD and healthy control plasma using Quanterix Simoa assay. RESULTS Our results revealed that, while there was no difference in total tau or pTau levels in HD PFC compared to controls, the levels of tau phosphorylated at S396 were increased in PFC samples from HD patients 60 years or older at time of death. Additionally, tau and pTau levels were not changed in HD ESC-derived cortical neurons and NSCs. Similarly, total tau or pTau levels were not altered in HttQ111 and transgenic R6/2 mice compared to wild-type littermates. Lastly, tau levels were not changed in plasma from a small cohort of HD patients compared to controls. CONCLUSIONS Together these findings demonstrate that pTau-S396 levels increase significantly with age in HD PFC.
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Affiliation(s)
- Tiziana Petrozziello
- Sean M. Healey & AMG Center for ALS at Mass General, MassGeneral Brigham, Boston, MA, USA
| | - Sommer S Huntress
- Sean M. Healey & AMG Center for ALS at Mass General, MassGeneral Brigham, Boston, MA, USA
| | | | - James P Quinn
- Department of Neurology, MassGeneral Brigham, Boston, MA, USA
| | | | - Corinne A Auger
- Department of Neurology, MassGeneral Brigham, Boston, MA, USA
| | - Alexandra N Mills
- Sean M. Healey & AMG Center for ALS at Mass General, MassGeneral Brigham, Boston, MA, USA
| | - Spencer E Kim
- Sean M. Healey & AMG Center for ALS at Mass General, MassGeneral Brigham, Boston, MA, USA
| | - Sophia Liu
- Department of Neurology, MassGeneral Brigham, Boston, MA, USA
| | - Farah Mahmood
- Department of Neurology, MassGeneral Brigham, Boston, MA, USA
| | - Adel Boudi
- Department of Neurology, MassGeneral Brigham, Boston, MA, USA
| | - Muzhou Wu
- Center for Genomic Medicine, MassGeneral Brigham, Boston, MA, USA
| | - Ellen Sapp
- Department of Neurology, MassGeneral Brigham, Boston, MA, USA
| | - Pia Kivisäkk
- Department of Neurology, MassGeneral Brigham, Boston, MA, USA
| | | | - Mahmoud A Pouladi
- Department of Medical Genetics, Centre for Molecular Medicine and Therapeutics, British Columbia Children's Hospital Research Institute, University of British Columbia, Vancouver, Canada
| | - Steven E Arnold
- Department of Neurology, MassGeneral Brigham, Boston, MA, USA
| | - Bradley T Hyman
- Department of Neurology, MassGeneral Brigham, Boston, MA, USA
| | - H Diana Rosas
- Department of Neurology, MassGeneral Brigham, Boston, MA, USA
| | - Marian DiFiglia
- Department of Neurology, MassGeneral Brigham, Boston, MA, USA
| | - Ricardo Mouro Pinto
- Department of Neurology, MassGeneral Brigham, Boston, MA, USA
- Center for Genomic Medicine, MassGeneral Brigham, Boston, MA, USA
- Department of Neurology, Harvard Medical School, Boston, MA, USA
| | | | - Ghazaleh Sadri-Vakili
- Sean M. Healey & AMG Center for ALS at Mass General, MassGeneral Brigham, Boston, MA, USA
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McColgan P, Gregory S, Zeun P, Zarkali A, Johnson EB, Parker C, Fayer K, Lowe J, Nair A, Estevez-Fraga C, Papoutsi M, Zhang H, Scahill RI, Tabrizi SJ, Rees G. Neurofilament light-associated connectivity in young-adult Huntington's disease is related to neuronal genes. Brain 2022; 145:3953-3967. [PMID: 35758263 PMCID: PMC9679168 DOI: 10.1093/brain/awac227] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2021] [Revised: 05/27/2022] [Accepted: 06/03/2022] [Indexed: 11/13/2022] Open
Abstract
Upregulation of functional network connectivity in the presence of structural degeneration is seen in the premanifest stages of Huntington's disease (preHD) 10-15 years from clinical diagnosis. However, whether widespread network connectivity changes are seen in gene carriers much further from onset has yet to be explored. We characterized functional network connectivity throughout the brain and related it to a measure of disease pathology burden (CSF neurofilament light, NfL) and measures of structural connectivity in asymptomatic gene carriers, on average 24 years from onset. We related these measurements to estimates of cortical and subcortical gene expression. We found no overall differences in functional (or structural) connectivity anywhere in the brain comparing control and preHD participants. However, increased functional connectivity, particularly between posterior cortical areas, correlated with increasing CSF NfL level in preHD participants. Using the Allen Human Brain Atlas and expression-weighted cell-type enrichment analysis, we demonstrated that this functional connectivity upregulation occurred in cortical regions associated with regional expression of genes specific to neuronal cells. This relationship was validated using single-nucleus RNAseq data from post-mortem Huntington's disease and control brains showing enrichment of neuronal-specific genes that are differentially expressed in Huntington's disease. Functional brain networks in asymptomatic preHD gene carriers very far from disease onset show evidence of upregulated connectivity correlating with increased disease burden. These changes occur among brain areas that show regional expression of genes specific to neuronal GABAergic and glutamatergic cells.
