Giampietro Schiavo | University College London (original) (raw)

Papers by Giampietro Schiavo

SUMMARYAxonal degeneration underlies neuromuscular disorders and neuropathies. Dysregulation of n... more SUMMARYAxonal degeneration underlies neuromuscular disorders and neuropathies. Dysregulation of neurotrophic factors, such as brain-derived neurotrophic factor (BDNF), in the peripheral nervous system has long been established to exacerbate axonopathy. However, the molecular programs controlled by BDNF that facilitate axonal regeneration and transport are not well-understood. Here, we unravel the transcriptomic and phosphorylation landscape shaped by BDNF in human iPSC-derived motor neurons. Using SLAM-Seq, we reveal BDNF stimulation increases global transcription rate in motor neurons and governs gene regulatory networks that converge with those engaged during axonal repair/outgrowth. Phosphoproteomic analyses demonstrate that BDNF remodels the phosphorylation landscape of cytoskeletal-binding proteins, especially of structural microtubule-associated proteins. Importantly, the localized axonal-specific activation of ERK1/2 is necessary for BDNF to enhance axonal transport of neurot...

Molecular Psychiatry, May 17, 2021

Scientific Reports, Jun 10, 2021

Research Square (Research Square), Jun 15, 2020

Biochemical and Biophysical Research Communications

Biology Open

Enterovirus 71 (EV71) is one of the causative agents of hand-foot-and-mouth disease, which in som... more Enterovirus 71 (EV71) is one of the causative agents of hand-foot-and-mouth disease, which in some circumstances could lead to severe neurological diseases. Despite of its importance for human health, little is known about the early stages of EV71 infection. EV71 starts uncoating with its receptor, human scavenger receptor B2 (hSCARB2), at low pH. We show that EV71 was not targeted to lysosomes in human rhabdomyosarcoma cells overexpressing hSCARB2 and that the autophagic pathway is not essential for EV71 productive uncoating. Instead, EV71 was efficiently uncoated 30 min after infection in late endosomes (LEs) containing hSCARB2, mannose-6-phosphate receptor (M6PR), RAB9, bis(monoacylglycero)phosphate and lysosomal associated membrane protein 2 (LAMP2). Furthering the notion that mature LEs are crucial for EV71 uncoating, cation-dependent (CD)-M6PR knockdown impairs EV71 infection. Since hSCARB2 interacts with cation-independent (CI)-M6PR through M6P-binding sites and CD-M6PR also ...

Journal of The Peripheral Nervous System, 2015

Journal of The Peripheral Nervous System, 2016

European Journal of Pain Supplements, 2011

Cell Death and Disease, Aug 4, 2023

In the adult mammalian brain, neural stem cells (NSCs) located in highly restricted niches sustai... more In the adult mammalian brain, neural stem cells (NSCs) located in highly restricted niches sustain the generation of new neurons that integrate into existing circuits. A reduction in adult neurogenesis is linked to ageing and neurodegeneration, whereas dysregulation of proliferation and survival of NSCs have been hypothesized to be at the origin of glioma. Thus, unravelling the molecular underpinnings of the regulated activation that NSCs must undergo to proliferate and generate new progeny is of considerable relevance. Current research has identified cues promoting or restraining NSCs activation. Yet, whether NSCs depend on external signals to survive or if intrinsic factors establish a threshold for sustaining their viability remains elusive, even if this knowledge could involve potential for devising novel therapeutic strategies. Kidins220 (Kinase D-interacting substrate of 220 kDa) is an essential effector of crucial pathways for neuronal survival and differentiation. It is dramatically altered in cancer and in neurological and neurodegenerative disorders, emerging as a regulatory molecule with important functions in human disease. Herein, we discover severe neurogenic deficits and hippocampal-based spatial memory defects accompanied by increased neuroblast death and high loss of newly formed neurons in Kidins220 deficient mice. Mechanistically, we demonstrate that Kidins220-dependent activation of AKT in response to EGF restraints GSK3 activity preventing NSCs apoptosis. We also show that NSCs with Kidins220 can survive with lower concentrations of EGF than the ones lacking this molecule. Hence, Kidins220 levels set a molecular threshold for survival in response to mitogens, allowing adult NSCs growth and expansion. Our study identifies Kidins220 as a key player for sensing the availability of growth factors to sustain adult neurogenesis, uncovering a molecular link that may help paving the way towards neurorepair.

