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Ansari U, Chen V, Sedighi R, Syed B, Muttalib Z, Ansari K, Ansari F, Nadora D, Razick D, Lui F. Role of the UNC13 family in human diseases: A literature review. AIMS Neurosci 2023; 10:388-400. [PMID: 38188011 PMCID: PMC10767061 DOI: 10.3934/neuroscience.2023029] [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: 09/15/2023] [Revised: 11/28/2023] [Accepted: 12/01/2023] [Indexed: 01/09/2024] Open
Abstract
This literature review explores the pivotal roles of the Uncoordinated-13 (UNC13) protein family, encompassing UNC13A, UNC13B, UNC13C, and UNC13D, in the pathogenesis of various human diseases. These proteins, which are evolutionarily conserved and crucial for synaptic vesicle priming and exocytosis, have been implicated in a range of disorders, spanning from neurodegenerative diseases like amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) to immune-related conditions such as familial hemophagocytic lymphohistiocytosis (FHL). The involvement of UNC13A in neurotransmitter release and synaptic plasticity is linked to ALS and FTD, with genetic variations affecting disease progression. UNC13B, which is closely related to UNC13A, plays a role in autism spectrum disorders (ASD), epilepsy, and schizophrenia. UNC13C is implicated in oral squamous cell carcinoma (OSCC) and hepatocellular carcinoma (HCC), and has a neuroprotective role in Alzheimer's disease (AD). UNC13D has an essential role in immune cell function, making it a key player in FHL. This review highlights the distinct molecular functions of each UNC13 family member and their implications in disease contexts, shedding light on potential therapeutic strategies and avenues for future research. Understanding these proteins' roles offers new insights into the management and treatment of neurological and immunological disorders.
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Affiliation(s)
- Ubaid Ansari
- California Northstate University College of Medicine, USA
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2
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Jun S, Kim M, Park H, Hwang E, Yamamoto Y, Tanaka-Yamamoto K. Organization of Purkinje cell development by neuronal MEGF11 in cerebellar granule cells. Cell Rep 2023; 42:113137. [PMID: 37708022 DOI: 10.1016/j.celrep.2023.113137] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2023] [Revised: 07/24/2023] [Accepted: 08/31/2023] [Indexed: 09/16/2023] Open
Abstract
As cerebellar granule cells (GCs) coordinate the formation of regular cerebellar networks during postnatal development, molecules in GCs are expected to be involved. Here, we test the effects of the knockdown (KD) of multiple epidermal growth factor-like domains protein 11 (MEGF11), which is a homolog of proteins mediating astrocytic phagocytosis but is substantially increased at the later developmental stages of GCs on cerebellar development. MEGF11-KD in GCs of developing mice results in abnormal cerebellar structures, including extensively ectopic Purkinje cell (PC) somas, and in impaired motor functions. MEGF11-KD also causes abnormally asynchronous synaptic release from GC axons, parallel fibers, before the appearance of abnormal cerebellar structures. Interestingly, blockade of this abnormal synaptic release restores most of the cerebellar structures. Thus, apart from phagocytic functions of its related homologs in astrocytes, MEGF11 in GCs promotes proper PC development and cerebellar network formation by regulating immature synaptic transmission.
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Affiliation(s)
- Soyoung Jun
- Brain Science Institute, Korea Institute of Science and Technology (KIST), Seoul 02792, Republic of Korea; Division of Bio-Medical Science and Technology, KIST School, Korea University of Science and Technology (UST), Seoul 02792, Republic of Korea
| | - Muwoong Kim
- Brain Science Institute, Korea Institute of Science and Technology (KIST), Seoul 02792, Republic of Korea; Division of Bio-Medical Science and Technology, KIST School, Korea University of Science and Technology (UST), Seoul 02792, Republic of Korea
| | - Heeyoun Park
- Brain Science Institute, Korea Institute of Science and Technology (KIST), Seoul 02792, Republic of Korea
| | - Eunmi Hwang
- Brain Science Institute, Korea Institute of Science and Technology (KIST), Seoul 02792, Republic of Korea; Division of Bio-Medical Science and Technology, KIST School, Korea University of Science and Technology (UST), Seoul 02792, Republic of Korea
| | - Yukio Yamamoto
- Brain Science Institute, Korea Institute of Science and Technology (KIST), Seoul 02792, Republic of Korea.
| | - Keiko Tanaka-Yamamoto
- Brain Science Institute, Korea Institute of Science and Technology (KIST), Seoul 02792, Republic of Korea; Division of Bio-Medical Science and Technology, KIST School, Korea University of Science and Technology (UST), Seoul 02792, Republic of Korea.
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3
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Nagaraja RY, Stiles MA, Sherry DM, Agbaga MP, Ahmad M. Synapse-Specific Defects in Synaptic Transmission in the Cerebellum of W246G Mutant ELOVL4 Rats-a Model of Human SCA34. J Neurosci 2023; 43:5963-5974. [PMID: 37491316 PMCID: PMC10436685 DOI: 10.1523/jneurosci.0378-23.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2023] [Revised: 06/30/2023] [Accepted: 07/20/2023] [Indexed: 07/27/2023] Open
Abstract
Elongation of very long fatty acids-4 (ELOVL4) mediates biosynthesis of very long chain-fatty acids (VLC-FA; ≥28 carbons). Various mutations in this enzyme result in spinocerebellar ataxia-34 (SCA34). We generated a rat model of human SCA34 by knock-in of a naturally occurring c.736T>G, p.W246G mutation in the Elovl4 gene. Our previous analysis of homozygous W246G mutant ELOVL4 rats (MUT) revealed early-onset gait disturbance and impaired synaptic transmission and plasticity at parallel fiber-Purkinje cell (PF-PC) and climbing fiber-Purkinje cell (CF-PC) synapses. However, the underlying mechanisms that caused these defects remained unknown. Here, we report detailed patch-clamp recordings from Purkinje cells that identify impaired synaptic mechanisms. Our results show that miniature EPSC (mEPSC) frequency is reduced in MUT rats with no change in mEPSC amplitude, suggesting a presynaptic defect of excitatory synaptic transmission on Purkinje cells. We also find alterations in inhibitory synaptic transmission as miniature IPSC (mIPSC) frequency and amplitude are increased in MUT Purkinje cells. Paired-pulse ratio is reduced at PF-PC synapses but increased at CF-PC synapses in MUT rats, which along with results from high-frequency stimulation suggest opposite changes in the release probability at these two synapses. In contrast, we identify exaggerated persistence of EPSC amplitude at CF-PC and PF-PC synapses in MUT cerebellum, suggesting a larger readily releasable pool (RRP) at both synapses. Furthermore, the dendritic spine density is reduced in MUT Purkinje cells. Thus, our results uncover novel mechanisms of action of VLC-FA at cerebellar synapses, and elucidate the synaptic dysfunction underlying SCA34 pathology.SIGNIFICANCE STATEMENT Very long chain-fatty acids (VLC-FA) are an understudied class of fatty acids that are present in the brain. They are critical for brain function as their deficiency caused by mutations in elongation of very long fatty acids-4 (ELOVL4), the enzyme that mediates their biosynthesis, results in neurologic diseases including spinocerebellar ataxia-34 (SCA34), neuroichthyosis, and Stargardt-like macular dystrophy. In this study, we investigated the synaptic defects present in a rat model of SCA34 and identified defects in presynaptic neurotransmitter release and dendritic spine density at synapses in the cerebellum, a brain region involved in motor coordination. These results advance our understanding of the synaptic mechanisms regulated by VLC-FA and describe the synaptic dysfunction that leads to motor incoordination in SCA34.
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Affiliation(s)
- Raghavendra Y Nagaraja
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104
- Department of Ophthalmology, Dean McGee Eye Institute, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104
| | - Megan A Stiles
- Department of Ophthalmology, Dean McGee Eye Institute, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104
| | - David M Sherry
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104
- Department of Neurosurgery, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104
- Department of Pharmaceutical Sciences, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104
| | - Martin-Paul Agbaga
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104
- Department of Ophthalmology, Dean McGee Eye Institute, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104
| | - Mohiuddin Ahmad
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104
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Kim MH, Radaelli C, Thomsen ER, Monet D, Chartrand T, Jorstad NL, Mahoney JT, Taormina MJ, Long B, Baker K, Bakken TE, Campagnola L, Casper T, Clark M, Dee N, D'Orazi F, Gamlin C, Kalmbach BE, Kebede S, Lee BR, Ng L, Trinh J, Cobbs C, Gwinn RP, Keene CD, Ko AL, Ojemann JG, Silbergeld DL, Sorensen SA, Berg J, Smith KA, Nicovich PR, Jarsky T, Zeng H, Ting JT, Levi BP, Lein E. Target cell-specific synaptic dynamics of excitatory to inhibitory neuron connections in supragranular layers of human neocortex. eLife 2023; 12:e81863. [PMID: 37249212 PMCID: PMC10332811 DOI: 10.7554/elife.81863] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2022] [Accepted: 05/29/2023] [Indexed: 05/31/2023] Open
Abstract
Rodent studies have demonstrated that synaptic dynamics from excitatory to inhibitory neuron types are often dependent on the target cell type. However, these target cell-specific properties have not been well investigated in human cortex, where there are major technical challenges in reliably obtaining healthy tissue, conducting multiple patch-clamp recordings on inhibitory cell types, and identifying those cell types. Here, we take advantage of newly developed methods for human neurosurgical tissue analysis with multiple patch-clamp recordings, post-hoc fluorescent in situ hybridization (FISH), machine learning-based cell type classification and prospective GABAergic AAV-based labeling to investigate synaptic properties between pyramidal neurons and PVALB- vs. SST-positive interneurons. We find that there are robust molecular differences in synapse-associated genes between these neuron types, and that individual presynaptic pyramidal neurons evoke postsynaptic responses with heterogeneous synaptic dynamics in different postsynaptic cell types. Using molecular identification with FISH and classifiers based on transcriptomically identified PVALB neurons analyzed by Patch-seq, we find that PVALB neurons typically show depressing synaptic characteristics, whereas other interneuron types including SST-positive neurons show facilitating characteristics. Together, these data support the existence of target cell-specific synaptic properties in human cortex that are similar to rodent, thereby indicating evolutionary conservation of local circuit connectivity motifs from excitatory to inhibitory neurons and their synaptic dynamics.
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Affiliation(s)
- Mean-Hwan Kim
- Allen Institute for Brain ScienceSeattleUnited States
| | | | | | - Deja Monet
- Allen Institute for Brain ScienceSeattleUnited States
| | | | | | | | | | - Brian Long
- Allen Institute for Brain ScienceSeattleUnited States
| | | | | | | | - Tamara Casper
- Allen Institute for Brain ScienceSeattleUnited States
| | - Michael Clark
- Allen Institute for Brain ScienceSeattleUnited States
| | - Nick Dee
- Allen Institute for Brain ScienceSeattleUnited States
| | | | - Clare Gamlin
- Allen Institute for Brain ScienceSeattleUnited States
| | - Brian E Kalmbach
- Allen Institute for Brain ScienceSeattleUnited States
- Department of Physiology & Biophysics, School of Medicine, University of WashingtonSeattleUnited States
| | - Sara Kebede
- Allen Institute for Brain ScienceSeattleUnited States
| | - Brian R Lee
- Allen Institute for Brain ScienceSeattleUnited States
| | - Lindsay Ng
- Allen Institute for Brain ScienceSeattleUnited States
| | - Jessica Trinh
- Allen Institute for Brain ScienceSeattleUnited States
| | | | | | - C Dirk Keene
- Department of Laboratory Medicine & Pathology, School of Medicine, University of WashingtonSeattleUnited States
| | - Andrew L Ko
- Department of Neurological Surgery, School of Medicine, University of WashingtonSeattleUnited States
| | - Jeffrey G Ojemann
- Department of Neurological Surgery, School of Medicine, University of WashingtonSeattleUnited States
| | - Daniel L Silbergeld
- Department of Neurological Surgery, School of Medicine, University of WashingtonSeattleUnited States
| | | | - Jim Berg
- Allen Institute for Brain ScienceSeattleUnited States
| | | | | | - Tim Jarsky
- Allen Institute for Brain ScienceSeattleUnited States
| | - Hongkui Zeng
- Allen Institute for Brain ScienceSeattleUnited States
| | - Jonathan T Ting
- Allen Institute for Brain ScienceSeattleUnited States
- Department of Physiology & Biophysics, School of Medicine, University of WashingtonSeattleUnited States
| | - Boaz P Levi
- Allen Institute for Brain ScienceSeattleUnited States
| | - Ed Lein
- Allen Institute for Brain ScienceSeattleUnited States
- Department of Laboratory Medicine & Pathology, School of Medicine, University of WashingtonSeattleUnited States
- Department of Neurological Surgery, School of Medicine, University of WashingtonSeattleUnited States
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5
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Martín R, Suárez-Pinilla AS, García-Font N, Laguna-Luque ML, López-Ramos JC, Oset-Gasque MJ, Gruart A, Delgado-García JM, Torres M, Sánchez-Prieto J. The activation of mGluR4 rescues parallel fiber synaptic transmission and LTP, motor learning and social behavior in a mouse model of Fragile X Syndrome. Mol Autism 2023; 14:14. [PMID: 37029391 PMCID: PMC10082511 DOI: 10.1186/s13229-023-00547-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2022] [Accepted: 04/03/2023] [Indexed: 04/09/2023] Open
Abstract
BACKGROUND Fragile X syndrome (FXS), the most common inherited intellectual disability, is caused by the loss of expression of the Fragile X Messenger Ribonucleoprotein (FMRP). FMRP is an RNA-binding protein that negatively regulates the expression of many postsynaptic as well as presynaptic proteins involved in action potential properties, calcium homeostasis and neurotransmitter release. FXS patients and mice lacking FMRP suffer from multiple behavioral alterations, including deficits in motor learning for which there is currently no specific treatment. METHODS We performed electron microscopy, whole-cell patch-clamp electrophysiology and behavioral experiments to characterise the synaptic mechanisms underlying the motor learning deficits observed in Fmr1KO mice and the therapeutic potential of positive allosteric modulator of mGluR4. RESULTS We found that enhanced synaptic vesicle docking of cerebellar parallel fiber to Purkinje cell Fmr1KO synapses was associated with enhanced asynchronous release, which not only prevents further potentiation, but it also compromises presynaptic parallel fiber long-term potentiation (PF-LTP) mediated by β adrenergic receptors. A reduction in extracellular Ca2+ concentration restored the readily releasable pool (RRP) size, basal synaptic transmission, β adrenergic receptor-mediated potentiation, and PF-LTP. Interestingly, VU 0155041, a selective positive allosteric modulator of mGluR4, also restored both the RRP size and PF-LTP in mice of either sex. Moreover, when injected into Fmr1KO male mice, VU 0155041 improved motor learning in skilled reaching, classical eyeblink conditioning and vestibuloocular reflex (VOR) tests, as well as the social behavior alterations of these mice. LIMITATIONS We cannot rule out that the activation of mGluR4s via systemic administration of VU0155041 can also affect other brain regions. Further studies are needed to stablish the effect of a specific activation of mGluR4 in cerebellar granule cells. CONCLUSIONS Our study shows that an increase in synaptic vesicles, SV, docking may cause the loss of PF-LTP and motor learning and social deficits of Fmr1KO mice and that the reversal of these changes by pharmacological activation of mGluR4 may offer therapeutic relief for motor learning and social deficits in FXS.