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Affiliation(s)
- Peter McColgan
- Huntington’s Disease Centre, Department of Neurodegenerative disease, UCL Queen Square Institute of Neurology, University College London, London WC1N 3BG, UK
| | - Sarah Gregory
- Huntington’s Disease Centre, Department of Neurodegenerative disease, UCL Queen Square Institute of Neurology, University College London, London WC1N 3BG, UK
| | - Paul Zeun
- Huntington’s Disease Centre, Department of Neurodegenerative disease, UCL Queen Square Institute of Neurology, University College London, London WC1N 3BG, UK
| | - Angeliki Zarkali
- Dementia Research Centre, University College London, London WC1N 3AR, UK
| | - Eileanoir B Johnson
- Huntington’s Disease Centre, Department of Neurodegenerative disease, UCL Queen Square Institute of Neurology, University College London, London WC1N 3BG, UK
| | - Christopher Parker
- Department of Computer Science and Centre for Medical Image Computing, University College London, London WC1V 6LJ, UK
| | - Kate Fayer
- Huntington’s Disease Centre, Department of Neurodegenerative disease, UCL Queen Square Institute of Neurology, University College London, London WC1N 3BG, UK
| | - Jessica Lowe
- Huntington’s Disease Centre, Department of Neurodegenerative disease, UCL Queen Square Institute of Neurology, University College London, London WC1N 3BG, UK
| | - Akshay Nair
- Huntington’s Disease Centre, Department of Neurodegenerative disease, UCL Queen Square Institute of Neurology, University College London, London WC1N 3BG, UK
- Max Planck University College London Centre for Computational Psychiatry and Ageing Research, UCL Queen Square Institute of Neurology, London WC1N 3BG, UK
| | - Carlos Estevez-Fraga
- Huntington’s Disease Centre, Department of Neurodegenerative disease, UCL Queen Square Institute of Neurology, University College London, London WC1N 3BG, UK
| | - Marina Papoutsi
- Huntington’s Disease Centre, Department of Neurodegenerative disease, UCL Queen Square Institute of Neurology, University College London, London WC1N 3BG, UK
| | - Hui Zhang
- Dementia Research Centre, University College London, London WC1N 3AR, UK
| | - Rachael I Scahill
- Huntington’s Disease Centre, Department of Neurodegenerative disease, UCL Queen Square Institute of Neurology, University College London, London WC1N 3BG, UK
| | - Sarah J Tabrizi
- Huntington’s Disease Centre, Department of Neurodegenerative disease, UCL Queen Square Institute of Neurology, University College London, London WC1N 3BG, UK
- Dementia Research Centre, University College London, London WC1N 3AR, UK
| | - Geraint Rees
- University College London Institute of Cognitive Neuroscience, University College London, London WC1N 3AZ, UK
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9
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Liu D, Li J, Rong X, Li J, Peng Y, Shen Q. Cdk5 Promotes Mitochondrial Fission via Drp1 Phosphorylation at S616 in Chronic Ethanol Exposure-Induced Cognitive Impairment. Mol Neurobiol 2022; 59:7075-7094. [PMID: 36083519 DOI: 10.1007/s12035-022-03008-w] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2022] [Accepted: 08/18/2022] [Indexed: 11/25/2022]
Abstract
