Biology subjects

Gunner, G.

Publications and source records attributed to Gunner, G..

4 recordsLinked to original sources

bioRxiv2024

Gasdermin D is activated but does not drive neurodegeneration in SOD1G93A model of ALS: Implications for targeting pyroptosis

Amyotrophic Lateral Sclerosis (ALS) is a fatal neurodegenerative disease characterized by progressive motor neuron loss, microgliosis, and neuroinflammation. While pyroptosis, an inflammatory form of programmed cell death, has been implicated in ALS, the specific role of Gasdermin D (GSDMD) - the primary executioner of pyroptosis - remains unexplored. In this study, we examined the function of GSDMD in the well-established SOD1G93A mouse model of ALS. Our results showed robust GSDMD activation in the spinal cords of SOD1G93A animals across two strain backgrounds, with elevated expression in Iba1+ microglia. To explore its role in disease progression, we bred B6.SOD1G93A mice onto a GSDMD-deficient background. In comparing SOD1G93A; Gsdmd+/+ and SOD1G93A; Gsdmd-/- mice, we found that Gsdmd loss did not affect disease onset, weight loss, or grip strength decline in either male or female animals. Notably, GSDMD deficiency resulted in a modest but statistically significant increase in mortality in SOD1G93A mice. Moreover, GSDMD absence had minimal impact on astrogliosis, microgliosis and motor neuron loss. These findings show that while GSDMD is activated in the ALS mouse model, its loss does not mitigate key ALS behavioral phenotypes, gliosis or motor neuron loss. This study provides insights into the potential therapeutic relevance of targeting pyroptosis and inflammatory pathways in ALS.

neuroscience↗

bioRxiv2024

Microglia-astrocyte crosstalk regulates synapse remodeling via Wnt signaling

Astrocytes and microglia are emerging key regulators of activity-dependent synapse remodeling that engulf and remove synapses in response to changes in neural activity. Yet, the degree to which these cells communicate to coordinate this process remains an open question. Here, we use whisker removal in postnatal mice to induce activity-dependent synapse removal in the barrel cortex. We show that astrocytes do not engulf synapses in this paradigm. Instead, astrocytes reduce their contact with synapses prior to microglia-mediated synapse engulfment. We further show that reduced astrocyte-contact with synapses is dependent on microglial CX3CL1-CX3CR1 signaling and release of Wnts from microglia following whisker removal. These results demonstrate an activity-dependent mechanism by which microglia instruct astrocyte-synapse interactions, which then provides a permissive environment for microglia to remove synapses. We further show that this mechanism is critical to remodel synapses in a changing sensory environment and this signaling is upregulated in several disease contexts.

neuroscience↗

bioRxiv2022

Gasdermin-E mediates mitochondrial damage in axons and neurodegeneration

Mitochondrial dysfunction and axon loss are hallmarks of neurologic diseases. Gasdermin (GSDM) proteins are executioner pore-forming molecules that mediate cell death, yet their roles in the central nervous system (CNS) are not well understood. Here, we find that one GSDM family member, GSDME is expressed by both mouse and human neurons. GSDME plays a role in mitochondrial damage and axon loss. Mitochondrial neurotoxins induced caspase-dependent GSDME cleavage and rapid localization to mitochondria in axons, where GSDME promoted mitochondrial depolarization, trafficking defects, and neurite retraction. The frontotemporal dementia (FTD)/amyotrophic lateral sclerosis (ALS)-associated proteins TDP-43 and PR-50 induced GSDME-mediated damage to mitochondria and neurite loss. GSDME deficiency prolonged survival, ameliorated motor dysfunction, and rescued motor neuron loss in the SOD1G93A mouse model of ALS. GSDME knockdown also protected against neurite loss in ALS patient iPSC-derived motor neurons. Thus, we identify GSDME as an executioner of neuronal mitochondrial dysfunction that contributes to neurodegeneration. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=178 SRC="FIGDIR/small/513927v1_ufig1.gif" ALT="Figure 1"> View larger version (25K): org.highwire.dtl.DTLVardef@113c13dorg.highwire.dtl.DTLVardef@1f3c5caorg.highwire.dtl.DTLVardef@13e75adorg.highwire.dtl.DTLVardef@19fdc93_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LIGSDME is expressed by neurons and activated by mitochondrial neurotoxins C_LIO_LIActivated GSDME drives axonal mitochondrial damage and neurite loss prior to cell death C_LIO_LIALS/FTD associated TDP-43 and PR-50 induces GSDME-driven neurite loss in mouse and human iPSC-derived neurons. C_LIO_LISOD1G93A mice show ameliorated disease progression and motor neuron loss in absence of GSDME C_LI

neuroscience↗

bioRxiv2019

Sensory lesioning induces microglial synapse elimination via ADAM10 and fractalkine signaling

Microglia rapidly respond to changes in neural activity and inflammation to regulate synaptic connectivity. The extracellular signals, particularly neuron-derived molecules, that drive these microglial functions at synapses remains a key open question. Here, whisker lesioning, known to dampen cortical activity, induces microglia-mediated synapse elimination. We show that this synapse elimination is dependent on the microglial fractalkine receptor, CX3CR1, but not complement receptor 3, signaling. Further, mice deficient in the CX3CR1 ligand (CX3CL1) also have profound defects in synapse elimination. Single-cell RNAseq then revealed that Cx3cl1 is cortical neuron-derived and ADAM10, a metalloprotease that cleaves CX3CL1 into a secreted form, is upregulated specifically in layer IV neurons and microglia following whisker lesioning. Finally, inhibition of ADAM10 phenocopies Cx3cr1-/- and Cx3cl1-/- synapse elimination defects. Together, these results identify novel neuron-to-microglia signaling necessary for cortical synaptic remodeling and reveal context-dependent immune mechanisms are utilized to remodel synapses in the mammalian brain.

neuroscience↗