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Neurovascular dysfunction in GRN-associated frontotemporal dementia identified by single-nucleus RNA-sequencing of human cerebral cortex

ABSTRACT: Frontotemporal dementia (FTD) is the second most prevalent form of early-onset dementia, affecting predominantly frontal and temporal cerebral lobes. Heterozygous mutations in the progranulin gene (GRN) cause autosomal-dominant FTD (FTD-GRN), associated with TDP-43 inclusions, neuronal loss, axonal degeneration and gliosis, but FTD-GRN pathogenesis is largely unresolved. Here we report single-nucleus RNA sequencing of microglia, astrocytes and the neurovasculature from frontal, temporal and occipital cortical tissue from control and FTD-GRN brains. We show that fibroblast and mesenchymal cell numbers were enriched in FTD-GRN, and we identified disease-associated subtypes of astrocytes and endothelial cells. Expression of gene modules associated with blood–brain barrier (BBB) dysfunction was significantly enriched in FTD-GRN endothelial cells. The vasculature supportive function and capillary coverage by pericytes was reduced in FTD-GRN tissue, with increased and hypertrophic vascularization and an enrichment of perivascular T cells. Our results indicate a perturbed BBB and suggest that the neurovascular unit is severely affected in FTD-GRN.

ORGANISM(S): Homo sapiens

PROVIDER: GSE163122 | GEO | 2022/06/03

REPOSITORIES: GEO

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Project description:Frontotemporal dementia is characterized by progressive atrophy of frontal and/or temporal cortices and an early age of onset. The disorder is highly heterogenic, comprising several genetic causes as well as a diverse phenotypic landscape of sporadic cases. Here we investigated the proteomic signatures of human brain frontal and temporal cortical lobes to identify key pathways involved in the three most frequent genetic subtypes of frontotemporal dementia. We included 38 patients with either an autosomal dominant repeat expansion in the C9ORF72 gene (n = 16), or a mutation in the GRN gene (n = 9) or the MAPT gene (n = 13), and 11 non-demented controls. Using data-independent quantitative proteomic analysis on laser-dissected tissues we identified brain region-specific protein signatures for these genetic frontotemporal dementia subtypes compared to non-demented controls. Using published single cell RNA expression data for cell type enrichment we deduced the involvement of major brain cell types in driving these different protein signatures. Using gene ontology analysis, we identified distinct genetic subtype- and cell type-specific biological processes. In the GRN-mediated subtype, we observed higher protein expression related to immune processes, with a role for endothelial cells and astrocytes, and lower protein expression implicating mitochondrial dysregulation, primarily in neurons. In the MAPT-mediated subtype, we observed higher protein expression associated with dysregulation of RNA processing in multiple cell types, and lower protein expression implicating altered neuronal functioning via dysregulation of oligodendrocytes. Comparison of the MAPT-mediated frontotemporal dementia signature with one obtained from Alzheimer’s disease brains demonstrated only partial overlap in protein dysregulation, thus separating general neurodegenerative processes and highlighting the frontotemporal dementia-specific involvement of altered RNA processing and oligodendrocyte dysfunction. Taken together, our results indicate a role for different brain cell types and biological mechanisms in frontotemporal dementia, revealing both genetic subtype-specific processes, and processes shared with other neurodegenerative diseases such as Alzheimer’s disease.

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Neurovascular dysfunction in GRN-associated frontotemporal dementia identified by single-nucleus RNA-sequencing of human cerebral cortex

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