Excessive alcohol consumption can lead to alterations in brain structure and function, even causing irreversible learning and memory disorders. The hippocampus is one of the most sensitive areas to alcohol neurotoxicity in the brain. Accumulating evidence indicates that mitochondrial dysfunction contributes to alcohol neurotoxicity. However, little is known about the underlying molecular mechanisms. In this study, we found that chronic exposure to ethanol caused abnormal mitochondrial fission/fusion and morphology by activating the mitochondrial fission protein dynamin-related protein 1 (Drp1) and upregulating Drp1 receptors, such as fission protein 1 (Fis1), mitochondrial dynamics protein of 49 kDa (Mid49), and mitochondrial fission factor (Mff), combined with decreasing optic atrophy 1 (Opa1) and mitochondrial fusion protein mitofusin 1 (Mfn1) levels. In addition, mitochondrial division inhibitor 1 (mdivi-1) abrogated ethanol-induced mitochondrial dysfunction and improved hippocampal synapses and cognitive function in ethanol-exposed mice. Chronic ethanol exposure also resulted in cyclin-dependent kinase 5 (Cdk5) overactivation, as shown by the increase in the levels of Cdk5 and its activator P25 in the hippocampus. Furthermore, a Cdk5/P25 inhibitor (roscovitine) or Cdk5 knockdown using small interfering RNA (LVi-Cdk5) exerted neuroprotection by inhibiting abnormal mitochondrial fission through Drp1 phosphorylation at Ser616 and mitochondrial translocation after chronic ethanol exposure. Taken together, the present study demonstrated that inhibition of aberrant Cdk5 activation attenuates hippocampal neuron injury and cognitive deficits induced by chronic exposure to ethanol through Drp1-mediated mitochondrial fission and mitochondrial dysfunction. Interfering with this pathway might serve as a potential therapeutic approach to prevent ethanol-induced neurotoxicity in the brain.
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Affiliation(s)
- Dandan Liu
- Department of Neurology, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, Guangzhou, China
| | - Jiande Li
- Department of Neurology, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, Guangzhou, China
| | - Xiaoming Rong
- Department of Neurology, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, Guangzhou, China
| | - Jie Li
- The Fourth Affiliated Hospital of Guangzhou Medical University, Guangzhou, China
| | - Ying Peng
- Department of Neurology, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, Guangzhou, China.
| | - Qingyu Shen
- Department of Neurology, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, Guangzhou, China.
- The Fourth Affiliated Hospital of Guangzhou Medical University, Guangzhou, China.
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Wennagel D, Braz BY, Capizzi M, Barnat M, Humbert S. Huntingtin coordinates dendritic spine morphology and function through cofilin-mediated control of the actin cytoskeleton. Cell Rep 2022; 40:111261. [PMID: 36044862 DOI: 10.1016/j.celrep.2022.111261] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2021] [Revised: 06/22/2022] [Accepted: 08/04/2022] [Indexed: 11/16/2022] Open
Abstract
Compelling evidence indicates that in Huntington's disease (HD), mutation of huntingtin (HTT) alters several aspects of early brain development such as synaptogenesis. It is not clear to what extent the partial loss of wild-type HTT function contributes to these abnormalities. Here we investigate the function of HTT in the formation of spines. Although larger spines normally correlate with more synaptic activity, cell-autonomous depletion of HTT leads to enlarged spines but reduced excitatory synaptic function. We find that HTT is required for the proper turnover of endogenous actin and to recruit AMPA receptors at active synapses; loss of HTT leads to LIM kinase (LIMK) hyperactivation, which maintains cofilin in its inactive state. HTT therefore influences actin dynamics through the LIMK-cofilin pathway. Loss of HTT uncouples spine structure from synaptic function, which may contribute to the ultimate development of HD symptoms.