International Journal of Molecular Sciences

Hearing loss and peripheral neuropathy are two clinical entities that are genetically and phenoty... more Hearing loss and peripheral neuropathy are two clinical entities that are genetically and phenotypically heterogeneous and sometimes co-occurring. Using exome sequencing and targeted segregation analysis, we investigated the genetic etiology of peripheral neuropathy and hearing loss in a large Ashkenazi Jewish family. Moreover, we assessed the production of the candidate protein via western blotting of lysates from fibroblasts from an affected individual and an unaffected control. Pathogenic variants in known disease genes associated with hearing loss and peripheral neuropathy were excluded. A homozygous frameshift variant in the BICD1 gene, c.1683dup (p.(Arg562Thrfs*18)), was identified in the proband and segregated with hearing loss and peripheral neuropathy in the family. The BIDC1 RNA analysis from patient fibroblasts showed a modest reduction in gene transcripts compared to the controls. In contrast, protein could not be detected in fibroblasts from a homozygous c.1683dup indiv...

bioRxiv (Cold Spring Harbor Laboratory), Apr 9, 2023

Charcot-Marie-Tooth disease (CMT) is a form of genetic peripheral neuropathy caused by mutations ... more Charcot-Marie-Tooth disease (CMT) is a form of genetic peripheral neuropathy caused by mutations in many functionally diverse genes. The aminoacyl-tRNA synthetase (ARS) enzymes, which charge amino acids to partner tRNAs for protein synthesis, represent the largest protein family linked to CMT aetiology, suggestive of pathomechanistic commonalities. Dominant intermediate CMT type C (DI-CMTC) is caused by YARS1 mutations driving a toxic gain-of-function in the encoded tyrosyl-tRNA synthetase (TyrRS), which is mediated by exposure of consensus neomorphic surfaces through conformational changes of the mutant protein. In this study, we first showed that DI-CMTC-causing TyrRS E196K mis-interacts with the extracellular domain of the BDNF receptor TrkB, an aberrant association we have previously characterised for CMT type 2D (CMT2D)-causing mutant glycyl-tRNA synthetase. We then performed temporal neuromuscular assessments of recently generated Yars E196K mice modelling DI-CMT. Through in vivo imaging of exposed sciatic nerves, we determined that Yars E196K homozygotes display a selective, agedependent impairment in axonal transport of neurotrophin-containing signalling endosomes, phenocopying CMT2D mice. Increasing BDNF in DI-CMTC mouse muscle, through injection of recombinant protein or muscle-specific gene therapy, resulted in complete axonal transport correction. Therefore, this work identifies a pathomechanism common to neuropathies caused by mutations in YARS1 and GARS1, and highlights the potential of boosting BDNF in muscles as a therapeutic strategy to treat ARS-related CMTs.

Pathological tau aggregates propagate across functionally connected neuronal networks in human ne... more Pathological tau aggregates propagate across functionally connected neuronal networks in human neurodegenerative pathologies, such as Alzheimer’s disease. However, the mechanism underlying this process is poorly understood. Several studies have showed that tau release is dependent on neuronal activity and that pathological tau is found in the extracellular space in free form, as well as in the lumen of extracellular vesicles. We recently showed that metabotropic glutamate receptor activity and the SNAP25 integrity modulate the release of pathological tau from human and mouse synaptosomes. Here, we have leveraged botulinum neurotoxins (BoNTs), which impair neurotransmitter release by cleaving specific synaptic SNARE proteins, to dissect molecular mechanisms related to tau release at synapses. In particular, we have tested the effect of botulinum neurotoxin A (BoNT/A) on the synaptic release of tau in primary mouse neurons. Hippocampal neurons were grown in microfluidic chambers and t...

