Papers by Francesco De Virgiliis
Following spinal cord injury, central nervous system neurons show extremely limited regenerative ... more Following spinal cord injury, central nervous system neurons show extremely limited regenerative response and fail to reconnect with their targets resulting in permanent disabilities. However, a conditioning lesion, which triggers a regenerative response, shows that the ability of adult neurons to regenerate could be reactivated. The conditioning lesion is displayed by dorsal root ganglia (DRG) neurons, where an injury to their peripheral branches induces regeneration of their central branches, which would otherwise fail to occur. The first part of the thesis investigated novel signalling mechanisms required for the conditioning lesion paradigm. After a peripheral injury, an inflammatory response occurs with the rapid recruitment of macrophages at the lesion site, which have been shown to be required for the conditioning lesion effect. These cells produce high levels of reactive oxygen species (ROS) and create an oxidative environment around the axons, which led us to hypothesize th...
NOX-dependent reactive oxygen species are essential regulators of axonal regeneration
Free Radical Biology and Medicine, 2021
Following spinal cord injury, central nervous system neurons show extremely limited regenerative ... more Following spinal cord injury, central nervous system neurons show extremely limited regenerative response and fail to reconnect with their targets resulting in permanent disabilities. However, a conditioning lesion, which triggers a regenerative response, shows that the ability of adult neurons to regenerate could be reactivated. The conditioning lesion is displayed by dorsal root ganglia (DRG) neurons, where an injury to their peripheral branches induces regeneration of their central branches, which would otherwise fail to occur. The first part of the thesis investigated novel signalling mechanisms required for the conditioning lesion paradigm. After a peripheral injury, an inflammatory response occurs with the rapid recruitment of macrophages at the lesion site, which have been shown to be required for the conditioning lesion effect. These cells produce high levels of reactive oxygen species (ROS) and create an oxidative environment around the axons, which led us to hypothesize th...
NOX-dependent reactive oxygen species are essential regulators of axonal regeneration
Free Radical Biology and Medicine, 2021
The interruption of spinal circuitry following spinal cord injury disrupts neural activity and is... more The interruption of spinal circuitry following spinal cord injury disrupts neural activity and is followed by a failure to mount an effective regenerative gene expression response resulting in permanent neurological disability. Functional recovery requires the enhancement of axonal and synaptic plasticity of spared as well as injured fibres, which need to sprout and/or regenerate to form new connections. Here we will investigate whether the combined epigenetic stimulation of the regenerative gene expression program with neuronal activity-dependent enhancement of neuroplasticity and guidance can overcome the current inability to promote neurological recovery in severe and chronic spinal cord injury. This will be carried out by delivering the small molecule CBP/p300 activator CSP-TTK21 in combination with environmental enrichment. We will deliver the CBP/p300 activator CSP-TTK21 weekly between week twelve and twenty following a severe transection model of spinal cord injury in the mou...
The regenerative potential of mammalian peripheral nervous system (PNS) neurons after injury is c... more The regenerative potential of mammalian peripheral nervous system (PNS) neurons after injury is critically limited by their slow axonal regenerative rate1. Since a delayed target re-innervation leads to irreversible loss of function of target organs2, accelerated axonal regeneration is required to enhance functional outcomes following injury. Regenerative ability is influenced by both injury-dependent and injury-independent mechanisms3. Among the latter, environmental factors such as exercise and environmental enrichment have been shown to affect signalling pathways that promote axonal regeneration4. Several of these pathways, including modifications in gene transcription and protein synthesis, mitochondrial metabolism and release of neurotrophins, can be activated by intermittent fasting (IF)5,6. IF has in turn been shown to increase synaptic plasticity7,8 and neurogenesis9, partially sharing molecular mechanisms with axonal regeneration. However, whether IF influences the axonal r...
