Article Figures & Data
Figures
- Figure 1.
BACE1 is not expressed in BACE1–/– mice. A, BACE1 expression was assessed in coronal sections of 2-month-old BACE1+/+ (left), BACE1+/– (middle), and BACE1–/– (right) mice using immunohistochemistry with a commercial BACE1 antibody. BACE1 immunoreactivity is present throughout BACE1+/+ sections, with higher levels in the mossy fiber pathway of the hippocampus (white arrow). Scale bar, 500 µm. Conversely, there is no BACE1 immunoreactivity in BACE1–/– brain sections. B, BACE1 expression is attenuated in BACE1+/– and abrogated in BACE1–/– mice. The expression and activity of BACE1 was assessed in BACE1+/+, BACE1+/–, and BACE1–/– mice with Western blot. BACE1 is expressed robustly in BACE1+/+ brain tissues, is weakly expressed in BACE1+/– brain tissues, and is not expressed in BACE1–/– brain tissues, while β-actin controls are expressed equally in all three. APP-CTFα, a product of the enzymatic cleaving of APP by α secretase, is present in tissues from all three genotypes. However, APP-CTFβ, a product of the enzymatic cleaving of APP by BACE1, is present in BACE1+/+ and BACE1+/– tissues, but not in BACE1–/– tissues. C, Densitometric analysis of APP-CTFα. F(2,6) = 6.557, p = 0.0309; *, p < 0.05.
- Figure 2.
Loss of BACE1 increases NPC proliferation without affecting NPC survival. A, Photomicrographs of BrdU+ cells 1 d after BrdU injection in the DG of BACE1+/+, BACE1+/–, and BACE1–/– mice. Green or yellow, BrdU+ cells; red, NeuN+ cells. Scale bar: 50 µm. B, Quantification of BrdU+ cells 1 d post-BrdU injection (mean ± SEM; n = 6 in BACE1+/+, 6 in BACE1+/–, and 5 in BACE1–/– mice; F(2,14) = 4.629, p = 0.0286); *, p < 0.05. C, Photomicrographs of Ki67+ cells in the DG of BACE1+/+, BACE1+/–, and BACE1–/– mice. Red, Ki67+ cells; blue, DAPI+ cells. Scale bar: 50 µm. D, Quantification of Ki67+ cells (mean ± SEM; n = 5 in each group; F(2,12) = 15.52, p = 0.0012); **, p < 0.01. E, To provide a measure of cell survival during the 4-week post-BrdU time period, the number of BrdU+ cells at the 4-week post-BrdU time point was expressed as a percentage of the number present at the 1-d post-BrdU time point (mean ± SEM; n = 6 in BACE1+/+, 8 in BACE1+/–, and 5 in BACE1–/– mice; F(2,16) = 1.654, p = 0.2224).
- Figure 3.
Loss of BACE1 alters neuronal fate differentiation of NPCs. A, Representative confocal images of BrdU+ cells colabeled with NeuN (upper panels) or GFAP (lower panels). Arrows indicate the position of BrdU+ cells. Scale bar: 20 µm. B, Percentage of BrdU+ cells colabeled with NeuN or GFAP, or neither of them (mean ± SEM; n = 6 in BACE1+/+, 8 in BACE1+/–, and 5 in BACE1–/– mice). For NeuN, F(2,16) = 9.501, p = 0.0019. For GFAP, F(2,16) = 0.786, p = 0.4725. For neither, F(2,16) = 7.551, p = 0.0049; *, p < 0.05; **, p < 0.01. C, Representative confocal images of BrdU+ cells colabeled with DCX but not NeuN (upper panels), or with DCX and NeuN (lower panels). D, Percentage of BrdU+ cells colabeled with NeuN or DCX, both, or neither of them (mean ± SEM; n = 6 in BACE1+/+, 8 in BACE1+/–, and 5 in BACE1–/– mice). For NeuN, F(2,16) = 28.34, p < 0.0001. For DCX, F(2,16) = 1.566, p = 0.2392. For both, F(2,16) = 0.03229, p = 0.9863. For neither, F(2,16) = 13.63, p = 0.0004; **, p < 0.01. E, Representative confocal images of BrdU+ cells colabeled with O2. F, Percentage of BrdU+ cells colabeled with NeuN or O2, or neither of them (mean ± SEM; n = 4 in BACE1+/+, 6 in BACE1+/–, and 4 in BACE1–/– mice). For NeuN, F(2,11) = 5.607, p = 0.0210. For O2, F(2,11) = 1.235, p = 0.3283. For neither, F(2,11) = 7.3, p = 0.0096; *, p < 0.05. G, Representative confocal images of GFAP+ astrocytes in the DG of BACE1+/+, BACE1+/–, and BACE1–/– mice. Red, GFAP+ cells; blue, NeuN+ cells. Scale bar: 50 µm. H, Quantification of GFAP+ cells (mean ± SEM; n = 5 per group; F(2,12) = 0.5162, p = 0.6095). I, GFAP signal intensity (mean ± SEM; n = 5 per group; F(2,12) = 0.0344, p = 0.9662).
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