Figure 5.

Targeted FIB-SEM on Selected Consecutive Sites of Semithick Sections in Familial Alzhiemer's Disease (FAD) Cortex Samples

(A) Schematic of ATUM-FIB on consecutive 5-μm-thick sections of mouse FAD cortex samples. Microglia (blue) contacts to plaques (orange) are targeted.

(B) Transmitted light image of one section (20x objective, left) and average projection SEM of 18 sections (middle) revealing plaques (arrowheads). The 3D model (right) was segmented from a set of 36 serial transmitted light images. Blood vessels (gray), plaques (yellow), and the target plaque (orange) are highlighted. Scale bar 100 μm.

(C–E) Schematics showing the imaging planes (gray) in the respective subfigures. (C) Three consecutive 5-μm-semithick sections of the FAD cortex sample on CNT tape. The microglial cell (blue), dystrophic neurites (orange), and amyloid core (yellow) are highlighted. The white box indicates the magnified image in (D). Scale bar, 5 μm. (D) Magnified surface image of the microglia to plaque contact site of section 1 (left). This region was targeted for FIB-SEM at 5 × 5 × 5 nm resolution. Reconstructions of two deeper levels within the semithick sections are shown (middle, right). Scale bar, 1 μm. (E) Stitched cross sections of corresponding areas in consecutive semithick sections 1 and 2 after FIB-SEM. Scale bar, 500 nm. (F) Region of interest of the selected section 1 of a FIB-SEM run. The 3D model shows the ER network (yellow) opposing the microglial plasma membrane (blue). Lysosomal structures are shown in light gray and mitochondria in dark gray (top). Scale bar, 500 nm. Representative SEM image revealing ER structures (black arrowheads) at sites of contact between microglia and dystrophic neurites (bottom). Scale bar, 200 nm.