Nature Reviews Neurology, 2021
Reversible CD8 T cell–neuron cross-talk causes aging-dependent neuronal regenerative decline
Science
Aging is associated with increased prevalence of axonal injuries characterized by poor regenerati... more Aging is associated with increased prevalence of axonal injuries characterized by poor regeneration and disability. However, the underlying mechanisms remain unclear. In our experiments, RNA sequencing of sciatic dorsal root ganglia (DRG) revealed significant aging-dependent enrichment in T cell signaling both before and after sciatic nerve injury (SNI) in mice. Lymphotoxin activated the transcription factor NF-κB, which induced expression of the chemokine CXCL13 by neurons. This in turn recruited CXCR5 + CD8 + T cells to injured DRG neurons overexpressing major histocompatibility complex class I. CD8 + T cells repressed the axonal regeneration of DRG neurons via caspase 3 activation. CXCL13 neutralization prevented CXCR5 + CD8 + T cell recruitment to the DRG and reversed aging-dependent regenerative decline, thereby promoting neurological recovery after SNI. Thus, axonal regeneration can be facilitated by antagonizing cross-talk between immune cells and neurons.
Nature Communications
Overcoming the restricted axonal regenerative ability that limits functional repair following a c... more Overcoming the restricted axonal regenerative ability that limits functional repair following a central nervous system injury remains a challenge. Here we report a regenerative paradigm that we call enriched conditioning, which combines environmental enrichment (EE) followed by a conditioning sciatic nerve axotomy that precedes a spinal cord injury (SCI). Enriched conditioning significantly increases the regenerative ability of dorsal root ganglia (DRG) sensory neurons compared to EE or a conditioning injury alone, propelling axon growth well beyond the spinal injury site. Mechanistically, we established that enriched conditioning relies on the unique neuronal intrinsic signaling axis PKC-STAT3-NADPH oxidase 2 (NOX2), enhancing redox signaling as shown by redox proteomics in DRG. Finally, NOX2 conditional deletion or overexpression respectively blocked or phenocopied enriched conditioning-dependent axon regeneration after SCI leading to improved functional recovery. These studies pr...
AMPK controls the axonal regenerative ability of dorsal root ganglia sensory neurons after spinal cord injury
Nature Metabolism
Cyclin-dependent–like kinase 5 is required for pain signaling in human sensory neurons and mouse models
Science Translational Medicine
Cyclin-dependent–like kinase 5 (CDKL5) gene mutations lead to an X-linked disorder that is charac... more Cyclin-dependent–like kinase 5 (CDKL5) gene mutations lead to an X-linked disorder that is characterized by infantile epileptic encephalopathy, developmental delay, and hypotonia. However, we found that a substantial percentage of these patients also report a previously unrecognized anamnestic deficiency in pain perception. Consistent with a role in nociception, we found that CDKL5 is expressed selectively in nociceptive dorsal root ganglia (DRG) neurons in mice and in induced pluripotent stem cell (iPS)–derived human nociceptors. CDKL5-deficient mice display defective epidermal innervation, and conditional deletion of CDKL5 in DRG sensory neurons impairs nociception, phenocopying CDKL5 deficiency disorder in patients. Mechanistically, CDKL5 interacts with calcium/calmodulin-dependent protein kinase II α (CaMKIIα) to control outgrowth and transient receptor potential cation channel subfamily V member 1 (TRPV1)–dependent signaling, which are disrupted in both CDKL5 mutant murine DRG ...
Cyclin-dependent–like kinase 5 is required for pain signaling in human sensory neurons and mouse models
Science Translational Medicine
Cyclin-dependent–like kinase 5 (CDKL5) gene mutations lead to an X-linked disorder that is charac... more Cyclin-dependent–like kinase 5 (CDKL5) gene mutations lead to an X-linked disorder that is characterized by infantile epileptic encephalopathy, developmental delay, and hypotonia. However, we found that a substantial percentage of these patients also report a previously unrecognized anamnestic deficiency in pain perception. Consistent with a role in nociception, we found that CDKL5 is expressed selectively in nociceptive dorsal root ganglia (DRG) neurons in mice and in induced pluripotent stem cell (iPS)–derived human nociceptors. CDKL5-deficient mice display defective epidermal innervation, and conditional deletion of CDKL5 in DRG sensory neurons impairs nociception, phenocopying CDKL5 deficiency disorder in patients. Mechanistically, CDKL5 interacts with calcium/calmodulin-dependent protein kinase II α (CaMKIIα) to control outgrowth and transient receptor potential cation channel subfamily V member 1 (TRPV1)–dependent signaling, which are disrupted in both CDKL5 mutant murine DRG ...
