Alzheimer's disease-like neuropathology of gene-targeted APP-SLxPS1mut mice expressing the amyloid precursor protein at endogenous levels

doi:10.1016/j.nbd.2005.04.009

Neurobiology of Disease

Volume 20, Issue 2, November 2005, Pages 528-540

https://doi.org/10.1016/j.nbd.2005.04.009 Get rights and content

Abstract

Most transgenic mice used for preclinical evaluation of potential disease-modifying treatments of Alzheimer's disease develop major histopathological features of this disease by several-fold overexpression of the human amyloid precursor protein. We studied the phenotype of three different strains of gene-targeted mice which express the amyloid precursor protein at endogenous levels. Only further crossing with transgenic mice overexpressing mutant human presenilin1 led to the deposition of extracellular amyloid, accompanied by the deposition of apolipoprotein E, an astrocyte and microglia reaction, and the occurrence of dilated cholinergic terminals in the cortex. Features of neurodegeneration, however, were absent. The pattern of plaque development and deposition in these mice was similar to that of amyloid precursor protein overproducing strains if crossed to presenilin1-transgenics. However, plaque development started much later and developed slowly until the age of 18 months but then increased more rapidly.

Introduction

Alzheimer's disease (AD) is characterized by amyloid plaque deposition, tangle formation, glial reaction, and cognitive impairment which is paralleled by a decline of the cholinergic system (Geula et al., 1998). Based on the hypothesis that the AD-associated neuropathology is driven by aberrant processing of the amyloid precursor protein (APP) leading to the accumulation of β-amyloid protein (Aβ) (Hardy and Selkoe, 2002), the major strategies in the search for disease-modifying treatments of AD are reduction of Aβ-deposits or inhibition of their development.

Several transgenic mouse lines, which develop cardinal features of AD-associated neuropathology, were generated for testing therapeutic approaches. The commonly used transgenic mouse models achieve elevated Aβ-levels by a three- to ten-fold overproduction of human APP caused by the insertion of an exogenous promoter in combination with familial Alzheimer's disease (FAD)-associated mutations (Games et al., 1995, Hsiao et al., 1996, Sturchler-Pierrat et al., 1997). Due to this overproduction, aggregated Aβ peptides accumulate to histologically apparent amyloid plaques in the brains of these transgenic mice during the course of their lives. AD-like pathology was further accelerated by crossing APP transgenic mice with other transgenic mice expressing a mutant human presenilin1 (PS1) protein, an essential component of the Aβ-producing enzyme complex γ-secretase (Borchelt et al., 1997, Holcomb et al., 1998, McGowan et al., 1999). The question of clinical predictability of treatment in current mouse models for human AD arose by the clinical outcome of a vaccination approach which was initially developed in transgenic mice. Vaccination with Aβ leading to endogenous production of antibodies was a reliable method to reduce the amyloid burden in transgenic mice (Schenk et al., 1999, Weiner et al., 2000) but turned out to produce subacute meningoencephalitis in 6% of patients in a clinical trial (Ferrer et al., 2004, Orgogozo et al., 2003).

As a step towards a mouse model of AD which resembles more the situation in man, i.e., without massive overproduction of APP, transgenic mice with a mutant APP bearing the Swedish FAD mutation and a “humanized” Aβ−sequence under the control of the endogenous mouse APP promoter were generated (Reaume et al., 1996). However, to date, only one report on the phenotype of these mice exists (Flood et al., 2002).

In order to get more information about mouse models of AD which do not overproduce APP, we studied plaque development, glial reaction, and the cholinergic system in three different strains of APP-gene-targeted mice with the human Aβ-sequence flanked by either the Swedish (APP-S) (Lannfelt et al., 1994), the London (V717I, APP-L) (Goate et al., 1991), or both the Swedish and London mutations (APP-SL). In addition, APP-gene-targeted mice carrying both the Swedish and London mutations were crossed with two different human PS1 expressing strains (PS1wt, PS1(M146L)) (Duff et al., 1996, Hartmann et al., 2004).