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Affiliation(s)
- Ricardo Martín
- Departamento de Bioquímica y Biología Molecular, Facultad de Veterinaria, Universidad Complutense, Instituto Universitario de Investigación en Neuroquímica, 28040, Madrid, Spain.
- Instituto de Investigación Sanitaria del Hospital Clínico San Carlos, 28040, Madrid, Spain.
- Departamento de Fisiología, Facultad de Medicina, Universidad Complutense, 28040, Madrid, Spain.
| | - Alberto Samuel Suárez-Pinilla
- Departamento de Bioquímica y Biología Molecular, Facultad de Veterinaria, Universidad Complutense, Instituto Universitario de Investigación en Neuroquímica, 28040, Madrid, Spain
- Instituto de Investigación Sanitaria del Hospital Clínico San Carlos, 28040, Madrid, Spain
| | - Nuria García-Font
- Departamento de Bioquímica y Biología Molecular, Facultad de Veterinaria, Universidad Complutense, Instituto Universitario de Investigación en Neuroquímica, 28040, Madrid, Spain
- Instituto de Investigación Sanitaria del Hospital Clínico San Carlos, 28040, Madrid, Spain
- Centre for Discovery Brain Sciences and Simon Initiative for Developing Brain, University of Edinburgh, Edinburgh, EH89JZ, UK
| | | | - Juan C López-Ramos
- Division de Neurociencias, Universidad Pablo de Olavide, 41013, Sevilla, Spain
| | - María Jesús Oset-Gasque
- Instituto de Investigación Sanitaria del Hospital Clínico San Carlos, 28040, Madrid, Spain
- Departamento de Bioquímica, Facultad de Farmacia, Universidad Complutense, Instituto Universitario Investigación en Neuroquímica, 28040, Madrid, Spain
| | - Agnes Gruart
- Division de Neurociencias, Universidad Pablo de Olavide, 41013, Sevilla, Spain
| | | | - Magdalena Torres
- Departamento de Bioquímica y Biología Molecular, Facultad de Veterinaria, Universidad Complutense, Instituto Universitario de Investigación en Neuroquímica, 28040, Madrid, Spain
- Instituto de Investigación Sanitaria del Hospital Clínico San Carlos, 28040, Madrid, Spain
| | - José Sánchez-Prieto
- Departamento de Bioquímica y Biología Molecular, Facultad de Veterinaria, Universidad Complutense, Instituto Universitario de Investigación en Neuroquímica, 28040, Madrid, Spain.
- Instituto de Investigación Sanitaria del Hospital Clínico San Carlos, 28040, Madrid, Spain.
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Uzay B, Kavalali ET. Genetic disorders of neurotransmitter release machinery. Front Synaptic Neurosci 2023; 15:1148957. [PMID: 37066095 PMCID: PMC10102358 DOI: 10.3389/fnsyn.2023.1148957] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2023] [Accepted: 03/10/2023] [Indexed: 04/03/2023] Open
Abstract
Synaptic neurotransmitter release is an evolutionarily conserved process that mediates rapid information transfer between neurons as well as several peripheral tissues. Release of neurotransmitters are ensured by successive events such as synaptic vesicle docking and priming that prepare synaptic vesicles for rapid fusion. These events are orchestrated by interaction of different presynaptic proteins and are regulated by presynaptic calcium. Recent studies have identified various mutations in different components of neurotransmitter release machinery resulting in aberrant neurotransmitter release, which underlie a wide spectrum of psychiatric and neurological symptoms. Here, we review how these genetic alterations in different components of the core neurotransmitter release machinery affect the information transfer between neurons and how aberrant synaptic release affects nervous system function.
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Affiliation(s)
- Burak Uzay
- Vanderbilt Brain Institute, Nashville, TN, United States
- Department of Pharmacology, Vanderbilt University, Nashville, TN, United States
| | - Ege T. Kavalali
- Vanderbilt Brain Institute, Nashville, TN, United States
- Department of Pharmacology, Vanderbilt University, Nashville, TN, United States
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Meunier FA, Hu Z. Functional Roles of UNC-13/Munc13 and UNC-18/Munc18 in Neurotransmission. ADVANCES IN NEUROBIOLOGY 2023; 33:203-231. [PMID: 37615868 DOI: 10.1007/978-3-031-34229-5_8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/25/2023]
Abstract
Neurotransmitters are released from synaptic and secretory vesicles following calcium-triggered fusion with the plasma membrane. These exocytotic events are driven by assembly of a ternary SNARE complex between the vesicle SNARE synaptobrevin and the plasma membrane-associated SNAREs syntaxin and SNAP-25. Proteins that affect SNARE complex assembly are therefore important regulators of synaptic strength. In this chapter, we review our current understanding of the roles played by two SNARE interacting proteins: UNC-13/Munc13 and UNC-18/Munc18. We discuss results from both invertebrate and vertebrate model systems, highlighting recent advances, focusing on the current consensus on molecular mechanisms of action and nanoscale organization, and pointing out some unresolved aspects of their functions.
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Affiliation(s)
- Frédéric A Meunier
- Clem Jones Centre for Ageing Dementia Research (CJCADR), Queensland Brain Institute, The University of Queensland, Brisbane, QLD, Australia.
- School of Biomedical Sciences, The University of Queensland, Brisbane, QLD, Australia.
| | - Zhitao Hu
- Clem Jones Centre for Ageing Dementia Research (CJCADR), Queensland Brain Institute, The University of Queensland, Brisbane, QLD, Australia.
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Tan C, de Nola G, Qiao C, Imig C, Born RT, Brose N, Kaeser PS. Munc13 supports fusogenicity of non-docked vesicles at synapses with disrupted active zones. eLife 2022; 11:79077. [PMID: 36398873 PMCID: PMC9822248 DOI: 10.7554/elife.79077] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2022] [Accepted: 11/17/2022] [Indexed: 11/19/2022] Open
Abstract
Active zones consist of protein scaffolds that are tightly attached to the presynaptic plasma membrane. They dock and prime synaptic vesicles, couple them to voltage-gated Ca2+ channels, and direct neurotransmitter release toward postsynaptic receptor domains. Simultaneous RIM + ELKS ablation disrupts these scaffolds, abolishes vesicle docking, and removes active zone-targeted Munc13, but some vesicles remain releasable. To assess whether this enduring vesicular fusogenicity is mediated by non-active zone-anchored Munc13 or is Munc13-independent, we ablated Munc13-1 and Munc13-2 in addition to RIM + ELKS in mouse hippocampal neurons. The hextuple knockout synapses lacked docked vesicles, but other ultrastructural features were near-normal despite the strong genetic manipulation. Removing Munc13 in addition to RIM + ELKS impaired action potential-evoked vesicle fusion more strongly than RIM + ELKS knockout by further decreasing the releasable vesicle pool. Hence, Munc13 can support some fusogenicity without RIM and ELKS, and presynaptic recruitment of Munc13, even without active zone anchoring, suffices to generate some fusion-competent vesicles.
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Affiliation(s)
- Chao Tan
- Department of Neurobiology, Harvard Medical School, Boston, United States
| | - Giovanni de Nola
- Department of Neurobiology, Harvard Medical School, Boston, United States
| | - Claire Qiao
- Department of Neurobiology, Harvard Medical School, Boston, United States
| | - Cordelia Imig
- Department of Neuroscience, University of Copenhagen, Copenhagen, Denmark.,Department of Molecular Neurobiology, Max Planck Institute for Multidisciplinary Sciences, Goettingen, Germany
| | - Richard T Born
- Department of Neurobiology, Harvard Medical School, Boston, United States
| | - Nils Brose
- Department of Molecular Neurobiology, Max Planck Institute for Multidisciplinary Sciences, Goettingen, Germany
| | - Pascal S Kaeser
- Department of Neurobiology, Harvard Medical School, Boston, United States
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Muacevic A, Adler JR. Homozygous UNC13A Variant in an Infant With Congenital Encephalopathy and Severe Neuromuscular Phenotype: A Case Report With Detailed Central Nervous System Neuropathologic Findings. Cureus 2022; 14:e30774. [PMID: 36447687 PMCID: PMC9701132 DOI: 10.7759/cureus.30774] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/27/2022] [Indexed: 01/25/2023] Open
Abstract
Uncoordinated 13 (UNC13A) affects movement in Caenorhabditis elegans (C. elegans). It is responsible for docking, priming, and stabilizing synaptic vesicle fusion complexes in the neuronal synapse and neuromuscular junction (NMJ). It also plays an important role in central nervous system development. We report the detailed clinical history and central nervous system neuropathologic findings in an infantile case with homozygous UNC13A loss of function variant, in order to advance the understanding of this critically important synaptic vesicle protein. This is the first detailed central nervous system neuropathologic report of this rare case of homozygous UNC13A loss.
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A fluorescent nanosensor paint detects dopamine release at axonal varicosities with high spatiotemporal resolution. Proc Natl Acad Sci U S A 2022; 119:e2202842119. [PMID: 35613050 DOI: 10.1073/pnas.2202842119] [Citation(s) in RCA: 20] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
SignificanceThe neurotransmitter dopamine controls normal behavior and dopaminergic dysfunction is prevalent in multiple brain diseases. To reach a detailed understanding of how dopamine release and signaling are regulated at the subcellular level, we developed a near infrared fluorescent dopamine nanosensor 'paint' (AndromeDA) to directly image dopamine release and its spatiotemporal characteristics. With AndromeDA, we can ascribe discrete DA release events to defined axonal varicosities, directly assess the heterogeneity of DA release events across such release sites, and determine the molecular components of the DA release machinery. AndromeDA thus provides a new method for gaining fundamental insights into the core mechanisms of dopamine release, which with greatly benefit our knowledge of dopamine biology and pathobiology.
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Takikawa K, Nishimune H. Similarity and Diversity of Presynaptic Molecules at Neuromuscular Junctions and Central Synapses. Biomolecules 2022; 12:biom12020179. [PMID: 35204679 PMCID: PMC8961632 DOI: 10.3390/biom12020179] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2021] [Revised: 01/17/2022] [Accepted: 01/19/2022] [Indexed: 12/04/2022] Open
Abstract
Synaptic transmission is essential for controlling motor functions and maintaining brain functions such as walking, breathing, cognition, learning, and memory. Neurotransmitter release is regulated by presynaptic molecules assembled in active zones of presynaptic terminals. The size of presynaptic terminals varies, but the size of a single active zone and the types of presynaptic molecules are highly conserved among neuromuscular junctions (NMJs) and central synapses. Three parameters play an important role in the determination of neurotransmitter release properties at NMJs and central excitatory/inhibitory synapses: the number of presynaptic molecular clusters, the protein families of the presynaptic molecules, and the distance between presynaptic molecules and voltage-gated calcium channels. In addition, dysfunction of presynaptic molecules causes clinical symptoms such as motor and cognitive decline in patients with various neurological disorders and during aging. This review focuses on the molecular mechanisms responsible for the functional similarities and differences between excitatory and inhibitory synapses in the peripheral and central nervous systems, and summarizes recent findings regarding presynaptic molecules assembled in the active zone. Furthermore, we discuss the relationship between functional alterations of presynaptic molecules and dysfunction of NMJs or central synapses in diseases and during aging.
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Affiliation(s)
- Kenji Takikawa
- Laboratory of Neurobiology of Aging, Tokyo Metropolitan Institute of Gerontology, 35-2 Sakaecho, Itabashi-ku, Tokyo 173-0015, Japan;
| | - Hiroshi Nishimune
- Laboratory of Neurobiology of Aging, Tokyo Metropolitan Institute of Gerontology, 35-2 Sakaecho, Itabashi-ku, Tokyo 173-0015, Japan;
- Department of Applied Biological Science, Tokyo University of Agriculture and Technology, 3-8-1 Harumi-cho, Fuchu-shi, Tokyo 183-8538, Japan
- Correspondence: ; Tel.: +81-3-3964-3241
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12
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Banerjee A, Imig C, Balakrishnan K, Kershberg L, Lipstein N, Uronen RL, Wang J, Cai X, Benseler F, Rhee JS, Cooper BH, Liu C, Wojcik SM, Brose N, Kaeser PS. Molecular and functional architecture of striatal dopamine release sites. Neuron 2022; 110:248-265.e9. [PMID: 34767769 PMCID: PMC8859508 DOI: 10.1016/j.neuron.2021.10.028] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2020] [Revised: 09/22/2021] [Accepted: 10/19/2021] [Indexed: 01/21/2023]
Abstract
Despite the importance of dopamine for striatal circuit function, mechanistic understanding of dopamine transmission remains incomplete. We recently showed that dopamine secretion relies on the presynaptic scaffolding protein RIM, indicating that it occurs at active zone-like sites similar to classical synaptic vesicle exocytosis. Here, we establish using a systematic gene knockout approach that Munc13 and Liprin-α, active zone proteins for vesicle priming and release site organization, are important for dopamine secretion. Furthermore, RIM zinc finger and C2B domains, which bind to Munc13 and Liprin-α, respectively, are needed to restore dopamine release after RIM ablation. In contrast, and different from typical synapses, the active zone scaffolds RIM-BP and ELKS, and RIM domains that bind to them, are expendable. Hence, dopamine release necessitates priming and release site scaffolding by RIM, Munc13, and Liprin-α, but other active zone proteins are dispensable. Our work establishes that efficient release site architecture mediates fast dopamine exocytosis.
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Affiliation(s)
- Aditi Banerjee
- Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA
| | - Cordelia Imig
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany
| | | | - Lauren Kershberg
- Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA
| | - Noa Lipstein
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany
| | - Riikka-Liisa Uronen
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany
| | - Jiexin Wang
- Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA
| | - Xintong Cai
- Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA
| | - Fritz Benseler
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany
| | - Jeong Seop Rhee
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany
| | - Benjamin H Cooper
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany
| | - Changliang Liu
- Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA
| | - Sonja M Wojcik
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany
| | - Nils Brose
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany
| | - Pascal S Kaeser
- Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA.
