Project description:The pathophysiology of neurodegenerative diseases is poorly understood, and therapeutic options are few. Neurodegenerative diseases are hallmarked by progressive neuronal dysfunction and loss, associated with chronic glial and immune activation1. Microglia are the resident macrophages of the nervous system thought to be important for the clearance of debris after neuronal damage and aid to repair and regeneration. Their activation is viewed in general as a reactive process in neurodegeneration1-3. Whether microglia itself may be causative of neurodegenerative diseases is unclear. Late-onset neurodegenerative disease is frequently observed in patients with histiocytoses4-10, which are clonal myeloid diseases associated with somatic mutations in the RAS/MEK/ERK pathway such as BRAFV600E 5,11,12, suggesting a possible role of somatic mutations in neurodegeneration. Yet, expression of BRAFV600E in the hematopoietic stem cell (HSC) lineage does not cause neurodegeneration13,14. However, recent works from our laboratories and other have revealed that microglia belong to a lineage of adult tissue-resident myeloid cells that develop during organogenesis from yolk sac erythro-myeloid progenitors (EMP) distinct from HSC15-18. We thus hypothesized that somatic BRAFV600E mutations in the resident macrophage lineage may cause neurodegeneration. We found that while BRAFV600E expression in the HSC lineage causes leukemic and tumoral diseases13,14, its expression in the EMP lineage instead results in a severe late-onset neurodegenerative disorder. Neurological symptoms, neuronal death, astrogliosis, immune activation, and amyloid precursor protein deposition were driven by ERK-activated microglia clones and preventable by RAF inhibition. These results identify the fetal precursors of tissue-resident macrophages as a potential cell-of-origin for histiocytoses, and demonstrate that a somatic mutation in the EMP lineage can drive late-onset neurodegeneration. Moreover, these data identify activation of the MAP kinase pathway in microglia as a cause of neurodegenerative disease, and provide opportunities for therapeutic intervention aimed at preventing neuronal death in neurodegenerative diseases
Project description:Microglia play a pivotal role in the maintenance of brain homeostasis, but lose their homeostatic function during the course of neurodegenerative disorders. We identified a specific APOE-dependent molecular signature in microglia isolated from mouse models of amyotrophic lateral sclerosis, multiple sclerosis and Alzheimer’s disease (SOD1, EAE and APP-PS1) and in microglia surrounding neuritic A-plaques in human Alzheimer’s disease brain. This is mediated by a switch from a (M0)-homeostatic to (MGnD)-neurodegenerative phenotype following phagocytosis of apoptotic neurons via the TREM2-APOE pathway. TREM2 induces APOE signaling which is a negative regulator of the transcription program in M0-homeostatic microglia. Targeting the TREM2-APOE pathway restores the M0-homeostatic signature of microglia in APP-PS1 and SOD1 mice and prevents from neuronal loss in an acute model of neurodegeneration. In SOD1 mice, TREM2 regulates MGnD in a gender-dependent manner. APOE-mediated MGnD microglia lose their tolerogenic function. Taken together, our work identifies the TREM2-APOE pathway as a major regulator of microglial functional phenotype in neurodegenerative diseases and serves as a novel target to restore homeostatic microglia.
Project description:Microglia play a pivotal role in the maintenance of brain homeostasis, but lose their homeostatic function during the course of neurodegenerative disorders. We identified a specific APOE-dependent molecular signature in microglia isolated from mouse models of amyotrophic lateral sclerosis, multiple sclerosis and Alzheimer’s disease (SOD1, EAE and APP-PS1) and in microglia surrounding neuritic A-plaques in human Alzheimer’s disease brain. This is mediated by a switch from a (M0)-homeostatic to (MGnD)-neurodegenerative phenotype following phagocytosis of apoptotic neurons via the TREM2-APOE pathway. TREM2 induces APOE signaling which is a negative regulator of the transcription program in M0-homeostatic microglia. Targeting the TREM2-APOE pathway restores the M0-homeostatic signature of microglia in APP-PS1 and SOD1 mice and prevents from neuronal loss in an acute model of neurodegeneration. In SOD1 mice, TREM2 regulates MGnD in a gender-dependent manner. APOE-mediated MGnD microglia lose their tolerogenic function. Taken together, our work identifies the TREM2-APOE pathway as a major regulator of microglial functional phenotype in neurodegenerative diseases and serves as a novel target to restore homeostatic microglia.
