Single-Nucleus Profiling Identifies Accelerated Oligodendrocyte Precursor Cell Senescence in a Mouse Model of Down Syndrome

Abstract

Down Syndrome (DS), the most common genetic cause of intellectual disability, is associated with lifelong cognitive deficits. However, the mechanisms by which triplication of chromosome 21 genes drive neuroinflammation and cognitive dysfunction are poorly understood. Here, using the Ts65Dn mouse model of DS, we performed an integrated single-nucleus ATAC and RNA-sequencing (snATAC-seq and snRNA-seq) analysis of the adult cortex. We identified cell type-specific transcriptional and chromatin-associated changes in the Ts65Dn cortex, including regulators of neuroinflammation, transcription and translation, myelination, and mitochondrial function. We discovered enrichment of a senescence-associated transcriptional signature in Ts65Dn oligodendrocyte precursor cells (OPCs) and epigenetic changes consistent with a loss of heterochromatin. We found that senescence is restricted to a subset of OPCs concentrated in deep cortical layers. Treatment of Ts65Dn mice with a senescence-reducing flavonoid rescued cortical OPC proliferation, restored microglial homeostasis, and improved contextual fear memory. Together, these findings suggest that cortical OPC senescence may be an important driver of neuropathology in DS.SIGNIFICANCE STATEMENTDown Syndrome (DS) is the most common genetic cause of intellectual disability worldwide, is characterized by chronic neuroinflammation, and results in a ubiquitous incidence of early-onset neurodegeneration. Here, we conduct single-nucleus multi-omic profiling of the mature adult cortex of an established mouse model of DS, and systematically identify key perturbations in pathways critical for neurogenesis, myelination, and neuroinflammation. We discover the enrichment of a senescence- associated gene signature in trisomic cortical oligodendrocyte precursor cells (OPCs), validate our computational findings using orthogonal approaches, and show that a senescence-reducing flavonoid significantly improves memory deficits. Our findings suggest that OPC senescence may play a role in the pathogenesis of DS and that senescence-reducing treatment may provide a novel approach for improving cognitive dysfunction in DS.