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13
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Hilton BJ, Husch A, Schaffran B, Lin TC, Burnside ER, Dupraz S, Schelski M, Kim J, Müller JA, Schoch S, Imig C, Brose N, Bradke F. An active vesicle priming machinery suppresses axon regeneration upon adult CNS injury. Neuron 2022; 110:51-69.e7. [PMID: 34706221 PMCID: PMC8730507 DOI: 10.1016/j.neuron.2021.10.007] [Citation(s) in RCA: 34] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Revised: 09/03/2021] [Accepted: 10/01/2021] [Indexed: 12/16/2022]
Abstract
Axons in the adult mammalian central nervous system fail to regenerate after spinal cord injury. Neurons lose their capacity to regenerate during development, but the intracellular processes underlying this loss are unclear. We found that critical components of the presynaptic active zone prevent axon regeneration in adult mice. Transcriptomic analysis combined with live-cell imaging revealed that adult primary sensory neurons downregulate molecular constituents of the synapse as they acquire the ability to rapidly grow their axons. Pharmacogenetic reduction of neuronal excitability stimulated axon regeneration after adult spinal cord injury. Genetic gain- and loss-of-function experiments uncovered that essential synaptic vesicle priming proteins of the presynaptic active zone, but not clostridial-toxin-sensitive VAMP-family SNARE proteins, inhibit axon regeneration. Systemic administration of Baclofen reduced voltage-dependent Ca2+ influx in primary sensory neurons and promoted their regeneration after spinal cord injury. These findings indicate that functional presynaptic active zones constitute a major barrier to axon regeneration.
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Affiliation(s)
- Brett J Hilton
- Laboratory of Axonal Growth and Regeneration, German Center for Neurodegenerative Diseases (DZNE), Venusberg Campus 1/99, 53127 Bonn, Germany
| | - Andreas Husch
- Laboratory of Axonal Growth and Regeneration, German Center for Neurodegenerative Diseases (DZNE), Venusberg Campus 1/99, 53127 Bonn, Germany
| | - Barbara Schaffran
- Laboratory of Axonal Growth and Regeneration, German Center for Neurodegenerative Diseases (DZNE), Venusberg Campus 1/99, 53127 Bonn, Germany
| | - Tien-Chen Lin
- Laboratory of Axonal Growth and Regeneration, German Center for Neurodegenerative Diseases (DZNE), Venusberg Campus 1/99, 53127 Bonn, Germany
| | - Emily R Burnside
- Laboratory of Axonal Growth and Regeneration, German Center for Neurodegenerative Diseases (DZNE), Venusberg Campus 1/99, 53127 Bonn, Germany
| | - Sebastian Dupraz
- Laboratory of Axonal Growth and Regeneration, German Center for Neurodegenerative Diseases (DZNE), Venusberg Campus 1/99, 53127 Bonn, Germany
| | - Max Schelski
- Laboratory of Axonal Growth and Regeneration, German Center for Neurodegenerative Diseases (DZNE), Venusberg Campus 1/99, 53127 Bonn, Germany
| | - Jisoo Kim
- Laboratory of Axonal Growth and Regeneration, German Center for Neurodegenerative Diseases (DZNE), Venusberg Campus 1/99, 53127 Bonn, Germany; Department of Stem Cell and Regenerative Biology, Center for Brain Science, and Harvard Stem Cell Institute, Harvard University, Cambridge, MA 02138, USA
| | | | - Susanne Schoch
- Institute of Neuropathology, Medical Faculty, University of Bonn, 53105 Bonn, Germany
| | - Cordelia Imig
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany
| | - Nils Brose
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany
| | - Frank Bradke
- Laboratory of Axonal Growth and Regeneration, German Center for Neurodegenerative Diseases (DZNE), Venusberg Campus 1/99, 53127 Bonn, Germany.
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14
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Sauvola CW, Littleton JT. SNARE Regulatory Proteins in Synaptic Vesicle Fusion and Recycling. Front Mol Neurosci 2021; 14:733138. [PMID: 34421538 PMCID: PMC8377282 DOI: 10.3389/fnmol.2021.733138] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Accepted: 07/20/2021] [Indexed: 01/01/2023] Open
Abstract
Membrane fusion is a universal feature of eukaryotic protein trafficking and is mediated by the soluble N-ethylmaleimide sensitive factor attachment protein receptor (SNARE) family. SNARE proteins embedded in opposing membranes spontaneously assemble to drive membrane fusion and cargo exchange in vitro. Evolution has generated a diverse complement of SNARE regulatory proteins (SRPs) that ensure membrane fusion occurs at the right time and place in vivo. While a core set of SNAREs and SRPs are common to all eukaryotic cells, a specialized set of SRPs within neurons confer additional regulation to synaptic vesicle (SV) fusion. Neuronal communication is characterized by precise spatial and temporal control of SNARE dynamics within presynaptic subdomains specialized for neurotransmitter release. Action potential-elicited Ca2+ influx at these release sites triggers zippering of SNAREs embedded in the SV and plasma membrane to drive bilayer fusion and release of neurotransmitters that activate downstream targets. Here we discuss current models for how SRPs regulate SNARE dynamics and presynaptic output, emphasizing invertebrate genetic findings that advanced our understanding of SRP regulation of SV cycling.
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Affiliation(s)
- Chad W Sauvola
- The Picower Institute for Learning and Memory, Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA, United States
| | - J Troy Littleton
- The Picower Institute for Learning and Memory, Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA, United States.,Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, United States
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15
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Liu H, Li L, Sheoran S, Yu Y, Richmond JE, Xia J, Tang J, Liu J, Hu Z. The M domain in UNC-13 regulates the probability of neurotransmitter release. Cell Rep 2021; 34:108828. [PMID: 33691106 PMCID: PMC8066380 DOI: 10.1016/j.celrep.2021.108828] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2020] [Revised: 12/25/2020] [Accepted: 02/16/2021] [Indexed: 12/30/2022] Open
Abstract
Synapses exhibit multiple forms of short-term plasticities, which have been attributed to the heterogeneity of neurotransmitter release probability. However, the molecular mechanisms that underlie the differential release states remain to be fully elucidated. The Unc-13 proteins appear to have key roles in synaptic function through multiple regulatory domains. Here, we report that deleting the M domain in Caenorhabditis elegans UNC-13MR leads to a significant increase in release probability, revealing an inhibitory function of this domain. The inhibitory effect of this domain is eliminated when the C1 and C2B domains are absent or activated, suggesting that the M domain inhibits release probability by suppressing the activity of C1 and C2B domains. When fused directly to the MUNC2C fragment of UNC-13, the M domain greatly enhances release probability. Thus, our findings reveal a mechanism by which the UNC-13 M domain regulates synaptic transmission and provides molecular insights into the regulation of release probability.
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Affiliation(s)
- Haowen Liu
- Queensland Brain Institute, Clem Jones Centre for Ageing Dementia Research (CJCADR), The University of Queensland, Brisbane, QLD 4072, Australia
| | - Lei Li
- Queensland Brain Institute, Clem Jones Centre for Ageing Dementia Research (CJCADR), The University of Queensland, Brisbane, QLD 4072, Australia
| | - Seema Sheoran
- Department of Biological Sciences, University of Illinois at Chicago, Chicago, IL 60607, USA
| | - Yi Yu
- Queensland Brain Institute, Clem Jones Centre for Ageing Dementia Research (CJCADR), The University of Queensland, Brisbane, QLD 4072, Australia
| | - Janet E Richmond
- Department of Biological Sciences, University of Illinois at Chicago, Chicago, IL 60607, USA
| | - Jingyao Xia
- Queensland Brain Institute, Clem Jones Centre for Ageing Dementia Research (CJCADR), The University of Queensland, Brisbane, QLD 4072, Australia
| | - Jing Tang
- Queensland Brain Institute, Clem Jones Centre for Ageing Dementia Research (CJCADR), The University of Queensland, Brisbane, QLD 4072, Australia
| | - Jie Liu
- Neuroscience Program, Monash Biomedicine Discovery Institute and Department of Anatomy and Developmental Biology, Monash University, Melbourne, VIC 3800, Australia
| | - Zhitao Hu
- Queensland Brain Institute, Clem Jones Centre for Ageing Dementia Research (CJCADR), The University of Queensland, Brisbane, QLD 4072, Australia.
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16
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Canet-Pons J, Sen NE, Arsović A, Almaguer-Mederos LE, Halbach MV, Key J, Döring C, Kerksiek A, Picchiarelli G, Cassel R, René F, Dieterlé S, Fuchs NV, König R, Dupuis L, Lütjohann D, Gispert S, Auburger G. Atxn2-CAG100-KnockIn mouse spinal cord shows progressive TDP43 pathology associated with cholesterol biosynthesis suppression. Neurobiol Dis 2021; 152:105289. [PMID: 33577922 DOI: 10.1016/j.nbd.2021.105289] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2020] [Revised: 12/11/2020] [Accepted: 02/03/2021] [Indexed: 12/12/2022] Open
Abstract
Large polyglutamine expansions in Ataxin-2 (ATXN2) cause multi-system nervous atrophy in Spinocerebellar Ataxia type 2 (SCA2). Intermediate size expansions carry a risk for selective motor neuron degeneration, known as Amyotrophic Lateral Sclerosis (ALS). Conversely, the depletion of ATXN2 prevents disease progression in ALS. Although ATXN2 interacts directly with RNA, and in ALS pathogenesis there is a crucial role of RNA toxicity, the affected functional pathways remain ill defined. Here, we examined an authentic SCA2 mouse model with Atxn2-CAG100-KnockIn for a first definition of molecular mechanisms in spinal cord pathology. Neurophysiology of lower limbs detected sensory neuropathy rather than motor denervation. Triple immunofluorescence demonstrated cytosolic ATXN2 aggregates sequestrating TDP43 and TIA1 from the nucleus. In immunoblots, this was accompanied by elevated CASP3, RIPK1 and PQBP1 abundance. RT-qPCR showed increase of Grn, Tlr7 and Rnaset2 mRNA versus Eif5a2, Dcp2, Uhmk1 and Kif5a decrease. These SCA2 findings overlap well with known ALS features. Similar to other ataxias and dystonias, decreased mRNA levels for Unc80, Tacr1, Gnal, Ano3, Kcna2, Elovl5 and Cdr1 contrasted with Gpnmb increase. Preterminal stage tissue showed strongly activated microglia containing ATXN2 aggregates, with parallel astrogliosis. Global transcriptome profiles from stages of incipient motor deficit versus preterminal age identified molecules with progressive downregulation, where a cluster of cholesterol biosynthesis enzymes including Dhcr24, Msmo1, Idi1 and Hmgcs1 was prominent. Gas chromatography demonstrated a massive loss of crucial cholesterol precursor metabolites. Overall, the ATXN2 protein aggregation process affects diverse subcellular compartments, in particular stress granules, endoplasmic reticulum and receptor tyrosine kinase signaling. These findings identify new targets and potential biomarkers for neuroprotective therapies.
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Affiliation(s)
- Júlia Canet-Pons
- Experimental Neurology, Medical Faculty, Goethe University, 60590 Frankfurt am Main, Germany
| | - Nesli-Ece Sen
- Experimental Neurology, Medical Faculty, Goethe University, 60590 Frankfurt am Main, Germany; Faculty of Biosciences, Goethe University, 60438 Frankfurt am Main, Germany
| | - Aleksandar Arsović
- Experimental Neurology, Medical Faculty, Goethe University, 60590 Frankfurt am Main, Germany
| | - Luis-Enrique Almaguer-Mederos
- Experimental Neurology, Medical Faculty, Goethe University, 60590 Frankfurt am Main, Germany; Center for Investigation and Rehabilitation of Hereditary Ataxias (CIRAH), Holguín, Cuba
| | - Melanie V Halbach
- Experimental Neurology, Medical Faculty, Goethe University, 60590 Frankfurt am Main, Germany
| | - Jana Key
- Experimental Neurology, Medical Faculty, Goethe University, 60590 Frankfurt am Main, Germany; Faculty of Biosciences, Goethe University, 60438 Frankfurt am Main, Germany
| | - Claudia Döring
- Dr. Senckenberg Institute of Pathology, Medical Faculty, Goethe University, 60590 Frankfurt am Main, Germany
| | - Anja Kerksiek
- Institute of Clinical Chemistry and Clinical Pharmacology, University Hospital Bonn, 53127 Bonn, Nordrhein-Westfalen, Germany
| | - Gina Picchiarelli
- UMRS-1118 INSERM, Faculty of Medicine, University of Strasbourg, 67000 Strasbourg, France
| | - Raphaelle Cassel
- UMRS-1118 INSERM, Faculty of Medicine, University of Strasbourg, 67000 Strasbourg, France
| | - Frédérique René
- UMRS-1118 INSERM, Faculty of Medicine, University of Strasbourg, 67000 Strasbourg, France
| | - Stéphane Dieterlé
- UMRS-1118 INSERM, Faculty of Medicine, University of Strasbourg, 67000 Strasbourg, France
| | - Nina V Fuchs
- Host-Pathogen Interactions, Paul-Ehrlich-Institute, 63225 Langen, Germany
| | - Renate König
- Host-Pathogen Interactions, Paul-Ehrlich-Institute, 63225 Langen, Germany
| | - Luc Dupuis
- UMRS-1118 INSERM, Faculty of Medicine, University of Strasbourg, 67000 Strasbourg, France
| | - Dieter Lütjohann
- Institute of Clinical Chemistry and Clinical Pharmacology, University Hospital Bonn, 53127 Bonn, Nordrhein-Westfalen, Germany
| | - Suzana Gispert
- Experimental Neurology, Medical Faculty, Goethe University, 60590 Frankfurt am Main, Germany
| | - Georg Auburger
- Experimental Neurology, Medical Faculty, Goethe University, 60590 Frankfurt am Main, Germany.
