Biology subjects

Czopka, T.

Publications and source records attributed to Czopka, T..

8 recordsLinked to original sources

bioRxiv2026

Diverging routes of oligodendrocyte recruitment in adaptive and regenerative myelination

Myelination by oligodendrocytes is dynamically regulated throughout life, supporting axon and circuit function during development, activity-dependent plasticity and repair after injury. How new oligodendrocytes are recruited from their lifelong pool of oligodendrocyte precursor cells (OPCs) in these distinct contexts remains unclear. Using high-resolution in vivo imaging in zebrafish, we directly compared activity-induced and demyelination-induced oligodendrogenesis under otherwise matched conditions. Although enhanced motor activity and demyelination both increased oligodendrocyte production, OPCs activated strikingly different transcriptional programmes. Demyelination, but not enhanced activity, induced acute expression of differentiation-associated genes, including the G-protein-coupled receptor Gpr17. Fate-tracking using a Gpr17 knock-in reporter revealed that all newly formed oligodendrocytes arise from Gpr17-positive states. In the healthy CNS, these states emerged exclusively through proliferation-linked OPC divisions, whereas demyelination unlocked a distinct, proliferation-independent conversion of homeostatic OPCs into Gpr17-positive, differentiation-primed cells. Our findings demonstrate the existence of diverging context-dependent routes of OPC recruitment engaged in adaptive and regenerative myelination.

neuroscience↗

bioRxiv2026

Neuronal synapses are stabilised by activity-dependent vesicular release from oligodendrocyte precursor cells

Activity-dependent regulation of synapses has long been attributed to interactions between neurons alone. Here, using in vivo imaging in the zebrafish visual system we show that one type of glia called the oligodendrocyte precursor cell (OPC) closely interacts with pre-synapses of retinal ganglion cell (RGC) axons, and exhibits activity-dependent Vamp2/3-mediated vesicular release. Critically, blocking OPC vesicle release using botulinum toxin, and silencing OPC activity integration through dampening calcium signalling, destabilises RGC pre-synapses. These observations suggest that OPCs provide a non-neuronal pathway for activity-dependent feedback to shape circuit wiring.

neuroscience↗

bioRxiv2025

Mislocalisation of TDP-43 to the cytoplasm of either neurons or oligodendrocytes causes axonopathy and dysmyelination

Neurons with large, myelinated axons are vulnerable to degeneration across the amyotrophic lateral sclerosis (ALS) frontotemporal dementia (FTD) disease spectrum. The defining molecular pathology of this spectrum is mislocalisation of the RNA binding protein TDP-43 from the nucleus to the cytoplasm. Even though cytoplasmic TDP-43 is prevalent in neurons and oligodendrocytes, how these molecular pathologies contribute to neurodegeneration remains unclear. Here we developed humanised zebrafish in which we restricted TDP-43 to the cytoplasm of either neurons or oligodendrocytes. Cytoplasmic TDP-43 restricted to neurons led to a severe axonopathy, with extreme distal axonal swelling and reduced myelination. Axonopathy was mirrored by cell type specific loss of TDP-43 function from neurons, pointing to loss of function, rather than a toxic gain of function of mislocalised TDP-43, as driving this phenotype. Preventing oligodendrocyte differentiation and myelination when TDP-43 was mislocalised in neurons exacerbated axonopathy, indicating that oligodendrocytes limit neurodegeneration. Indeed, when TDP-43 was mislocalised to the cytoplasm of oligodendrocytes this also led to axonopathy and reduced myelination, pointing to complex contributions of neurons and oligodendrocytes to neurodegeneration.

neuroscience↗

bioRxiv2022

Synapses in oligodendrocyte precursor cells are dynamic and contribute to Ca2+ activity

