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Chou S, Fish KN, Lewis DA, Sweet RA. Terminal type-specific cannabinoid CB1 receptor alterations in patients with schizophrenia: A pilot study. Neurobiol Dis 2023; 185:106262. [PMID: 37586566 PMCID: PMC10958392 DOI: 10.1016/j.nbd.2023.106262] [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: 02/28/2023] [Revised: 08/11/2023] [Accepted: 08/14/2023] [Indexed: 08/18/2023] Open
Abstract
BACKGROUND Individuals with schizophrenia are at elevated genetic risks for comorbid cannabis use, and often experience exacerbations of cognitive and psychotic symptoms when exposed to cannabis. These findings have led a number of investigators to examine cannabinoid CB1 receptor (CB1R) alterations in schizophrenia, though with conflicting results. We recently demonstrated the presence of CB1R in both excitatory and inhibitory boutons in the human prefrontal cortex, with differential levels of the receptor between bouton types. We hypothesized that the differential enrichment of CB1R between bouton types - a factor previously unaccounted for when examining CB1R changes in schizophrenia - may resolve prior discrepant reports and increase our insight into the effects of CB1R alterations on the pathophysiology of schizophrenia. METHODS Using co-labeling immunohistochemistry and fluorescent microscopy, we examined total CB1R levels and CB1R levels within excitatory (vGlut1-positive) and inhibitory (vGAT-positive) boutons of prefrontal cortex samples from ten pairs of individuals (nine male pairs and one female pair) diagnosed with schizophrenia and non-psychiatric comparisons. RESULTS Significantly higher total CB1R levels were found within samples from individuals with schizophrenia. Terminal type-specific analyses identified significantly higher CB1R levels within excitatory boutons in samples from individuals with schizophrenia relative to comparisons. In contrast, CB1R levels within the subset of inhibitory boutons that normally express high CB1R levels (presumptive cholecystokinin neuron boutons) were lower in samples from individuals with schizophrenia relative to comparison samples. CONCLUSION Given CB1R's role in suppressing neurotransmission upon activation, these results suggest an overall shift in excitatory and inhibitory balance regulation toward a net reduction of excitatory activity in schizophrenia.
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Affiliation(s)
- Shinnyi Chou
- Translational Neuroscience Program, Department of Psychiatry, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, United States of America
| | - Kenneth N Fish
- Translational Neuroscience Program, Department of Psychiatry, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, United States of America
| | - David A Lewis
- Translational Neuroscience Program, Department of Psychiatry, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, United States of America
| | - Robert A Sweet
- Translational Neuroscience Program, Department of Psychiatry, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, United States of America.
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Chou S, Fish KN, Lewis DA, Sweet RA. Terminal type-specific cannabinoid CB1 receptor alterations in patients with schizophrenia: a pilot study. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.04.11.536217. [PMID: 37090672 PMCID: PMC10120624 DOI: 10.1101/2023.04.11.536217] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/25/2023]
Abstract
Background Individuals with schizophrenia are at elevated genetic risks for comorbid cannabis use, and often experience exacerbations of cognitive and psychotic symptoms when exposed to cannabis. These findings have led a number of investigators to examine cannabinoid CB1 receptor (CB1R) alterations in schizophrenia, though with conflicting results. We recently demonstrated the presence of CB1R in both excitatory and inhibitory boutons in the human prefrontal cortex, with differential levels of the receptor between bouton types. We hypothesized that the differential enrichment of CB1R between bouton types - a factor previously unaccounted for when examining CB1R changes in schizophrenia - may resolve prior discrepant reports and increase our insight into the effects of CB1R alterations on the pathophysiology of schizophrenia. Methods Using co-labeling immunohistochemistry and fluorescent microscopy, we examined total CB1R levels and CB1R levels within excitatory (vGlut1-positive) and inhibitory (vGAT-positive) boutons of prefrontal cortex samples from ten pairs of individuals diagnosed with schizophrenia and non-psychiatric comparisons. Results Significantly higher total CB1R levels were found within samples from individuals with schizophrenia. Terminal type-specific analyses identified significantly higher CB1R levels within excitatory boutons in samples from individuals with schizophrenia relative to comparisons. In contrast, CB1R levels within the subset of inhibitory boutons that normally express high CB1R levels (presumptive cholecystokinin neuron boutons) were lower in samples from individuals with schizophrenia relative to comparison samples. Conclusion Given CB1R's role in suppressing neurotransmission upon activation, these results suggest an overall shift in excitatory and inhibitory balance regulation toward a net reduction of excitatory activity in schizophrenia.
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Affiliation(s)
- Shinnyi Chou
- Translational Neuroscience Program, Department of Psychiatry, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, 15261
| | - Kenneth N Fish
- Translational Neuroscience Program, Department of Psychiatry, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, 15261
| | - David A Lewis
- Translational Neuroscience Program, Department of Psychiatry, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, 15261
| | - Robert A Sweet
- Translational Neuroscience Program, Department of Psychiatry, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, 15261
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Mi Z, Abrahamson EE, Ryu AY, Malek-Ahmadi M, Kofler JK, Fish KN, Sweet RA, Villemagne VL, Schneider JA, Mufson EJ, Ikonomovic MD. Vesicular Glutamate Transporter Changes in the Cortical Default Mode Network During the Clinical and Pathological Progression of Alzheimer's Disease. J Alzheimers Dis 2023; 94:227-246. [PMID: 37212097 PMCID: PMC10994206 DOI: 10.3233/jad-221063] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
BACKGROUND Altered glutamatergic neurotransmission may contribute to impaired default mode network (DMN) function in Alzheimer's disease (AD). Among the DMN hub regions, frontal cortex (FC) was suggested to undergo a glutamatergic plasticity response in prodromal AD, while the status of glutamatergic synapses in the precuneus (PreC) during clinical-neuropathological AD progression is not known. OBJECTIVE To quantify vesicular glutamate transporter VGluT1- and VGluT2-containing synaptic terminals in PreC and FC across clinical stages of AD. METHODS Unbiased sampling and quantitative confocal immunofluorescence of cortical VGluT1- and VGluT2-immunoreactive profiles and spinophilin-labeled dendritic spines were performed in cases with no cognitive impairment (NCI), mild cognitive impairment (MCI), mild-moderate AD (mAD), or moderate-severe AD (sAD). RESULTS In both regions, loss of VGluT1-positive profile density was seen in sAD compared to NCI, MCI, and mAD. VGluT1-positive profile intensity in PreC did not differ across groups, while in FC it was greater in MCI, mAD, and sAD compared to NCI. VGluT2 measures were stable in PreC while FC had greater VGluT2-positive profile density in MCI compared to sAD, but not NCI or mAD. Spinophilin measures in PreC were lower in mAD and sAD compared to NCI, while in FC they were stable across groups. Lower VGluT1 and spinophilin measures in PreC, but not FC, correlated with greater neuropathology. CONCLUSION Frank loss of VGluT1 in advanced AD relative to NCI occurs in both DMN regions. In FC, an upregulation of VGluT1 protein content in remaining glutamatergic terminals may contribute to this region's plasticity response in AD.
