Biology subjects

Fawcett, J.

Publications and source records attributed to Fawcett, J..

9 recordsLinked to original sources

bioRxiv2026

Intertwined Autophagy and Integrin Dynamics Shape Axon Growth and Regeneration

Autophagy is a central pathway for cellular homeostasis, mediating degradation and recycling of cytoplasmic components through lysosomal processing. Although autophagy has been implicated in axon growth and neuronal injury responses, its role in axon regeneration remains incompletely understood. In parallel, integrin trafficking and focal adhesion dynamics are critical determinants of axonal growth, and increasing evidence indicates that autophagy regulates focal adhesion turnover in non-neuronal cells; however, whether this mechanism operates in neurons remains unknown. Here, we investigated the dynamics of autophagy during axon growth and regeneration in adult sensory neurons and examined its relationship with integrin trafficking. Using live imaging, we analyzed autophagic vesicles and integrin-containing compartments in axons under basal conditions and following axotomy. We find that axonal injury induces marked short- and long-term alterations in distal axon and growth cone autophagic vesicle dynamics, integrin trafficking, and autophagy-associated integrin turnover. Importantly, these changes correlate with axonal growth and regenerative capacity. Furthermore, we identify a functional interplay between autophagy and integrins, suggesting bidirectional regulation in which autophagy contributes to adhesion receptor recycling, while integrins feedback to modulate autophagy. Finally, pharmacological modulation indicates that autophagy plays a critical role in both axonal growth and regeneration, and that rapamycin enhances regenerative responses, likely through modulation of autophagy-dependent integrin recycling rather than a general increase in autophagic activity. Together, these findings reveal a bidirectional feedback system between integrin-mediated extracellular cues and autophagy-dependent intracellular trafficking that jointly orchestrates axon growth and regeneration.

neuroscience↗

bioRxiv2026

Schwann cell dysfunction contributes to diabetic wound pathology which is partially ameliorated by oncostatin M treatment

Chronic diabetic wounds represent a major clinical burden and are strongly associated with peripheral neuropathy, yet the contribution of nerve-associated Schwann cells to impaired healing remains poorly defined. Here, we investigated Schwann cell dynamics in cutaneous wound repair using the db/db model of type 2 diabetes. Full-thickness excisional wounds in db/db mice exhibited delayed closure, reduced dermal and epidermal thickness, and diminished cellular proliferation compared to non-diabetic controls. Diabetic wounds also demonstrated impaired re-innervation and a marked reduction in both total (S100{beta}+) and dedifferentiated (p75NTR+) Schwann cells, including decreased Schwann cell proliferation. These findings indicate that diabetes disrupts the injury-induced Schwann cell response that is essential for normal repair. Transcriptomic analyses revealed that injury-activated Schwann cells upregulate multiple trophic factors, including oncostatin M (OSM), while single-cell RNA sequencing demonstrated broad expression of OSM receptors (Osmr and Il6st) across wound-resident keratinocytes, fibroblasts, and vascular-associated cells, suggesting widespread responsiveness to OSM signalling during repair. Therapeutic administration of OSM to diabetic wounds significantly accelerated closure, reduced wound width and area, and increased dermal and epidermal thickness. Mechanistically, OSM enhanced epidermal proliferation, angiogenesis, and cutaneous axon regeneration. Collectively, these data identify Schwann cell dysfunction as a contributor to impaired diabetic wound healing and demonstrate that augmenting a Schwann cell-derived paracrine signal can partially rescue key reparative processes. Our findings support a regulatory role for Schwann cells in coordinating epithelial, vascular, and neural repair responses and highlight OSM signalling as a potential therapeutic strategy for chronic diabetic wounds.

cell biology↗

bioRxiv2026

Long-Term Expression and Safety of AAV1-Mediated PI3Kδ Overexpression in the Adult Rat Cortex

