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Distinct transcriptomic responses to Ab plaques, neurofibrillary tangles, and APOE in Alzheimer’s disease

ABSTRACT: INTRODUCTION: Omics studies have revealed that various brain cell types undergo profound molecular changes in Alzheimer’s disease (AD) but the spatial relationships with plaques and tangles and APOE-linked differences remain unclear. METHODS: We performed laser capture microdissection of Ab plaques, the 50mm halo around them, tangles with the 50mm halo around them, and areas distant (>50mm) from plaques and tangles in the temporal cortex of AD and control donors, followed by RNA-sequencing. RESULTS: Ab plaques exhibited upregulated microglial (neuroinflammation) and downregulated neuronal (neurotransmission/energy metabolism) genes, whereas tangles had mostly downregulated neuronal genes. Ab plaques had more differentially expressed genes than tangles. We identified a gradient Ab plaque>peri-plaque>tangle>distant for these changes. AD APOEe4 homozygotes had greater changes than APOEe3 across locations, especially within Ab plaques. DISCUSSION: Transcriptomic changes in AD consist primarily of neuroinflammation and neuronal dysfunction, are spatially associated mainly with Ab plaques, and are exacerbated by the APOEe4 allele.

ORGANISM(S): Homo sapiens

PROVIDER: GSE226901 | GEO | 2024/02/14

REPOSITORIES: GEO

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Project description:Alzheimer's Disease (AD) is a devastating neurodegenerative disorder affecting approximately 4 million people in the U.S. alone. AD is characterized by the presence of senile plaques and neurofibrillary tangles in cortical regions of the brain. These pathological markers are thought to be responsible for the massive cortical neurodegeneration and concomitant loss of memory, reasoning, and often aberrant behaviors that are seen in patients with AD. Understanding the molecular mechanisms whereby these histopathological markers develop will greatly enhance our understanding of AD development and progression. A clearer understanding of the mechanisms underlying neurofibrillary tangle formation specifically may help to clarify the basis for dementia of AD as well as the dementias associated with other diseases that are collectively referred to as "tauopathies."; To expression profile both neurons containing neurofibrillary tangles and normal neurons from the entorhinal cortex of 10 mid-stage AD cases. The gene expression profile of neurons that contain neurofibrillary tangles will differ from the expression profile of histopathologically normal neurons from the same patient and from the same brain region. Some of these differences will be informative as to the mechanisms of tangle formation. Experiment Overall Design: First use laser capture microdissection to select 1000 neurons bearing neurofibrillary tangles and 1000 normal neurons from the layer 2 stellate island neurons of the entorhinal cortex of 10 mid-stage AD cases. Second, to isolate the RNA from these captured neurons, perform double round linear amplification and hybridize the labeled cRNA to affymetrix U133A arrays. Third, to use paired, permutational t-tests to analyze the microarray data to select tangle-specific differences in gene expression. For the purposes of submitting this proposal, a value of 1 ug of RNA was entered due to web site constraints on values placed in that field. However, all samples are from LCM captured cells and the actual RNA yield is likely closer to 100 pg.

Project description:GFAP and vimentin deficiency alters gene expression in astrocytes and microglia in wild-type mice and changes the transcriptional response of reactive glia in mouse model for Alzheimer's disease. Reactive astrocytes with an increased expression of intermediate filament (IF) proteins Glial Fibrillary Acidic Protein (GFAP) and Vimentin (VIM) surround amyloid plaques in Alzheimer's disease (AD). The functional consequences of this upregulation are unclear. To identify molecular pathways coupled to IF regulation in reactive astrocytes, and to study the interaction with microglia, we examined WT and APPswe/PS1dE9 (AD) mice lacking either GFAP, or both VIM and GFAP, and determined the transcriptome of cortical astrocytes and microglia from 15- to 18-month-old mice. Genes involved in lysosomal degradation (including several cathepsins) and in inflammatory response (including Cxcl5, Tlr6, Tnf, Il1b) exhibited a higher AD-induced increase when GFAP, or VIM and GFAP, were absent. The expression of Aqp4 and Gja1 displayed the same pattern. The downregulation of neuronal support genes in astrocytes from AD mice was absent in GFAP/VIM null mice. In contrast, the absence of IFs did not affect the transcriptional alterations induced by AD in microglia, nor was the cortical plaque load altered. Visualizing astrocyte morphology in GFAP-eGFP mice showed no clear structural differences in GFAP/VIM null mice, but did show diminished interaction of astrocyte processes with plaques. Microglial proliferation increased similarly in all AD groups. In conclusion, absence of GFAP, or both GFAP and VIM, alters AD-induced changes in gene expression profile of astrocytes, showing a compensation of the decrease of neuronal support genes and a trend for a slightly higher inflammatory expression profile. However, this has no consequences for the development of plaque load, microglial proliferation, or microglial activation. 2 cell types from 6 conditions: cortical microglia and cortical astrocytes from 15-18 month old APPswe/PS1dE9 mice compared to wildtype littermates. Biological replicates: microglia from APPswe/PS1dE9, N=7, microglia from WT, N=7, astrocytes from APPswe/PS1dE9, N=4, microglia from WT, N=4

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Distinct transcriptomic responses to Ab plaques, neurofibrillary tangles, and APOE in Alzheimer’s disease

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