Project description:Recently we demonstrated that amoeboid microglia in white matter regions are essential for proper oligodendrocyte homeostasis and myelinogenesis in the first postnatal week of mice. Amoeboid microglia in the corpus callosum change their activation profile already within few days after postnatal day (P)7 and microglia of the cerebellum show similar features to callosal microglia. Here we expanded our previous transcriptional analysis and performed bulk RNA sequencing of microglia during development in a detailed way in P7, P10 and P42 microglia from corpus callosum, cortex and cerebellum. The goal of this study was to identify a specific gene profile for both, white matter and grey matter microglia during development.
Project description:Microglia were FACS-isolated from developing mouse corpus callosum at postnatal days 0, 7, and 21, then sequenced by 10X Genomics single-cell sequencing.
Project description:Aging results in both grey and white matter degeneration, but the specific microglial responses are unknown. Using single-cell RNA sequencing from white and grey matter separately, we identified white matter associated microglia (WAM), which share parts of the disease-associated microglia (DAM) gene signature and are characterized by the activation of genes implicated in phagocytic activity and lipid metabolism. WAM depend on triggering receptor expressed on myeloid cells 2 (TREM2) signaling and are aging dependent. In the aged brain, WAM form independently of apolipoprotein E (APOE), which is in contrast to mouse models of Alzheimer’s disease, in which microglia with WAM gene signature are generated prematurely and in an APOE-dependent pathway similar to DAM. Within the white matter, microglia frequently cluster in nodules, where they are engaged in clearing degenerated myelin. Thus, WAM may represent a potentially protective response required to clear degenerated myelin accumulating during white matter aging and disease.
Project description:Microglia are brain-resident, myelin-phagocytosing cells, yet their role in lesion initiation in grey and white matter regions in multiple sclerosis (MS) is unclear. We isolated primary microglia from both, occipital cortex and corpus callosum, of 10 MS and 11 control donors and studied their transcriptional profile by RNA sequencing, thereby identifying regional and MS-associated changes. Identification of pathways underlying regional differences showed a relatively increased type I interferon response in cortical grey matter microglia, while white matter microglia more highly expressed NF-κB pathway genes. In normal-appearing white matter MS tissue, lipid metabolism genes were increased, suggesting processing of myelin by microglia already in areas seemingly devoid of MS pathology. Normal-appearing grey matter MS microglia showed increased activation of glycolysis and metal ion homeostasis, possibly reflecting microglia reacting to iron depositions. Notably, expression of genes associated with microglia homeostasis were hardly changed, suggesting that subtle regional changes in MS-associated microglia do not yet affect their resting state.
Project description:A hallmark of nervous system aging is a decline of white matter volume and function, but the underlying mechanisms leading to white matter pathology are unknown. Here, we found age-related alterations of oligodendrocytes with a reduction of total oligodendrocyte density in the aging murine white matter. Using single-cell RNA sequencing, we identify interferon-responsive oligodendrocytes, which localize in proximity of CD8+ T cells in the aging white matter. Absence of functional lymphocytes decreased oligodendrocyte reactivity and rescued oligodendrocyte loss, while T-cell checkpoint inhibition worsened the aging effect. In addition, we identified a subpopulation of immune cell dependent interferon-responsive microglia in the aging white matter, and co-culture experiments revealed that interferon- activated microglia triggered oligodendrocytes cell death. In summary, we provide evidence that T cells induced interferon-responsive oligodendrocytes and microglia are important modifiers of white matter aging.
Project description:The repair of white matter damage is of paramount importance for functional recovery after brain injuries.We report that interleukin-4 (IL-4) promotes oligodendrocyte regeneration and remyelination. IL-4 receptor expression was detected in a variety of glial cells after ischemic brain injury, including oligodendrocyte lineage cells. IL-4 deficiency in knockout mice resulted in greater deterioration of white matter over 14 days after stroke. Consistent with these findings, intranasal delivery of IL-4 nanoparticles after stroke improved white matter integrity and attenuated long-term sensorimotor and cognitive deficits in wild-type mice, as revealed by histological immunostaining, electron microscopy, diffusion tensor imaging, and electrophysiology. The selective effect of IL-4 on remyelination was verified in an ex vivo organotypic model of demyelination. By leveraging primary oligodendrocyte progenitor cells (OPCs), microglia-depleted mice, and conditional OPC-specific PPARγ knockout mice, we discovered a direct salutary effect of IL-4 on oligodendrocyte differentiation that was mediated by the PPARγ axis. Our findings reveal a new regenerative role of IL-4 in the CNS, which lies beyond its known immunoregulatory functions on microglia/macrophages or peripheral lymphocytes. Therefore, intranasal IL-4 delivery may represent a novel therapeutic strategy to improve white matter integrity in stroke and other brain injuries.
