Dendritic spine loss is recognized as an early feature of Alzheimer's disease (AD), but the underlying mechanisms are poorly understood. Dendritic spine structure is defined by filamentous actin (F-actin) and we observed depolymerization of synaptosomal F-actin accompanied by increased globular-actin (G-actin) at as early as 1 month of age in a mouse model of AD (APPswe/PS1ΔE9, male mice). This led to recall deficit after contextual fear conditioning (cFC) at 2 months of age in APPswe/PS1ΔE9 male mice, which could be reversed by the actin-polymerizing agent jasplakinolide. Further, the F-actin-depolymerizing agent latrunculin induced recall deficit after cFC in WT mice, indicating the importance of maintaining F-/G-actin equilibrium for optimal behavioral response. Using direct stochastic optical reconstruction microscopy (dSTORM), we show that F-actin depolymerization in spines leads to a breakdown of the nano-organization of outwardly radiating F-actin rods in cortical neurons from APPswe/PS1ΔE9 mice. Our results demonstrate that synaptic dysfunction seen as F-actin disassembly occurs very early, before onset of pathological hallmarks in AD mice, and contributes to behavioral dysfunction, indicating that depolymerization of F-actin is causal and not consequent to decreased spine density. Further, we observed decreased synaptosomal F-actin levels in postmortem brain from mild cognitive impairment and AD patients compared with subjects with normal cognition. F-actin decrease correlated inversely with increasing AD pathology (Braak score, Aβ load, and tangle density) and directly with performance in episodic and working memory tasks, suggesting its role in human disease pathogenesis and progression.SIGNIFICANCE STATEMENT Synaptic dysfunction underlies cognitive deficits in Alzheimer's disease (AD). The cytoskeletal protein actin plays a critical role in maintaining structure and function of synapses. Using cultured neurons and an AD mouse model, we show for the first time that filamentous actin (F-actin) is lost selectively from synapses early in the disease process, long before the onset of classical AD pathology. We also demonstrate that loss of synaptic F-actin contributes directly to memory deficits. Loss of synaptosomal F-actin in human postmortem tissue correlates directly with decreased performance in memory test and inversely with AD pathology. Our data highlight that synaptic cytoarchitectural changes occur early in AD and they may be targeted for the development of therapeutics.
Pubmed ID: 29246925 RIS Download
Publication data is provided by the National Library of Medicine ® and PubMed ®. Data is retrieved from PubMed ® on a weekly schedule. For terms and conditions see the National Library of Medicine Terms and Conditions.
Neurolucida is advanced scientific software for brain mapping, neuron reconstruction, anatomical mapping, and morphometry. Since its debut more than 20 years ago, Neurolucida has continued to evolve and has become the worldwide gold-standard for neuron reconstruction and 3D mapping. Neurolucida has the flexibility to handle data in many formats: using live images from digital or video cameras; stored image sets from confocal microscopes, electron microscopes, and scanning tomographic sources, or through the microscope oculars using the patented LucividTM. Neurolucida controls a motorized XYZ stage for integrated navigation through tissue sections, allowing for sophisticated analysis from many fields-of-view. Neurolucidas Serial Section Manager integrates unlimited sections into a single data file, maintaining each section in aligned 3D space for full quantitative analysis. Neurolucidas neuron tracing capabilities include 3D measurement and reconstruction of branching processes. Neurolucida also features sophisticated tools for mapping delineate and map anatomical regions for detailed morphometric analyses. Neurolucida uses advanced computer-controlled microscopy techniques to obtain accurate results and speed your work. Plug-in modules are available for confocal and MRI analysis, 3D solid modeling, and virtual slide creation. The user-friendly interface gives you rapid results, allowing you to acquire data and capture the full 3D extent of neurons and brain regions. You can reconstruct neurons or create 3D serial reconstructions directly from slides or acquired images, and Neurolucida offers full microscope control for brightfield, fluorescent, and confocal microscopes. Its added compatibility with 64-bit Microsoft Vista enables reconstructions with even larger images, image stacks, and virtual slides. Adding the Solid Modeling Module allows you to rotate and view your reconstructions in real time. Neurolucida is available in two separate versions Standard and Workstation. The Standard version enables control of microscope hardware, whereas the Workstation version is used for offline analysis away from the microscope. Neurolucida provides quantitative analysis with results presented in graphical or spreadsheet format exportable to Microsoft Excel. Overall, features include: - Tracing Neurons - Anatomical Mapping - Image Processing and Analysis Features - Editing - Morphometric Analysis - Hardware Integration - Cell Analysis - Visualization Features Sponsors: Neurolucida is supported by MBF Bioscience.
View all literature mentionsSoftware tool for automated microscope acquisition, device control, and image analysis. Used for integrating dissimilar fluorescent microscope hardware and peripherals into a single custom workstation, while providing all the tools needed to perform analysis of acquired images. Offers user friendly application modules for analysis such as cell signaling, cell counting, and protein expression.
View all literature mentionsMus musculus with name B6.Cg-Tg(APPswe,PSEN1dE9)85Dbo/Mmjax from MMRRC.
View all literature mentionsMus musculus with name C57BL/6J from IMSR.
View all literature mentionsThis unknown targets
View all literature mentionsThis monoclonal targets beta-Amyloid 1-42
View all literature mentionsThis monoclonal targets CFL1
View all literature mentionsThis monoclonal targets
View all literature mentionsThis polyclonal targets PSD95
View all literature mentionsThis polyclonal targets Drebrin antibody
View all literature mentionsThis unknown targets
View all literature mentionsThis monoclonal targets beta-Amyloid 1-42
View all literature mentionsThis monoclonal targets CFL1
View all literature mentionsThis monoclonal targets
View all literature mentionsThis polyclonal targets PSD95
View all literature mentionsThis polyclonal targets Drebrin antibody
View all literature mentions