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Affiliation(s)
- Doris Wennagel
- University Grenoble Alpes, Inserm, U1216, Grenoble Institute Neurosciences, Bâtiment Edmond J. Safra, Chemin Fortuné Ferrini, 38000 Grenoble, La Tronche, France
| | - Barbara Yael Braz
- University Grenoble Alpes, Inserm, U1216, Grenoble Institute Neurosciences, Bâtiment Edmond J. Safra, Chemin Fortuné Ferrini, 38000 Grenoble, La Tronche, France
| | - Mariacristina Capizzi
- University Grenoble Alpes, Inserm, U1216, Grenoble Institute Neurosciences, Bâtiment Edmond J. Safra, Chemin Fortuné Ferrini, 38000 Grenoble, La Tronche, France; Institut du Cerveau-Paris Brain Institute (ICM), Sorbonne Université, Inserm, CNRS, Hôpital Pitié-Salpêtrière, Paris, France
| | - Monia Barnat
- University Grenoble Alpes, Inserm, U1216, Grenoble Institute Neurosciences, Bâtiment Edmond J. Safra, Chemin Fortuné Ferrini, 38000 Grenoble, La Tronche, France
| | - Sandrine Humbert
- University Grenoble Alpes, Inserm, U1216, Grenoble Institute Neurosciences, Bâtiment Edmond J. Safra, Chemin Fortuné Ferrini, 38000 Grenoble, La Tronche, France; Institut du Cerveau-Paris Brain Institute (ICM), Sorbonne Université, Inserm, CNRS, Hôpital Pitié-Salpêtrière, Paris, France.
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11
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Pérez-Sisqués L, Solana-Balaguer J, Campoy-Campos G, Martín-Flores N, Sancho-Balsells A, Vives-Isern M, Soler-Palazón F, Garcia-Forn M, Masana M, Alberch J, Pérez-Navarro E, Giralt A, Malagelada C. RTP801/REDD1 Is Involved in Neuroinflammation and Modulates Cognitive Dysfunction in Huntington's Disease. Biomolecules 2021; 12:34. [PMID: 35053183 PMCID: PMC8773874 DOI: 10.3390/biom12010034] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2021] [Revised: 12/21/2021] [Accepted: 12/24/2021] [Indexed: 12/03/2022] Open
Abstract
RTP801/REDD1 is a stress-regulated protein whose levels are increased in several neurodegenerative diseases such as Parkinson's, Alzheimer's, and Huntington's diseases (HD). RTP801 downregulation ameliorates behavioral abnormalities in several mouse models of these disorders. In HD, RTP801 mediates mutant huntingtin (mhtt) toxicity in in vitro models and its levels are increased in human iPSCs, human postmortem putamen samples, and in striatal synaptosomes from mouse models of the disease. Here, we investigated the role of RTP801 in the hippocampal pathophysiology of HD. We found that RTP801 levels are increased in the hippocampus of HD patients in correlation with gliosis markers. Although RTP801 expression is not altered in the hippocampus of the R6/1 mouse model of HD, neuronal RTP801 silencing in the dorsal hippocampus with shRNA containing AAV particles ameliorates cognitive alterations. This recovery is associated with a partial rescue of synaptic markers and with a reduction in inflammatory events, especially microgliosis. Altogether, our results indicate that RTP801 could be a marker of hippocampal neuroinflammation in HD patients and a promising therapeutic target of the disease.
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Affiliation(s)
- Leticia Pérez-Sisqués
- Departament de Biomedicina, Facultat de Medicina i Ciències de la Salut, Institut de Neurociències, Universitat de Barcelona, 08036 Barcelona, Spain; (L.P.-S.); (J.S.-B.); (G.C.-C.); (N.M.-F.); (A.S.-B.); (M.V.-I.); (F.S.-P.); (M.G.-F.); (M.M.); (J.A.); (E.P.-N.)
| | - Júlia Solana-Balaguer
- Departament de Biomedicina, Facultat de Medicina i Ciències de la Salut, Institut de Neurociències, Universitat de Barcelona, 08036 Barcelona, Spain; (L.P.-S.); (J.S.-B.); (G.C.-C.); (N.M.-F.); (A.S.-B.); (M.V.-I.); (F.S.-P.); (M.G.-F.); (M.M.); (J.A.); (E.P.-N.)