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Affiliation(s)
- Zhiping Mi
- Department of Neurology, University of Pittsburgh School of
Medicine, Pittsburgh, PA, USA
- Geriatric Research Education and Clinical Center, VA
Pittsburgh Healthcare System, Pittsburgh, PA, USA
| | - Eric E. Abrahamson
- Department of Neurology, University of Pittsburgh School of
Medicine, Pittsburgh, PA, USA
- Geriatric Research Education and Clinical Center, VA
Pittsburgh Healthcare System, Pittsburgh, PA, USA
| | - Angela Y. Ryu
- Department of Neurology, University of Pittsburgh School of
Medicine, Pittsburgh, PA, USA
| | - Michael Malek-Ahmadi
- Banner Alzheimer’s Institute, Phoenix, AZ, USA
- Department of Biomedical Informatics, University of Arizona
College of Medicine, Phoenix, AZ, USA
| | - Julia K. Kofler
- Department of Pathology, University of Pittsburgh School of
Medicine, Pittsburgh, PA, USA
| | - Kenneth N. Fish
- Department of Psychiatry, University of Pittsburgh School
of Medicine, Pittsburgh, PA, USA
| | - Robert A. Sweet
- Department of Neurology, University of Pittsburgh School of
Medicine, Pittsburgh, PA, USA
- Department of Psychiatry, University of Pittsburgh School
of Medicine, Pittsburgh, PA, USA
| | - Victor L. Villemagne
- Department of Psychiatry, University of Pittsburgh School
of Medicine, Pittsburgh, PA, USA
| | - Julie A. Schneider
- Rush Alzheimer’s Disease Center, Rush University
Medical Center, Chicago, IL, USA
| | - Elliott J. Mufson
- Banner Alzheimer’s Institute, Phoenix, AZ, USA
- Departments of Translational Neurosciences and Neurology,
Barrow Neurological Institute, Phoenix, AZ, USA
| | - Milos D. Ikonomovic
- Department of Neurology, University of Pittsburgh School of
Medicine, Pittsburgh, PA, USA
- Geriatric Research Education and Clinical Center, VA
Pittsburgh Healthcare System, Pittsburgh, PA, USA
- Department of Psychiatry, University of Pittsburgh School
of Medicine, Pittsburgh, PA, USA
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Cell type specific cannabinoid CB1 receptor distribution across the human and non-human primate cortex. Sci Rep 2022; 12:9605. [PMID: 35688916 PMCID: PMC9187707 DOI: 10.1038/s41598-022-13724-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2022] [Accepted: 05/13/2022] [Indexed: 11/30/2022] Open
Abstract
Alterations in cannabinoid CB1 receptor (CB1R) are implicated in various psychiatric disorders. CB1R participates in both depolarization induced suppression of inhibition (DSI) and depolarization induced suppression of excitation (DSE), suggesting its involvement in regulating excitatory and inhibitory (E/I) balance. Prior studies examining neuronal cell type specific CB1R distribution have been conducted near exclusively within rodents. Identification of these distribution patterns within the human and non-human primate cortex is essential to increase our insight into its function. Using co-labeling immunohistochemistry and fluorescent microscopy, we examined CB1R protein levels within excitatory and inhibitory boutons of male human and non-human primate prefrontal cortex and auditory cortices, regions involved in the behavioral effects of exogenous cannabinoid exposures. We found that CB1R was present in both bouton populations within all brain regions examined in both species. Significantly higher CB1R levels were found within inhibitory than within excitatory boutons across all regions in both species, although the cell type by brain region interactions differed between the two species. Our results support the importance of conducting more in-depth CB1R examinations to understand how cell type and brain region dependent differences contribute to regional E/I balance regulation, and how aberrations in CB1R distribution may contribute to pathology.
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Coviello S, Gramuntell Y, Klimczak P, Varea E, Blasco-Ibañez JM, Crespo C, Gutierrez A, Nacher J. Phenotype and Distribution of Immature Neurons in the Human Cerebral Cortex Layer II. Front Neuroanat 2022; 16:851432. [PMID: 35464133 PMCID: PMC9027810 DOI: 10.3389/fnana.2022.851432] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2022] [Accepted: 03/22/2022] [Indexed: 11/13/2022] Open
Abstract
This work provides evidence of the presence of immature neurons in the human brain, specifically in the layer II of the cerebral cortex. Using surgical samples from epileptic patients and post-mortem tissue, we have found cells with different levels of dendritic complexity (type I and type II cells) expressing DCX and PSA-NCAM and lacking expression of the mature neuronal marker NeuN. These immature cells belonged to the excitatory lineage, as demonstrated both by the expression of CUX1, CTIP2, and TBR1 transcription factors and by the lack of the inhibitory marker GAD67. The type II cells had some puncta expressing inhibitory and excitatory synaptic markers apposed to their perisomatic and peridendritic regions and ultrastructural analysis suggest the presence of synaptic contacts. These cells did not present glial cell markers, although astroglial and microglial processes were found in close apposition to their somata and dendrites, particularly on type I cells. Our findings confirm the presence of immature neurons in several regions of the cerebral cortex of humans of different ages and define their lineage. The presence of some mature features in some of these cells suggests the possibility of a progressively integration as excitatory neurons, as described in the olfactory cortex of rodents.
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Affiliation(s)
- Simona Coviello
- Neurobiology Unit, Program in Neurosciences and Institute of Biotechnology and Biomedicine (BIOTECMED), Universitat de València, Burjassot, Spain
| | - Yaiza Gramuntell
- Neurobiology Unit, Program in Neurosciences and Institute of Biotechnology and Biomedicine (BIOTECMED), Universitat de València, Burjassot, Spain
| | - Patrycja Klimczak
- Neurobiology Unit, Program in Neurosciences and Institute of Biotechnology and Biomedicine (BIOTECMED), Universitat de València, Burjassot, Spain
- Spanish National Network for Research in Mental Health, Centro de Investigación Biomédica en Red de Salud Mental (CIBERSAM), Madrid, Spain
| | - Emilio Varea
- Neurobiology Unit, Program in Neurosciences and Institute of Biotechnology and Biomedicine (BIOTECMED), Universitat de València, Burjassot, Spain
| | - José Miguel Blasco-Ibañez
- Neurobiology Unit, Program in Neurosciences and Institute of Biotechnology and Biomedicine (BIOTECMED), Universitat de València, Burjassot, Spain
| | - Carlos Crespo
- Neurobiology Unit, Program in Neurosciences and Institute of Biotechnology and Biomedicine (BIOTECMED), Universitat de València, Burjassot, Spain
| | - Antonio Gutierrez
- Unidad de Cirugía de la Epilepsia, Hospital Universitario La Fe, Valencia, Spain
| | - Juan Nacher
- Neurobiology Unit, Program in Neurosciences and Institute of Biotechnology and Biomedicine (BIOTECMED), Universitat de València, Burjassot, Spain
- Spanish National Network for Research in Mental Health, Centro de Investigación Biomédica en Red de Salud Mental (CIBERSAM), Madrid, Spain
- Fundación Investigación Hospital Clínico de Valencia (INCLIVA), Valencia, Spain
- *Correspondence: Juan Nacher,
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Glausier JR, Datta D, Fish KN, Chung DW, Melchitzky DS, Lewis DA. Laminar Differences in the Targeting of Dendritic Spines by Cortical Pyramidal Neurons and Interneurons in Human Dorsolateral Prefrontal Cortex. Neuroscience 2021; 452:181-191. [PMID: 33212224 PMCID: PMC7770119 DOI: 10.1016/j.neuroscience.2020.10.022] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2020] [Revised: 10/05/2020] [Accepted: 10/21/2020] [Indexed: 01/05/2023]
Abstract
Activation of specific neural circuits in different layers of the primate dorsolateral prefrontal cortex (DLPFC) is essential for working memory, a core cognitive function. Recurrent excitation between pyramidal neurons in middle and deep layers of the DLPFC contributes to the laminar-specific activity associated with different working memory subprocesses. Excitation between cortical pyramidal neurons is mediated by glutamatergic synapses on dendritic spines, but whether the relative abundance of spines receiving cortical inputs differs between middle and deep cortical layers in human DLPFC is unknown. Additionally, GABAergic inputs to spines sculpt pyramidal neuron activity. Whether dendritic spines that receive a glutamatergic input from a cortical pyramidal neuron are targeted by GABAergic interneurons in the human DLPFC is unknown. Using triple-label fluorescence confocal microscopy, we found that 1) the density of spines receiving an input from a cortical pyramidal neuron is greater in the middle than in the deep laminar zone, 2) dendritic spines dually innervated by a cortical pyramidal neuron and an interneuron are present in the human DLPFC, and 3) the density of spines dually innervated by a cortical pyramidal neuron and an interneuron is also greater in the middle than in the deep laminar zone. Ultrastructural analyses support the presence of spines that receive a cortical pyramidal neuron synapse and an interneuron synapse in human and monkey DLPFC. These data support the notion that the DLPFC middle laminar zone is particularly endowed with a microcircuit structure that supports the gating, integrating and fine-tuning of synaptic information in recurrent excitatory microcircuits.