Section snippets

Generation of gene-targeted mice

The ES cell line G1 was electroporated with gene-targeting vectors encoding Swedish/London-FAD mutations of APP (Fig. 1) (Robertson, 1987). Targeted ES cells were identified and then injected into blastocysts to generate chimeric mice (Bradley, 1987). High percentage chimeric male mice were mated with 129/SvEv and Black Swiss female mice to establish germline transmission of the targeted mouse APP gene. Homozygous APP knock-in mice were then crossed with PS1(M146L) or PS1wt mice (Duff et al.,

Amyloid-plaques occur only in APP-SLxPS1mut mice

The human Aβ-specific monoclonal antibody 6E10 labeled granules and elongated structures in the cytoplasm of neurons, often extending into the apical dendrite. Because 6E10 is not only specific for Aβ but also labels uncleaved APP and sAPPα fragments, the observed immunoreactivity might represent both APP and intracytoplasmatic Aβ. Immunoreactivity was present in the APP-S, APP-L, APP-SL, APP-SLxPS1wt, and APP-SLxPS1mut strains but absent in wild-type control mice of the Black Swiss strain.

Discussion

The histological phenotype of three strains of APP-gene-targeted mice, expressing the human Aβ-sequence together with FAD-linked mutations and two strains of APP-gene-targeted mice crossed with human PS1 overexpressing strains, was analyzed in respect to major neuropathological features of AD: plaque development, plaque-associated glial reaction, neurodegeneration, and changes in the cholinergic innervation of the cortex and hippocampus. APP-gene-targeted mice do not overexpress APP because the

Acknowledgments

This work was supported by Bayer Health Care AG, Wuppertal, Germany (BARN-Project). The authors thank U. Gillert, K. Pilz for excellent technical assistance, and N. Moser for providing organotypic slice cultures.

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¹: Present address: Abbott GmbH & Co. KG, Neuroscience Research GGRP, D-67061 Ludwigshafen, Germany.

²: Present address: F. Hoffmann-La Roche Ltd., Pharmaceuticals Division, Preclinical, Research CNS, CH-4070 Basel, Switzerland.

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Alzheimer's disease-like neuropathology of gene-targeted APP-SLxPS1mut mice expressing the amyloid precursor protein at endogenous levels

Abstract

Introduction

Section snippets

Generation of gene-targeted mice

Amyloid-plaques occur only in APP-SLxPS1mut mice

Discussion

Acknowledgments

Neurobiol. Dis.

Neuron

Neuron

Biochem. Biophys. Res. Commun.

Am. J. Pathol.

Neurobiol. Aging

Exp. Neurol.

Am. J. Pathol.

Neuroscience

J. Biol. Chem.

Brain Res. Mol. Brain Res.

Neuron

Am. J. Pathol.

Neurobiol. Dis.

Prog. Neuropsychopharmacol. Biol. Psychiatry

J. Biol. Chem.

Brain Res.

Neuroscience

Neuroscience

Neuropathological stageing of Alzheimer-related changes

Acta Neuropathol.

Teratocarcinomas and Embryonic Stem Cells

Alzheimer amyloid protein precursor in the rat hippocampus: transport and processing through the perforant path

J. Neurosci.

Mutant presenilins of Alzheimer's disease increase production of 42-residue amyloid β-protein in both transfected cells and transgenic mice

Nat. Med.

Evidence that neurones accumulating amyloid can undergo lysis to form amyloid plaques in Alzheimer's disease

Histopathology

Production of intracellular amyloid-containing fragments in hippocampal neurons expressing human amyloid precursor protein and protection against amyloidogenesis by subtle amino acid substitutions in the rodent sequence

EMBO J.

Increased amyloid-β42(43) in brains of mice expressing mutant presenilin 1

Nature

Neuropathology and pathogenesis of encephalitis following amyloid-beta immunization in Alzheimer's disease

Brain Pathol.

The cholinergic pathology in Alzheimer's disease—discrepancies between clinical experience and pathophysiological findings

J. Neural Transm.

Alzheimer-type neuropathology in transgenic mice overexpressing V717F β-amyloid precursor protein

Nature