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Updated: Mar 19, 2026
Correlative Light and Electron Microscopy to Study Microglial Interactions with β-Amyloid Plaques
Published on: June 1, 2016
Correlative Light and Electron Microscopy to Study Microglial Interactions with β-Amyloid Plaques
Kanchan Bisht1, Hassan El Hajj1, Julie C Savage1
1Neurosciences Axis, CHU de Québec Research Center.
Abstract:
A detailed protocol is provided here to identify amyloid Aβ plaques in brain sections from Alzheimer's disease mouse models before pre-embedding immunostaining (specifically for ionized calcium-binding adapter molecule 1 (IBA1), a calcium binding protein expressed by microglia) and tissue processing for electron microscopy (EM). Methoxy-X04 is a fluorescent dye that crosses the blood-brain barrier and selectively binds to β-pleated sheets found in dense core Aβ plaques. Injection of the animals with methoxy-X04 prior to sacrifice and brain fixation allows pre-screening and selection of the plaque-containing brain sections for further processing with time-consuming manipulations. This is particularly helpful when studying early AD pathology within specific brain regions or layers that may contain very few plaques, present in only a small fraction of the sections. Post-mortem processing of tissue sections with Congo Red, Thioflavin S, and Thioflavin T (or even with methoxy-X04) can label β-pleated sheets, but requires extensive clearing with ethanol to remove excess dye and these procedures are incompatible with ultrastructural preservation. It would also be inefficient to perform labeling for Aβ (and other cellular markers such as IBA1) on all brain sections from the regions of interest, only to yield a small fraction containing Aβ plaques at the right location. Importantly, Aβ plaques are still visible after tissue processing for EM, allowing for a precise identification of the areas (generally down to a few square millimeters) to examine with the electron microscope.
Insights
This protocol uses Methoxy-X04 dye to pre-identify amyloid plaques in Alzheimer
Area of Science:
- Neuroscience
- Biochemistry
- Pathology
Background:
- Alzheimer's disease (AD) is characterized by amyloid-beta (Aβ) plaques in the brain.
- Identifying these plaques is crucial for studying AD pathology, especially in early stages or specific brain regions.
- Traditional methods for Aβ plaque detection are often incompatible with subsequent electron microscopy (EM) processing.
Purpose of the Study:
- To provide a detailed protocol for identifying Aβ plaques in Alzheimer's disease mouse models.
- To enable pre-screening of brain sections for Aβ plaques before time-consuming electron microscopy (EM) preparation.
- To facilitate the selection of relevant brain sections for ultrastructural analysis.
Main Methods:
- In vivo injection of Methoxy-X04, a fluorescent dye that selectively binds to Aβ plaques.
- Pre-embedding immunostaining for ionized calcium-binding adapter molecule 1 (IBA1) to identify microglia.
- Tissue processing for electron microscopy (EM) while preserving Aβ plaque visibility.
Main Results:
- Methoxy-X04 allows for selective labeling and pre-screening of brain sections containing Aβ plaques.
- This method enables efficient selection of sections for further analysis, even when plaques are sparse.
- Aβ plaques remain visible after EM processing, allowing precise localization for ultrastructural examination.
Conclusions:
- This protocol streamlines the identification of Aβ plaques in AD mouse models.
- It significantly improves efficiency for researchers studying early AD pathology and performing ultrastructural analysis.
- The method ensures Aβ plaque visibility is maintained throughout the EM preparation workflow.