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17
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Heterogeneous Presynaptic Distribution of Munc13 Isoforms at Retinal Synapses and Identification of an Unconventional Bipolar Cell Type with Dual Expression of Munc13 Isoforms: A Study Using Munc13-EXFP Knock-in Mice. Int J Mol Sci 2020; 21:ijms21217848. [PMID: 33105896 PMCID: PMC7660176 DOI: 10.3390/ijms21217848] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2020] [Revised: 10/19/2020] [Accepted: 10/20/2020] [Indexed: 12/19/2022] Open
Abstract
Munc13 isoforms are constituents of the presynaptic compartment of chemical synapses, where they govern important steps in preparing synaptic vesicles for exocytosis. The role of Munc13-1, -2 and -3 is well documented in brain neurons, but less is known about their function and distribution among the neurons of the retina and their conventional and ribbon-type chemical synapses. Here, we examined the retinae of Munc13-1-, -2-, and -3-EXFP knock-in (KI) mice with a combination of immunocytochemistry, physiology, and electron microscopy. We show that knock-in of Munc13-EXFP fusion proteins did not affect overall retinal anatomy or synapse structure, but slightly affected synaptic transmission. By labeling Munc13-EXFP KI retinae with specific antibodies against Munc13-1, -2 and -3, we found that unlike in the brain, most retinal synapses seem to operate with a single Munc13 isoform. A surprising exception to this rule was type 6 ON bipolar cells, which expressed two Munc13 isoforms in their synaptic terminals, ubMunc13-2 and Munc13-3. The results of this study provide an important basis for future studies on the contribution of Munc13 isoforms in visual signal processing in the mammalian retina.
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18
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He W, Wu G. Metabolism of Amino Acids in the Brain and Their Roles in Regulating Food Intake. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2020; 1265:167-185. [PMID: 32761576 DOI: 10.1007/978-3-030-45328-2_10] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Amino acids (AAs) and their metabolites play an important role in neurological health and function. They are not only the building blocks of protein but are also neurotransmitters. In the brain, glutamate and aspartate are the major excitatory neurotransmitters, whereas γ-aminobutyrate (GABA, a metabolite of glutamate) and glycine are the major inhibitory neurotransmitters. Nitric oxide (NO, a metabolite of arginine), H2S (a metabolite of cysteine), serotonin (a metabolite of tryptophan) and histamine (a metabolite of histidine), as well as dopamine and norepinephrine (metabolites of tyrosine) are neurotransmitters to modulate synaptic plasticity, neuronal activity, learning, motor control, motivational behavior, emotion, and executive function. Concentrations of glutamine (a precursor of glutamate and aspartate), branched-chain AAs (precursors of glutamate, glutamine and aspartate), L-serine (a precursor of glycine and D-serine), methionine and phenylalanine in plasma are capable of affecting neurotransmission through the syntheses of glutamate, aspartate, and glycine, as well as the competitive transport of tryptophan and tyrosine across from the blood-brain barrier. Adequate consumption of AAs is crucial to maintain their concentrations and the production of neurotransmitters in the central nervous system. Thus, the content and balance of AAs in diets have a profound impact on food intake by animals. Knowledge of AA transport and metabolism in the brain is beneficial for improving the health and well-being of humans and animals.
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Affiliation(s)
- Wenliang He
- Department of Animal Science, Texas A&M University, College Station, TX, USA
| | - Guoyao Wu
- Department of Animal Science, Texas A&M University, College Station, TX, USA.
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19
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Distinct Nanoscale Calcium Channel and Synaptic Vesicle Topographies Contribute to the Diversity of Synaptic Function. Neuron 2019; 104:693-710.e9. [PMID: 31558350 DOI: 10.1016/j.neuron.2019.08.014] [Citation(s) in RCA: 65] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2018] [Revised: 05/31/2019] [Accepted: 08/08/2019] [Indexed: 12/22/2022]
Abstract
The nanoscale topographical arrangement of voltage-gated calcium channels (VGCC) and synaptic vesicles (SVs) determines synaptic strength and plasticity, but whether distinct spatial distributions underpin diversity of synaptic function is unknown. We performed single bouton Ca2+ imaging, Ca2+ chelator competition, immunogold electron microscopic (EM) localization of VGCCs and the active zone (AZ) protein Munc13-1, at two cerebellar synapses. Unexpectedly, we found that weak synapses exhibited 3-fold more VGCCs than strong synapses, while the coupling distance was 5-fold longer. Reaction-diffusion modeling could explain both functional and structural data with two strikingly different nanotopographical motifs: strong synapses are composed of SVs that are tightly coupled (∼10 nm) to VGCC clusters, whereas at weak synapses VGCCs were excluded from the vicinity (∼50 nm) of docked vesicles. The distinct VGCC-SV topographical motifs also confer differential sensitivity to neuromodulation. Thus, VGCC-SV arrangements are not canonical, and their diversity could underlie functional heterogeneity across CNS synapses.
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20
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Schmidt H. Control of Presynaptic Parallel Fiber Efficacy by Activity-Dependent Regulation of the Number of Occupied Release Sites. Front Syst Neurosci 2019; 13:30. [PMID: 31379524 PMCID: PMC6650762 DOI: 10.3389/fnsys.2019.00030] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2019] [Accepted: 07/01/2019] [Indexed: 11/13/2022] Open
Abstract
Parallel fiber (PF) synapses show pronounced and lasting facilitation during bursts of high-frequency activity. They typically connect to their target neurons via a single active zone (AZ), harboring few release sites (~2-8) with moderate initial vesicular release probability (~0.2-0.4). In light of these biophysical characteristics, it seems surprising that PF synapses can sustain facilitation during high-frequency periods of tens of action potentials (APs). Recent findings suggest an increase in the number of occupied release sites due to ultra-rapid (~180 s-1), Ca2+ dependent recruitment of synaptic vesicles (SVs) from replenishment sites as major presynaptic mechanism of this lasting facilitation. On the molecular level, Synaptotagmin 7 or Munc13s have been suggested to be involved in mediating facilitation at PF synapses. The recruitment of SVs from replenishment sites appears to be reversible on a slower time-scale, thereby, explaining that PF synapses rapidly depress and ultimately become silent during low-frequency activity. Hence, PF synapses show high-frequency facilitation (HFF) but low-frequency depression (LFD). This behavior is explained by regulation of the number of occupied release sites at the AZ by AP frequency.
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Affiliation(s)
- Hartmut Schmidt
- Carl-Ludwig Institute for Physiology, Medical Faculty, University of Leipzig, Leipzig, Germany
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21
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Blanco FA, Czikora A, Kedei N, You Y, Mitchell GA, Pany S, Ghosh A, Blumberg PM, Das J. Munc13 Is a Molecular Target of Bryostatin 1. Biochemistry 2019; 58:3016-3030. [PMID: 31243993 PMCID: PMC6620733 DOI: 10.1021/acs.biochem.9b00427] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
![]()
Bryostatin
1 is a natural macrolide shown to improve neuronal connections and
enhance memory in mice. Its mechanism of action is largely attributed
to the modulation of novel and conventional protein kinase Cs (PKCs)
by binding to their regulatory C1 domains. Munc13-1 is a C1 domain-containing
protein that shares common endogenous and exogenous activators with
novel and conventional PKC subtypes. Given the essential role of Munc13-1
in the priming of synaptic vesicles and neuronal transmission overall,
we explored the potential interaction between bryostatin 1 and Munc13-1.
Our results indicate that in vitro bryostatin 1 binds
to both the isolated C1 domain of Munc13-1 (Ki = 8.07 ± 0.90 nM) and the full-length Munc13-1 protein
(Ki = 0.45 ± 0.04 nM). Furthermore,
confocal microscopy and immunoblot analysis demonstrated that in intact
HT22 cells bryostatin 1 mimics the actions of phorbol esters, a previously
established class of Munc13-1 activators, and induces plasma membrane
translocation of Munc13-1, a hallmark of its activation. Consistently,
bryostatin 1 had no effect on the Munc13-1H567K construct
that is insensitive to phorbol esters. Effects of bryostatin 1 on
the other Munc13 family members, ubMunc13-2 and bMunc13-2, resembled
those of Munc13-1 for translocation. Lastly, we observed an increased
level of expression of Munc13-1 following a 24 h incubation with bryostatin
1 in both HT22 and primary mouse hippocampal cells. This study characterizes
Munc13-1 as a molecular target of bryostatin 1. Considering the crucial
role of Munc13-1 in neuronal function, these findings provide strong
support for the potential role of Munc13s in the actions of bryostatin
1.
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Affiliation(s)
- Francisco A Blanco
- Department of Pharmacological & Pharmaceutical Sciences, College of Pharmacy , University of Houston , Houston , Texas 77204 , United States
| | - Agnes Czikora
- Laboratory of Cancer Biology and Genetics, Center for Cancer Research, National Cancer Institute , National Institutes of Health , Bethesda , Maryland 20892 , United States
| | - Noemi Kedei
- Laboratory of Cancer Biology and Genetics, Center for Cancer Research, National Cancer Institute , National Institutes of Health , Bethesda , Maryland 20892 , United States
| | - Youngki You
- Department of Pharmacological & Pharmaceutical Sciences, College of Pharmacy , University of Houston , Houston , Texas 77204 , United States
| | - Gary A Mitchell
- Laboratory of Cancer Biology and Genetics, Center for Cancer Research, National Cancer Institute , National Institutes of Health , Bethesda , Maryland 20892 , United States
| | - Satyabrata Pany
- Department of Pharmacological & Pharmaceutical Sciences, College of Pharmacy , University of Houston , Houston , Texas 77204 , United States
| | - Anamitra Ghosh
- Department of Pharmacological & Pharmaceutical Sciences, College of Pharmacy , University of Houston , Houston , Texas 77204 , United States
| | - Peter M Blumberg
- Laboratory of Cancer Biology and Genetics, Center for Cancer Research, National Cancer Institute , National Institutes of Health , Bethesda , Maryland 20892 , United States
| | - Joydip Das
- Department of Pharmacological & Pharmaceutical Sciences, College of Pharmacy , University of Houston , Houston , Texas 77204 , United States
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22
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Kusch V, Bornschein G, Loreth D, Bank J, Jordan J, Baur D, Watanabe M, Kulik A, Heckmann M, Eilers J, Schmidt H. Munc13-3 Is Required for the Developmental Localization of Ca 2+ Channels to Active Zones and the Nanopositioning of Ca v2.1 Near Release Sensors. Cell Rep 2019; 22:1965-1973. [PMID: 29466725 DOI: 10.1016/j.celrep.2018.02.010] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2017] [Revised: 12/01/2017] [Accepted: 01/31/2018] [Indexed: 12/20/2022] Open
Abstract
Spatial relationships between Cav channels and release sensors at active zones (AZs) are a major determinant of synaptic fidelity. They are regulated developmentally, but the underlying molecular mechanisms are largely unclear. Here, we show that Munc13-3 regulates the density of Cav2.1 and Cav2.2 channels, alters the localization of Cav2.1, and is required for the development of tight, nanodomain coupling at parallel-fiber AZs. We combined EGTA application and Ca2+-channel pharmacology in electrophysiological and two-photon Ca2+ imaging experiments with quantitative freeze-fracture immunoelectron microscopy and mathematical modeling. We found that a normally occurring developmental shift from release being dominated by Ca2+ influx through Cav2.1 and Cav2.2 channels with domain overlap and loose coupling (microdomains) to a nanodomain Cav2.1 to sensor coupling is impaired in Munc13-3-deficient synapses. Thus, at AZs lacking Munc13-3, release remained triggered by Cav2.1 and Cav2.2 microdomains, suggesting a critical role of Munc13-3 in the formation of release sites with calcium channel nanodomains.
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Affiliation(s)
- Valentin Kusch
- Carl-Ludwig-Institute for Physiology, Medical Faculty, University of Leipzig, Liebigstrasse 27, 04103 Leipzig, Germany
| | - Grit Bornschein
- Carl-Ludwig-Institute for Physiology, Medical Faculty, University of Leipzig, Liebigstrasse 27, 04103 Leipzig, Germany
| | - Desiree Loreth
- Institute of Physiology II, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany
| | - Julia Bank
- Institute of Physiology II, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany
| | - Johannes Jordan
- Institute of Physiology II, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany
| | - David Baur
- Carl-Ludwig-Institute for Physiology, Medical Faculty, University of Leipzig, Liebigstrasse 27, 04103 Leipzig, Germany
| | - Masahiko Watanabe
- Department of Anatomy, Graduate School of Medicine, Hokkaido University, Sapporo 060-8638, Japan
| | - Akos Kulik
- Institute of Physiology II, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany; BIOSS Centre for Biological Signalling Studies, University of Freiburg, 79104 Freiburg, Germany
| | - Manfred Heckmann
- Department of Physiology, Neurophysiology, Medical Faculty, University of Würzburg, Röntgenring 9, 97070 Würzburg, Germany
| | - Jens Eilers
- Carl-Ludwig-Institute for Physiology, Medical Faculty, University of Leipzig, Liebigstrasse 27, 04103 Leipzig, Germany
| | - Hartmut Schmidt
- Carl-Ludwig-Institute for Physiology, Medical Faculty, University of Leipzig, Liebigstrasse 27, 04103 Leipzig, Germany.
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Mattern-Schain SI, Fisher RK, West PC, Grimsley LB, Harris TM, Grandas OH, Best MD, Mountain DJH. Cell mimetic liposomal nanocarriers for tailored delivery of vascular therapeutics. Chem Phys Lipids 2018; 218:149-157. [PMID: 30582896 DOI: 10.1016/j.chemphyslip.2018.12.009] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2018] [Revised: 12/19/2018] [Accepted: 12/20/2018] [Indexed: 11/20/2022]
Abstract
Liposomal delivery systems (LDSs) have been at the forefront of medicinal nanotechnology for over three decades. Increasing LDS association to target cells and cargo delivery is crucial to bolstering overall nanodrug efficacy. Our laboratory aims to develop LDSs for molecular therapeutics aimed at vascular pathology. We have previously established a liposome platform that is an effective delivery system for RNA interference in vascular cell types by using polyethylene glycol (PEG) decorated liposomes bearing an octa-arginine (R8) cell penetrating peptide (CPP). Further tailoring liposome membranes to mimic vascular cell membrane lipid constituents may be a promising strategy for increasing cargo delivery. Here we aimed to develop liposomal formulations that could make use of diacylglycerol (DAG) and phosphatidylserine (PS), naturally occurring lipid species that are known to influence vascular cell function, as a facile and efficient means to increase nanodrug efficacy without compromising clinical viability. We investigated the ability of DAG and PS to amplify the cellular uptake of our previously established LDS platform loaded with small interfering ribonucleic acid (siRNA) cargo. Cellular fluorescence microscopy experiments were performed in conjunction with quantitative cell association assays and cytotoxicity assays to analyze the effect of DAG/PS on the differential delivery of fluorescently-tagged liposomes to vascular smooth muscle cells (VSMCs) and vascular endothelial cells (VECs) and on liposomal-mediated toxicity. In these studies, significant, dose-dependent increases in association to target cells were observed, as well as cell-type specific effects on cell viability. The stability and encapsulation-efficiency of the DAG/PS-modified LDSs were analyzed by standard nanoparticle characterization methods, and siRNA transfection efficacy was quantified to gauge delivery potential as a function of DAG/PS modification. Our results suggest that the signaling lipids tested here imbue our LDS architectures with increased therapeutic potential, without compromising stability, encapsulation efficiency, or biocompatibility, thus presenting a natural strategy to increase nanodrug efficacy and specificity.
