Differential transgene expression patterns in Alzheimer mouse models revealed by novel human amyloid precursor protein-specific antibodies.

Corinna Höfling,Alperen Serdaroglu,Elisa R Zanier,Stephan Hörsten,Markus Morawski,Peer‐Hendrik Kuhn,Katrin Moschke,Elisabeth Kremmer,Stefan F Lichtenthaler,Steffen Roßner,Maria‐Grazia De Simoni,Ulrike Zeitschel,Carsten Jäger,Fabio Canneva,Gianluigi Forloni

doi:10.1111/acel.12508

Abstract

SummaryAlzheimer's disease (AD) is histopathologically characterized by neurodegeneration, the formation of intracellular neurofibrillary tangles and extracellular Aβ deposits that derive from proteolytic processing of the amyloid precursor protein (APP). As rodents do not normally develop Aβ pathology, various transgenic animal models of AD were designed to overexpress human APP with mutations favouring its amyloidogenic processing. However, these mouse models display tremendous differences in the spatial and temporal appearance of Aβ deposits, synaptic dysfunction, neurodegeneration and the manifestation of learning deficits which may be caused by age‐related and brain region‐specific differences in APP transgene levels. Consequentially, a comparative temporal and regional analysis of the pathological effects of Aβ in mouse brains is difficult complicating the validation of therapeutic AD treatment strategies in different mouse models. To date, no antibodies are available that properly discriminate endogenous rodent and transgenic human APP in brains of APP‐transgenic animals. Here, we developed and characterized rat monoclonal antibodies by immunohistochemistry and Western blot that detect human but not murine APP in brains of three APP‐transgenic mouse and one APP‐transgenic rat model. We observed remarkable differences in expression levels and brain region‐specific expression of human APP among the investigated transgenic mouse lines. This may explain the differences between APP‐transgenic models mentioned above. Furthermore, we provide compelling evidence that our new antibodies specifically detect endogenous human APP in immunocytochemistry, FACS and immunoprecipitation. Hence, we propose these antibodies as standard tool for monitoring expression of endogenous or transfected APP in human cells and APP expression in transgenic animals.

Highlights

Alzheimer’s disease (AD) is the most frequent neurodegenerative disorder worldwide
We developed and characterized rat monoclonal antibodies by immunohistochemistry and Western blot that detect human but not murine amyloid precursor protein (APP) in brains of three APP-transgenic mouse and one APP-transgenic rat model
We provide compelling evidence that our new antibodies detect endogenous human APP in immunocytochemistry, fluorescence-activated cell sorting (FACS) and immunoprecipitation

Summary

Introduction

Alzheimer’s disease (AD) is the most frequent neurodegenerative disorder worldwide. It is marked by the generation and deposition of small, neurotoxic Aβ peptides in form of oligomeric aggregates and plaques in the brain parenchyma and vasculature. When using rodent animal models, it has to be taken into account that Aβ from mice and rats contains three amino acid substitutions as compared to human Aβ (R5G, Y10F and H13R) These alterations were shown to influence APP processing (De Strooper et al, 1995; Reaume et al, 1996) and the ability of Aβ peptides to form secondary structures such as oligomers and fibrils (Dyrks et al, 1993; Otvos et al, 1993). Transgenic models of Aβ pathology have been developed that overexpress human APP (hAPP) with AD-associated mutations which favour the amyloidogenic b-secretase pathway of APP processing (Games et al, 1995; Hsiao et al, 1996; Sturchler-Pierrat et al, 1997) These mice have been used to test therapeutic strategies that aim at reducing Aβ generation, for example by treatment with b-secretase inhibitors and by active and passive immunization approaches (Solomon et al, 1996; Schenk et al, 1999; Eketjall et al, 2013). Aging Cell published by the Anatomical Society and John Wiley & Sons Ltd

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