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Affiliation(s)
- Jill R Glausier
- Department of Psychiatry, Translational Neuroscience Program, University of Pittsburgh School of Medicine, Biomedical Science Tower W1654, 3811 O'Hara Street, Pittsburgh, PA 15213, USA
| | - Dibyadeep Datta
- Department of Psychiatry, Translational Neuroscience Program, University of Pittsburgh School of Medicine, Biomedical Science Tower W1654, 3811 O'Hara Street, Pittsburgh, PA 15213, USA; Department of Neuroscience, University of Pittsburgh, A210 Langley Hall, Pittsburgh, PA 15260, USA; Department of Neuroscience, Yale University, Sterling Hall of Medicine, 333 Cedar Street, New Haven, CT 06510, USA
| | - Kenneth N Fish
- Department of Psychiatry, Translational Neuroscience Program, University of Pittsburgh School of Medicine, Biomedical Science Tower W1654, 3811 O'Hara Street, Pittsburgh, PA 15213, USA; Department of Neuroscience, University of Pittsburgh, A210 Langley Hall, Pittsburgh, PA 15260, USA
| | - Daniel W Chung
- Department of Psychiatry, Translational Neuroscience Program, University of Pittsburgh School of Medicine, Biomedical Science Tower W1654, 3811 O'Hara Street, Pittsburgh, PA 15213, USA; Department of Neuroscience, University of Pittsburgh, A210 Langley Hall, Pittsburgh, PA 15260, USA
| | - Darlene S Melchitzky
- Department of Psychiatry, Translational Neuroscience Program, University of Pittsburgh School of Medicine, Biomedical Science Tower W1654, 3811 O'Hara Street, Pittsburgh, PA 15213, USA
| | - David A Lewis
- Department of Psychiatry, Translational Neuroscience Program, University of Pittsburgh School of Medicine, Biomedical Science Tower W1654, 3811 O'Hara Street, Pittsburgh, PA 15213, USA; Department of Neuroscience, University of Pittsburgh, A210 Langley Hall, Pittsburgh, PA 15260, USA.
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7
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Slomianka L. Basic quantitative morphological methods applied to the central nervous system. J Comp Neurol 2020; 529:694-756. [PMID: 32639600 PMCID: PMC7818269 DOI: 10.1002/cne.24976] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2020] [Revised: 06/15/2020] [Accepted: 06/16/2020] [Indexed: 12/19/2022]
Abstract
Generating numbers has become an almost inevitable task associated with studies of the morphology of the nervous system. Numbers serve a desire for clarity and objectivity in the presentation of results and are a prerequisite for the statistical evaluation of experimental outcomes. Clarity, objectivity, and statistics make demands on the quality of the numbers that are not met by many methods. This review provides a refresher of problems associated with generating numbers that describe the nervous system in terms of the volumes, surfaces, lengths, and numbers of its components. An important aim is to provide comprehensible descriptions of the methods that address these problems. Collectively known as design‐based stereology, these methods share two features critical to their application. First, they are firmly based in mathematics and its proofs. Second and critically underemphasized, an understanding of their mathematical background is not necessary for their informed and productive application. Understanding and applying estimators of volume, surface, length or number does not require more of an organizational mastermind than an immunohistochemical protocol. And when it comes to calculations, square roots are the gravest challenges to overcome. Sampling strategies that are combined with stereological probes are efficient and allow a rational assessment if the numbers that have been generated are “good enough.” Much may be unfamiliar, but very little is difficult. These methods can no longer be scapegoats for discrepant results but faithfully produce numbers on the material that is assessed. They also faithfully reflect problems that associated with the histological material and the anatomically informed decisions needed to generate numbers that are not only valid in theory. It is within reach to generate practically useful numbers that must integrate with qualitative knowledge to understand the function of neural systems.
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Affiliation(s)
- Lutz Slomianka
- University of Zürich, Institute of Anatomy, Zürich, Switzerland
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8
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Alhourani A, Fish KN, Wozny TA, Sudhakar V, Hamilton RL, Richardson RM. GABA bouton subpopulations in the human dentate gyrus are differentially altered in mesial temporal lobe epilepsy. J Neurophysiol 2019; 123:392-406. [PMID: 31800363 DOI: 10.1152/jn.00523.2018] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Medically intractable temporal lobe epilepsy is a devastating disease, for which surgical removal of the seizure onset zone is the only known cure. Multiple studies have found evidence of abnormal dentate gyrus network circuitry in human mesial temporal lobe epilepsy (MTLE). Principal neurons within the dentate gyrus gate entorhinal input into the hippocampus, providing a critical step in information processing. Crucial to that role are GABA-expressing neurons, particularly parvalbumin (PV)-expressing basket cells (PVBCs) and chandelier cells (PVChCs), which provide strong, temporally coordinated inhibitory signals. Alterations in PVBC and PVChC boutons have been described in epilepsy, but the value of these studies has been limited due to methodological hurdles associated with studying human tissue. We developed a multilabel immunofluorescence confocal microscopy and a custom segmentation algorithm to quantitatively assess PVBC and PVChC bouton densities and to infer relative synaptic protein content in the human dentate gyrus. Using en bloc specimens from MTLE subjects with and without hippocampal sclerosis, paired with nonepileptic controls, we demonstrate the utility of this approach for detecting cell-type specific synaptic alterations. Specifically, we found increased density of PVBC boutons, while PVChC boutons decreased significantly in the dentate granule cell layer of subjects with hippocampal sclerosis compared with matched controls. In contrast, bouton densities for either PV-positive cell type did not differ between epileptic subjects without sclerosis and matched controls. These results may explain conflicting findings from previous studies that have reported both preserved and decreased PV bouton densities and establish a new standard for quantitative assessment of interneuron boutons in epilepsy.NEW & NOTEWORTHY A state-of-the-art, multilabel immunofluorescence confocal microscopy and custom segmentation algorithm technique, developed previously for studying synapses in the human prefrontal cortex, was modified to study the hippocampal dentate gyrus in specimens surgically removed from patients with temporal lobe epilepsy. The authors discovered that chandelier and basket cell boutons in the human dentate gyrus are differentially altered in mesial temporal lobe epilepsy.
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Affiliation(s)
- Ahmad Alhourani
- Department of Neurological Surgery, University of Louisville School of Medicine, Louisville, Kentucky
| | - Kenneth N Fish
- Department of Psychiatry, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Thomas A Wozny
- Department of Neurological Surgery, University of California, San Francisco, California
| | - Vivek Sudhakar
- Department of Neurological Surgery, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Ronald L Hamilton
- Department of Pathology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - R Mark Richardson
- Department of Neurological Surgery, Massachusetts General Hospital, Boston, Massachusetts.,Harvard Medical School, Boston, Massachusetts
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Automated Macro Approach to Quantify Synapse Density in 2D Confocal Images from Fixed Immunolabeled Neural Tissue Sections. Methods Mol Biol 2019. [PMID: 31432476 DOI: 10.1007/978-1-4939-9686-5_5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2023]
Abstract
This chapter describes an ImageJ/Fiji automated macro approach to estimate synapse densities in 2D fluorescence confocal microscopy images. The main step-by-step imaging workflow is explained, including example macro language scripts that perform all steps automatically for multiple images. Such tool provides a straightforward method for exploratory synapse screenings where hundreds to thousands of images need to be analyzed in order to render significant statistical information. The method can be adapted to any particular set of images where fixed brain slices have been immunolabeled against validated presynaptic and postsynaptic markers.
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10
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Varando G, Benavides-Piccione R, Muñoz A, Kastanauskaite A, Bielza C, Larrañaga P, DeFelipe J. MultiMap: A Tool to Automatically Extract and Analyse Spatial Microscopic Data From Large Stacks of Confocal Microscopy Images. Front Neuroanat 2018; 12:37. [PMID: 29875639 PMCID: PMC5974206 DOI: 10.3389/fnana.2018.00037] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2018] [Accepted: 04/24/2018] [Indexed: 11/13/2022] Open
Abstract
The development of 3D visualization and reconstruction methods to analyse microscopic structures at different levels of resolutions is of great importance to define brain microorganization and connectivity. MultiMap is a new tool that allows the visualization, 3D segmentation and quantification of fluorescent structures selectively in the neuropil from large stacks of confocal microscopy images. The major contribution of this tool is the posibility to easily navigate and create regions of interest of any shape and size within a large brain area that will be automatically 3D segmented and quantified to determine the density of puncta in the neuropil. As a proof of concept, we focused on the analysis of glutamatergic and GABAergic presynaptic axon terminals in the mouse hippocampal region to demonstrate its use as a tool to provide putative excitatory and inhibitory synaptic maps. The segmentation and quantification method has been validated over expert labeled images of the mouse hippocampus and over two benchmark datasets, obtaining comparable results to the expert detections.
