Cell Type-Specific Human APP Transgene Expression by Hippocampal Interneurons in the Tg2576 Mouse Model of Alzheimer’s Disease

Amyloid precursor protein (APP) transgenic animal models of Alzheimer’s disease have become versatile tools for basic and translational research. However, there is great heterogeneity of histological, biochemical, and functional data between transgenic mouse lines, which might be due to different transgene expression patterns. Here, the expression of human APP (hAPP) by GABAergic hippocampal interneurons immunoreactive for the calcium binding proteins parvalbumin, calbindin, calretinin, and for the peptide hormone somatostatin was analyzed in Tg2576 mice by double immunofluorescent microscopy. Overall, there was no GABAergic interneuron subpopulation that did not express the transgene. On the other hand, in no case all neurons of such a subpopulation expressed hAPP. In dentate gyrus molecular layer and in stratum lacunosum moleculare less than 10% of hAPP-positive interneurons co-express any of these interneuron markers, whereas in stratum oriens hAPP-expressing neurons frequently co-express these interneuron markers to different proportions. We conclude that these neurons differentially contribute to deficits in young Tg2576 mice before the onset of Abeta plaque pathology. The detailed analysis of distinct brain region and neuron type-specific APP transgene expression patterns is indispensable to understand particular pathological features and mouse line-specific differences in neuronal and systemic functions

Endogenous mouse huntingtin is highly abundant in cranial nerve nuclei, co-aggregates to Abeta plaques and is induced in reactive astrocytes in a transgenic mouse model of Alzheimer’s disease

Pathogenic variants of the huntingtin (HTT) protein and their aggregation have been investigated in great detail in brains of Huntington’s disease patients and HTT-transgenic animals. However, little is known about the physiological brain region- and cell type-specific HTT expression pattern in wild type mice and a potential recruitment of endogenous HTT to other pathogenic protein aggregates such as amyloid plaques in cross seeding events. Employing a monoclonal anti-HTT antibody directed against the HTT mid-region and using brain tissue of three different mouse strains, we detected prominent immunoreactivity in a number of brain areas, particularly in cholinergic cranial nerve nuclei, while ubiquitous neuronal staining appeared faint. The region-specific distribution of endogenous HTT was found to be comparable in wild type rat and hamster brain. In human amyloid precursor protein transgenic Tg2576 mice with amyloid plaque pathology, similar neuronal HTT expression patterns and a distinct association of HTT with Abeta plaques were revealed by immunohistochemical double labelling. Additionally, the localization of HTT in reactive astrocytes was demonstrated for the first time in a transgenic Alzheimer’s disease animal model. Both, plaque association of HTT and occurrence in astrocytes appeared to be age-dependent. Astrocytic HTT gene and protein expression was confirmed in primary cultures by RT-qPCR and by immunocytochemistry. We provide the first detailed analysis of physiological HTT expression in rodent brain and, under pathological conditions, demonstrate HTT aggregation in proximity to Abeta plaques and Abeta-induced astrocytic expression of endogenous HTT in Tg2576 mice

Identification of thyrotropin-releasing hormone as hippocampal glutaminyl cyclase substrate in neurons and reactive astrocytes

Recently, Aβ peptide variants with an N-terminal truncation and pyroglutamate modification were identified and shown to be highly neurotoxic and prone to aggregation. This modification of Aβ is catalyzed by glutaminyl cyclase (QC) and pharmacological inhibition of QC diminishes Aβ deposition and accompanying gliosis and ameliorates memory impairment in transgenic mouse models of Alzheimer's disease (AD). QC expression was initially described in the hypothalamus, where thyrotropin-releasing hormone (TRH) is one of its physiological substrates. In addition to its hormonal role, a novel neuroprotective function of TRH following excitotoxicity and Aβ-mediated neurotoxicity has been reported in the hippocampus. Functionally matching this finding, we recently demonstrated QC expression by hippocampal interneurons in mouse brain. Here, we detected neuronal co-expression of QC and TRH in the hippocampus of young adult wild type mice using double immunofluorescence labeling. This provides evidence for TRH being a physiological QC substrate in hippocampus. Additionally, in neocortex of aged but not of young mice transgenic for amyloid precursor protein an increase of QC mRNA levels was found compared to wild type littermates. This phenomenon was not observed in hippocampus, which is later affected by Aβ pathology. However, in hippocampus of transgenic - but not of wild type mice - a correlation between QC and TRH mRNA levels was revealed. This co-regulation of the enzyme QC and its substrate TRH was reflected by a co-induction of both proteins in reactive astrocytes in proximity of Aβ deposits. Also, in primary mouse astrocytes a co-induction of QC and TRH was demonstrated upon Aβ stimulation

