Article Figures & Data
Figures
- Fig. 1.
Entorhinal axonal projections in APP23 mice.a, PHAL-labeled projection from the medial entorhinal cortex to the middle molecular layer (MML;arrow) of the dentate gyrus (DG) in an 18-month-old nontransgenic control mouse. Minor projections were identified to CA3 and CA1 of the hippocampus and to the thalamus (TH). The same pattern was observed in young APP23 mice that lack amyloid plaque formation. b, PHAL-labeled projection in an 18-month-old APP23 mouse. Main termination pattern in the MML (arrow) is similar to that seen in the control mouse with the most notable difference being the hyperinnervation of the thalamus. Note the amyloid deposits (blue–gray reaction product) throughout the hippocampus, the thalamus, and within the alveus (ALV). c, d, High magnification of the inferior blade of DG from the control mouse shown in a, and APP23 mouse shown in b. Note the thickened PHAL-labeled axons (arrow) and ballooned, spheroidal axon terminals (arrowheads) in the vicinity of amyloid plaques. In the MML, amyloid plaques were completely engulfed by entorhinal dystrophic terminals, whereas outside of the main entorhinal termination zone only a subpopulation of dystrophic boutons were PHAL-labeled. e, High magnification of PHAL-labeled axons with the characteristic dystrophic terminals around an amyloid plaque in the stratum-lacunosum moleculare of CA3. Many PHAL-labeled axons appear normal until directly adjacent to the amyloid (arrow), then typically curve around the amyloid periphery, forming several small swellings followed by a large terminal balloon-shaped swelling that turns away from the plaque (arrowhead). GC, granule cell layer of the dentate gyrus; IML, inner molecular layer;OML, outer molecular layer. Scale bars:a, 300 μm; c, e, 25 μm; panels a and b, andc and d have the same magnification.
- Fig. 2.
Ultrastructure of PHAL-labeled dystrophic entorhinal boutons in the hippocampus. a, Light micrograph of an amyloid plaque (asterisk) in the molecular layer of the dentate gyrus surrounded by numerous large PHAL-labeled entorhinal boutons (arrows).b, Electron micrograph of the bottom half of the plaque shown in a. The amyloid (asterisk) is surrounded by several dystrophic PHAL-labeled entorhinal boutons (arrows). c, Light micrograph of an amyloid plaque (asterisk) in the molecular layer of the dentate gyrus. The arrow points to a heavily PHAL-labeled entorhinal bouton. d, Electron micrograph of the PHAL-labeled entorhinal bouton illustrated in c. The bouton is filled with numerous multilamellar bodies, characteristic of dystrophic neurites. These structures are surrounded by electron dense immunoprecipitate. e, PHAL-labeled entorhinal bouton in the vicinity of a plaque. This dystrophic bouton contains synaptic vesicles and forms a synapse with a spine. Thearrow points to the synaptic cleft. An unlabeled dystrophic neurite (DN), as well as a normal axon terminal (A) are also illustrated. Scale bars:a, c, 10 μm; b, 2.5 μm; d, 1 μm; e, 0.5 μm.
- Fig. 3.
Plaque-associated ectopic axon terminals.a, Disruption of the layer-specific termination of the PHAL-labeled entorhinal axons in the vicinity of an amyloid plaque (asterisk) is evidenced by the invasion of these fibers (brown reaction product) into the inner molecular layer (IML) of the dentate gyrus, which is labeled for calretinin (blue–gray reaction product). Calretinin is specific for the commissural fibers in the mouse and labels specifically the IML (Liu et al., 1996). b, Calretinin-labeled commissural fibers (brown) also form dystrophic terminals (arrow) and deviate from their normally specific termination in the IML when in vicinity of amyloid (blue–gray). c, High magnification of the amyloid plaque (blue–gray) shown in Figure1b. PHAL-labeled entorhinal axons are inbrown and reveal a hyperinnervation of the thalamic region around the amyloid plaque (see Fig. 1a for control). Here, entorhinal axons curve around the amyloid and form dystrophic boutons directly adjacent to the amyloid. Interestingly, PHAL-labeled entorhinal axons also formed dystrophic boutons around vascular amyloid deposits (arrow). GC,Granule cell layer of the dentate gyrus. Scale bars: a, 10 μm; c, 50 μm; panels a andb have the same magnification.
- Fig. 4.
Axonal growth associated with amyloid plaques in the white matter. a, PHAL-labeled entorhinal axons form dystrophic terminals around an amyloid plaque (asterisk) in the alveus, b, Immunohistochemistry with an antibody against GAP-43 reveals that throughout the neuropil and interestingly, as shown here, within the alveus, many dystrophic boutons (brown) associated with amyloid deposits (blue, asterisk) were GAP-43 positive. c, Similar dystrophic neurites were also identified around plaques (asterisk), shown here within the alveus, when sections were immunolabeled for the synaptic marker synaptophysin. d–f, Double fluorescent immunolabeling for PHAL (d,green) and GAP-43 (e, red) revealed that a percentage of PHAL-labeled entorhinal terminals are positive for the growth-associated marker GAP-43 (d–f, arrows). Scale bars: a, 20 μm; b, 20 μm;d, 5 μm; panels b and c, and d–f have the same magnification.
- Fig. 5.
Ultrastructure of entorhinal dystrophic boutons in the white matter. a, Light micrograph of an amyloid plaque (asterisk) in the alveus of the hippocampus. Three PHAL-labeled entorhinal boutons surround the plaque (arrows). b, Electron micrograph of the plaque illustrated in a. The amyloid core (asterisk) is surrounded by numerous dystrophic neurites. The three large entorhinal boutons illustrated ina are indicated by arrows. One of the unlabeled dystrophic neurites is myelinated (short arrow). c, Serial section of the middle PHAL-labeled bouton illustrated in b. The heavily immunolabeled bouton is filled with multilamellar bodies.d, Serial section of the rectangleillustrated in c. This part of the dystrophic bouton shows elements of synaptic specialization, i.e., clustered vesicles. Scale bars: a, 10 μm; b, 5 μm;c, 1 μm; d, 0.25 μm.