Mature CNS neurons are incapable of sufficiently regenerating their axons following spinal cord injury (SCI). This is largely due to developmental changes in epigenetic control leading to suppression of axon growth transcriptomic profile, leading to a shift towards synapse function support. Recently, manipulating the PI3K/Akt/mTOR pathway through PI3K{delta} overexpression in cortical neurons enhanced axonal regeneration of corticospinal tract axons, which was accompanied by functional recovery monitored for up to 16 weeks. However, PI3K is more widely known for its role as an oncogene, and since overexpression is achieved by the use of AAVs, valid safety concerns are raised as it is unknown what the long-term consequences of sustained PI3K{delta} expression in the brain are, which may be necessary to achieve complete re-establishment of the motor pathway. In this study, AAV1-hSYN-PIK3CD was injected into the motor cortex of rats, which survived for 1 year. Comparison with uninjected control animals reveal stable PI3K{delta} expression and sustained pathway activation through increased pS6. PI3K{delta}-treated animals show absence of tumour formation, neural soma hypertrophy, glial cell activation, or haematological or biochemical abnormalities. Thus, long-term neuronal PI3K{delta} expression appears to be well tolerated and may provide a safe and durable strategy to promote functional repair following SCI.

neuroscience↗

bioRxiv2023

Gene drive and genetic sex conversion in the global agricultural pest Ceratitis capitata

Homing-based gene drives are novel interventions promising the area-wide, species-specific genetic control of harmful insect populations. Here we characterise a first set of gene drives in a tephritid agricultural pest species, the Mediterranean fruit fly Ceratitis capitata (medfly). Our results show that the medfly is highly amenable to homing-based gene drive strategies. By targeting the medfly transformer gene, we also demonstrate two different mechanisms by which CRISPR-Cas9 gene drive can be coupled to sex conversion, whereby genetic females are transformed into fertile and harmless XX males. Given this unique malleability of sex determination, we modelled gene drive interventions that couple sex conversion and female sterility and found that such approaches could be effective and tolerant of resistant allele selection in the target population. Our results open the door for developing gene drive strains for the population suppression of the medfly and related tephritid pests by co-targeting female reproduction and shifting the reproductive sex ratio towards males. They demonstrate the untapped potential for gene drives to tackle agricultural pests in an environmentally friendly and economical way.

synthetic biology↗

bioRxiv2022

Regenerative capacity of neural tissue scales with changes in tissue mechanics post injury

Spinal cord injuries have devastating consequences for humans, as mammalian neurons of the central nervous system (CNS) cannot regenerate. In the peripheral nervous system (PNS), however, neurons may regenerate to restore lost function following injury. While mammalian CNS tissue softens after injury, how PNS tissue mechanics changes in response to mechanical trauma is currently poorly understood. Here we characterised mechanical rat nerve tissue properties before and after in vivo crush and transection injuries using atomic force microscopy-based indentation measurements. Unlike CNS tissue, PNS tissue significantly stiffened after both types of tissue damage, likely mainly due to an increase in collagen I levels. Schwann cells, which crucially support PNS regeneration, became more motile and proliferative on stiffer substrates in vitro, suggesting that changes in tissue stiffness may play a key role in facilitating or impeding nervous system regeneration.

neuroscience↗

bioRxiv2021

Integrin-driven Axon Regeneration in the Spinal Cord Activates a Distinctive CNS Regeneration Program

The peripheral branch of sensory dorsal root ganglion (DRG) neurons regenerates readily after injury unlike their central branch in the spinal cord. However extensive regeneration and reconnection of sensory axons in the spinal cord can be driven by the expression of 9 integrin and its activator kindlin- 1(9k1), which enable axons to interact with tenascin-C. To elucidate the mechanisms and downstream pathways affected by activated integrin expression and central regeneration, we conducted transcriptomic analyses of DRG sensory neurons transduced with 9k1, and controls, with and without axotomy of the central branch. Expression of 9k1 without the central axotomy led to upregulation of a known PNS regeneration program, including many genes associated with peripheral nerve regeneration. Coupling 9k1 treatment with dorsal root axotomy led to extensive central axonal regeneration and caused expression of a distinctive CNS regeneration program, including genes associated with ubiquitination, autophagy, endoplasmic reticulum, trafficking, and signalling. Pharmacological inhibition of these processes blocked the regeneration of axons from DRGs and human iPS-derived sensory neurons, validating their causal contributions. This CNS regeneration- associated program showed little correlation with either embryonic development or PNS regeneration programs. Potential transcriptional drivers of this CNS program coupled to regeneration include Mef2a, Runx3, E2f4, Tfeb, Yy1. Signalling from integrins primes sensory neurons for regeneration, but their axon growth in the CNS is associated with a distinctive program that differs from that involved in PNS regeneration.