| | - Genís Campoy-Campos
- Departament de Biomedicina, Facultat de Medicina i Ciències de la Salut, Institut de Neurociències, Universitat de Barcelona, 08036 Barcelona, Spain; (L.P.-S.); (J.S.-B.); (G.C.-C.); (N.M.-F.); (A.S.-B.); (M.V.-I.); (F.S.-P.); (M.G.-F.); (M.M.); (J.A.); (E.P.-N.)
| | - Núria Martín-Flores
- Departament de Biomedicina, Facultat de Medicina i Ciències de la Salut, Institut de Neurociències, Universitat de Barcelona, 08036 Barcelona, Spain; (L.P.-S.); (J.S.-B.); (G.C.-C.); (N.M.-F.); (A.S.-B.); (M.V.-I.); (F.S.-P.); (M.G.-F.); (M.M.); (J.A.); (E.P.-N.)
| | - Anna Sancho-Balsells
- Departament de Biomedicina, Facultat de Medicina i Ciències de la Salut, Institut de Neurociències, Universitat de Barcelona, 08036 Barcelona, Spain; (L.P.-S.); (J.S.-B.); (G.C.-C.); (N.M.-F.); (A.S.-B.); (M.V.-I.); (F.S.-P.); (M.G.-F.); (M.M.); (J.A.); (E.P.-N.)
- Institut d’Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), 08036 Barcelona, Spain
- Centro de Investigación Biomédica en Red Sobre Enfermedades Neurodegenerativas (CIBERNED), 28031 Madrid, Spain
| | - Marcel Vives-Isern
- Departament de Biomedicina, Facultat de Medicina i Ciències de la Salut, Institut de Neurociències, Universitat de Barcelona, 08036 Barcelona, Spain; (L.P.-S.); (J.S.-B.); (G.C.-C.); (N.M.-F.); (A.S.-B.); (M.V.-I.); (F.S.-P.); (M.G.-F.); (M.M.); (J.A.); (E.P.-N.)
| | - Ferran Soler-Palazón
- Departament de Biomedicina, Facultat de Medicina i Ciències de la Salut, Institut de Neurociències, Universitat de Barcelona, 08036 Barcelona, Spain; (L.P.-S.); (J.S.-B.); (G.C.-C.); (N.M.-F.); (A.S.-B.); (M.V.-I.); (F.S.-P.); (M.G.-F.); (M.M.); (J.A.); (E.P.-N.)
| | - Marta Garcia-Forn
- Departament de Biomedicina, Facultat de Medicina i Ciències de la Salut, Institut de Neurociències, Universitat de Barcelona, 08036 Barcelona, Spain; (L.P.-S.); (J.S.-B.); (G.C.-C.); (N.M.-F.); (A.S.-B.); (M.V.-I.); (F.S.-P.); (M.G.-F.); (M.M.); (J.A.); (E.P.-N.)
- Institut d’Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), 08036 Barcelona, Spain
- Centro de Investigación Biomédica en Red Sobre Enfermedades Neurodegenerativas (CIBERNED), 28031 Madrid, Spain
| | - Mercè Masana
- Departament de Biomedicina, Facultat de Medicina i Ciències de la Salut, Institut de Neurociències, Universitat de Barcelona, 08036 Barcelona, Spain; (L.P.-S.); (J.S.-B.); (G.C.-C.); (N.M.-F.); (A.S.-B.); (M.V.-I.); (F.S.-P.); (M.G.-F.); (M.M.); (J.A.); (E.P.-N.)
- Institut d’Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), 08036 Barcelona, Spain
- Centro de Investigación Biomédica en Red Sobre Enfermedades Neurodegenerativas (CIBERNED), 28031 Madrid, Spain
| | - Jordi Alberch
- Departament de Biomedicina, Facultat de Medicina i Ciències de la Salut, Institut de Neurociències, Universitat de Barcelona, 08036 Barcelona, Spain; (L.P.-S.); (J.S.-B.); (G.C.-C.); (N.M.-F.); (A.S.-B.); (M.V.-I.); (F.S.-P.); (M.G.-F.); (M.M.); (J.A.); (E.P.-N.)