Defined astrocytic expression of human amyloid precursorprotein in Tg2576 mouse brain

Transgenic Tg2576 mice expressing human amyloid precursor protein (hAPP) with the Swedish mutation are among the most frequently used animal models to study the amyloid pathology related to Alzheimer's disease (AD). The transgene expression in this model is considered to be neuron‐specific. Using a novel hAPP‐specific antibody in combination with cell type‐specific markers for double immunofluorescent labelings and laser scanning microscopy, we here report that—in addition to neurons throughout the brain—astrocytes in the corpus callosum and to a lesser extent in neocortex express hAPP. This astrocytic hAPP expression is already detectable in young Tg2576 mice before the onset of amyloid pathology and still present in aged Tg2576 mice with robust amyloid pathology in neocortex, hippocampus, and corpus callosum. Surprisingly, hAPP immunoreactivity in cortex is restricted to resting astrocytes distant from amyloid plaques but absent from reactive astrocytes in close proximity to amyloid plaques. In contrast, neither microglial cells nor oligodendrocytes of young or aged Tg2576 mice display hAPP labeling. The astrocytic expression of hAPP is substantiated by the analyses of hAPP mRNA and protein expression in primary cultures derived from Tg2576 offspring. We conclude that astrocytes, in particular in corpus callosum, may contribute to amyloid pathology in Tg2576 mice and thus mimic this aspect of AD pathology

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

Alzheimer's disease (AD) is histopathologically characterized by neurodegeneration, the formation of intracellular neurofibrillary tangles and extracellular A deposits that derive from proteolytic processing of the amyloid precursor protein (APP). As rodents do not normally develop A 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 A 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 A 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

Early pathologic amyloid induces hypersynchrony of BOLD resting-state networks in transgenic mice and provides an early therapeutic window before amyloid plaque deposition

In Alzheimer's disease (AD), pathologic amyloid-beta (Aβ) is synaptotoxic and impairs neuronal function at the microscale, influencing brain networks at the macroscale before Aβ deposition. The latter can be detected noninvasively, in vivo, using resting-state functional MRI (rsfMRI), a technique used to assess brain functional connectivity (FC).publisher: Elsevier articletitle: Early pathologic amyloid induces hypersynchrony of BOLD resting-state networks in transgenic mice and provides an early therapeutic window before amyloid plaque deposition journaltitle: Alzheimer's & Dementia articlelink: http://dx.doi.org/10.1016/j.jalz.2016.03.010 content_type: article copyright: © 2016 The Alzheimer's Association. Published by Elsevier Inc. All rights reserved.status: publishe

Early pathologic amyloid induces hypersynchrony of BOLD resting-state networks in transgenic mice and provides an early therapeutic window before amyloid plaque deposition

INTRODUCTION: In Alzheimer's disease (AD), pathologic amyloid-beta (Aβ) is synaptotoxic and impairs neuronal function at the microscale, influencing brain networks at the macroscale before Aβ deposition. The latter can be detected noninvasively, in vivo, using resting-state functional MRI (rsfMRI), a technique used to assess brain functional connectivity (FC). METHODS: RsfMRI was performed longitudinally in TG2576 and PDAPP mice, starting before Aβ deposition to determine the earliest FC changes. Additionally, the role of pathologic Aβ on early FC alterations was investigated by treating TG2576 mice with the 3D6 anti-Aβ-antibody. RESULTS: Both transgenic models showed hypersynchronized FC before Aβ deposition and hyposynchronized FC at later stages. Early anti-Aβ treatment in TG2576 mice prevented hypersynchronous FC and the associated synaptic impairments and excitatory/inhibitory disbalances. DISCUSSION: Hypersynchrony of FC may be used as a new noninvasive read out of early AD and can be recovered by anti-Aβ treatment, encouraging preventive treatment strategies in familial AD

Ausschreibungen für erneuerbare Energien. Wissenschaftliche Empfehlungen: Studie im Auftrag des Bundesministeriums für Wirtschaft und Energie. Projektnummer: DESDE15240. 07. Juli 2015

Eine Grundlage für die Eckpunkte zur Ausschreibung für die Förderung erneuerbarer Energien sind die Zwischenergebnisse einer wissenschaftlichen Studie zum Ausschreibungsdesign erneuerbarer Energien. Der Bericht analysiert die Marktsituation der verschiedenen erneuerbaren Energien und spricht Empfehlungen für ein Ausschreibungsdesign aus. Er wurde von einem Forschungskonsortium, das sich aus Ecofys, Fraunhofer ISI, Consentec, dem Zentrum für Sonnenenergie- und Wasserstoff-Forschung Baden-Württemberg (ZSW), Takon und den Rechtsanwaltskanzleien Görg sowie BBG und Partner zusammensetzt, erarbeitet