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Affiliation(s)
- Gherardo Varando
- Computational Intelligence Group, Department of Artificial Intelligence, Universidad Politécnica de Madrid, Madrid, Spain
| | - Ruth Benavides-Piccione
- Departamento de Neurobiología Funcional y de Sistemas, Instituto Cajal (CSIC), Madrid, Spain.,Laboratorio Cajal de Circuitos Corticales, Centro de Tecnología Biomédica, Universidad Politécnica de Madrid, Madrid, Spain
| | - Alberto Muñoz
- Departamento de Neurobiología Funcional y de Sistemas, Instituto Cajal (CSIC), Madrid, Spain.,Laboratorio Cajal de Circuitos Corticales, Centro de Tecnología Biomédica, Universidad Politécnica de Madrid, Madrid, Spain.,Departamento de Biología Celular, Universidad Complutense, Madrid, Spain
| | - Asta Kastanauskaite
- Departamento de Neurobiología Funcional y de Sistemas, Instituto Cajal (CSIC), Madrid, Spain.,Laboratorio Cajal de Circuitos Corticales, Centro de Tecnología Biomédica, Universidad Politécnica de Madrid, Madrid, Spain
| | - Concha Bielza
- Computational Intelligence Group, Department of Artificial Intelligence, Universidad Politécnica de Madrid, Madrid, Spain
| | - Pedro Larrañaga
- Computational Intelligence Group, Department of Artificial Intelligence, Universidad Politécnica de Madrid, Madrid, Spain
| | - Javier DeFelipe
- Departamento de Neurobiología Funcional y de Sistemas, Instituto Cajal (CSIC), Madrid, Spain.,Laboratorio Cajal de Circuitos Corticales, Centro de Tecnología Biomédica, Universidad Politécnica de Madrid, Madrid, Spain
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11
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Poon CC, Ebacher V, Liu K, Yong VW, Kelly JJP. Automated Slide Scanning and Segmentation in Fluorescently-labeled Tissues Using a Widefield High-content Analysis System. J Vis Exp 2018. [PMID: 29781988 PMCID: PMC6101103 DOI: 10.3791/57440] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Automated slide scanning and segmentation of fluorescently-labeled tissues is the most efficient way to analyze whole slides or large tissue sections. Unfortunately, many researchers spend large amounts of time and resources developing and optimizing workflows that are only relevant to their own experiments. In this article, we describe a protocol that can be used by those with access to a widefield high-content analysis system (WHCAS) to image any slide-mounted tissue, with options for customization within pre-built modules found in the associated software. Not originally intended for slide scanning, the steps detailed in this article make it possible to acquire slide scanning images in the WHCAS which can be imported into the associated software. In this example, the automated segmentation of brain tumor slides is demonstrated, but the automated segmentation of any fluorescently-labeled nuclear or cytoplasmic marker is possible. Furthermore, there are a variety of other quantitative software modules including assays for protein localization/translocation, cellular proliferation/viability/apoptosis, and angiogenesis that can be run. This technique will save researchers time and effort and create an automated protocol for slide analysis.
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Affiliation(s)
- Candice C Poon
- Department of Clinical Neurosciences, Arnie Charbonneau Cancer Institute, University of Calgary;
| | - Vincent Ebacher
- Department of Cell Biology and Anatomy, Hotchkiss Brain Institute, University of Calgary
| | - Katherine Liu
- Department of Clinical Neurosciences, Arnie Charbonneau Cancer Institute, University of Calgary
| | - Voon Wee Yong
- Department of Clinical Neurosciences, Arnie Charbonneau Cancer Institute, University of Calgary; Department of Oncology, Hotchkiss Brain Institute, University of Calgary
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12
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Parker EM, Sweet RA. Stereological Assessments of Neuronal Pathology in Auditory Cortex in Schizophrenia. Front Neuroanat 2018; 11:131. [PMID: 29375326 PMCID: PMC5767177 DOI: 10.3389/fnana.2017.00131] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2017] [Accepted: 12/18/2017] [Indexed: 12/21/2022] Open
Abstract
It has long been known that auditory processing is disrupted in schizophrenia. More recently, postmortem studies have provided direct evidence that morphological alterations to neurons in auditory cortex are implicated in the pathophysiology of this illness, confirming previous predictions. Potential neural substrates for auditory impairment and gray matter loss in auditory cortex in schizophrenia have been identified, described, and are the focus of this review article. Pyramidal cell somal volume is reduced in auditory cortex, as are dendritic spine density and number in schizophrenia. Pyramidal cells are not lost in this region in schizophrenia, indicating that dendritic spine reductions reflect fewer spines per pyramidal cell, consistent with the reduced neuropil hypothesis of schizophrenia. Stereological methods have aided in the proper collection, reporting and interpretation of this data. Mechanistic studies exploring relationships between genetic risk for schizophrenia and altered dendrite morphology represent an important avenue for future research in order to further elucidate cellular pathology in auditory cortex in schizophrenia.
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Affiliation(s)
- Emily M Parker
- Department of Psychiatry, University of Pittsburgh, Pittsburgh, PA, United States
| | - Robert A Sweet
- Department of Psychiatry, University of Pittsburgh, Pittsburgh, PA, United States.,Department of Neurology, University of Pittsburgh, Pittsburgh, PA, United States.,VISN 4 Mental Illness Research, Education and Clinical Center (MIRECC), VA Pittsburgh Healthcare System, Pittsburgh, PA, United States
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13
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Alegro M, Theofilas P, Nguy A, Castruita PA, Seeley W, Heinsen H, Ushizima DM, Grinberg LT. Automating cell detection and classification in human brain fluorescent microscopy images using dictionary learning and sparse coding. J Neurosci Methods 2017; 282:20-33. [PMID: 28267565 PMCID: PMC5600818 DOI: 10.1016/j.jneumeth.2017.03.002] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2016] [Revised: 02/28/2017] [Accepted: 03/02/2017] [Indexed: 10/20/2022]
Abstract
BACKGROUND Immunofluorescence (IF) plays a major role in quantifying protein expression in situ and understanding cell function. It is widely applied in assessing disease mechanisms and in drug discovery research. Automation of IF analysis can transform studies using experimental cell models. However, IF analysis of postmortem human tissue relies mostly on manual interaction, often subjected to low-throughput and prone to error, leading to low inter and intra-observer reproducibility. Human postmortem brain samples challenges neuroscientists because of the high level of autofluorescence caused by accumulation of lipofuscin pigment during aging, hindering systematic analyses. We propose a method for automating cell counting and classification in IF microscopy of human postmortem brains. Our algorithm speeds up the quantification task while improving reproducibility. NEW METHOD Dictionary learning and sparse coding allow for constructing improved cell representations using IF images. These models are input for detection and segmentation methods. Classification occurs by means of color distances between cells and a learned set. RESULTS Our method successfully detected and classified cells in 49 human brain images. We evaluated our results regarding true positive, false positive, false negative, precision, recall, false positive rate and F1 score metrics. We also measured user-experience and time saved compared to manual countings. COMPARISON WITH EXISTING METHODS We compared our results to four open-access IF-based cell-counting tools available in the literature. Our method showed improved accuracy for all data samples. CONCLUSION The proposed method satisfactorily detects and classifies cells from human postmortem brain IF images, with potential to be generalized for applications in other counting tasks.
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Affiliation(s)
- Maryana Alegro
- Memory and Aging Center, University of California San Francisco, 675 Nelson Rising Lane, San Francisco, CA 94158, USA.
| | - Panagiotis Theofilas
- Memory and Aging Center, University of California San Francisco, 675 Nelson Rising Lane, San Francisco, CA 94158, USA.
| | - Austin Nguy
- Memory and Aging Center, University of California San Francisco, 675 Nelson Rising Lane, San Francisco, CA 94158, USA.
| | - Patricia A Castruita
- Memory and Aging Center, University of California San Francisco, 675 Nelson Rising Lane, San Francisco, CA 94158, USA.
| | - William Seeley
- Memory and Aging Center, University of California San Francisco, 675 Nelson Rising Lane, San Francisco, CA 94158, USA.
| | - Helmut Heinsen
- Medical School of the University of São Paulo, Av. Reboucas 381, São Paulo, SP 05401-000, Brazil.
| | - Daniela M Ushizima
- Computational Research Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Rd, Berkeley, CA 94720, USA; Berkeley Institute for Data Science, University of California Berkeley, Berkeley, CA 94720, USA.
| | - Lea T Grinberg
- Memory and Aging Center, University of California San Francisco, 675 Nelson Rising Lane, San Francisco, CA 94158, USA.