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Affiliation(s)
- Samuel I Mattern-Schain
- Department of Chemistry, University of Tennessee, 1420 Circle Drive, Knoxville, TN, 37996, United States
| | - Richard K Fisher
- Department of Surgery, University of Tennessee Graduate School of Medicine, 1924 Alcoa Highway, Knoxville, 37920, TN, United States
| | - Philip C West
- Department of Surgery, University of Tennessee Graduate School of Medicine, 1924 Alcoa Highway, Knoxville, 37920, TN, United States
| | - Lauren B Grimsley
- Department of Surgery, University of Tennessee Graduate School of Medicine, 1924 Alcoa Highway, Knoxville, 37920, TN, United States
| | - Taylor M Harris
- Department of Surgery, University of Tennessee Graduate School of Medicine, 1924 Alcoa Highway, Knoxville, 37920, TN, United States
| | - Oscar H Grandas
- Department of Surgery, University of Tennessee Graduate School of Medicine, 1924 Alcoa Highway, Knoxville, 37920, TN, United States
| | - Michael D Best
- Department of Chemistry, University of Tennessee, 1420 Circle Drive, Knoxville, TN, 37996, United States.
| | - Deidra J H Mountain
- Department of Surgery, University of Tennessee Graduate School of Medicine, 1924 Alcoa Highway, Knoxville, 37920, TN, United States.
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24
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Calahorro F, Izquierdo PG. The presynaptic machinery at the synapse of C. elegans. INVERTEBRATE NEUROSCIENCE : IN 2018; 18:4. [PMID: 29532181 PMCID: PMC5851683 DOI: 10.1007/s10158-018-0207-5] [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] [Subscribe] [Scholar Register] [Received: 11/02/2017] [Accepted: 02/22/2018] [Indexed: 11/17/2022]
Abstract
Synapses are specialized contact sites that mediate information flow between neurons and their targets. Important physical interactions across the synapse are mediated by synaptic adhesion molecules. These adhesions regulate formation of synapses during development and play a role during mature synaptic function. Importantly, genes regulating synaptogenesis and axon regeneration are conserved across the animal phyla. Genetic screens in the nematode Caenorhabditis elegans have identified a number of molecules required for synapse patterning and assembly. C. elegans is able to survive even with its neuronal function severely compromised. This is in comparison with Drosophila and mice where increased complexity makes them less tolerant to impaired function. Although this fact may reflect differences in the function of the homologous proteins in the synapses between these organisms, the most likely interpretation is that many of these components are equally important, but not absolutely essential, for synaptic transmission to support the relatively undemanding life style of laboratory maintained C. elegans. Here, we review research on the major group of synaptic proteins, involved in the presynaptic machinery in C. elegans, showing a strong conservation between higher organisms and highlight how C. elegans can be used as an informative tool for dissecting synaptic components, based on a simple nervous system organization.
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Affiliation(s)
- Fernando Calahorro
- Biological Sciences, University of Southampton, Life Sciences Building 85, Southampton, SO17 1BJ, UK.
| | - Patricia G Izquierdo
- Biological Sciences, University of Southampton, Life Sciences Building 85, Southampton, SO17 1BJ, UK
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25
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Higashio H, Satoh YI, Saino T. Inhibitory role of Munc13-1 in antigen-induced mast cell degranulation. Biomed Res 2017; 38:321-329. [PMID: 29225210 DOI: 10.2220/biomedres.38.321] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Secretory granules (SGs) of mast cells are lysosome-related organelles that contain various inflammatory molecules such as histamine, which are stored in the cytoplasm. Mast cell degranulation is the regulated exocytosis of SGs in response to external stimuli, such as the antigen-mediated cross-linking of the high-affinity IgE receptor, FcεRI. Upon stimulation, SGs undergo priming to become fusion-competent prior to fusing with the plasma membrane, which is mediated by Munc13-4, one of the five members of the vesicle-priming Munc13 protein family. Although Munc13-4 is shown to be crucial for mast cell degranulation, the functional involvement of other Munc13 isoform(s) remains unknown. Herein, this was investigated using the RBL-2H3 mast cell line. We found that Munc13-1 and Munc13-4 are the only Munc13 isoforms that are expressed in the RBL-2H3 cells, and Munc13-1 is distributed in the cytoplasm, but highly concentrated on the late endosome and/or lysosome. Unexpectedly, antigen-induced degranulation was considerably increased by Munc13-1 knockdown, but decreased by its overexpression. Further, we found that the hypersecretion phenotype of the Munc13-1-knockdown cells was attenuated by simultaneous Munc13-4 knockdown. These results suggested that Munc13-1 has an inhibitory role in antigen-induced mast cell degranulation, which is performed in a Munc13-4-dependent manner.
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Affiliation(s)
- Hironori Higashio
- Department of Chemistry, Center for Liberal Arts and Sciences, Iwate Medical University
| | - Yoh-Ichi Satoh
- Department of Anatomy (Cell Biology), Iwate Medical University.,Department of Medical Education, Iwate Medical University
| | - Tomoyuki Saino
- Department of Anatomy (Cell Biology), Iwate Medical University
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26
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Effects of Aging and Tocotrienol-Rich Fraction Supplementation on Brain Arginine Metabolism in Rats. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2017; 2017:6019796. [PMID: 29348790 PMCID: PMC5733770 DOI: 10.1155/2017/6019796] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/21/2017] [Revised: 10/04/2017] [Accepted: 10/09/2017] [Indexed: 12/31/2022]
Abstract
Accumulating evidence suggests that altered arginine metabolism is involved in the aging and neurodegenerative processes. This study sought to determine the effects of age and vitamin E supplementation in the form of tocotrienol-rich fraction (TRF) on brain arginine metabolism. Male Wistar rats at ages of 3 and 21 months were supplemented with TRF orally for 3 months prior to the dissection of tissue from five brain regions. The tissue concentrations of L-arginine and its nine downstream metabolites were quantified using high-performance liquid chromatography and liquid chromatography tandem mass spectrometry. We found age-related alterations in L-arginine metabolites in the chemical- and region-specific manners. Moreover, TRF supplementation reversed age-associated changes in arginine metabolites in the entorhinal cortex and cerebellum. Multiple regression analysis revealed a number of significant neurochemical-behavioral correlations, indicating the beneficial effects of TRF supplementation on memory and motor function.
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27
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Doussau F, Schmidt H, Dorgans K, Valera AM, Poulain B, Isope P. Frequency-dependent mobilization of heterogeneous pools of synaptic vesicles shapes presynaptic plasticity. eLife 2017; 6:28935. [PMID: 28990927 PMCID: PMC5648531 DOI: 10.7554/elife.28935] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2017] [Accepted: 10/06/2017] [Indexed: 12/03/2022] Open
Abstract
The segregation of the readily releasable pool of synaptic vesicles (RRP) in sub-pools that are differentially poised for exocytosis shapes short-term plasticity. However, the frequency-dependent mobilization of these sub-pools is poorly understood. Using slice recordings and modeling of synaptic activity at cerebellar granule cell to Purkinje cell synapses of mice, we describe two sub-pools in the RRP that can be differentially recruited upon ultrafast changes in the stimulation frequency. We show that at low-frequency stimulations, a first sub-pool is gradually silenced, leading to full blockage of synaptic transmission. Conversely, a second pool of synaptic vesicles that cannot be released by a single stimulus is recruited within milliseconds by high-frequency stimulation and support an ultrafast recovery of neurotransmitter release after low-frequency depression. This frequency-dependent mobilization or silencing of sub-pools in the RRP in terminals of granule cells may play a role in the filtering of sensorimotor information in the cerebellum.
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Affiliation(s)
- Frédéric Doussau
- Institut des Neurosciences Cellulaires et Intégratives, CNRS, Université de Strasbourg, Strasbourg, France
| | - Hartmut Schmidt
- Carl-Ludwig Institute for Physiology, University of Leipzig, Leipzig, Germany
| | - Kevin Dorgans
- Institut des Neurosciences Cellulaires et Intégratives, CNRS, Université de Strasbourg, Strasbourg, France
| | - Antoine M Valera
- Institut des Neurosciences Cellulaires et Intégratives, CNRS, Université de Strasbourg, Strasbourg, France
| | - Bernard Poulain
- Institut des Neurosciences Cellulaires et Intégratives, CNRS, Université de Strasbourg, Strasbourg, France
| | - Philippe Isope
- Institut des Neurosciences Cellulaires et Intégratives, CNRS, Université de Strasbourg, Strasbourg, France
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28
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Lipstein N, Verhoeven-Duif NM, Michelassi FE, Calloway N, van Hasselt PM, Pienkowska K, van Haaften G, van Haelst MM, van Empelen R, Cuppen I, van Teeseling HC, Evelein AMV, Vorstman JA, Thoms S, Jahn O, Duran KJ, Monroe GR, Ryan TA, Taschenberger H, Dittman JS, Rhee JS, Visser G, Jans JJ, Brose N. Synaptic UNC13A protein variant causes increased neurotransmission and dyskinetic movement disorder. J Clin Invest 2017; 127:1005-1018. [PMID: 28192369 DOI: 10.1172/jci90259] [Citation(s) in RCA: 76] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2016] [Accepted: 12/15/2016] [Indexed: 12/13/2022] Open
Abstract
Munc13 proteins are essential regulators of neurotransmitter release at nerve cell synapses. They mediate the priming step that renders synaptic vesicles fusion-competent, and their genetic elimination causes a complete block of synaptic transmission. Here we have described a patient displaying a disorder characterized by a dyskinetic movement disorder, developmental delay, and autism. Using whole-exome sequencing, we have shown that this condition is associated with a rare, de novo Pro814Leu variant in the major human Munc13 paralog UNC13A (also known as Munc13-1). Electrophysiological studies in murine neuronal cultures and functional analyses in Caenorhabditis elegans revealed that the UNC13A variant causes a distinct dominant gain of function that is characterized by increased fusion propensity of synaptic vesicles, which leads to increased initial synaptic vesicle release probability and abnormal short-term synaptic plasticity. Our study underscores the critical importance of fine-tuned presynaptic control in normal brain function. Further, it adds the neuronal Munc13 proteins and the synaptic vesicle priming process that they control to the known etiological mechanisms of psychiatric and neurological synaptopathies.
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29
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Engel AG, Selcen D, Shen XM, Milone M, Harper CM. Loss of MUNC13-1 function causes microcephaly, cortical hyperexcitability, and fatal myasthenia. NEUROLOGY-GENETICS 2016; 2:e105. [PMID: 27648472 PMCID: PMC5017540 DOI: 10.1212/nxg.0000000000000105] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/30/2016] [Accepted: 08/04/2016] [Indexed: 11/16/2022]
Abstract
Objective: To identify the molecular basis of a fatal syndrome of microcephaly, cortical hyperexcitability, and myasthenia. Methods: We performed clinical and in vitro microelectrode studies of neuromuscular transmission, examined neuromuscular junctions cytochemically and by electron microscopy (EM), and searched for mutations by Sanger and exome sequencing. Results: Neuromuscular transmission was severely compromised by marked depletion of the readily releasable pool of quanta, but the probability of quantal release was normal. Cytochemical and EM studies revealed normal endplate architecture. Exome sequencing identified a homozygous nonsense mutation in the N-terminal domain of MUNC13-1 (UNC13A) truncating the protein after 101 residues. Conclusions: Loss of Munc13-1 function predicts that syntaxin 1B is consigned to a nonfunctional closed state; this inhibits cholinergic transmission at the neuromuscular junction and glutamatergic transmission in the brain. Inactivation of syntaxin 1B likely accounts for the patient's cortical hyperexcitability because mutations of syntaxin 1B cause febrile seizures with or without epilepsy, haploinsufficiency of the STX1B is associated with myoclonic astatic epilepsy, and antisense knockdown of stx1b in zebrafish larvae elicits epileptiform discharges. A very recent publication also shows that syntaxin 1B has a separate obligatory role for maintenance of developing and mature neurons and illustrates impaired brain development in syntaxin 1A/1B double knockout mice. We therefore attribute our patient's microcephaly to the truncating homozygous Munc13-1 mutation that consigns syntaxin 1B to a permanently closed nonfunctional state akin to a knockout.
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Affiliation(s)
| | - Duygu Selcen
- Department of Neurology, Mayo Clinic, Rochester, MN
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30
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Schreurs BG. Classical Conditioning and Modification of the Rabbit's (Oryctolagus Cuniculus) Unconditioned Nictitating Membrane Response. ACTA ACUST UNITED AC 2016. [DOI: 10.1177/1534582303002002001] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
A fundamental tenet of behavior is that a reflex is automatic, unconscious, involuntary, and relatively invariant. However, we have discovered that a reflex can change dramatically as a function of classical conditioning, and this change can be demonstrated independently of the conditioned stimulus. We have termed this phenomenon conditioning-specific reflex modification (CRM). Although the behavioral laws and neural substrates of nonassociative reflex changes have been identified, the behavioral laws and neural substrates of CRM are only now being revealed. For example, CRM is similar to classical conditioning in that (a) it is a function of both the strength of conditioning and (b) the strength of the unconditioned stimulus, (c) it can be extinguished, and (d) it can be generalized from one unconditioned stimulus to another. Preliminary analysis suggests that CRM may have some features in common with post-traumatic stress disorder and may provide insights into treatment of the disorder.
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31
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Netrakanti PR, Cooper BH, Dere E, Poggi G, Winkler D, Brose N, Ehrenreich H. Fast cerebellar reflex circuitry requires synaptic vesicle priming by munc13-3. THE CEREBELLUM 2016; 14:264-83. [PMID: 25617111 PMCID: PMC4441738 DOI: 10.1007/s12311-015-0645-0] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Munc13-3 is a member of the Munc13 family of synaptic vesicle priming proteins and mainly expressed in cerebellar neurons. Munc13-3 null mutant (Munc13-3−/−) mice show decreased synaptic release probability at parallel fiber to Purkinje cell, granule cell to Golgi cell, and granule cell to basket cell synapses and exhibit a motor learning deficit at highest rotarod speeds. Since we detected Munc13-3 immunoreactivity in the dentate gyrus, as reported here for the first time, and current studies indicated a crucial role for the cerebellum in hippocampus-dependent spatial memory, we systematically investigated Munc13-3−/− mice versus wild-type littermates of both genders with respect to hippocampus-related cognition and a range of basic behaviors, including tests for anxiety, sensory functions, motor performance and balance, sensorimotor gating, social interaction and competence, and repetitive and compulsive behaviors. Neither basic behavior nor hippocampus-dependent cognitive performance, evaluated by Morris water maze, hole board working and reference memory, IntelliCage-based place learning including multiple reversals, and fear conditioning, showed any difference between genotypes. However, consistent with a disturbed cerebellar reflex circuitry, a reliable reduction in the acoustic startle response in both male and female Munc13-3−/− mice was found. To conclude, complete deletion of Munc13-3 leads to a robust decrease in the acoustic startle response. This readout of a fast cerebellar reflex circuitry obviously requires synaptic vesicle priming by Munc13-3 for full functionality, in contrast to other behavioral or cognitive features, where a nearly perfect compensation of Munc13-3 deficiency by related synaptic proteins has to be assumed.
