Project description:Astrocytic morphogenesis and maturation are critical steps in CNS development. The time window of astrocyte morphological development is well defined, but the molecular underpinnings are still unclear. BDNF is a critical growth factor involved in the development of the CNS, including synapse refinement. Here we demonstrate the BDNF receptor at Ntrk2 is enriched in astrocytes relative to all CNS cell populations. RNA sequencing indicates Ntrk2 falls in the top 0.001% of all gene transcripts expressed in juvenile astrocytes, almost exclusively due to truncated TrkB.T1. Astrocyte complexity is increased in the presence of BNDF in vitro, which is dependent upon the presence of TrkB.T1. Furthermore, deletion of TrkB.T1 in vivo revealed astrocytes with significantly reduced volume and branching complexities. Indicating a role for functional astrocyte maturation via BDNF/TrkB.T1 signaling, TrkB.T1 KO astrocytes do not support normal excitatory synaptogenesis. Together, these data suggest a significant role for BDNF/TrkB.T1 signaling in astrocyte morphogenesis and indicate this signaling may contribute to astrocyte regulation of neuronal synapse development.
Project description:Astrocyte activation is a common feature of neurodegenerative diseases. However, the ways in which dying neurons influence the activity of astrocytes is poorly understood. RIPK3 signaling has recently been described as a key regulator of neuroinflammation, but whether this kinase mediates astrocytic responsiveness to neuronal death has not yet been studied. Here, we used the MPTP model of Parkinson’s disease to show that activation of astrocytic RIPK3 drives dopaminergic cell death and axon damage. Transcriptomic profiling revealed that astrocytic RIPK3 promoted gene expression associated with neuroinflammation and movement disorders, and this coincided with significant engagement of DAMP signaling. Using human cell culture systems, we show that factors released from dying neurons signal through RAGE to induce RIPK3-dependent astrocyte activation. These findings highlight a mechanism of neuron-glia crosstalk in which neuronal death perpetuates further neurodegeneration by engaging inflammatory astrocyte activation via RIPK3.
Project description:Astrocyte activation is associated with progressive inflammatory demyelination in multiple sclerosis (MS). The molecular mechanisms underlying astrocyte activation remain incompletely understood. Recent studies have suggested that classical neurotransmitter receptors are implicated in the modulation of brain innate immunity. We investigated the role of dopamine signaling in the process of astrocyte activation. Here, we show the upregulation of dopamine D2 receptor (DRD2) in reactive astrocytes in MS brain and non-canonical role of astrocytic DRD2 in MS pathogenesis. Mice deficient in astrocytic Drd2 exhibit a remarkable suppression of reactive astrocytes and inflammation which are highly correlated with the amelioration of experimental autoimmune encephalomyelitis (EAE). Mechanistically, DRD2 regulates the expression of 6-pyruvoyl-tetrahydropterin synthase which modulates NF-κB activity through protein kinase C-δ. Pharmacological blockade of astrocytic DRD2 with a DRD2 antagonist dehydrocorybulbine remarkably inhibits the inflammatory response in mice lacking Drd2 in neurons. Together, our findings reveal previously uncharted roles for a DRD2 in astrocyte activation during EAE-associated CNS inflammation. Its therapeutic inhibition may provide a potent lever to alleviate autoimmune diseases.
Project description:Pancreatic cancer is characterized by a high frequency of cachexia, pain and neural invasion (N-inv). Neural damage is occurred by N-inv and modulates pain and muscle atrophy via the activation of astrocyte in the connected spine. The activated astrocyte by N-inv, thus, may affect cachexia in pancreatic cancer. Clinical studies in patients and autopsy cases with pancreatic cancer have revealed that N-inv is related to cachexia and astrocytic activation. We established a novel murine model of cancer cachexia using N-inv of human pancreatic cancer cells. Mice with N-inv showed a loss of body weight, skeletal muscle, and fat mass without appetite loss, which are compatible with an animal model of cancer cachexia. Activation of astrocytes in the spinal cord connected with N-inv was observed in our model. Experimental cachexia was suppressed by disrupting neural routes or inhibiting the activation of astrocytes. These data provide the first evidence that N-inv induces cachexia via astrocytic activation of neural route in pancreatic cancer. We produced neural invasion (N-inv) model using intraneural injection of Capan-1 cells to left sciatic nerve of male SCID mouse. For controls, subcutaneous model (SC) and PBS model were produced. Microarray analysis was performed using the first lumbar cord (L1) from PBS, SC, and N-inv mice at 6 w (n = 2 each).
Project description:Extracellular vesicles (EVs) are emerging as novel mediators of cellular communication, in part via the delivery of their contents including microRNAs; small non-coding RNAs that regulate gene expression and are crucial for neuronal circuit formation and function. Whether microRNAs are transferred between differentiated neurons is so far unknown. Moreover, the physiological role of EVs in inter-neuronal signaling is largely elusive. We observed that EVs derived from brain-derived neurotrophic factor (BDNF)-treated neurons induced dendrite complexity, synapse maturation and neuronal firing in recipient hippocampal neurons. This was dependent on the activity of three microRNAs, miR-132-5p, miR-218-5p and miR-690, that were specifically up-regulated in BDNF-induced EVs. Transcriptomic analysis further showed the differential expression of genes related to synaptogenesis in BDNF-EV-treated neurons, many of which are conserved targets of these miRNAs. Overall, this work demonstrates a novel mechanism of inter-neuronal communication, which may be highly relevant in neurological disorders characterized by aberrant BDNF signaling.
Project description:A strocytes are essential for synapse formation, maturation and plasticity, yet their function during developmental neuronal remodeling is largely unknown To identify astrocytic molecules required for axon pruning of mushroom body ( γ neurons in Drosophi la we profile d the expression of astrocytes before ( and after ( remodeling. F ocus ing on genes enriched in larval astrocytes we identified 12 genes that are required in astrocytes, for axon pruning including the F actin regulat ors Arpc1 and form3 Interestingly, perturbing astrocytic actin dynamics did not affect their gross morphology migration or TGF β secretion In contrast, actin dynamics was required for astrocyte infiltration into the axon bundle at the onset of pruning. Remarkably, decreasing axonal adhesion facilitated the infiltration of Arpc1 KD astrocytes, and suppressed the pruning defect driven by the astrocytic perturbation Together, our findings suggest that actin dependent astrocytic infiltration is a key step in axon pruning thus promoting our understanding of neuron glia interactions during remodeling
Project description:Our research showed that astrocytic OGT could influence the expression of proteins in the mPFC. Most of these altered proteins participate in metabolic process, transferase activity, and biosynthetic process. GFAP, an astrocyte maker, was increased after OGT deletion. These results provide a framework for further study on the role of astrocytic OGT/O-GlcNAcylation in the mPFC.