Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2022.08.29.505610v1?rss=1

Authors: Broadhead, M. J., Doucet, K., Kantelberg, O. G., Zhu, F., Grant, S. G. N., Horrocks, M. H., Miles, G. B.

Abstract: Cellular inclusions of hyperphosphorylated TAR-DNA-Binding Protein 43 (TDP-43) are a key hallmark of neurodegenerative diseases such as Amyotrophic Lateral Sclerosis (ALS). ALS is characterised by a loss of motor neurons in the brain and spinal cord that is preceded by early-stage changes in synaptic function that may be associated with TDP-43 pathology. However, there has been little characterisation of the synaptic expression of TDP-43 in spinal cord synapses. This study utilises a range of high-resolution and super-resolution microscopy techniques with immunolabelling, as well as an aptamer-based TDP-43 labelling strategy visualised with single-molecule localisation microscopy, to characterise and quantify the presence of phosphorylated TDP-43 (pTDP-43) in spinal cord synapses. We observe that TDP-43 is expressed in the majority of spinal cord synapses as nanoscale clusters as small as 60 nm in diameter. Synaptic TDP-43 expression is more frequently associated with presynaptic terminals than postsynaptic densities, and is more enriched in VGLUT1-associated synapses, compared to VGLUT2-associated synapses. Our nanoscopy techniques showed no difference in the subsynaptic expression of pTDP-43 in the ALS mouse model, SOD1G93a compared to healthy controls. This research characterizes the basic synaptic expression of TDP-43 with nanoscale precision and provides a framework with which to investigate the potential relationship between TDP-43 pathology and synaptic pathology in neurodegenerative diseases.

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