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Affiliation(s)
- Pallavi Rao Netrakanti
- Clinical Neuroscience, Max Planck Institute of Experimental Medicine, Göttingen, Germany
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32
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Man KNM, Imig C, Walter AM, Pinheiro PS, Stevens DR, Rettig J, Sørensen JB, Cooper BH, Brose N, Wojcik SM. Identification of a Munc13-sensitive step in chromaffin cell large dense-core vesicle exocytosis. eLife 2015; 4. [PMID: 26575293 PMCID: PMC4798968 DOI: 10.7554/elife.10635] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2015] [Accepted: 11/16/2015] [Indexed: 01/16/2023] Open
Abstract
It is currently unknown whether the molecular steps of large dense-core vesicle (LDCV) docking and priming are identical to the corresponding reactions in synaptic vesicle (SV) exocytosis. Munc13s are essential for SV docking and priming, and we systematically analyzed their role in LDCV exocytosis using chromaffin cells lacking individual isoforms. We show that particularly Munc13-2 plays a fundamental role in LDCV exocytosis, but in contrast to synapses lacking Munc13s, the corresponding chromaffin cells do not exhibit a vesicle docking defect. We further demonstrate that ubMunc13-2 and Munc13-1 confer Ca(2+)-dependent LDCV priming with similar affinities, but distinct kinetics. Using a mathematical model, we identify an early LDCV priming step that is strongly dependent upon Munc13s. Our data demonstrate that the molecular steps of SV and LDCV priming are very similar while SV and LDCV docking mechanisms are distinct.
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Affiliation(s)
- Kwun Nok M Man
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Cordelia Imig
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | | | - Paulo S Pinheiro
- Department of Neuroscience and Pharmacology, Faculty of Health and Medical Sciences and Lundbeck Foundation Center for Biomembranes in Nanomedicine, University of Copenhagen, Copenhagen, Denmark
| | - David R Stevens
- Department of Physiology, Saarland University, Homburg, Germany
| | - Jens Rettig
- Department of Physiology, Saarland University, Homburg, Germany
| | - Jakob B Sørensen
- Department of Neuroscience and Pharmacology, Faculty of Health and Medical Sciences and Lundbeck Foundation Center for Biomembranes in Nanomedicine, University of Copenhagen, Copenhagen, Denmark
| | - Benjamin H Cooper
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Nils Brose
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Sonja M Wojcik
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, Göttingen, Germany
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33
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Reddy B, Kelawala DN, Shah T, Patel AB, Patil DB, Parikh PV, Patel N, Parmar N, Mohapatra AB, Singh KM, Menon R, Pandya D, Jakhesara SJ, Koringa PG, Rao MV, Joshi CG. Identification of putative SNPs in progressive retinal atrophy affected Canis lupus familiaris using exome sequencing. Mamm Genome 2015; 26:638-49. [PMID: 26515695 DOI: 10.1007/s00335-015-9607-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2015] [Accepted: 10/08/2015] [Indexed: 11/30/2022]
Abstract
Progressive retinal atrophy (PRA) is one of the major causes of retinal photoreceptor cell degeneration in canines. The inheritance pattern of PRA is autosomal recessive and genetically heterogeneous. Here, using targeted sequencing technology, we have performed exome sequencing of 10 PRA-affected (Spitz=7, Cocker Spaniel=1, Lhasa Aphso=1 and Spitz-Labrador cross breed=1) and 6 normal (Spitz=5, Cocker Spaniel=1) dogs. The high-throughput sequencing using 454-Roche Titanium sequencer generated about 2.16 Giga bases of raw data. Initially, we have successfully identified 25,619 single nucleotide polymorphisms (SNPs) that passed the stringent SNP calling parameters. Further, we performed association study on the cohort, and the highly significant (0.001) associations were short-listed and investigated in-depth. Out of the 171 significant SNPs, 113 were previously unreported. Interestingly, six among them were non-synonymous coding (NSC) SNPs, which includes CPPED1 A>G (p.M307V), PITRM1 T>G (p.S715A), APP G>A (p.T266M), RNF213 A>G (p.V1482A), C>A (p.V1456L), and SLC46A3 G>A (p.R168Q). On the other hand, 35 out of 113 unreported SNPs were falling in regulatory regions such as 3'-UTR, 5'-UTR, etc. In-depth bioinformatics analysis revealed that majority of NSC SNPs have damaging effect and alter protein stability. This study highlighted the genetic markers associated with PRA, which will help to develop genetic assay-based screening in effective breeding.
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Affiliation(s)
- Bhaskar Reddy
- Ome Research Facility, Department of Animal Biotechnology, Anand Agricultural University, Anand, Gujarat, 388001, India.,Department of Zoology, Genetic Diagnostic Centre, University School of Sciences, Gujarat University, Ahmedabad, Gujarat, 380009, India
| | - Divyesh N Kelawala
- Department of Veterinary Surgery & Radiology, College of Veterinary Science & Animal Husbandry, Anand Agricultural University, Anand, Gujarat, 388001, India
| | - Tejas Shah
- Ome Research Facility, Department of Animal Biotechnology, Anand Agricultural University, Anand, Gujarat, 388001, India
| | - Anand B Patel
- Ome Research Facility, Department of Animal Biotechnology, Anand Agricultural University, Anand, Gujarat, 388001, India
| | - Deepak B Patil
- Department of Veterinary Surgery & Radiology, College of Veterinary Science & Animal Husbandry, Anand Agricultural University, Anand, Gujarat, 388001, India
| | - Pinesh V Parikh
- Department of Veterinary Surgery & Radiology, College of Veterinary Science & Animal Husbandry, Anand Agricultural University, Anand, Gujarat, 388001, India
| | - Namrata Patel
- Ome Research Facility, Department of Animal Biotechnology, Anand Agricultural University, Anand, Gujarat, 388001, India
| | - Nidhi Parmar
- Ome Research Facility, Department of Animal Biotechnology, Anand Agricultural University, Anand, Gujarat, 388001, India
| | - Amit B Mohapatra
- Ome Research Facility, Department of Animal Biotechnology, Anand Agricultural University, Anand, Gujarat, 388001, India
| | - Krishna M Singh
- Datar Genetics Ltd, F-8, D Road, Ambad, Nasik, Maharashtra, 422010, India
| | - Ramesh Menon
- Ome Research Facility, Department of Animal Biotechnology, Anand Agricultural University, Anand, Gujarat, 388001, India
| | - Dipal Pandya
- Ome Research Facility, Department of Animal Biotechnology, Anand Agricultural University, Anand, Gujarat, 388001, India
| | - Subhash J Jakhesara
- Ome Research Facility, Department of Animal Biotechnology, Anand Agricultural University, Anand, Gujarat, 388001, India
| | - Prakash G Koringa
- Ome Research Facility, Department of Animal Biotechnology, Anand Agricultural University, Anand, Gujarat, 388001, India
| | - Mandava V Rao
- Department of Zoology, Genetic Diagnostic Centre, University School of Sciences, Gujarat University, Ahmedabad, Gujarat, 380009, India
| | - Chaitanya G Joshi
- Ome Research Facility, Department of Animal Biotechnology, Anand Agricultural University, Anand, Gujarat, 388001, India.
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Meyer SU, Krebs S, Thirion C, Blum H, Krause S, Pfaffl MW. Tumor Necrosis Factor Alpha and Insulin-Like Growth Factor 1 Induced Modifications of the Gene Expression Kinetics of Differentiating Skeletal Muscle Cells. PLoS One 2015; 10:e0139520. [PMID: 26447881 PMCID: PMC4598026 DOI: 10.1371/journal.pone.0139520] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2015] [Accepted: 09/13/2015] [Indexed: 12/19/2022] Open
Abstract
Introduction TNF-α levels are increased during muscle wasting and chronic muscle degeneration and regeneration processes, which are characteristic for primary muscle disorders. Pathologically increased TNF-α levels have a negative effect on muscle cell differentiation efficiency, while IGF1 can have a positive effect; therefore, we intended to elucidate the impact of TNF-α and IGF1 on gene expression during the early stages of skeletal muscle cell differentiation. Methodology/Principal Findings This study presents gene expression data of the murine skeletal muscle cells PMI28 during myogenic differentiation or differentiation with TNF-α or IGF1 exposure at 0 h, 4 h, 12 h, 24 h, and 72 h after induction. Our study detected significant coregulation of gene sets involved in myoblast differentiation or in the response to TNF-α. Gene expression data revealed a time- and treatment-dependent regulation of signaling pathways, which are prominent in myogenic differentiation. We identified enrichment of pathways, which have not been specifically linked to myoblast differentiation such as doublecortin-like kinase pathway associations as well as enrichment of specific semaphorin isoforms. Moreover to the best of our knowledge, this is the first description of a specific inverse regulation of the following genes in myoblast differentiation and response to TNF-α: Aknad1, Cmbl, Sepp1, Ndst4, Tecrl, Unc13c, Spats2l, Lix1, Csdc2, Cpa1, Parm1, Serpinb2, Aspn, Fibin, Slc40a1, Nrk, and Mybpc1. We identified a gene subset (Nfkbia, Nfkb2, Mmp9, Mef2c, Gpx, and Pgam2), which is robustly regulated by TNF-α across independent myogenic differentiation studies. Conclusions This is the largest dataset revealing the impact of TNF-α or IGF1 treatment on gene expression kinetics of early in vitro skeletal myoblast differentiation. We identified novel mRNAs, which have not yet been associated with skeletal muscle differentiation or response to TNF-α. Results of this study may facilitate the understanding of transcriptomic networks underlying inhibited muscle differentiation in inflammatory diseases.
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Affiliation(s)
- Swanhild U Meyer
- Physiology Weihenstephan, ZIEL Research Center for Nutrition and Food Sciences, Technische Universität München, Freising, Germany
| | - Stefan Krebs
- Laboratory for Functional Genome Analysis (LAFUGA), Gene Center, University of Munich, Ludwig-Maximilians-Universität München, München, Germany
| | | | - Helmut Blum
- Laboratory for Functional Genome Analysis (LAFUGA), Gene Center, University of Munich, Ludwig-Maximilians-Universität München, München, Germany
| | - Sabine Krause
- Friedrich-Baur-Institute, Department of Neurology, Ludwig-Maximilians-Universität München, München, Germany
| | - Michael W Pfaffl
- Physiology Weihenstephan, ZIEL Research Center for Nutrition and Food Sciences, Technische Universität München, Freising, Germany
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35
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Ashley-Koch AE, Garrett ME, Gibson J, Liu Y, Dennis MF, Kimbrel NA, Beckham JC, Hauser MA. Genome-wide association study of posttraumatic stress disorder in a cohort of Iraq-Afghanistan era veterans. J Affect Disord 2015; 184:225-34. [PMID: 26114229 PMCID: PMC4697755 DOI: 10.1016/j.jad.2015.03.049] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/10/2015] [Accepted: 03/26/2015] [Indexed: 10/23/2022]
Abstract
BACKGROUND Posttraumatic stress disorder (PTSD) is a psychiatric disorder that can develop after experiencing traumatic events. A genome-wide association study (GWAS) design was used to identify genetic risk factors for PTSD within a multi-racial sample primarily composed of U.S. veterans. METHODS Participants were recruited at multiple medical centers, and structured interviews were used to establish diagnoses. Genotypes were generated using three Illumina platforms and imputed with global reference data to create a common set of SNPs. SNPs that increased risk for PTSD were identified with logistic regression, while controlling for gender, trauma severity, and population substructure. Analyses were run separately in non-Hispanic black (NHB; n = 949) and non-Hispanic white (NHW; n = 759) participants. Meta-analysis was used to combine results from the two subsets. RESULTS SNPs within several interesting candidate genes were nominally significant. Within the NHB subset, the most significant genes were UNC13C and DSCAM. Within the NHW subset, the most significant genes were TBC1D2, SDC2 and PCDH7. In addition, PRKG1 and DDX60L were identified through meta-analysis. The top genes for the three analyses have been previously implicated in neurologic processes consistent with a role in PTSD. Pathway analysis of the top genes identified alternative splicing as the top GO term in all three analyses (FDR q < 3.5 × 10(-5)). LIMITATIONS No individual SNPs met genome-wide significance in the analyses. CONCLUSIONS This multi-racial PTSD GWAS identified biologically plausible candidate genes and suggests that post-transcriptional regulation may be important to the pathology of PTSD; however, replication of these findings is needed.
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Affiliation(s)
| | | | - Jason Gibson
- Department of Medicine, Duke University Medical Center, Durham, NC
| | - Yutao Liu
- Department of Medicine, Duke University Medical Center, Durham, NC
| | - Michelle F. Dennis
- Durham Veterans Affairs Medical Center, Durham, NC,The VA Mid-Atlantic Mental Illness Research, Education, and Clinical Center, Durham, NC,Department of Psychiatry and Behavioral Sciences, Duke University Medical Center, Durham, NC
| | - Nathan A. Kimbrel
- Durham Veterans Affairs Medical Center, Durham, NC,The VA Mid-Atlantic Mental Illness Research, Education, and Clinical Center, Durham, NC,Department of Psychiatry and Behavioral Sciences, Duke University Medical Center, Durham, NC
| | | | - Jean C. Beckham
- Durham Veterans Affairs Medical Center, Durham, NC,The VA Mid-Atlantic Mental Illness Research, Education, and Clinical Center, Durham, NC,Department of Psychiatry and Behavioral Sciences, Duke University Medical Center, Durham, NC
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36
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Vogl C, Cooper BH, Neef J, Wojcik SM, Reim K, Reisinger E, Brose N, Rhee JS, Moser T, Wichmann C. Unconventional molecular regulation of synaptic vesicle replenishment in cochlear inner hair cells. J Cell Sci 2015; 128:638-44. [PMID: 25609709 DOI: 10.1242/jcs.162099] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Ribbon synapses of cochlear inner hair cells (IHCs) employ efficient vesicle replenishment to indefatigably encode sound. In neurons, neuroendocrine and immune cells, vesicle replenishment depends on proteins of the mammalian uncoordinated 13 (Munc13, also known as Unc13) and Ca(2+)-dependent activator proteins for secretion (CAPS) families, which prime vesicles for exocytosis. Here, we tested whether Munc13 and CAPS proteins also regulate exocytosis in mouse IHCs by combining immunohistochemistry with auditory systems physiology and IHC patch-clamp recordings of exocytosis in mice lacking Munc13 and CAPS isoforms. Surprisingly, we did not detect Munc13 or CAPS proteins at IHC presynaptic active zones and found normal IHC exocytosis as well as auditory brainstem responses (ABRs) in Munc13 and CAPS deletion mutants. Instead, we show that otoferlin, a C2-domain protein that is crucial for vesicular fusion and replenishment in IHCs, clusters at the plasma membrane of the presynaptic active zone. Electron tomography of otoferlin-deficient IHC synapses revealed a reduction of short tethers holding vesicles at the active zone, which might be a structural correlate of impaired vesicle priming in otoferlin-deficient IHCs. We conclude that IHCs use an unconventional priming machinery that involves otoferlin.
