Uncovering the role of Synaptotagmin13 in determining motor neuron vulnerability

• Applicant: Professor Dr. Alberto Catanese, Ph.D.
• Subject Area: Experimental Models for the Understanding of Nervous System Diseases ; Molecular and Cellular Neurology and Neuropathology
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 570151964

Spinal motor neurons (MNs) are a specialised neuronal population localized in the ventral horn of the spinal cord and responsible for the innervation and contraction of skeletal muscles. Loss of MNs is the main pathological aspect characterizing (among others) amyotrophic lateral sclerosis (ALS), a lethal and genetically heterogenous neurodegenerative disease. Despite our understanding of the complex genetic component of this pathology is increasing, it is still not clear where the selective vulnerability of MNs originates from. More than 30 genes have been indeed causally linked to ALS, representing an additional obstacle to the identification of effective therapeutic targets. In a recent effort to identify commonly-shared pathological features across the ALS spectrum, we identified a convergent presynaptic phenotype characterizing hiPSC-derived MNs with mutations in the major ALS genes. Our analysis revealed that the biological machinery involved in the release of synaptic vesicles, which includes the Synaptotagmins, is detrimentally impaired in ALS. Interestingly, mutant MNs were also characterized by a common loss of phospho-Synaptotagmin13 (SYT13), whose overexpression has been shown to be neuroprotective in ALS-related models). Since the role of SYT13 in the (patho)physiology of MNs is still unclear, we aimed at elucidating the biological function of this unconventional synaptotagmin. To this end, we created heterozygous SYT13 KO hiPSCs (SYT13+/-) and differentiated them into MNs. Notably, we observed a striking correlation between the transcriptome of SYT13+/- human MNs and ALS signatures, suggesting that a better understating of the role played by SYT13 in determining MN vulnerability might highlight important aspects of neuronal sufferance and help to identify novel therapeutic strategies for the treatment of this disease. In this project, we will take advantage of our expertise in hiSPC-derived models and multi-omics approaches to pinpoint how reduced levels of SYT13 contribute to MN degeneration. We will use 2D MN culture to investigate the effect of SYT13 deficiency on neuronal stress, aggregate accumulation, synaptic dysfunction and apoptosis. We will also integrate our preliminary RNAseq data with proteomic and phospho-proteomic analysis to dissect the pathobiological cascades triggered in MNs when SYT13 levels are detrimentally reduced. Finally, we will combine single-nuclei RNA- and ATAC-seq from SYT13+/- hiPSC-derived spinal organoids and post mortem spinal cord samples from ALS patients to a) clarify the selective vulnerability of MNs to reduced levels of SYT13 and b) link the alterations triggered by SYT13 deficiency to specific pathological features contributing to neurodegeneration. All in all, we are convinced that our approach will highlight novel molecular aspects of MN vulnerability that might be pharmacologically targeted to contrast ALS progression.

• DFG Programme: Research Grants