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| Home > Publications Database > Translatome analysis and in vivo Ca2+ imaging of astrocytes in an Alzheimer's disease mouse model |
| Home > Publications Database > Translatome analysis and in vivo Ca2+ imaging of astrocytes in an Alzheimer's disease mouse model |
| Dissertation / PhD Thesis | DZNE-2021-00614 |
2021
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Please use a persistent id in citations: urn:nbn:de:hbz:5-61197
Abstract: One of the most prominent hallmarks of Alzheimer's Disease (AD) is the accumulation of amyloid-beta (Aß) species, which have the Lendency to form extracellular insoluble Aß plaques and induce reactive astrogliosis in surrounding astrocytes. We have previously shown that periplaque reactive astrocytes become hyperactive in mouse models of AD (APP /PSl and APPPSl-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 /PSl mice, and what the consequences of altered gene expression are for astroglial signaling 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 /PSl 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 (AA V) 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 APPPSl-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 /PSl 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 al-adrenoceptor (al-AR) Adrald was upregulated in the stage before disease onset and in the early stage of Aß pathology in APP /PSl mice as well as during aging in wild type mice. To validate this result, we performed in situ hybridization of two different al-AR genes, Adrala and Adrald, confirming an increased expression of both genes in cortical reactive astrocytes in APPPSl-21 mice. In other studies, it has been shown that Ca2+ responses in cortical astrocytes are induced by activation of al-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 APPPSl-21 mice. Together, these results indicate a contribution of al-ARs in behaviour-associated Ca2+ signalling of cortical astrocytes related to Aß pathology, which may lead to a better understanding of the role of al-adrenergic signalling in astroglial-neuronal network dysfunction in AD.
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