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Affiliation(s)
- Christian Vogl
- Institute for Auditory Neuroscience and InnerEarLab, Department of Otolaryngology, University Medical Center Göttingen, 37099 Göttingen, Germany
| | - Benjamin H Cooper
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany
| | - Jakob Neef
- Institute for Auditory Neuroscience and InnerEarLab, Department of Otolaryngology, University Medical Center Göttingen, 37099 Göttingen, Germany
| | - Sonja M Wojcik
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany
| | - Kerstin Reim
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany
| | - Ellen Reisinger
- Molecular Biology of Cochlear Neurotransmission Group, InnerEarLab, Department of Otolaryngology, University Medical Center Göttingen, 37075 Göttingen, Germany
| | - Nils Brose
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany Collaborative Research Center 889, University of Göttingen, 37099 Göttingen, Germany Center for Nanoscale Microscopy and Molecular Physiology of the Brain, University of Göttingen, 37073 Göttingen, Germany
| | - Jeong-Seop Rhee
- Neurophysiology Group, Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany
| | - Tobias Moser
- Institute for Auditory Neuroscience and InnerEarLab, Department of Otolaryngology, University Medical Center Göttingen, 37099 Göttingen, Germany Collaborative Research Center 889, University of Göttingen, 37099 Göttingen, Germany Center for Nanoscale Microscopy and Molecular Physiology of the Brain, University of Göttingen, 37073 Göttingen, Germany
| | - Carolin Wichmann
- Institute for Auditory Neuroscience and InnerEarLab, Department of Otolaryngology, University Medical Center Göttingen, 37099 Göttingen, Germany Collaborative Research Center 889, University of Göttingen, 37099 Göttingen, Germany Molecular Architecture of Synapses Group, Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, 37099 Göttingen, Germany
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King DA, Fitzgerald TW, Miller R, Canham N, Clayton-Smith J, Johnson D, Mansour S, Stewart F, Vasudevan P, Hurles ME. A novel method for detecting uniparental disomy from trio genotypes identifies a significant excess in children with developmental disorders. Genome Res 2014; 24:673-87. [PMID: 24356988 PMCID: PMC3975066 DOI: 10.1101/gr.160465.113] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2013] [Accepted: 12/13/2013] [Indexed: 01/04/2023]
Abstract
Exome sequencing of parent-offspring trios is a popular strategy for identifying causative genetic variants in children with rare diseases. This method owes its strength to the leveraging of inheritance information, which facilitates de novo variant calling, inference of compound heterozygosity, and the identification of inheritance anomalies. Uniparental disomy describes the inheritance of a homologous chromosome pair from only one parent. This aberration is important to detect in genetic disease studies because it can result in imprinting disorders and recessive diseases. We have developed a software tool to detect uniparental disomy from child-mother-father genotype data that uses a binomial test to identify chromosomes with a significant burden of uniparentally inherited genotypes. This tool is the first to read VCF-formatted genotypes, to perform integrated copy number filtering, and to use a statistical test inherently robust for use in platforms of varying genotyping density and noise characteristics. Simulations demonstrated superior accuracy compared with previously developed approaches. We implemented the method on 1057 trios from the Deciphering Developmental Disorders project, a trio-based rare disease study, and detected six validated events, a significant enrichment compared with the population prevalence of UPD (1 in 3500), suggesting that most of these events are pathogenic. One of these events represents a known imprinting disorder, and exome analyses have identified rare homozygous candidate variants, mainly in the isodisomic regions of UPD chromosomes, which, among other variants, provide targets for further genetic and functional evaluation.
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Affiliation(s)
- Daniel A. King
- Wellcome Trust Sanger Institute, Hinxton, Cambridge CB10 1HH, United Kingdom
| | - Tomas W. Fitzgerald
- Wellcome Trust Sanger Institute, Hinxton, Cambridge CB10 1HH, United Kingdom
| | - Ray Miller
- Wellcome Trust Sanger Institute, Hinxton, Cambridge CB10 1HH, United Kingdom
| | - Natalie Canham
- North West Thames Regional Genetics Service, North West London Hospitals NHS Trust, Harrow, Middlesex HA1 3UJ, United Kingdom
| | - Jill Clayton-Smith
- Centre for Genetic Medicine, Institute of Human Development, Faculty of Medical and Human Sciences, University of Manchester and Central Manchester University Hospitals NHS Foundation Trust, Manchester M13 9WU, United Kingdom
| | - Diana Johnson
- Sheffield Genetics Service, Sheffield Children’s NHS Foundation Trust, Sheffield S10 2TH, United Kingdom
| | - Sahar Mansour
- South West Thames Regional Genetics Service, St. George’s Healthcare NHS Trust, London SW17 0QT, United Kingdom
| | - Fiona Stewart
- Northern Ireland Regional Genetics Centre, Belfast City Hospital, Belfast BT9 7AB, United Kingdom
| | - Pradeep Vasudevan
- Leicestershire Genetics Centre, Leicester Royal Infirmary, University Hospitals of Leicester, NHS Trust Infirmary Square, Leicester LE1 5WW, United Kingdom
| | - Matthew E. Hurles
- Wellcome Trust Sanger Institute, Hinxton, Cambridge CB10 1HH, United Kingdom
| | - the DDD Study1
- Wellcome Trust Sanger Institute, Hinxton, Cambridge CB10 1HH, United Kingdom
- North West Thames Regional Genetics Service, North West London Hospitals NHS Trust, Harrow, Middlesex HA1 3UJ, United Kingdom
- Centre for Genetic Medicine, Institute of Human Development, Faculty of Medical and Human Sciences, University of Manchester and Central Manchester University Hospitals NHS Foundation Trust, Manchester M13 9WU, United Kingdom
- Sheffield Genetics Service, Sheffield Children’s NHS Foundation Trust, Sheffield S10 2TH, United Kingdom
- South West Thames Regional Genetics Service, St. George’s Healthcare NHS Trust, London SW17 0QT, United Kingdom
- Northern Ireland Regional Genetics Centre, Belfast City Hospital, Belfast BT9 7AB, United Kingdom
- Leicestershire Genetics Centre, Leicester Royal Infirmary, University Hospitals of Leicester, NHS Trust Infirmary Square, Leicester LE1 5WW, United Kingdom
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Zhou K, Stawicki TM, Goncharov A, Jin Y. Position of UNC-13 in the active zone regulates synaptic vesicle release probability and release kinetics. eLife 2013; 2:e01180. [PMID: 24220508 PMCID: PMC3821175 DOI: 10.7554/elife.01180] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The presynaptic active zone proteins UNC-13/Munc13s are essential for synaptic vesicle (SV) exocytosis by directly interacting with SV fusion apparatus. An open question is how their association with active zones, hence their position to Ca2+ entry sites, regulates SV release. The N-termini of major UNC-13/Munc13 isoforms contain a non-calcium binding C2A domain that mediates protein homo- or hetero-meric interactions. Here, we show that the C2A domain of Caenorhabditis elegans UNC-13 regulates release probability of evoked release and its precise active zone localization. Kinetics analysis of SV release supports that the proximity of UNC-13 to Ca2+ entry sites, mediated by the C2A-domain containing N-terminus, is critical for accelerating neurotransmitter release. Additionally, the C2A domain is specifically required for spontaneous release. These data reveal multiple roles of UNC-13 C2A domain, and suggest that spontaneous release and the fast phase of evoked release may involve a common pool of SVs at the active zone. DOI:http://dx.doi.org/10.7554/eLife.01180.001 Neurons are connected to each other by junctions called synapses. When an electrical signal travelling along a neuron arrives at a synapse, it causes the release of bubble-like structures called synaptic vesicles that contain chemicals called neurotransmitters. When released by the vesicles these neurotransmitters bind to receptors on a second neuron and allow the signal to continue on its way through the nervous system. The release of synaptic vesicles from the neuron depends largely on the number of calcium ions that enter this neuron via structures called ion channels, and also on the rate at which they enter. Vesicles are released in one of three ways: they can be released quickly (within a few milliseconds) in response to the influx of calcium ions; they can be released slowly (over a period of tens or hundreds of milliseconds) in response to the influx; or they can be released at random times that are not related to the influx. It is known that the sensitivity of certain calcium sensors near the synapse influences the release of the vesicles. It had been thought that the distance between the “active zone” where the calcium ions enter the neuron and the region where the vesicles reside might also influence rate of release, but the molecular mechanism underlying this hypothesis is poorly understood. Zhou et al. have now shed new light on this question by performing a series of experiments that involved manipulating a protein called UNC-13 – which is known to be involved in the release of vesicles – in neurons from C. elegans, a nematode worm. First it was shown that the precise position of UNC-13 in the active zone depended on a domain within the protein called the C2A domain. Next it was shown that the distance between the UNC-13 protein and the calcium ion channels strongly influences the quick mode of vesicle release. Finally, Zhou et al. showed that the C2A domain also had a significant influence on the spontaneous release of vesicles, which suggests that a common fleet of vesicles might be used for both the quick and the spontaneous modes of vesicle release. Zhou et al. also generated mutant worms that mimicked a neurological disease, epileptic seizure, and showed that eliminating the C2A domain can relieve some of the symptoms associated with the disease. Many neurological diseases are caused by signals not being transmitted properly at synapses, so in addition to providing insights into the basic mechanism underlying synaptic action, these results could also assist with the development of new strategies for managing neurological diseases. DOI:http://dx.doi.org/10.7554/eLife.01180.002
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Affiliation(s)
- Keming Zhou
- Section of Neurobiology, Division of Biological Sciences, University of California, San Diego, La Jolla, United States
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39
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Lesch KP, Merker S, Reif A, Novak M. Dances with black widow spiders: dysregulation of glutamate signalling enters centre stage in ADHD. Eur Neuropsychopharmacol 2013; 23:479-91. [PMID: 22939004 DOI: 10.1016/j.euroneuro.2012.07.013] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/23/2012] [Revised: 07/10/2012] [Accepted: 07/24/2012] [Indexed: 11/26/2022]
Abstract
Attention-deficit/hyperactivity disorder (ADHD) is a common neurodevelopmental disorder with impairments across the lifespan. The persistence of ADHD is associated with considerable liability to neuropsychiatric co-morbidity such as depression, anxiety and substance use disorder. The substantial heritability of ADHD is well documented and recent genome-wide analyses for risk genes revealed synaptic adhesion molecules (e.g. latrophilin-3, LPHN3; fibronectin leucine-rich repeat transmembrane protein-3, FLRT3), glutamate receptors (e.g. metabotropic glutamate receptor-5, GRM5) and mediators of intracellular signalling pathways (e.g. nitric oxide synthase-1, NOS1). These genes encode principal components of the molecular machinery that connects pre- and postsynaptic neurons, facilitates glutamatergic transmission, controls synaptic plasticity and empowers intersecting neural circuits to process and refine information. Thus, identification of genetic variation affecting molecules essential for the formation, specification and function of excitatory synapses is refocusing research efforts on ADHD pathogenesis to include the long-neglected glutamate system.
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Affiliation(s)
- K P Lesch
- Division of Molecular Psychiatry, Laboratory of Translational Neuroscience, ADHD Clinical Research Network, Department of Psychiatry, Psychosomatics and Psychotherapy, University of Würzburg, Füchsleinstr. 15, 97080 Würzburg, Germany.
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40
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Neuron-specific expression of tomosyn1 in the mouse hippocampal dentate gyrus impairs spatial learning and memory. Neuromolecular Med 2013; 15:351-63. [PMID: 23519441 DOI: 10.1007/s12017-013-8223-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2012] [Accepted: 02/16/2013] [Indexed: 01/20/2023]
Abstract
Tomosyn, a syntaxin-binding protein, is known to inhibit vesicle priming and synaptic transmission via interference with the formation of SNARE complexes. Using a lentiviral vector, we specifically overexpressed tomosyn1 in hippocampal dentate gyrus neurons in adult mice. Mice were then subjected to spatial learning and memory tasks and electrophysiological measurements from hippocampal slices. Tomosyn1-overexpression significantly impaired hippocampus-dependent spatial memory while tested in the Morris water maze. Further, tomosyn1-overexpressing mice utilize swimming strategies of lesser cognitive ability in the Morris water maze compared with control mice. Electrophysiological measurements at mossy fiber-CA3 synapses revealed impaired paired-pulse facilitation in the mossy fiber of tomosyn1-overexpressing mice. This study provides evidence for novel roles for tomosyn1 in hippocampus-dependent spatial learning and memory, potentially via decreased synaptic transmission in mossy fiber-CA3 synapses. Moreover, it provides new insight regarding the role of the hippocampal dentate gyrus and mossy fiber-CA3 synapses in swimming strategy preference, and in learning and memory.
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41
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Nonconserved Ca(2+)/calmodulin binding sites in Munc13s differentially control synaptic short-term plasticity. Mol Cell Biol 2012; 32:4628-41. [PMID: 22966208 DOI: 10.1128/mcb.00933-12] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Munc13s are presynaptic proteins that mediate synaptic vesicle priming and thereby control the size of the readily releasable pool of vesicles. During high synaptic activity, Munc13-1 and its closely related homolog, ubMunc13-2, bind Ca(2+)/calmodulin, resulting in enhanced priming activity and in changes of short-term synaptic plasticity characteristics. Here, we studied whether bMunc13-2 and Munc13-3, two remote isoforms of Munc13-1 with a neuronal subtype-specific expression pattern, mediate synaptic vesicle priming and regulate short-term synaptic plasticity in a Ca(2+)/calmodulin-dependent manner. We identified a single functional Ca(2+)/calmodulin binding site in these isoforms and provide structural evidence that all Munc13s employ a common mode of interaction with calmodulin despite the lack of sequence homology between their Ca(2+)/calmodulin binding sites. Electrophysiological analysis showed that, during high-frequency activity, Ca(2+)/calmodulin binding positively regulates the priming activity of bMunc13-2 and Munc13-3, resulting in an increase in the size of the readily releasable pool of vesicles and subsequently in strong short-term synaptic enhancement of neurotransmission. We conclude that Ca(2+)/calmodulin-dependent regulation of priming activity is structurally and functionally conserved in all Munc13 proteins, and that the composition of Munc13 isoforms in a neuron differentially controls its short-term synaptic plasticity characteristics.