Project description:Microglia play a pivotal role in the maintenance of brain homeostasis, but lose their homeostatic function during the course of neurodegenerative disorders. We identified a specific APOE-dependent molecular signature in microglia isolated from mouse models of amyotrophic lateral sclerosis, multiple sclerosis and Alzheimer’s disease (SOD1, EAE and APP-PS1) and in microglia surrounding neuritic A-plaques in human Alzheimer’s disease brain. This is mediated by a switch from a (M0)-homeostatic to (MGnD)-neurodegenerative phenotype following phagocytosis of apoptotic neurons via the TREM2-APOE pathway. TREM2 induces APOE signaling which is a negative regulator of the transcription program in M0-homeostatic microglia. Targeting the TREM2-APOE pathway restores the M0-homeostatic signature of microglia in APP-PS1 and SOD1 mice and prevents from neuronal loss in an acute model of neurodegeneration. In SOD1 mice, TREM2 regulates MGnD in a gender-dependent manner. APOE-mediated MGnD microglia lose their tolerogenic function. Taken together, our work identifies the TREM2-APOE pathway as a major regulator of microglial functional phenotype in neurodegenerative diseases and serves as a novel target to restore homeostatic microglia.
Project description:Microglia play a pivotal role in the maintenance of brain homeostasis, but lose their homeostatic function during the course of neurodegenerative disorders. We identified a specific APOE-dependent molecular signature in microglia isolated from mouse models of amyotrophic lateral sclerosis, multiple sclerosis and Alzheimer’s disease (SOD1, EAE and APP-PS1) and in microglia surrounding neuritic A-plaques in human Alzheimer’s disease brain. This is mediated by a switch from a (M0)-homeostatic to (MGnD)-neurodegenerative phenotype following phagocytosis of apoptotic neurons via the TREM2-APOE pathway. TREM2 induces APOE signaling which is a negative regulator of the transcription program in M0-homeostatic microglia. Targeting the TREM2-APOE pathway restores the M0-homeostatic signature of microglia in APP-PS1 and SOD1 mice and prevents from neuronal loss in an acute model of neurodegeneration. In SOD1 mice, TREM2 regulates MGnD in a gender-dependent manner. APOE-mediated MGnD microglia lose their tolerogenic function. Taken together, our work identifies the TREM2-APOE pathway as a major regulator of microglial functional phenotype in neurodegenerative diseases and serves as a novel target to restore homeostatic microglia. MG550 custom-design Nanosting chips were used to identify disease-associated vs. homeostatic molecular microglia signature in microglia in different disease models and transgenic models.
Project description:Microglia play a pivotal role in the maintenance of brain homeostasis, but lose their homeostatic function during the course of neurodegenerative disorders. We identified a specific APOE-dependent molecular signature in microglia isolated from mouse models of amyotrophic lateral sclerosis, multiple sclerosis and Alzheimer’s disease (SOD1, EAE and APP-PS1) and in microglia surrounding neuritic A-plaques in human Alzheimer’s disease brain. This is mediated by a switch from a (M0)-homeostatic to (MGnD)-neurodegenerative phenotype following phagocytosis of apoptotic neurons via the TREM2-APOE pathway. TREM2 induces APOE signaling which is a negative regulator of the transcription program in M0-homeostatic microglia. Targeting the TREM2-APOE pathway restores the M0-homeostatic signature of microglia in APP-PS1 and SOD1 mice and prevents from neuronal loss in an acute model of neurodegeneration. In SOD1 mice, TREM2 regulates MGnD in a gender-dependent manner. APOE-mediated MGnD microglia lose their tolerogenic function. Taken together, our work identifies the TREM2-APOE pathway as a major regulator of microglial functional phenotype in neurodegenerative diseases and serves as a novel target to restore homeostatic microglia. MG534 custom-design Nanosting chips were used to identify disease-associated vs. homeostatic molecular microglia signature in microglia in different disease models and transgenic models.
Project description:Microglia play a pivotal role in the maintenance of brain homeostasis, but lose their homeostatic function during the course of neurodegenerative disorders. We identified a specific APOE-dependent molecular signature in microglia isolated from mouse models of amyotrophic lateral sclerosis, multiple sclerosis and Alzheimer’s disease (SOD1, EAE and APP-PS1) and in microglia surrounding neuritic A-plaques in human Alzheimer’s disease brain. This is mediated by a switch from a (M0)-homeostatic to (MGnD)-neurodegenerative phenotype following phagocytosis of apoptotic neurons via the TREM2-APOE pathway. TREM2 induces APOE signaling which is a negative regulator of the transcription program in M0-homeostatic microglia. Targeting the TREM2-APOE pathway restores the M0-homeostatic signature of microglia in APP-PS1 and SOD1 mice and prevents from neuronal loss in an acute model of neurodegeneration. In SOD1 mice, TREM2 regulates MGnD in a gender-dependent manner. APOE-mediated MGnD microglia lose their tolerogenic function. Taken together, our work identifies the TREM2-APOE pathway as a major regulator of microglial functional phenotype in neurodegenerative diseases and serves as a novel target to restore homeostatic microglia. MG468 custom-design Nanosting chips were used to identify disease-associated vs. homeostatic molecular microglia signature in microglia in different disease models and transgenic models.