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Loss of precuneus dendritic spines immunopositive for spinophilin is related to cognitive impairment in early Alzheimer's disease. Neurobiol Aging 2017; 55:159-166. [PMID: 28259365 PMCID: PMC5440205 DOI: 10.1016/j.neurobiolaging.2017.01.022] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2016] [Revised: 01/27/2017] [Accepted: 01/27/2017] [Indexed: 01/25/2023]
Abstract
Precuneus (PreC) cortex is affected with amyloid plaques early in Alzheimer's disease (AD), and this pathology may be associated with alterations in PreC synapses and cognitive impairment. We quantified the spinophilin-immunoreactive (ir) dendritic spine density and the intensity of spinophilin immunofluorescence, the latter as a measure of relative protein levels of spinophilin, in PreC lamina III from 33 subjects with clinical diagnoses of no cognitive impairment (NCI), mild cognitive impairment (MCI), mild-moderate AD (mAD), or severe AD (sAD). Both measures of spinophilin were lower in mAD and sAD compared with NCI. The MCI group had higher protein levels of spinophilin compared with mAD and sAD, and higher spinophilin-ir dendritic spine density compared with sAD. Lower spinophilin-ir dendritic spine density and relative protein levels of spinophilin were associated with greater amyloid beta (Aβ) plaque burden, detected with a derivative of Pittsburgh compound-B (6-CN-PiB), and worse cognitive performance. Clinical onset of AD is marked by the loss of PreC spinophilin-ir dendritic spines that is related to Aβ pathology and may contribute to cognitive symptoms early in the disease.
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Abstract
Labeling fixed brain tissue with fluorescent synaptic and cellular markers can help assess circuit connectivity. Despite the diffraction-limited resolution of light microscopy there are several approaches to identify synaptic contacts onto a cell-of-interest. Understanding which image quantification methods can be applied to estimate cellular and synaptic connectivity at the light microscope level is beneficial to answer a range of questions, from mapping appositions between cellular structures or synaptic proteins to assessing synaptic contact density onto a cell-of-interest. This chapter provides the reader with details of the image analysis methods that can be applied to quantify in situ connectivity patterns at the level of cellular contacts and synaptic appositions.
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Affiliation(s)
- Mrinalini Hoon
- Department of Biological Structure, University of Washington, Seattle, 98195, WA, USA.
| | - Raunak Sinha
- Department of Physiology and Biophysics, University of Washington, Seattle, 98195, WA, USA
| | - Haruhisa Okawa
- Department of Biological Structure, University of Washington, Seattle, 98195, WA, USA.
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16
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Luff SA, Papoutsakis ET. Megakaryocytic Maturation in Response to Shear Flow Is Mediated by the Activator Protein 1 (AP-1) Transcription Factor via Mitogen-activated Protein Kinase (MAPK) Mechanotransduction. J Biol Chem 2016; 291:7831-43. [PMID: 26814129 DOI: 10.1074/jbc.m115.707174] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2015] [Indexed: 12/26/2022] Open
Abstract
Megakaryocytes (MKs) are exposed to shear flow as they migrate from the bone marrow hematopoietic compartment into circulation to release pro/preplatelets into circulating blood. Shear forces promote DNA synthesis, polyploidization, and maturation in MKs, and platelet biogenesis. To investigate mechanisms underlying these MK responses to shear, we carried out transcriptional analysis on immature and mature stem cell-derived MKs exposed to physiological shear. In immature (day (d)9) MKs, shear exposure up-regulated genes related to growth and MK maturation, whereas in mature (d12) MKs, it up-regulated genes involved in apoptosis and intracellular transport. Following shear-flow exposure, six activator protein 1 (AP-1) transcripts (ATF4,JUNB,JUN,FOSB,FOS, andJUND) were up-regulated at d9 and two AP-1 proteins (JunD and c-Fos) were up-regulated both at d9 and d12. We show that mitogen-activated protein kinase (MAPK) signaling is linked to both the shear stress response and AP-1 up-regulation. c-Jun N-terminal kinase (JNK) phosphorylation increased significantly following shear stimulation, whereas JNK inhibition reduced shear-induced JunD expression. Although p38 phosphorylation did not increase following shear flow, its inhibition reduced shear-induced JunD and c-Fos expression. JNK inhibition reduced fibrinogen binding and P-selectin expression of d12 platelet-like particles (PLPs), whereas p38 inhibition reduced fibrinogen binding of d12 PLPs. AP-1 expression correlated with increased MK DNA synthesis and polyploidization, which might explain the observed impact of shear on MKs. To summarize, we show that MK exposure to shear forces results in JNK activation, AP-1 up-regulation, and downstream transcriptional changes that promote maturation of immature MKs and platelet biogenesis in mature MKs.
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Affiliation(s)
- Stephanie A Luff
- From the Department of Biological Sciences, Delaware Biotechnology Institute, and
| | - Eleftherios T Papoutsakis
- From the Department of Biological Sciences, Delaware Biotechnology Institute, and Department of Chemical and Biomolecular Engineering, University of Delaware, Newark, Delaware 19711
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Loss of Microtubule-Associated Protein 2 Immunoreactivity Linked to Dendritic Spine Loss in Schizophrenia. Biol Psychiatry 2015; 78:374-85. [PMID: 25818630 PMCID: PMC4520801 DOI: 10.1016/j.biopsych.2014.12.029] [Citation(s) in RCA: 72] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/06/2014] [Revised: 11/25/2014] [Accepted: 12/19/2014] [Indexed: 02/05/2023]
Abstract
BACKGROUND Microtubule-associated protein 2 (MAP2) is a neuronal protein that plays a role in maintaining dendritic structure through its interaction with microtubules. In schizophrenia (Sz), numerous studies have revealed that the typically robust immunoreactivity (IR) of MAP2 is significantly reduced across several cortical regions. The relationship between MAP2-IR reduction and lower dendritic spine density, which is frequently reported in Sz, has not been explored in previous studies, and MAP2-IR loss has not been investigated in the primary auditory cortex (Brodmann area 41), a site of conserved pathology in Sz. METHODS Using quantitative spinning disk confocal microscopy in two cohorts of subjects with Sz and matched control subjects (Sz subjects, n = 20; control subjects, n = 20), we measured MAP2-IR and dendritic spine density and spine number in deep layer 3 of BA41. RESULTS Subjects with Sz exhibited a significant reduction in MAP2-IR. The reductions in MAP2-IR were not associated with neuron loss, loss of MAP2 protein, clinical confounders, or technical factors. Dendritic spine density and number also were reduced in Sz and correlated with MAP2-IR. In 12 (60%) subjects with Sz, MAP2-IR values were lower than the lowest values in control subjects; only in this group were spine density and number significantly reduced. CONCLUSIONS These findings demonstrate that MAP2-IR loss is closely linked to dendritic spine pathology in Sz. Because MAP2 shares substantial sequence, regulatory, and functional homology with MAP tau, the wealth of knowledge regarding tau biology and the rapidly expanding field of tau therapeutics provide resources for identifying how MAP2 is altered in Sz and possible leads to novel therapeutics.
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18
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MacDonald ML, Ding Y, Newman J, Hemby S, Penzes P, Lewis DA, Yates N, Sweet RA. Altered glutamate protein co-expression network topology linked to spine loss in the auditory cortex of schizophrenia. Biol Psychiatry 2015; 77:959-68. [PMID: 25433904 PMCID: PMC4428927 DOI: 10.1016/j.biopsych.2014.09.006] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/27/2014] [Revised: 08/11/2014] [Accepted: 09/02/2014] [Indexed: 12/31/2022]
Abstract
BACKGROUND Impaired glutamatergic signaling is believed to underlie auditory cortex pyramidal neuron dendritic spine loss and auditory symptoms in schizophrenia. Many schizophrenia risk loci converge on the synaptic glutamate signaling network. We therefore hypothesized that alterations in glutamate signaling protein expression and co-expression network features are present in schizophrenia. METHODS Gray matter homogenates were prepared from auditory cortex gray matter of 22 schizophrenia and 23 matched control subjects, a subset of whom had been previously assessed for dendritic spine density. One hundred fifty-five selected synaptic proteins were quantified by targeted mass spectrometry. Protein co-expression networks were constructed using weighted gene co-expression network analysis. RESULTS Proteins with evidence for altered expression in schizophrenia were significantly enriched for glutamate signaling pathway proteins (GRIA4, GRIA3, ATP1A3, and GNAQ). Synaptic protein co-expression was significantly decreased in schizophrenia with the exception of a small group of postsynaptic density proteins, whose co-expression increased and inversely correlated with spine density in schizophrenia subjects. CONCLUSIONS We observed alterations in the expression of glutamate signaling pathway proteins. Among these, the novel observation of reduced ATP1A3 expression is supported by strong genetic evidence indicating it may contribute to psychosis and cognitive impairment phenotypes. The observations of altered protein network topology further highlight the complexity of glutamate signaling network pathology in schizophrenia and provide a framework for evaluating future experiments to model the contribution of genetic risk to disease pathology.