neuroscience↗

bioRxiv2021

Perineuronal nets affect memory and learning after synapse withdrawal

Perineuronal nets (PNNs) enwrap mature neurons, playing a role in the control of plasticity and synapse dynamics. PNNs have been shown to have effects on memory formation, retention and extinction in a variety of animal models. It has been proposed that the cavities in PNNs which contain synapses can act as a memory store, which remains stable after events that cause synaptic withdrawal such as anoxia or hibernation. We examine this idea by monitoring positional memory before and after synaptic withdrawal caused by acute hibernation-like state (HLS). Animals lacking hippocampal PNNs due to enzymatic digestion by chondroitinase ABC or knockout of the PNN component aggrecan were compared with wild type controls. HLS-induced synapse withdrawal caused a memory deficit, but not to the level of naive animals and not worsened by PNN attenuation. After HLS, animals lacking PNNs showed faster relearning. Absence of PNNs affected the restoration of inhibitory and excitatory synapses on PNN-bearing neurons. The results support a role for hippocampal PNNs in learning, but not in long-term memory storage.

neuroscience↗

bioRxiv2020

Restoring the pattern of perineuronal net sulphation corrects age-related memory loss

Memory loss is a usual consequence of ageing and aged mice show progressive deficits in memory tasks. In aged brains, perineuronal nets (PNNs), which are implicated in plasticity and memory, become inhibitory due to decreased 6-sulphation of their glycan chains (C6S). Removal of PNNs or digestion of their glycosaminoglycans rescued age-related memory loss. Premature reduction of permissive C6S by transgenic deletion of chondroitin 6-sulfotransferase led to very early memory loss. However, restoring C6S levels in aged animals by AAV delivery or transgenic expression of 6-sulfotransferase restored memory. Low C6S levels caused loss of cortical long-term potentiation, which was restored by AAV-mediated 6-sulfotransferase delivery. The study shows that loss of C6S in the aged brain leads to declining memory and cognition. Age-related memory impairment was restored by C6S replacement or other interventions targeting perineuronal nets

neuroscience↗

bioRxiv2017

EFA6 regulates selective polarised transport and axon regeneration from the axon initial segment

It is not clear why central nervous system (CNS) axons lose their intrinsic ability to regenerate with maturity, whilst peripheral (PNS) axons do not. A key difference between these neuronal types is their ability to transport integrins into axons. Integrins can mediate PNS regeneration, but are excluded from adult CNS axons along with their rab11 positive carriers. We reasoned that this exclusion might contribute to the intrinsic inability of CNS neurons to regenerate, and investigated this hypothesis using laser axotomy. We identify a novel regulator of selective axon transport and regeneration, the ARF6 GEF EFA6. EFA6 exerts its effects from a previously unreported location within the axon initial segment (AIS). EFA6 does not localise here in DRG axons, and in these neurons, ARF activation is counteracted by an ARF-GAP which is absent from the CNS, ACAP1. Depleting EFA6 from cortical neurons permits endosomal integrin transport and enhances regeneration, whilst overexpressing EFA6 prevents DRG regeneration. Our results demonstrate that ARF6 is an intrinsic regulator of regenerative capacity, implicating EFA6 as a focal molecule linking the axon initial segment, signalling and transport.\n\nSummary StatementWe identify a novel resident of the axon initial segment, EFA6. This functions to prevent growth-promoting molecules from entering mature CNS axons. Removing EFA6 elevates the axons regenerative potential.

cell biology↗