Characterization of Nanoscale Organization of F-Actin in Morphologically Distinct Dendritic Spines<i>In Vitro</i>Using Supervised Learning

Nanguneri, Siddharth; Pramod, R. T.; Efimova, Nadia; Das, Debajyoti; Jose, Mini; Svitkina, Tatyana; Nair, Deepak

doi:10.1523/eneuro.0425-18.2019

Cited by 16 publications

(16 citation statements)

References 34 publications

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“…These images were analyzed with especially adopted supervised learning methods to understand the heterogeneity in the organization of F-actin in dendritic spines of primary neuronal cultures from rodents. The results were validated using ultrastructural data obtained from platinum replica electron microscopy [112].…”

Section: Super-resolution Imagingmentioning

confidence: 89%

Digging Deeper: Advancements in Visualization of Inhibitory Synapses in Neurodegenerative Disorders

Radulović

Sunkara

Maurer

et al. 2021

IJMS

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Recent research has provided strong evidence that neurodegeneration may develop from an imbalance between synaptic structural components in the brain. Lately, inhibitory synapses communicating via the neurotransmitters GABA or glycine have come to the center of attention. Increasing evidence suggests that imbalance in the structural composition of inhibitory synapses affect deeply the ability of neurons to communicate effectively over synaptic connections. Progressive failure of synaptic plasticity and memory are thus hallmarks of neurodegenerative diseases. In order to prove that structural changes at synapses contribute to neurodegeneration, we need to visualize single-molecule interactions at synaptic sites in an exact spatial and time frame. This visualization has been restricted in terms of spatial and temporal resolution. New developments in electron microscopy and super-resolution microscopy have improved spatial and time resolution tremendously, opening up numerous possibilities. Here we critically review current and recently developed methods for high-resolution visualization of inhibitory synapses in the context of neurodegenerative diseases. We present advantages, strengths, weaknesses, and current limitations for selected methods in research, as well as present a future perspective. A range of new options has become available that will soon help understand the involvement of inhibitory synapses in neurodegenerative disorders.

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Section: Super-resolution Imagingmentioning

confidence: 89%

Digging Deeper: Advancements in Visualization of Inhibitory Synapses in Neurodegenerative Disorders

Radulović

Sunkara

Maurer

et al. 2021

IJMS

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“…The imaging was carried out using ×100 TIRF/1.49NA at an inclined TIRF angle at the near membrane surface using 647 laser. dSTORM imaging was done as described in Reference 52,53. Under these experimental conditions, the precision of localization for single molecules in dSTORM was between 21 ± 4.3 nm for Alexa 647 as quantified from 2D intensity distributions of 25 isolated single molecules.…”

Section: Methodsmentioning

confidence: 99%

Cryptic association of B7‐2 molecules and its implication for clustering

et al. 2021

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T‐cell co‐stimulation through CD28/CTLA4:B7‐1/B7‐2 axis is one of the extensively studied pathways that resulted in the discovery of several FDA‐approved drugs for autoimmunity and cancer. However, many aspects of the signaling mechanism remain elusive, including oligomeric association and clustering of B7‐2 on the cell surface. Here, we describe the structure of the IgV domain of B7‐2 and its cryptic association into 1D arrays that appear to represent the pre‐signaling state of B7‐2 on the cell membrane. Super‐resolution microscopy experiments on heterologous cells expressing B7‐2 and B7‐1 suggest, B7‐2 form relatively elongated and larger clusters compared to B7‐1. The sequence and structural comparison of other B7 family members, B7‐1:CTLA4 and B7‐2:CTLA‐4 complex structures, support our view that the observed B7‐2 1D zipper array is physiologically important. This observed 1D zipper‐like array also provides an explanation for its clustering, and upright orientation on the cell surface, and avoidance of spurious signaling.

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“…To objectively analyze dSTORM data sets of F-actin in spines, we performed segmentation followed by automatic ridge detection within spines (40). Using a fully automated and an objective workflow for analysis, we measured the extent of F-actin ridges in excitatory synapses marked positive for Homer1c.…”

Section: Image Analysismentioning

confidence: 99%

Glutaredoxin1 Diminishes Amyloid Beta-Mediated Oxidation of F-Actin and Reverses Cognitive Deficits in an Alzheimer's Disease Mouse Model

Kommaddi

Tomar

Karunakaran

et al. 2019

Antioxidants & Redox Signaling

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Aims: Reactive oxygen species (ROS) generated during Alzheimer's disease (AD) pathogenesis through multiple sources are implicated in synaptic pathology observed in the disease. We have previously shown Factin disassembly in dendritic spines in early AD (34). The actin cytoskeleton can be oxidatively modified resulting in altered F-actin dynamics. Therefore, we investigated whether disruption of redox signaling could contribute to actin network disassembly and downstream effects in the amyloid precursor protein/presenilin-1 double transgenic (APP/PS1) mouse model of AD. Results: Synaptosomal preparations from 1-month-old APP/PS1 mice showed an increase in ROS levels, coupled with a decrease in the reduced form of F-actin and increase in glutathionylated synaptosomal actin. Furthermore, synaptic glutaredoxin 1 (Grx1) and thioredoxin levels were found to be lowered. Overexpressing Grx1 in the brains of these mice not only reversed F-actin loss seen in APP/PS1 mice but also restored memory recall after contextual fear conditioning. F-actin levels and F-actin nanoarchitecture in spines were also stabilized by Grx1 overexpression in APP/PS1 primary cortical neurons, indicating that glutathionylation of Factin is a critical event in early pathogenesis of AD, which leads to spine loss. Innovation: Loss of thiol/disulfide oxidoreductases in the synapse along with increase in ROS can render Factin nanoarchitecture susceptible to oxidative modifications in AD. Conclusions: Our findings provide novel evidence that altered redox signaling in the form of S-glutathionylation and reduced Grx1 levels can lead to synaptic dysfunction during AD pathogenesis by directly disrupting the Factin nanoarchitecture in spines. Increasing Grx1 levels is a potential target for novel disease-modifying therapies for AD.

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Characterization of Nanoscale Organization of F-Actin in Morphologically Distinct Dendritic SpinesIn VitroUsing Supervised Learning

Abstract: Visual Abstract

Cited by 16 publications

References 34 publications

Digging Deeper: Advancements in Visualization of Inhibitory Synapses in Neurodegenerative Disorders

Digging Deeper: Advancements in Visualization of Inhibitory Synapses in Neurodegenerative Disorders

Cryptic association of B7‐2 molecules and its implication for clustering

Glutaredoxin1 Diminishes Amyloid Beta-Mediated Oxidation of F-Actin and Reverses Cognitive Deficits in an Alzheimer's Disease Mouse Model

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