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Affiliation(s)
| | - Ying Ding
- Department of Biostatistics, University of Pittsburgh, Pittsburgh, PA
| | - Jason Newman
- Department of Psychiatry, University of Pittsburgh, Pittsburgh, PA
| | - Scott Hemby
- Neuroscience Program, Wake Forest University School of Medicine, Winston-Salem, NC,Department of Physiology & Pharmacology, Wake Forest University School of Medicine, Winston-Salem, NC
| | - Peter Penzes
- Department of Physiology, Northwestern University Feinberg School of Medicine, Chicago, Il,Department of Psychiatry and Behavioral Sciences, Northwestern University Feinberg School of Medicine, Chicago, Il
| | - David A. Lewis
- Department of Psychiatry, University of Pittsburgh, Pittsburgh, PA
| | | | - Robert A. Sweet
- Department of Psychiatry, University of Pittsburgh, Pittsburgh, PA,VISN 4 Mental Illness Research, Education and Clinical Center (MIRECC), VA Pittsburgh Healthcare System, Pittsburgh, PA,Department of Neurology, University of Pittsburgh, Pittsburgh, PA
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19
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Rocco BR, Sweet RA, Lewis DA, Fish KN. GABA-Synthesizing Enzymes in Calbindin and Calretinin Neurons in Monkey Prefrontal Cortex. Cereb Cortex 2015; 26:2191-2204. [PMID: 25824535 DOI: 10.1093/cercor/bhv051] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Non-overlapping groups of cortical γ-aminobutyric acid-releasing (GABAergic) neurons are identifiable by the presence of calbindin (CB), calretinin (CR), or parvalbumin (PV). Boutons from PV neuron subtypes are also distinguishable by differences in protein levels of the GABA-synthesizing enzymes GAD65 and GAD67. Multilabel fluorescence microscopy was used to determine if this diversity extends to boutons of CB and CR neurons in monkey prefrontal cortex. CB and CR neurons gave rise to 3 subpopulations of GAD-containing boutons: GAD65+, GAD67+, and GAD65/GAD67+. Somatostatin and vasoactive intestinal peptide-expressing neurons, subtypes of CB and CR neurons, respectively, also gave rise to these distinct bouton subpopulations. At the transcript level, CB and CR neurons contained mRNA encoding GAD67-only or both GADs. Thus, the distinct subpopulations of CB/GAD+ and CR/GAD+ boutons arise from 2 unique subtypes of CB and CR neurons. The different CB and CR GAD-expressing neurons targeted the same projection neurons and neuronal structures immunoreactive for PV, CR, or CB. These findings suggest that GABA synthesis from CB/GAD67+ and CR/GAD67+ neurons would presumably be more vulnerable to disease-associated deficits in GAD67 expression, such as in schizophrenia, than neurons that also contain GAD65.
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Affiliation(s)
| | - Robert A Sweet
- Department of Psychiatry.,Department of Neurology.,VISN 4 Mental Illness Research, Education and Clinical Center (MIRECC), VA Pittsburgh Healthcare System, Pittsburgh, PA 15213, USA
| | - David A Lewis
- Department of Psychiatry.,Department of Neuroscience, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA
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20
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Moyer CE, Erickson SL, Fish KN, Thiels E, Penzes P, Sweet RA. Developmental Trajectories of Auditory Cortex Synaptic Structures and Gap-Prepulse Inhibition of Acoustic Startle Between Early Adolescence and Young Adulthood in Mice. Cereb Cortex 2015; 26:2115-26. [PMID: 25759333 DOI: 10.1093/cercor/bhv040] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Cortical excitatory and inhibitory synapses are disrupted in schizophrenia, the symptoms of which often emerge during adolescence, when cortical excitatory synapses undergo pruning. In auditory cortex, a brain region implicated in schizophrenia, little is known about the development of excitatory and inhibitory synapses between early adolescence and young adulthood, and how these changes impact auditory cortex function. We used immunohistochemistry and quantitative fluorescence microscopy to quantify dendritic spines and GAD65-expressing inhibitory boutons in auditory cortex of early adolescent, late adolescent, and young adult mice. Numbers of spines decreased between early adolescence and young adulthood, during which time responses increased in an auditory cortex-dependent sensory task, silent gap-prepulse inhibition of the acoustic startle reflex (gap-PPI). Within-bouton GAD65 protein and GAD65-expressing bouton numbers decreased between late adolescence and young adulthood, a delay in onset relative to spine and gap-PPI changes. In mice lacking the spine protein kalirin, there were no significant changes in spine number, within-bouton GAD65 protein, or gap-PPI between adolescence and young adulthood. These results illustrate developmental changes in auditory cortex spines, inhibitory boutons, and auditory cortex function between adolescence and young adulthood, and provide insights into how disrupted adolescent neurodevelopment could contribute to auditory cortex synapse pathology and auditory impairments.
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Affiliation(s)
- Caitlin E Moyer
- Center for Neuroscience Translational Neuroscience Program, Department of Psychiatry
| | | | - Kenneth N Fish
- Center for Neuroscience Translational Neuroscience Program, Department of Psychiatry
| | - Edda Thiels
- Center for Neuroscience Department of Neurobiology
| | - Peter Penzes
- Department of Physiology Department of Psychiatry and Behavioral Sciences, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
| | - Robert A Sweet
- Center for Neuroscience Translational Neuroscience Program, Department of Psychiatry Department of Neurology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA Mental Illness Research, Education, and Clinical Center, VA Pittsburgh Healthcare System, Pittsburgh, PA, USA
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21
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Weiler NC, Collman F, Vogelstein JT, Burns R, Smith SJ. Synaptic molecular imaging in spared and deprived columns of mouse barrel cortex with array tomography. Sci Data 2014; 1:140046. [PMID: 25977797 PMCID: PMC4411012 DOI: 10.1038/sdata.2014.46] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2014] [Accepted: 10/21/2014] [Indexed: 01/26/2023] Open
Abstract
A major question in neuroscience is how diverse subsets of synaptic connections in neural circuits are affected by experience dependent plasticity to form the basis for behavioral learning and memory. Differences in protein expression patterns at individual synapses could constitute a key to understanding both synaptic diversity and the effects of plasticity at different synapse populations. Our approach to this question leverages the immunohistochemical multiplexing capability of array tomography (ATomo) and the columnar organization of mouse barrel cortex to create a dataset comprising high resolution volumetric images of spared and deprived cortical whisker barrels stained for over a dozen synaptic molecules each. These dataset has been made available through the Open Connectome Project for interactive online viewing, and may also be downloaded for offline analysis using web, Matlab, and other interfaces.
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Affiliation(s)
- Nicholas C Weiler
- Graduate Program in Neurosciences, Stanford University School of Medicine, Stanford, California 94305, USA
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, California 94305, USA
| | - Forrest Collman
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, California 94305, USA
- Allen Institute for Brain Science, Seattle, Washington 98103, USA
| | - Joshua T Vogelstein
- Department of Statistical Science, Duke University, Durham, North Carolina 27708, USA
- Department of Biomedical Engineering, The Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - Randal Burns
- Department of Computer Science, The Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - Stephen J Smith
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, California 94305, USA
- Allen Institute for Brain Science, Seattle, Washington 98103, USA
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22
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Murray PS, Kirkwood CM, Gray MC, Fish KN, Ikonomovic MD, Hamilton RL, Kofler JK, Klunk WE, Lopez OL, Sweet RA. Hyperphosphorylated tau is elevated in Alzheimer's disease with psychosis. J Alzheimers Dis 2014; 39:759-73. [PMID: 24270207 DOI: 10.3233/jad-131166] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Psychosis occurs in 40-60% of Alzheimer's disease (AD) subjects, is heritable, and indicates a more rapidly progressive disease phenotype. Neuroimaging and postmortem evidence support an exaggerated prefrontal cortical synaptic deficit in AD with psychosis. Microtubule-associated protein tau is a key mediator of amyloid-β-induced synaptotoxicity in AD, and differential mechanisms of progressive intraneuronal phospho-tau accumulation and interneuronal spread of tau aggregates have recently been described. We hypothesized that psychosis in AD would be associated with greater intraneuronal concentration of phospho-tau and greater spread of tau aggregates in prefrontal cortex. We therefore evaluated prefrontal cortex phospho-tau in a cohort of 45 AD cases with and without psychosis. Intraneuronal phospho-tau concentration was higher in subjects with psychosis, while a measure of phospho-tau spread, volume fraction, was not. Across groups both measures were associated with lower scores on the Mini-Mental State Examination and Digit Span Backwards test. These novel findings indicate that tau phosphorylation may be accelerated in AD with psychosis, indicating a more dynamic, exaggerated pathology in AD with psychosis.