In the nervous system, only one type of neuron-glial synapse is known to exist: that between neurons and oligodendrocyte precursor cells (OPCs). Neuron-OPC synapses are thought to bridge neuronal activity to OPCs. However, their composition, assembly, downstream signaling, and in vivo functions remain largely unclear. Here, we use zebrafish to address these questions and identify postsynaptic molecules PSD-95 and Gephyrin in OPCs. They increase during early development and decrease upon OPC differentiation. PSD-95 and Gephyrin in OPCs are highly dynamic and frequently assemble at "hotspots." Gephyrin hotspots and synapse-associated Ca2+ activity in OPCs predict where a subset of myelin sheaths form in oligodendrocytes. Further analyses reveal that spontaneous synaptic release is integral to OPC Ca2+ activity, while evoked synaptic release contributes only in early development. Finally, disruption of the synaptic genes dlg4a&b, gephyrinb, and nlgn3b impairs OPC differentiation and myelination. Together, we propose that neuron-OPC synapses are dynamically assembled and can predetermine myelination patterns through Ca2+ signaling.

neuroscience↗

bioRxiv2021

Clusters of neuronal Neurofascin prefigure node of Ranvier position along single axons

The spacing of nodes of Ranvier crucially affects conduction properties along myelinated axons. It has been assumed that node position is primarily driven by the growth of myelin sheaths. Here, we reveal an additional mechanism of node positioning that is driven by the axon. We show through longitudinal live imaging of node formation dynamics that stable clusters of the cell adhesion molecule Neurofascin A accumulate at specific sites along axons prior to myelination. While some of these clusters change position upon encounter with growing myelin sheaths, others restrict sheath extension and are therefore predictive of future node position. Animals that lack full-length Neurofascin A showed increased internodal distances and less regular spacing of nodes along single axons. Together, our data reveal the existence of an axonal mechanism to position its nodes of Ranvier that does not depend on regulation of myelin sheath length.

neuroscience↗

bioRxiv2021

Oligodendrocyte Precursor Cells Sculpt the Visual System by Regulating Axonal Remodeling

Many oligodendrocyte precursor cells (OPCs) do not differentiate to form myelin, suggesting additional roles of this cell population. The zebrafish optic tectum contains OPCs in regions devoid of myelin. Elimination of these OPCs impaired precise control of retinal ganglion cell axon arbor size during formation and maturation of retinotectal connectivity, and in consequence impaired visual acuity. Therefore, OPCs fine-tune neural circuit structure and function independently of their canonical role to make myelin.

neuroscience↗

bioRxiv2019

Functionally Distinct Subgroups of Oligodendrocyte Precursor Cells Integrate Neural Activity and Execute Myelin Formation

Recent reports revealed heterogeneity of oligodendrocyte precursor cells (OPCs). It remains unclear if heterogeneity reflects different types of cells with distinct functions, or rather transiently acquired states of cells with the same function. By integrating lineage formation of individual OPC clones, single-cell transcriptomics, calcium imaging and manipulation of neural activity, we show that OPCs in the zebrafish spinal cord can be divided into two functionally distinct entities. One subgroup forms elaborate networks of processes and exhibits a high degree of calcium signalling, but infrequently differentiates, despite contact to permissive axons. Instead, these OPCs divide in an activity and calcium dependent manner to produce another subgroup with higher process motility and less calcium signaling, which readily differentiates. Our data show that OPC subgroups are functionally diverse in responding to neurons and reveal that activity regulates proliferation of a subset of OPCs that is distinct from the cells that generate differentiated oligodendrocytes.

neuroscience↗

bioRxiv2018

Systemic loss of Sarm1 is glioprotective after neurotrauma

The obligate pro-degenerative protein Sarm1 is essential for Wallerian axon degeneration. Inhibition of Sarm1 has been proposed as a promising neuroprotective strategy with clinical relevance. Yet, the conditions that will most benefit from inhibiting Sarm1 remain undefined. Here we use genetics and pharmacology in zebrafish to show that systemic elimination of Sarm1 is glioprotective. Loss of Sarm1 does not affect macrophage recruitment to the wound microenvironment, focal injury resolution, or nerve repair. Unexpectedly, Sarm1 deficiency increases Schwann-cell resistance to toxicity by diverse chemotherapeutic agents after neuronal injury. Yet, synthetic degradation of Sarm1-deficient severed axons reversed this effect, suggesting that glioprotection is non-cell-autonomous. These findings anticipate that interventions aimed at inhibiting Sarm1 can counter heightened glial vulnerability to chemical stressors and may be an effective strategy to reduce chronic consequences of neurotrauma.

cell biology↗