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First published online 8 April 2004
doi: 10.1242/dev.01103

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Soluble form of amyloid precursor protein regulates proliferation of progenitors in the adult subventricular zone

¹ CNRS UMR 8542, Ecole Normale Supérieure, 46 rue d'Ulm, 75005 Paris, France
² Department of Neurochemistry, Max Planck Institute for Brain Research, D-60528 Frankfurt, Germany

View larger version (25K): [in a new window]   Fig. 3. Changes in sAPP concentration modify the number of SVZ progenitors through regulation of their proliferation. (A-D) Mice were intraventricularly infused with human IgG (control), sAPP-Fc (sAPP), 0.09% NaCl (saline), batimastat (bat), batimastat and sAPP (bat+sAPP), sense or antisense APP oligonucleotides (S, AS). In A and C, NS were prepared from the SVZ ipsilateral to the side of infusion and counted. In B and D, BrdU was injected 1 hour before sacrifice and the percentage of BrdU-positive EGFR immunoreactive cells on the side of infusion was counted. Results are shown as mean±s.e.m. of six infused mice. (A,B) Augmentation of sAPP concentration leads to an increased number of EGF-responsive NS progenitors in the SVZ (A) and to their increased proliferation (B). (C) Reduction of sAPP secretion by batimastat or of APP synthesis by antisense oligonucleotides decreases the number of EGF-responsive NS progenitors. (Bottom panel) APP immunoblotting of the SVZ from two sense (S) or two antisense (AS) oligonucleotide-infused mice reveals a 30% reduction in APP levels in AS. (D) Reduction of APP synthesis through antisense oligonucleotide infusion downregulates EGFR immunoreactive cell proliferation and sAPP compensates this downregulation. (E) Ara-C infusion was followed by a 3 day intraventricular infusion of control IgG (Ara-C and IgG) or 6 E10 antibody (Ara-C and 6 E10) and the total number of BrdU-positive cells was counted in whole-mount preparations of the anterior SVZ. During SVZ regeneration, reduction of circulating sAPP downregulates EGF-responsive cell proliferation.

View larger version (61K): [in a new window]   Fig. 1. sAPP-binding sites are present on SVZ cells. Single (A-D,F,G,I,J,L-N) or double (E,H,K) immunofluorescent stainings of frontal sections through the SVZ. (A) SVZ cells express APP. The SVZ is outlined by two white lines. (B) SVZ cells express sAPP-binding sites. (C-E) sAPP-binding sites (D) are present on EGFR immunopositive SVZ cells (C). (F-H) sAPP-binding sites (G) are present on PSA-NCAM immunoreactive neuroblasts (F). (I-K) S100 immunoreactive astrocytes (arrowheads) and ependymal cells (arrow) (I) do not express sAPP binding sites (J). (L-N) L1-binding sites are detected by the same technique in the SVZ (L), hippocampus (M) and cortex (N). St, striatum; LV, lateral ventricle. Scale bars: 10 µm.

View larger version (32K): [in a new window]   Fig. 2. sAPP participates in the EGF-induced proliferation of neurospheres. (A) Schematic structure of human APP (695 amino acid form) indicating the positions of the epitopes of 22C11 and 6 E10 antibodies. -sAPP, soluble APP; Aß, amyloid ß-peptide; TM, transmembrane region. (B) sAPP-binding sites (red) are detected on plated undifferentiated NS as a punctuate membrane staining. Nuclei are counterstained with DAPI. Scale bar: 5 µm. (C) A constant number of NS were seeded in media with different concentrations of EGF (0, 2 or 20 ng/ml). Secreted (upper panel) and cellular (lower panel) APP were detected by immunoblotting. Secretion of sAPP is augmented by increasing concentrations of EGF (2 ng/ml, 3.5 fold; 20 ng/ml, 5.9 fold increase relative to EGF-free medium) while cellular APP remains largely constant. (D) Percentage of BrdU-positive NS cells after 15 hours of culture in medium containing EGF (2 ng/ml) and BrdU without (control) or with antibodies directed against sAPP (22C11, 6E10). Both antibodies decrease proliferation of NS cells. This decrease is abolished by pre-adsorption of the antibodies with their epitopes or by co-incubating 22C11 and sAPP. Results are shown as mean±s.e.m. of three independent experiments.

View larger version (49K): [in a new window]   Fig. 4. sAPLP2 is functionally redundant with sAPP in the SVZ. (A) SVZ cells do not express sAPLP1 binding sites. (B) SVZ cells express sAPLP2 binding sites. (C, left panel) APLP1 immunoblotting showing APLP1 expression in the SVZ. (C, right panel) APLP2 immunoblotting of the SVZ from sense (S) or antisense (AS) APLP2 oligonucleotides infused mice reveals a 30% reduction in APLP2 levels in AS. (D) Augmentation of sAPLP2 concentration upon sAPLP2-Fc infusion increases the number of EGF-responsive NS progenitors in the SVZ, whereas reduction of APLP2 synthesis by antisense oligonucleotide infusion decreases their number. Results are shown as mean±s.e.m. of six infused mice. Scale bars: 10 µm

View larger version (150K): [in a new window]   Fig. 5. sAPP-binding sites are present on NS from the embryonic brain (E14). Scale bar: 10 µm.

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