Project description:Age-associated deep-subcortical white matter lesions (DSCL) are an independent risk factor for dementia, displaying high levels of CD68+ microglia. This study aimed to characterise the transcriptomic profile of microglia in DSCL and surrounding radiologically normal-appearing white matter (NAWM) compared to non-lesional control white matter. CD68+ microglia were isolated from white matter groups (n=4 cases per group) from the Cognitive Function and Ageing Study neuropathology cohort by immuno-laser capture microdissection. Microarray gene expression profiling, but not RNA-sequencing, was found to be compatible with immuno-LCM-ed post-mortem material and identified significantly differentially expressed genes (DEG). Functional grouping and pathway analysis was assessed using DAVID, and immunohistochemistry was performed to validate gene expression changes at the protein level. Transcriptomic profiling of microglia in DSCL compared to non-lesional control white matter identified 181 significant DEG (93 upregulated and 88 downregulated). Functional clustering analysis revealed dysregulation of haptoglobin-hemoglobin binding (Enrichment score 2.15, p=0.017), confirmed by CD163 immunostaining, suggesting a neuroprotective microglial response to blood-brain barrier dysfunction in DSCL. In NAWM versus control white matter, microglia exhibited 347 DEGs (209 upregulated, 138 downregulated), with significant dysregulation of protein de-ubiquitination (Enrichment score 5.14, p<0.0001), implying an inability to maintain protein homeostasis in NAWM that may contribute to lesion spread. These findings enhance understanding of microglial transcriptomic changes in aging white matter pathology, highlighting a neuroprotective adaptation in DSCL microglia and a potentially lesion-promoting phenotype in NAWM microglia.
Project description:Age-associated deep-subcortical white matter lesions (DSCL) are an independent risk factor for dementia, displaying high levels of CD68+ microglia. This study aimed to characterise the transcriptomic profile of microglia in DSCL and surrounding radiologically normal-appearing white matter (NAWM) compared to non-lesional control white matter. CD68+ microglia were isolated from white matter groups (n=4 cases per group) from the Cognitive Function and Ageing Study neuropathology cohort by immuno-laser capture microdissection. Microarray gene expression profiling, but not RNA-sequencing, was found to be compatible with immuno-LCM-ed post-mortem material and identified significantly differentially expressed genes (DEG). Functional grouping and pathway analysis was assessed using DAVID, and immunohistochemistry was performed to validate gene expression changes at the protein level. Transcriptomic profiling of microglia in DSCL compared to non-lesional control white matter identified 181 significant DEG (93 upregulated and 88 downregulated). Functional clustering analysis revealed dysregulation of haptoglobin-hemoglobin binding (Enrichment score 2.15, p=0.017), confirmed by CD163 immunostaining, suggesting a neuroprotective microglial response to blood-brain barrier dysfunction in DSCL. In NAWM versus control white matter, microglia exhibited 347 DEGs (209 upregulated, 138 downregulated), with significant dysregulation of protein de-ubiquitination (Enrichment score 5.14, p<0.0001), implying an inability to maintain protein homeostasis in NAWM that may contribute to lesion spread. These findings enhance understanding of microglial transcriptomic changes in aging white matter pathology, highlighting a neuroprotective adaptation in DSCL microglia and a potentially lesion-promoting phenotype in NAWM microglia.
Project description:Vanishing white matter (VWM) is a leukodystrophy that primarily manifests in young children. In this disease, the brain white matter is differentially affected in a predictable pattern with telencephalic brain areas being more severely affected, while others remain allegedly completely spared. Using high-resolution mass spectrometry-based proteomics, we investigated the proteome patterns of the severely affected white matter in the frontal lobe and normal appearing pons in VWM and control cases to identify molecular bases underlying regional vulnerability. By comparing VWM patients to controls, we identified disease-specific proteome patterns. We showed substantial pathogenic changes in both the frontal white matter and pons at the protein level. Side-by-side comparison of brain region-specific proteome patterns further revealed regional differences. We found that different cell types are affected in the VWM frontal white matter than in the pons. Gene ontology and pathway analyses identified involvement of region distinct biological processes, of which pathways implicated in cellular respiratory metabolism were overarching features. In the VWM frontal white matter, proteome changes were associated with decrease in glycolysis/gluconeogenesis and metabolism of various amino acids. By contrast, in the VWM pons white matter, we found a decrease in oxidative phosphorylation. Taken together, our data show that brain regions are affected in parallel in VWM, but to different degrees. We found region-specific involvement of different cell types and discovered that cellular respiratory metabolism is differently affected across white matter regions in VWM. These region-specific changes help explain regional vulnerability to pathology in VWM.