- Institut d’Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), 08036 Barcelona, Spain
- Centro de Investigación Biomédica en Red Sobre Enfermedades Neurodegenerativas (CIBERNED), 28031 Madrid, Spain
- Production and Validation Center of Advanced Therapies (Creatio), Faculty of Medicine and Health Science, Universitat de Barcelona, 08036 Barcelona, Spain
| | - Esther Pérez-Navarro
- Departament de Biomedicina, Facultat de Medicina i Ciències de la Salut, Institut de Neurociències, Universitat de Barcelona, 08036 Barcelona, Spain; (L.P.-S.); (J.S.-B.); (G.C.-C.); (N.M.-F.); (A.S.-B.); (M.V.-I.); (F.S.-P.); (M.G.-F.); (M.M.); (J.A.); (E.P.-N.)
- Institut d’Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), 08036 Barcelona, Spain
- Centro de Investigación Biomédica en Red Sobre Enfermedades Neurodegenerativas (CIBERNED), 28031 Madrid, Spain
| | - Albert Giralt
- Departament de Biomedicina, Facultat de Medicina i Ciències de la Salut, Institut de Neurociències, Universitat de Barcelona, 08036 Barcelona, Spain; (L.P.-S.); (J.S.-B.); (G.C.-C.); (N.M.-F.); (A.S.-B.); (M.V.-I.); (F.S.-P.); (M.G.-F.); (M.M.); (J.A.); (E.P.-N.)
- Institut d’Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), 08036 Barcelona, Spain
- Centro de Investigación Biomédica en Red Sobre Enfermedades Neurodegenerativas (CIBERNED), 28031 Madrid, Spain
- Production and Validation Center of Advanced Therapies (Creatio), Faculty of Medicine and Health Science, Universitat de Barcelona, 08036 Barcelona, Spain
| | - Cristina Malagelada
- Departament de Biomedicina, Facultat de Medicina i Ciències de la Salut, Institut de Neurociències, Universitat de Barcelona, 08036 Barcelona, Spain; (L.P.-S.); (J.S.-B.); (G.C.-C.); (N.M.-F.); (A.S.-B.); (M.V.-I.); (F.S.-P.); (M.G.-F.); (M.M.); (J.A.); (E.P.-N.)
- Centro de Investigación Biomédica en Red Sobre Enfermedades Neurodegenerativas (CIBERNED), 28031 Madrid, Spain
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12
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Decet M, Verstreken P. Presynaptic Autophagy and the Connection With Neurotransmission. Front Cell Dev Biol 2021; 9:790721. [PMID: 34988081 PMCID: PMC8722708 DOI: 10.3389/fcell.2021.790721] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2021] [Accepted: 12/01/2021] [Indexed: 01/14/2023] Open
Abstract
Autophagy is an evolutionary conserved catabolic pathway essential for the maintenance of cellular homeostasis. Defective proteins and organelles are engulfed by autophagosomal membranes which fuse with lysosomes for cargo degradation. In neurons, the orchestrated progression of autophagosome formation and maturation occurs in distinct subcellular compartments. For synapses, the distance from the soma and the oxidative stress generated during intense neuronal activity pose a challenge to maintain protein homeostasis. Autophagy constitutes a crucial mechanism for proper functioning of this unique and vulnerable cellular compartment. We are now beginning to understand how autophagy is regulated at pre-synaptic terminals and how this pathway, when imbalanced, impacts on synaptic function and -ultimately- neuronal survival. We review here the current state of the art of "synaptic autophagy", with an emphasis on the biogenesis of autophagosomes at the pre-synaptic compartment. We provide an overview of the existing knowledge on the signals inducing autophagy at synapses, highlight the interplay between autophagy and neurotransmission, and provide perspectives for future research.