Cyclin-dependent-like kinase 5 (Cdkl5) controls nociception in patients and murine models of Cdkl... more Cyclin-dependent-like kinase 5 (Cdkl5) controls nociception in patients and murine models of Cdkl5 deficiency disorder via CaMKII-dependent mechanisms
Science Translational Medicine, Apr 10, 2019
Environmental enrichment or pharmacological mediated CBPdependent histone acetylation increases r... more Environmental enrichment or pharmacological mediated CBPdependent histone acetylation increases regeneration potential of specific classes of neurons.
The molecular mechanisms discriminating between regenerative failure and success remain elusive. ... more The molecular mechanisms discriminating between regenerative failure and success remain elusive. While a regeneration-competent peripheral nerve injury mounts a regenerative gene expression response in bipolar dorsal root ganglia (DRG) sensory neurons, a regeneration-incompetent central spinal cord injury does not. This dichotomic response offers a unique opportunity to investigate the fundamental biological mechanisms underpinning regenerative ability. Following a pharmacological screen with small molecule inhibitors targeting key epigenetic enzymes in DRG neurons we identified HDAC3 signalling as a novel candidate brake to axonal regenerative growth. In vivo, we determined that only a regenerative peripheral but not a central spinal injury induces an increase in calcium, which activates protein phosphatase 4 that in turn dephosphorylates HDAC3 thus impairing its activity and enhancing histone acetylation. Bioinformatics analysis of ex vivo H3K9ac ChIPseq and RNAseq from DRG follow...
Cyclin-dependent-like kinase 5 (Cdkl5) gene mutations lead to an X-linked disorder that is charac... more Cyclin-dependent-like kinase 5 (Cdkl5) gene mutations lead to an X-linked disorder that is characterized by infantile epileptic encephalopathy, developmental delay and hypotonia. However, we found that a substantial percentage of these patients also report a previously unrecognised anamnestic deficiency in pain perception. Consistent with a role in nociception, we discovered that Cdkl5 is expressed selectively in nociceptive dorsal root ganglia (DRG) neurons in mice and in iPS-derived human nociceptors. CDKL5 deficient mice display defective epidermal innervation and conditional deletion of Cdkl5 in DRG sensory neurons significantly impairs nociception, phenocopying CDKL5 deficiency disorder in patients. Mechanistically, Cdkl5 interacts with CaMKIIα to control outgrowth as well as TRPV1-dependent signalling, which are disrupted in both Cdkl5 mutant murine DRG and human iPS-derived nociceptors. Together, these findings unveil a previously unrecognized role for Cdkl5 in nociception, p...
SUMMARYRegeneration after injury occurs in axons that lie in the peripheral nervous system but it... more SUMMARYRegeneration after injury occurs in axons that lie in the peripheral nervous system but it fails in the central nervous system limiting functional recovery. Despite recent progress, the signalling response to injury of peripheral versus central projecting axons that might underpin this differential regenerative ability is currently largely uncharacterized. To fill this knowledge gap, here we combined axoplasmic proteomics from peripheral sciatic or central projecting dorsal root axons from sciatic DRG neurons. Proteomics was combined with cell body RNAseq to compare axonal and soma responses between a spinal regeneration-incompetent versus sciatic regeneration-competent nerve injury. This allowed the identification of injury-dependent signalling pathways uniquely represented in peripheral versus central projecting sciatic DRG axons. RNAseq and proteomics analysis suggested AMPK as a putative regulator of axonal regenerative signalling pathways. AMPK immunoprecipitation follow...
PP4‐dependent HDAC3 dephosphorylation discriminates between axonal regeneration and regenerative failure
The EMBO Journal
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Papers by Francesco De Virgiliis