ABSTRACTIn the adult mammalian brain, neural stem cells (NSCs) located in highly restricted niche... more ABSTRACTIn the adult mammalian brain, neural stem cells (NSCs) located in highly restricted niches sustain the generation of new neurons that integrate into existing circuits. A reduction in adult neurogenesis is linked to ageing and neurodegeneration, whereas dysregulation of proliferation and survival of NSCs have been hypothesized to be at the origin of glioma. Thus, unravelling the molecular underpinnings of the regulated activation that NSCs must undergo to proliferate and generate new progeny is of considerable relevance. current research has identified cues promoting or restraining NSCs activation. Yet, whether NSCs depend on external signals to survive or if intrinsic factors establish a threshold for sustaining their viability remains elusive, even if this knowledge could involve potential for devising novel therapeutic strategies. Kidins220 (Kinase D-interacting substrate of 220 kDa) is an essential effector of crucial pathways for neuronal survival and differentiation. It...

Journal of Pharmacology and Experimental Therapeutics

Using synaptosomes purified from the brains of two transgenic mouse models overexpressing mutated... more Using synaptosomes purified from the brains of two transgenic mouse models overexpressing mutated human tau (TgP301S and Tg4510) and brains of patients with sporadic Alzheimer's disease, we showed that aggregated and hyperphosphorylated Tau was both present in purified synaptosomes and released in a calcium-and SNAP25-dependent manner. In all mouse and human synaptosomal preparations, Tau release was prevented by the selective mGlu2/3 receptor agonist LY379268, an effect blocked by the selective mGlu2/3 antagonist LY341495. LY379268 was also able to block pathological tau propagation between primary neurons in an in vitro microfluidic cellular model. These novel results are transformational for our understanding of the molecular mechanisms mediating tau release and propagation at synaptic terminals in Alzheimer's disease and suggest these processes could be inhibited therapeutically by the selective activation of presynaptic G-protein-coupled receptors.

Nature, 2022

Variants of UNC13A, a critical gene for synapse function, increase the risk of amyotrophic latera... more Variants of UNC13A, a critical gene for synapse function, increase the risk of amyotrophic lateral sclerosis and frontotemporal dementia1–3, two related neurodegenerative diseases defined by mislocalization of the RNA-binding protein TDP-434,5. Here we show that TDP-43 depletion induces robust inclusion of a cryptic exon in UNC13A, resulting in nonsense-mediated decay and loss of UNC13A protein. Two common intronic UNC13A polymorphisms strongly associated with amyotrophic lateral sclerosis and frontotemporal dementia risk overlap with TDP-43 binding sites. These polymorphisms potentiate cryptic exon inclusion, both in cultured cells and in brains and spinal cords from patients with these conditions. Our findings, which demonstrate a genetic link between loss of nuclear TDP-43 function and disease, reveal the mechanism by which UNC13A variants exacerbate the effects of decreased TDP-43 function. They further provide a promising therapeutic target for TDP-43 proteinopathies.

Set of primers used to analyze the molecular organization of the GLTx gene. sheet a Primer used t... more Set of primers used to analyze the molecular organization of the GLTx gene. sheet a Primer used to amplify GLTx fragments before cloning into the pGEMŽ -T Vector (pGEMŽ-T Vector System I, Promega Corporation, Madison, WI). sheet b Primer used for primer walking (Cons_clone_5A, 6A, and 7). sheet c Primer used to analyze the intron-exon-structure in genomic DNA of G. tridactyla. GW, Genome walking. (XLSX 14 kb)

The neuromuscular junction (NMJ) is the highly specialised peripheral synapse formed between lowe... more The neuromuscular junction (NMJ) is the highly specialised peripheral synapse formed between lower motor neuron terminals and muscle fibres. Post-synaptic acetylcholine receptors (AChRs), which are found in high density in the muscle membrane, bind to acetylcholine released into the synaptic cleft of the NMJ, ultimately facilitating the conversion of motor action potentials to muscle contractions. NMJs have been studied for many years as a general model for synapse formation, development and function, and are known to be early sites of pathological changes in many neuromuscular diseases. However, information is limited on the diversity of NMJs in different muscles, whether muscle fibre type impacts NMJ morphology and growth, and the relevance of these parameters to neuropathology. Here, this crucial gap was addressed using a robust and standardised semi-automated workflow called NMJ-morph to quantify features of pre- and post-synaptic NMJ architecture in an unbiased manner. Five who...