Blank, Nelli: Translatome analysis and in vivo Ca2+ imaging of astrocytes in an Alzheimer’s disease mouse model. - Bonn, 2021. - Dissertation, Rheinische Friedrich-Wilhelms-Universität Bonn.
Online-Ausgabe in bonndoc: https://nbn-resolving.org/urn:nbn:de:hbz:5-61197
@phdthesis{handle:20.500.11811/8990,
urn: https://nbn-resolving.org/urn:nbn:de:hbz:5-61197,
author = {{Nelli Blank}},
title = {Translatome analysis and in vivo Ca2+ imaging of astrocytes in an Alzheimer’s disease mouse model},
school = {Rheinische Friedrich-Wilhelms-Universität Bonn},
year = 2021,
month = mar,

note = {One of the most prominent hallmarks of Alzheimer’s Disease (AD) is the accumulation of amyloid beta (Abeta) species, which have the tendency to form extracellular insoluble Abeta plaques and induce reactive astrogliosis in surrounding astrocytes. We have previously shown that peri-plaque reactive astrocytes become hyperactive in mouse models of AD (APP/PS1 and APPPS1 21), and that one key signalling pathway for this hyperactivity is mediated by purinergic signalling. However, it has remained unclear how astrocytes and astrocytic hyperactivity contribute to the onset and progression of AD, how astrocytic gene expression is altered in APP/PS1 mice, and what the consequences of altered gene expression are for astroglial signalling pathways. To identify transcriptional alterations in astrocytes associated with disease progression and/or aging, we precipitated astrocyte-specific messenger RNA (mRNA) in a RiboTag approach that allowed us to perform bulk RNA sequencing specifically from astrocytes isolated from wild type and APP/PS1 mice. To investigate alterations on a functional level, we performed in vivo Ca2+ imaging in astrocytes of awake behaving mice. To this end, we intravenously injected an adeno-associated virus (AAV) encoding for the green fluorescent calcium indicator GCaMP6f under the control of the astrocyte-specific short GFAP promoter. This approach enabled us to longitudinally measure spontaneous Ca2+ transients in cortical astrocytes of APPPS1 21 mice and their wild type littermates and moreover, to correlate these data to behaviour and disease progression. Gene set enrichment analysis (GSEA) of upregulated differentially expressed genes (DEGs) in APP/PS1 mice uncovered specific enrichment in genes involved in Ca2+ signalling pathways, including several G protein coupled receptors (GPCRs). Based on this investigation, we found the alpha1-adrenoceptor (alpha1-AR) Adra1d was upregulated in the stage before disease onset and in the early stage of Abeta pathology in APP/PS1 mice as well as during aging in wild type mice. To validate this result, we performed in situ hybridization of two different alpha1 AR genes, Adra1a and Adra1d, confirming an increased expression of both genes in cortical reactive astrocytes in APPPS1-21 mice. In other studies, it has been shown that Ca2+ responses in cortical astrocytes are induced by activation of alpha1-adrenergic signalling and that the release of the neurotransmitter (NT) norepinephrine (NE) is dependent on the behavioural state. Indeed, we detected a locomotion-triggered increase of Ca2+ transient frequency and prolonged signals in cortical astrocytes in APPPS1-21 mice. Together, these results indicate a contribution of alpha1-ARs in behaviour-associated Ca2+ signalling of cortical astrocytes related to Abeta pathology, which may lead to a better understanding of the role of alpha1 adrenergic signalling in astroglial neuronal network dysfunction in AD.},
url = {https://hdl.handle.net/20.500.11811/8990}
}

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