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Affiliation(s)
- Marianna Decet
- VIB-KU Leuven Center for Brain & Disease Research, Leuven, Belgium
- KU Leuven, Department of Neurosciences, Leuven Brain Institute, Mission Lucidity, Leuven, Belgium
| | - Patrik Verstreken
- VIB-KU Leuven Center for Brain & Disease Research, Leuven, Belgium
- KU Leuven, Department of Neurosciences, Leuven Brain Institute, Mission Lucidity, Leuven, Belgium
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13
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Aleksejenko N, Heller J. Super-resolution imaging to reveal the nanostructure of tripartite synapses. Neuronal Signal 2021; 5:NS20210003. [PMID: 34737894 PMCID: PMC8536832 DOI: 10.1042/ns20210003] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2021] [Revised: 09/24/2021] [Accepted: 09/28/2021] [Indexed: 12/13/2022] Open
Abstract
Even though neurons are the main drivers of information processing in the brain and spinal cord, other cell types are important to mediate adequate flow of information. These include electrically passive glial cells such as microglia and astrocytes, which recently emerged as active partners facilitating proper signal transduction. In disease, these cells undergo pathophysiological changes that propel disease progression and change synaptic connections and signal transmission. In the healthy brain, astrocytic processes contact pre- and postsynaptic structures. These processes can be nanoscopic, and therefore only electron microscopy has been able to reveal their structure and morphology. However, electron microscopy is not suitable in revealing dynamic changes, and it is labour- and time-intensive. The dawn of super-resolution microscopy, techniques that 'break' the diffraction limit of conventional light microscopy, over the last decades has enabled researchers to reveal the nanoscopic synaptic environment. In this review, we highlight and discuss recent advances in our understanding of the nano-world of the so-called tripartite synapses, the relationship between pre- and postsynapse as well as astrocytic processes. Overall, novel super-resolution microscopy methods are needed to fully illuminate the intimate relationship between glia and neuronal cells that underlies signal transduction in the brain and that might be affected in diseases such as Alzheimer's disease and epilepsy.
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Affiliation(s)
- Natalija Aleksejenko
- School of Biotechnology and National Institute for Cellular Biotechnology (NICB), Dublin City University, Glasnevin, Ireland
| | - Janosch P. Heller
- School of Biotechnology and National Institute for Cellular Biotechnology (NICB), Dublin City University, Glasnevin, Ireland
- Queen Square Institute of Neurology, University College London, London, United Kingdom
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14
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Barron JC, Hurley EP, Parsons MP. Huntingtin and the Synapse. Front Cell Neurosci 2021; 15:689332. [PMID: 34211373 PMCID: PMC8239291 DOI: 10.3389/fncel.2021.689332] [Citation(s) in RCA: 36] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2021] [Accepted: 05/24/2021] [Indexed: 12/16/2022] Open
Abstract
Huntington disease (HD) is a monogenic disease that results in a combination of motor, psychiatric and cognitive symptoms. HD is caused by a CAG trinucleotide repeat expansion in the huntingtin (HTT) gene, which results in the production of a pathogenic mutant HTT protein (mHTT). Although there is no cure at present for HD, a number of RNA-targeting therapies have recently entered clinical trials which aim to lower mHTT production through the use of antisense oligonucleotides (ASOs) and RNAi. However, many of these treatment strategies are non-selective in that they cannot differentiate between non-pathogenic wild type HTT (wtHTT) and the mHTT variant. As HD patients are already born with decreased levels of wtHTT, these genetic therapies may result in critically low levels of wtHTT. The consequence of wtHTT reduction in the adult brain is currently under debate, and here we argue that wtHTT loss is not well-tolerated at the synaptic level. Synaptic dysfunction is an extremely sensitive measure of subsequent cell death, and is known to precede neurodegeneration in numerous brain diseases including HD. The present review focuses on the prominent role of wtHTT at the synapse and considers the consequences of wtHTT loss on both pre- and postsynaptic function. We discuss how wtHTT is implicated in virtually all major facets of synaptic neurotransmission including anterograde and retrograde transport of proteins to/from terminal buttons and dendrites, neurotransmitter release, endocytic vesicle recycling, and postsynaptic receptor localization and recycling. We conclude that wtHTT presence is essential for proper synaptic function.
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Affiliation(s)
- Jessica C Barron
- Division of Biomedical Sciences, Faculty of Medicine, Memorial University, St. John's, NL, Canada
| | - Emily P Hurley
- Division of Biomedical Sciences, Faculty of Medicine, Memorial University, St. John's, NL, Canada
| | - Matthew P Parsons
- Division of Biomedical Sciences, Faculty of Medicine, Memorial University, St. John's, NL, Canada
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