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Affiliation(s)
- Patrick S Murray
- Department of Psychiatry, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA VISN 4 Mental Illness Research, Education and Clinical Center, VA Pittsburgh Healthcare System, Pittsburgh, PA, USA
| | - Caitlin M Kirkwood
- Department of Psychiatry, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - Megan C Gray
- Department of Psychiatry, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - Kenneth N Fish
- Department of Psychiatry, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - Milos D Ikonomovic
- Department of Psychiatry, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA Department of Neurology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA Geriatric Research Educational and Clinical Center, VA Pittsburgh Healthcare System, Pittsburgh, PA, USA
| | - Ronald L Hamilton
- Department of Pathology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - Julia K Kofler
- Department of Pathology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - William E Klunk
- Department of Psychiatry, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA Department of Neurology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - Oscar L Lopez
- Department of Psychiatry, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA Department of Neurology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - Robert A Sweet
- Department of Psychiatry, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA VISN 4 Mental Illness Research, Education and Clinical Center, VA Pittsburgh Healthcare System, Pittsburgh, PA, USA Department of Neurology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
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Iwabuchi S, Kakazu Y, Koh JY, Charles Harata N. Evaluation of the effectiveness of Gaussian filtering in distinguishing punctate synaptic signals from background noise during image analysis. J Neurosci Methods 2014; 223:92-113. [DOI: 10.1016/j.jneumeth.2013.12.003] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2013] [Revised: 11/28/2013] [Accepted: 12/03/2013] [Indexed: 01/22/2023]
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24
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Glausier JR, Fish KN, Lewis DA. Altered parvalbumin basket cell inputs in the dorsolateral prefrontal cortex of schizophrenia subjects. Mol Psychiatry 2014; 19:30-6. [PMID: 24217255 PMCID: PMC3874728 DOI: 10.1038/mp.2013.152] [Citation(s) in RCA: 111] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/31/2013] [Revised: 08/26/2013] [Accepted: 09/30/2013] [Indexed: 01/08/2023]
Abstract
Cortical circuitry dysfunction in schizophrenia has been studied at many different levels of resolution, but not at the most basic unit of network organization--synaptic inputs. Multi-label electron or confocal light microscopy is required to examine specific types of synaptic inputs, and application of these methods to quantitatively study disease-related changes in human postmortem tissue has not been feasible for technical reasons. We recently developed a multi-label confocal light microscopic approach that makes possible the systematic identification and quantification of synaptic inputs, and of the relative levels of proteins localized to these inputs, in human postmortem tissue. We applied this approach to quantify parvalbumin basket cell (PVBC) inputs in area 9 of the dorsolateral prefrontal cortex from schizophrenia and matched comparison subjects. Tissue sections were triple-labeled for the 65 kD isoform of glutamic acid decarboxylase (GAD65), PV and the GABA(A) receptor α1 subunit. PVBC axonal boutons were defined as PV/GAD65 dual-labeled puncta, and PVBC inputs were defined as a PVBC bouton that overlapped a GABA(A) receptor α1 subunit punctum. The density of PVBC inputs was unchanged in subjects with schizophrenia, but levels of PV protein were lower in PVBC boutons. In concert with prior reports, these findings indicate that PVBC dysfunction in schizophrenia reflects molecular and not structural alterations in these cells and their axon terminals.
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Affiliation(s)
- JR Glausier
- Department of Psychiatry, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - KN Fish
- Department of Psychiatry, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - DA Lewis
- Department of Psychiatry, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA,Department of Neuroscience, University of Pittsburgh, Pittsburgh, PA, USA
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25
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Dendritic spine density, morphology, and fibrillar actin content surrounding amyloid-β plaques in a mouse model of amyloid-β deposition. J Neuropathol Exp Neurol 2013; 72:791-800. [PMID: 23860033 DOI: 10.1097/nen.0b013e31829ecc89] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Dendritic spines are the site of most excitatory synapses, the loss of which correlates with cognitive impairment in patients with Alzheimer disease. Substantial evidence indicates that amyloid-β (Aβ) peptide, either insoluble fibrillar Aβ deposited into plaques or soluble nonfibrillar Aβ species, can cause spine loss but the concurrent contributions of fibrillar Aβ and nonfibrillar Aβ to spine loss has not been previously assessed. We used multiple-label immunohistochemistry to measure spine density, size, and F-actin content surrounding plaques in the cerebral cortex in the PSAPP mouse model of Aβ deposition. Our approach allowed us to measure fibrillar Aβ plaque content and an index of nonfibrillar Aβ species concurrently. We found that spine density was reduced within 6 μm of the plaque perimeter, remaining spines were more compact, and F-actin content per spine was increased. Measures of fibrillar Aβ plaque content were associated with reduced spine density near plaques, whereas measures of nonfibrillar Aβ species were associated with reduced spine density and size but not altered F-actin content. These findings suggest that strategies to preserve dendritic spines in AD patients may need to address both nonfibrillar and fibrillar forms of Aβ and that nonfibrillar Aβ may exert spine toxicity through pathways not mediated by depolymerization of F-actin.
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26
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Reduced glutamate decarboxylase 65 protein within primary auditory cortex inhibitory boutons in schizophrenia. Biol Psychiatry 2012; 72:734-43. [PMID: 22624794 PMCID: PMC3465514 DOI: 10.1016/j.biopsych.2012.04.010] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/01/2011] [Revised: 04/12/2012] [Accepted: 04/12/2012] [Indexed: 12/20/2022]
Abstract
BACKGROUND Schizophrenia is associated with perceptual and physiological auditory processing impairments that may result from primary auditory cortex excitatory and inhibitory circuit pathology. High-frequency oscillations are important for auditory function and are often reported to be disrupted in schizophrenia. These oscillations may, in part, depend on upregulation of gamma-aminobutyric acid synthesis by glutamate decarboxylase 65 (GAD65) in response to high interneuron firing rates. It is not known whether levels of GAD65 protein or GAD65-expressing boutons are altered in schizophrenia. METHODS We studied two cohorts of subjects with schizophrenia and matched control subjects, comprising 27 pairs of subjects. Relative fluorescence intensity, density, volume, and number of GAD65-immunoreactive boutons in primary auditory cortex were measured using quantitative confocal microscopy and stereologic sampling methods. Bouton fluorescence intensities were used to compare the relative expression of GAD65 protein within boutons between diagnostic groups. Additionally, we assessed the correlation between previously measured dendritic spine densities and GAD65-immunoreactive bouton fluorescence intensities. RESULTS GAD65-immunoreactive bouton fluorescence intensity was reduced by 40% in subjects with schizophrenia and was correlated with previously measured reduced spine density. The reduction was greater in subjects who were not living independently at time of death. In contrast, GAD65-immunoreactive bouton density and number were not altered in deep layer 3 of primary auditory cortex of subjects with schizophrenia. CONCLUSIONS Decreased expression of GAD65 protein within inhibitory boutons could contribute to auditory impairments in schizophrenia. The correlated reductions in dendritic spines and GAD65 protein suggest a relationship between inhibitory and excitatory synapse pathology in primary auditory cortex.
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Abstract
The cytoskeletal matrix of the active zone and synaptic voltage-dependent calcium channels (VDCCs) are both necessary components for the organization and regulation of synaptic vesicle release. In this study, we report a novel interaction between the cytoskeletal matrix of the active zone protein, ELKS1b, and the VDCC subunit, β4, in the molecular layer of the cerebellum. We found that the two proteins coimmunoprecipitated using antibodies against each protein. Using fluorescent immunohistochemistry, we observed colocalization between ELKS1b and VDCC β4 in the molecular layer of the cerebellum, suggesting that these proteins are both present in molecular layer synapses. Analysis of a P/Q-type VDCC knockout mouse (Cacna1a(-/-)) revealed that the localization of the VDCC β4 subunit to the molecular layer was disrupted, although ELKS1b protein localization was not affected. These results demonstrate that these two proteins interact in vitro and colocalize in the cerebellum, and suggest that their interaction may play a role at the molecular layer synapses of the cerebellum.