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42
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Veeramah KR, O'Brien JE, Meisler MH, Cheng X, Dib-Hajj SD, Waxman SG, Talwar D, Girirajan S, Eichler EE, Restifo LL, Erickson RP, Hammer MF. De novo pathogenic SCN8A mutation identified by whole-genome sequencing of a family quartet affected by infantile epileptic encephalopathy and SUDEP. Am J Hum Genet 2012; 90:502-10. [PMID: 22365152 DOI: 10.1016/j.ajhg.2012.01.006] [Citation(s) in RCA: 303] [Impact Index Per Article: 25.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2011] [Revised: 12/20/2011] [Accepted: 01/09/2012] [Indexed: 12/25/2022] Open
Abstract
Individuals with severe, sporadic disorders of infantile onset represent an important class of disease for which discovery of the underlying genetic architecture is not amenable to traditional genetic analysis. Full-genome sequencing of affected individuals and their parents provides a powerful alternative strategy for gene discovery. We performed whole-genome sequencing (WGS) on a family quartet containing an affected proband and her unaffected parents and sibling. The 15-year-old female proband had a severe epileptic encephalopathy consisting of early-onset seizures, features of autism, intellectual disability, ataxia, and sudden unexplained death in epilepsy. We discovered a de novo heterozygous missense mutation (c.5302A>G [p.Asn1768Asp]) in the voltage-gated sodium-channel gene SCN8A in the proband. This mutation alters an evolutionarily conserved residue in Nav1.6, one of the most abundant sodium channels in the brain. Analysis of the biophysical properties of the mutant channel demonstrated a dramatic increase in persistent sodium current, incomplete channel inactivation, and a depolarizing shift in the voltage dependence of steady-state fast inactivation. Current-clamp analysis in hippocampal neurons transfected with p.Asn1768Asp channels revealed increased spontaneous firing, paroxysmal-depolarizing-shift-like complexes, and an increased firing frequency, consistent with a dominant gain-of-function phenotype in the heterozygous proband. This work identifies SCN8A as the fifth sodium-channel gene to be mutated in epilepsy and demonstrates the value of WGS for the identification of pathogenic mutations causing severe, sporadic neurological disorders.
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Affiliation(s)
- Krishna R Veeramah
- Arizona Research Laboratories, Division of Biotechnology, University of Arizona, Tucson, 85721, USA
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Kopplin LJ, Igo RP, Wang Y, Sivakumaran TA, Hagstrom SA, Peachey NS, Francis PJ, Klein ML, SanGiovanni JP, Chew EY, Pauer GJT, Sturgill GM, Joshi T, Tian L, Xi Q, Henning AK, Lee KE, Klein R, Klein BEK, Iyengar SK. Genome-wide association identifies SKIV2L and MYRIP as protective factors for age-related macular degeneration. Genes Immun 2010; 11:609-21. [PMID: 20861866 PMCID: PMC3375062 DOI: 10.1038/gene.2010.39] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2010] [Revised: 05/17/2010] [Accepted: 05/17/2010] [Indexed: 01/11/2023]
Abstract
Age-related macular degeneration (AMD) is the leading cause of blindness in the elderly in the developed world. We conducted a genome-wide association study in a series of families enriched for AMD and completed a meta-analysis of this new data with results from reanalysis of an existing study of a late-stage case-control cohort. We tested the top findings for replication in 1896 cases and 1866 controls and identified two novel genetic protective factors for AMD. In addition to the complement factor H (CFH) (P=2.3 × 10⁻⁶⁴) and age-related maculopathy susceptibility 2 (ARMS2) (P=1.2 × 10⁻⁶⁰) loci, we observed a protective effect at rs429608, an intronic SNP in SKIV2L (P=5.3 × 10⁻¹⁵), a gene near the complement component 2 (C2)/complement factor B (BF) locus, that indicates the protective effect may be mediated by variants other than the C2/BF variants previously studied. Haplotype analysis at this locus identified three protective haplotypes defined by the rs429608 protective allele. We also identified a new potentially protective effect at rs2679798 in MYRIP (P=2.9 × 10⁻⁴), a gene involved in retinal pigment epithelium melanosome trafficking. Interestingly, MYRIP was initially identified in the family-based scan and was confirmed in the case-control set. From these efforts, we report the identification of two novel protective factors for AMD and confirm the previously known associations at CFH, ARMS2 and C3.
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Affiliation(s)
- L J Kopplin
- Department of Genetics, Case Western Reserve University, Cleveland, OH 44106, USA
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Increased expression of alpha-synuclein reduces neurotransmitter release by inhibiting synaptic vesicle reclustering after endocytosis. Neuron 2010; 65:66-79. [PMID: 20152114 DOI: 10.1016/j.neuron.2009.12.023] [Citation(s) in RCA: 786] [Impact Index Per Article: 56.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/10/2009] [Indexed: 12/18/2022]
Abstract
The protein alpha-synuclein accumulates in the brain of patients with sporadic Parkinson's disease (PD), and increased gene dosage causes a severe, dominantly inherited form of PD, but we know little about the effects of synuclein that precede degeneration. alpha-Synuclein localizes to the nerve terminal, but the knockout has little if any effect on synaptic transmission. In contrast, we now find that the modest overexpression of alpha-synuclein, in the range predicted for gene multiplication and in the absence of overt toxicity, markedly inhibits neurotransmitter release. The mechanism, elucidated by direct imaging of the synaptic vesicle cycle, involves a specific reduction in size of the synaptic vesicle recycling pool. Ultrastructural analysis demonstrates reduced synaptic vesicle density at the active zone, and imaging further reveals a defect in the reclustering of synaptic vesicles after endocytosis. Increased levels of alpha-synuclein thus produce a specific, physiological defect in synaptic vesicle recycling that precedes detectable neuropathology.
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Munc13 C2B domain is an activity-dependent Ca2+ regulator of synaptic exocytosis. Nat Struct Mol Biol 2010; 17:280-8. [PMID: 20154707 PMCID: PMC2916016 DOI: 10.1038/nsmb.1758] [Citation(s) in RCA: 180] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2009] [Accepted: 12/04/2009] [Indexed: 11/08/2022]
Abstract
Munc13 is a multidomain protein present in presynaptic active zones that mediates the priming and plasticity of synaptic vesicle exocytosis, but the mechanisms involved remain unclear. Here we use biophysical, biochemical and electrophysiological approaches to show that the central C(2)B domain of Munc13 functions as a Ca(2+) regulator of short-term synaptic plasticity. The crystal structure of the C(2)B domain revealed an unusual Ca(2+)-binding site with an amphipathic alpha-helix. This configuration confers onto the C(2)B domain unique Ca(2+)-dependent phospholipid-binding properties that favor phosphatidylinositolphosphates. A mutation that inactivated Ca(2+)-dependent phospholipid binding to the C(2)B domain did not alter neurotransmitter release evoked by isolated action potentials, but it did depress release evoked by action-potential trains. In contrast, a mutation that increased Ca(2+)-dependent phosphatidylinositolbisphosphate binding to the C(2)B domain enhanced release evoked by isolated action potentials and by action-potential trains. Our data suggest that, during repeated action potentials, Ca(2+) and phosphatidylinositolphosphate binding to the Munc13 C(2)B domain potentiate synaptic vesicle exocytosis, thereby offsetting synaptic depression induced by vesicle depletion.
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Breustedt J, Gundlfinger A, Varoqueaux F, Reim K, Brose N, Schmitz D. Munc13-2 differentially affects hippocampal synaptic transmission and plasticity. ACTA ACUST UNITED AC 2009; 20:1109-20. [PMID: 19700493 DOI: 10.1093/cercor/bhp170] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The short-term dynamics of synaptic communication between neurons provides neural networks with specific frequency-filter characteristics for information transfer. The direction of short-term synaptic plasticity, that is, facilitation versus depression, is highly dependent on and inversely correlated to the basal release probability of a synapse. Amongst the processes implicated in shaping the release probability, proteins that regulate the docking and priming of synaptic vesicles at the active zone are of special importance. Here, we found that a member of the Munc13 protein family of priming proteins, namely Munc13-2, is essential for normal release probability at hippocampal mossy fiber synapses. Paired pulse and frequency facilitation were strongly increased, whereas mossy fiber long-term potentiation was unaffected in the absence of Munc13-2. In contrast, transmission at 3 other types of hippocampal synapses, Schaffer-collateral, associational-commissural, as well as inhibitory synapses onto CA3 pyramidal neurons was unaffected by the loss of Munc13-2.
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Affiliation(s)
- J Breustedt
- Neurowissenschaftliches Forschungszentrum, Charité-Universitätsmedizin Berlin, 10117 Berlin, Germany
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Rab3a-mediated vesicle recruitment regulates short-term plasticity at the mouse diaphragm synapse. Mol Cell Neurosci 2009; 41:286-96. [DOI: 10.1016/j.mcn.2009.03.008] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2008] [Revised: 03/04/2009] [Accepted: 03/24/2009] [Indexed: 11/24/2022] Open
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Insights into a molecular switch that gates sensory neuron synapses during habituation in Aplysia. Neurobiol Learn Mem 2009; 92:155-65. [PMID: 19345275 DOI: 10.1016/j.nlm.2009.03.006] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2008] [Revised: 03/15/2009] [Accepted: 03/16/2009] [Indexed: 11/20/2022]
Abstract
This review focuses on synaptic depression at sensory neuron-to-motor neuron synapses in the defensive withdrawal circuit of Aplysia as a model system for analysis of molecular mechanisms of sensory gating and habituation. We address the following topics: 1. Of various possible mechanisms that might underlie depression at these sensory neuron-to-motor neuron synapses in Aplysia, historically the most widely-accepted explanation has been depletion of the readily releasable pool of vesicles. Depletion is also believed to account for synaptic depression at long interstimulus intervals in a variety of other systems. 2. Multiple lines of evidence now indicate that vesicle depletion is not an important contributing mechanism to synaptic depression at Aplysia sensory neuron-to-motor neuron synapses. More generally, it appears that vesicle depletion does not contribute substantially to depression that occurs with those stimulus patterns that are typically used in studying behavioral habituation. 3. Recent evidence suggests that at these sensory neuron-to-motor neuron synapses in Aplysia, synaptic depression is mediated by an activity-dependent, but release-independent, switching of individual release sites to a silent state. This switching off of release sites is initiated by Ca2+ influx during individual action potentials. We discuss signaling proteins that may be regulated by Ca2+ during the silencing of release sites that underlies synaptic depression. 4. Bursts of 2-4 action potentials in presynaptic sensory neurons in Aplysia prevent the switching off of release sites via a mechanism called "burst-dependent protection" from synaptic depression. 5. This molecular switch may explain the sensory gating that allows animals to discriminate which stimuli are innocuous and appropriate to ignore and which stimuli are more important and should continue to elicit responses.
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Abstract
Exocytosis of insulin vesicles in the pancreatic beta-cell involves a sequence of regulated events, whose normal function and efficient adaptation to increased demand are essential for the maintenance of glucose homeostasis. These exocytotic events comprise the trafficking and docking of vesicles to the plasma membrane, followed by fusion triggered by Ca(2+). Recent studies have unravelled post-docking steps mediated by novel factors, which, by their interactions with soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE)- and SNARE-associated proteins, confer the docked vesicles fusion competence. These priming steps define the releasable pool of insulin vesicles, which accounts for the first phase of insulin secretion, and controls the rate at which vesicles are replenished for the second phase of secretion. This article aims to summarize what is currently known about the mechanisms that underlie the priming activity of these proteins, focusing on Munc13, a topic to which we have made some recent contributions. Abnormal glucose homeostasis in type 2 diabetes is because of the failure of islet beta-cells to augment insulin secretion sufficiently to compensate for reduced insulin sensitivity. A better understanding of the priming steps may help develop novel approaches to increase insulin secretory capacity and thereby prevent the progression to type 2 diabetes.
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Affiliation(s)
- E P Kwan
- Departments of Physiology and Medicine, University of Toronto, Toronto, Ontario, Canada
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Bidirectional regulation of Munc13-3 protein expression by age and dark rearing during the critical period in mouse visual cortex. Neuroscience 2007; 150:603-8. [PMID: 17997229 DOI: 10.1016/j.neuroscience.2007.09.053] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2007] [Revised: 09/21/2007] [Accepted: 09/28/2007] [Indexed: 11/24/2022]
Abstract
Rearing in darkness slows the time course of the visual cortical critical period, such that at 5 weeks of age normal cats are more plastic than dark-reared cats, while at 20 weeks dark-reared cats are more plastic [Mower GD (1991) The effect of dark rearing on the time course of the critical period in cat visual cortex. Dev Brain Res 58:151-158]. Thus, genes that are important for visual cortical plasticity should show differences in expression between normal and dark-reared visual cortex that are of opposite direction in young versus older animals. Previously, we showed by differential display polymerase chain reaction and northern blotting that mRNA for Munc13-3, a mammalian homologue of the C. elegans uncoordinated (unc) gene, shows such bidirectional regulation in cat visual cortex [Yang CB, Zheng YT, Li GY, Mower GD (2002) Identification of Munc13-3 as a candidate gene for critical period neuroplasticity in visual cortex. J Neurosci 22:8614-8618]. Here, the analysis is extended to Munc13-3 protein in mouse visual cortex, which will provide the basis for gene manipulation analysis. In mice, Munc13-3 protein was elevated 2.3-fold in dark-reared compared with normal visual cortex at 3.5 weeks and 2.0-fold in normal compared with dark-reared visual cortex at 9.5 weeks. Analysis of variance of protein levels showed a significant interaction, indicating that the effect of dark rearing depended on age. This bidirectional regulation was restricted to visual cortex and did not occur in frontal cortex. Bidirectional regulation was also specific to Munc13-3 and was not found for other Munc13 family members. Munc13 proteins serve a central priming function in synaptic vesicle exocytosis at glutamatergic and GABAergic synapses and this work contributes to the growing evidence indicating a role of Munc13 genes in synaptic plasticity.
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