Development of cell imaging-tools to identify prognostic and predictive biomarkers in Hereditary Spastic Paraplegia (HSP)

Hereditary spastic paraplegia (HSP) are motor neuron diseases characterized by axonal degeneration involving the lateral corticospinal tracts. HSPs are caused by several types of mutations and the most common are haploinsufficient mutations in the SPG4 gene, which encodes spastin, a microtubule severing ATPase, that controls cytokinesis, endosomal traffic, lipid droplet (LDs) homeostasis and axonal transport. Truncating and missense mutations in the SPG4 gene have been identified in HSP patients; most missense mutations are located in the ATPase domain and affect the MT severing ability. As spastin-elevating therapies are emerging, there is a need to identify biomarkers that can be used to monitor the effects of spastin recovery treatments. We have developed an automated, simple, rapid, and non-invasive cell imaging-based method to quantify the organization of the MT cytoskeleton, which can distinguish HSP-SPG4 from healthy donor lymphoblastoid and peripheral blood mononuclear cells. It is also able to detect changes in spastin protein levels. We are now extending the imaging-based method to a large cohort of SPG4 patient cells to evaluate its sensitivity and specificity in relation with molecular and clinical patient features and to detect the effects of different spastin-elevating drugs. Additionally, we are focusing on other subcellular components affected by spastin mutations, such as LDs, exploring their behaviour in HSP-SPG4 patient-derived cells.