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GABA neuron alterations, cortical circuit dysfunction and cognitive deficits in schizophrenia. Neural Plast 2011; 2011:723184. [PMID: 21904685 PMCID: PMC3167184 DOI: 10.1155/2011/723184] [Citation(s) in RCA: 170] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2011] [Accepted: 05/01/2011] [Indexed: 01/01/2023] Open
Abstract
Schizophrenia is a brain disorder associated with cognitive deficits that severely affect the patients' capacity for daily functioning. Whereas our understanding of its pathophysiology is limited, postmortem studies suggest that schizophrenia is associated with deficits of GABA-mediated synaptic transmission. A major role of GABA-mediated transmission may be producing synchronized network oscillations which are currently hypothesized to be essential for normal cognitive function. Therefore, cognitive deficits in schizophrenia may result from a GABA synapse dysfunction that disturbs neural synchrony. Here, we highlight recent studies further suggesting alterations of GABA transmission and network oscillations in schizophrenia. We also review current models for the mechanisms of GABA-mediated synchronization of neural activity, focusing on parvalbumin-positive GABA neurons, which are altered in schizophrenia and whose function has been strongly linked to the production of neural synchrony. Alterations of GABA signaling that impair gamma oscillations and, as a result, cognitive function suggest paths for novel therapeutic interventions.
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Curley AA, Arion D, Volk DW, Asafu-Adjei JK, Sampson AR, Fish KN, Lewis DA. Cortical deficits of glutamic acid decarboxylase 67 expression in schizophrenia: clinical, protein, and cell type-specific features. Am J Psychiatry 2011; 168:921-9. [PMID: 21632647 PMCID: PMC3273780 DOI: 10.1176/appi.ajp.2011.11010052] [Citation(s) in RCA: 213] [Impact Index Per Article: 16.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
OBJECTIVE Cognitive deficits in schizophrenia are associated with altered activity of the dorsolateral prefrontal cortex, which has been attributed to lower expression of the 67 kDa isoform of glutamic acid decarboxylase (GAD67), the major γ-aminobutyric acid (GABA)-synthesizing enzyme. However, little is known about the relationship of prefrontal GAD67 mRNA levels and illness severity, translation of the transcript into protein, and protein levels in axon terminals, the key site of GABA production and function. METHOD Quantitative polymerase chain reaction was used to measure GAD67 mRNA levels in postmortem specimens of dorsolateral prefrontal cortex from subjects with schizophrenia and matched comparison subjects with no known history of psychiatric or neurological disorders (N=42 pairs). In a subset of this cohort in which potential confounds of protein measures were controlled (N=19 pairs), Western blotting was used to quantify tissue levels of GAD67 protein in tissue. In five of these pairs, multilabel confocal immunofluorescence was used to quantify GAD67 protein levels in the axon terminals of parvalbumin-containing GABA neurons, which are known to have low levels of GAD67 mRNA in schizophrenia. RESULTS GAD67 mRNA levels were significantly lower in schizophrenia subjects (by 15%), but transcript levels were not associated with predictors or measures of illness severity or chronicity. In schizophrenia subjects, GAD67 protein levels were significantly lower in total gray matter (by 10%) and in parvalbumin axon terminals (by 49%). CONCLUSIONS The findings that lower GAD67 mRNA expression is common in schizophrenia, that it is not a consequence of having the illness, and that it leads to less translation of the protein, especially in the axon terminals of parvalbumin-containing neurons, support the hypothesis that lower GABA synthesis in parvalbumin neurons contributes to dorsolateral prefrontal cortex dysfunction and impaired cognition in schizophrenia.
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Fish KN, Sweet RA, Lewis DA. Differential distribution of proteins regulating GABA synthesis and reuptake in axon boutons of subpopulations of cortical interneurons. ACTA ACUST UNITED AC 2011; 21:2450-60. [PMID: 21422269 DOI: 10.1093/cercor/bhr007] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Subclasses of γ-aminobutyric acid (GABA) interneurons differentially influence cortical network activity. The contribution of differences in GABA synthesis and reuptake in axon boutons to cell type-specific functions is unknown. GABA is synthesized within boutons by glutamic acid decarboxylase 65 (GAD65) and GAD67, while GAT1 is responsible for GABA reuptake. Using an imaging methodology capable of determining the colocalization frequency of different immunocytochemical labels in the same bouton and the quantification of the fluorescence intensity of each label in these same structures, we assessed the bouton levels of GAD65, GAD67, and GAT1 in parvalbumin-expressing chandelier (PV(ch)) and basket (PV(b)) neurons and cannabinoid 1 receptor-expressing basket (CB1r(b)) neurons in the monkey prefrontal cortex. We show that PV(ch) boutons almost exclusively contained GAD67, relative to GAD65, whereas CB1r(b) boutons contained mostly GAD65. In contrast, both GAD65 and GAD67 were easily detected in PV(b) boutons. Furthermore, in comparison with PV(ch) boutons, CB1r(b) boutons expressed low to undetectable levels of GAT1. Our findings provide a new basis for the distinctive functional roles of these perisomatic-innervating interneurons in cortical circuits. In addition, they strongly suggest that altered levels of GAD67 or GAD65, as seen in some psychiatric diseases, would have cell type-specific consequences on the modulation of GABA neurotransmission.
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Affiliation(s)
- Kenneth N Fish
- Translational Neuroscience Program, Department of Psychiatry, University of Pittsburgh, Pittsburgh, PA 15213, USA.
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Sweet RA, Fish KN, Lewis DA. Mapping Synaptic Pathology within Cerebral Cortical Circuits in Subjects with Schizophrenia. Front Hum Neurosci 2010; 4:44. [PMID: 20631852 PMCID: PMC2903233 DOI: 10.3389/fnhum.2010.00044] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2009] [Accepted: 04/26/2010] [Indexed: 11/18/2022] Open
Abstract
Converging lines of evidence indicate that schizophrenia is characterized by impairments of synaptic machinery within cerebral cortical circuits. Efforts to localize these alterations in brain tissue from subjects with schizophrenia have frequently been limited to the quantification of structures that are non-selectively identified (e.g., dendritic spines labeled in Golgi preparations, axon boutons labeled with synaptophysin), or to quantification of proteins using methods unable to resolve relevant cellular compartments. Multiple label fluorescence confocal microscopy represents a means to circumvent many of these limitations, by concurrently extracting information regarding the number, morphology, and relative protein content of synaptic structures. An important adaptation required for studies of human disease is coupling this approach to stereologic methods for systematic random sampling of relevant brain regions. In this review article we consider the application of multiple label fluorescence confocal microscopy to the mapping of synaptic alterations in subjects with schizophrenia and describe the application of a novel, readily automated, iterative intensity/morphological segmentation algorithm for the extraction of information regarding synaptic structure number, size, and relative protein level from tissue sections obtained using unbiased stereological principles of sampling. In this context, we provide examples of the examination of pre- and post-synaptic structures within excitatory and inhibitory circuits of the cerebral cortex.
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Affiliation(s)
- Robert A Sweet
- Translational Neuroscience Program, Department of Psychiatry, University of Pittsburgh Pittsburgh, PA, USA
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Abstract
During neuron development, the biosynthetic needs of the axon initially outweigh those of dendrites. However, although a localized role for the early secretory pathway in dendrite development has been observed, such a role in axon growth remains undefined. We therefore studied the localization of Sar1, a small GTPase that controls ER export, during early stages of neuronal development that are characterized by selective and robust axon growth. At these early stages, Sar1 was selectively targeted to the axon where it gradually concentrated within varicosities in which additional proteins that function in the early secretory pathway were detected. Sar1 targeting to the axon followed axon specification and was dependent on localized actin instability. Changes in Sar1 expression levels at these early development stages modulated axon growth. Specifically, reduced expression of Sar1, which was initially only detectable in the axon, correlated with reduced axon growth, where as overexpression of Sar1 supported the growth of longer axons. In support of the former finding, expression of dominant negative Sar1 inhibited axon growth. Thus, as observed in lower organisms, mammalian cells use temporal and spatial regulation of endoplasmic reticulum exit site (ERES) to address developmental biosynthetic demands. Furthermore, axons, such as dendrites, rely on ERES targeting and assembly for growth.
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Affiliation(s)
- Meir Aridor
- Department of Cell Biology and Physiology, University of Pittsburgh School of Medicine, 3500 Terrace St, Pittsburgh, PA 15261, USA
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