Project description:The diversity of cell types and regulatory states in the brain, and how these change during ageing, remains largely unknown. We present a single-cell transcriptome atlas of the entire adult Drosophila melanogaster brain sampled across its lifespan. Cell clustering identified 87 initial cell clusters that are further subclustered and validated by targeted cell-sorting. Our data shows high granularity and identifies a wide range of cell types. Gene network analyses using SCENIC revealed regulatory heterogeneity linked to energy consumption. During ageing, RNA content declines exponentially without affecting neuronal identity in old brains. This single-cell brain atlas covers nearly all cells in the normal brain and provides the tools to study cellular diversity alongside other Drosophila and mammalian single-cell datasets in our unique single-cell analysis platform. These results allow comprehensive exploration of all transcriptional states of an entire ageing brain.
Project description:We have shown previously that older flies are intrinsically more susceptible to Aβ42 toxicity. Building upon these findings, this study aimed to determine the mechanisms by which ageing increases this vulnerability to damage in the brain. A fixed dose of Aβ42 peptide was induced in young (5d) versus older (20d) fly neurons, and then gene and protein expression changes examined in dissected fly brains using microarray analyses. This unbiased approach has revealed genes and pathways that correlate with increased susceptibility of the ageing brain to proteotoxicity.
Project description:With advances in single-cell genomics, molecular signatures of cells comprising the brain vasculature are revealed in unprecedented detail, yet the ageing-associated cell subtype transcriptomic changes which may contribute to neurovascular dysfunction in neurodegenerative diseases remain elusive. Here, we performed single-cell transcriptomic profiling of brain endothelial cells (EC) in young adult and aged mice to characterize their ageing-associated genome-wide expression changes. We identified zonation-dependent transcriptomic changes in aged brain EC subtypes, with capillary ECs exhibiting the most transcriptomic alterations. Pathway enrichment analysis revealed altered immune/cytokine signaling in ECs of all vascular segments, while functional changes impacting the blood-brain barrier (BBB) and glucose/energy metabolism were most prominently implicated in ECs of the capillary bed – the primary site where ECs and other neurovascular unit (NVU) cell types closely interact and coordinate to regulate BBB and cerebral blood flow in health and diseased conditions. Furthermore, an overrepresentation of Alzheimer’s disease (AD)-associated genes identified from GWAS studies was evident among the human orthologs of differentially expressed genes of aged capillary ECs but not other EC subtypes. Importantly, for numerous EC-enriched differentially expressed genes with important functional roles at the BBB and/or association with AD, we found concordant expression changes in human aged or AD brains. Finally, we demonstrated that treatment with exenatide, a glucagon-like peptide-1 receptor (GLP-1R) agonist, strongly reverses transcriptomic changes in ECs and largely reduces BBB leakage in the aged brain. Thus, our study revealed novel vascular ageing-associations of AD in the brain capillary endothelium, and provides insights into detailed transcriptomic alterations underlying brain EC ageing that are complex with subtype specificity yet amenable to pharmacological interventions.