Project description:Complement component C3 mediates pathology in several CNS neurodegenerative diseases, but the cellular and molecular mechanisms leading to neuronal injury remain unclear. Herein, we examined how C3 deletion affects glial profiles and anterior visual pathway pathology in an animal model of neuroinflammation. scRNA-seq from mouse brain and optic nerve revealed that C3 expression defined disease-associated glial subtypes which were characterized by increased mTOR activation, cell metabolism, and translation. Deletion of C3 restored these glia towards homeostatic profiles. Myeloid-derived C3 mediated injury in optic nerve axons and retinal ganglion cells (RGCs) at the peak of EAE. To elucidate the timing of pathology we examined retinas prior to symptom onset and found reductions in Brn3a, an RGC transcription factor involved in dendritic arborization and protection from apoptosis. Our study supports a direct role for C3 in activating the mTOR-ribosomal biogenesis axis in glia which subsequently mediate early neuro-axonal stress and later synapse loss.
Project description:Complement component C3 mediates pathology in several CNS neurodegenerative diseases, but the cellular and molecular mechanisms leading to neuronal injury remain unclear. Herein, we examined how C3 deletion affects glial profiles and anterior visual pathway pathology in an animal model of neuroinflammation. scRNA-seq from mouse brain and optic nerve revealed that C3 expression defined disease-associated glial subtypes which were characterized by increased mTOR activation, cell metabolism, and translation. Deletion of C3 restored these glia towards homeostatic profiles. Myeloid-derived C3 mediated injury in optic nerve axons and retinal ganglion cells (RGCs) at the peak of EAE. To elucidate the timing of pathology we examined retinas prior to symptom onset and found reductions in Brn3a, an RGC transcription factor involved in dendritic arborization and protection from apoptosis. Our study supports a direct role for C3 in activating the mTOR-ribosomal biogenesis axis in glia which subsequently mediate early neuro-axonal stress and later synapse loss.
Project description:Excess noise damages sensory hair cells, resulting in loss of synaptic connections with auditory nerves and, in some cases, hair-cell death. The cellular mechanisms underlying mechanically induced hair-cell damage and subsequent repair are not completely understood. Hair cells in neuromasts of larval zebrafish are structurally and functionally comparable to mammalian hair cells but undergo robust regeneration following ototoxic damage. We therefore developed a model for mechanically induced hair-cell damage in this highly tractable system. Free swimming larvae exposed to strong water wave stimulus for 2 hr displayed mechanical injury to neuromasts, including afferent neurite retraction, damaged hair bundles, and reduced mechanotransduction. Synapse loss was observed in apparently intact exposed neuromasts, and this loss was exacerbated by inhibiting glutamate uptake. Mechanical damage also elicited an inflammatory response and macrophage recruitment. Remarkably, neuromast hair-cell morphology and mechanotransduction recovered within hours following exposure, suggesting severely damaged neuromasts undergo repair. Our results indicate functional changes and synapse loss in mechanically damaged lateral-line neuromasts that share key features of damage observed in noise-exposed mammalian ear. Yet, unlike the mammalian ear, mechanical damage to neuromasts is rapidly reversible.
Project description:Mice heterozygous for the bifunctional enzyme glucosamine-2-epimerase/N-acetylmannosamine kinase (GNE+/-), which is essential for sialic acid biosynthesis, showed reduced gne transcription and sialylation in different brain regions. We found synapse loss in the hippocampus of GNE+/- mice at 6 months followed by a gradual loss of neurons in the hippocampus and substantia nigra at 12 months. Moreover, GNE+/- mice showed reduced arborization of microglia already at 6 months. A transcriptomic analysis revealed only minor inflammatory changes with slightly increased Interleukin 1β levels, indicating a homeostatic removal of synapses and neurons. Crossbreeding with complement component 3-deficient mice rescued the early onset loss of neurons and synapses in the GNE+/- mice. Thus, an intact sialic acid covered glycocalyx plays an essential role in maintaining brain homeostasis. Even a minor reduction in the sialic acid level leads to reduced microglial arborization and complement-mediated loss of neurons and synapses.
Project description:De-ubiquitinating enzyme BAP1 is mutated in a hereditary cancer syndrome with increased risk of mesothelioma and uveal melanoma. Somatic BAP1 mutations occur in various malignancies. We show that mouse Bap1 gene deletion is lethal during embryogenesis, but systemic or hematopoietic-restricted deletion in adults recapitulates features of human myelodysplastic syndrome (MDS). Knockin mice expressing BAP1 with a 3xFlag tag revealed that BAP1 interacts with host cell factor-1 (HCF-1), O-linked N-acetylglucosamine transferase (OGT), and the polycomb group proteins ASXL1 and ASXL2 in vivo. OGT and HCF-1 levels were decreased by Bap1 deletion, indicating a critical role for BAP1 in stabilizing these epigenetic regulators. Human ASXL1 is mutated frequently in chronic myelomonocytic leukemia (CMML) so an ASXL/BAP1 complex may suppress CMML. A BAP1 catalytic mutation found in a MDS patient implies that BAP1 loss of function has similar consequences in mice and humans.