B003 Dysregulated neuronal maturation in Huntington’s disease immortalized human striatal neurons (ISPN) derived from iPSCs

<h3></h3> Although Huntington’s disease (HD) is categorized as a neurodegenerative disease, evidence indicates that mutant Huntingtin disrupts neurodevelopment as well. Previously we established a human neuronal model by immortalizing and differentiating HD patient-derived iPSCs into highly homogeneous immortalized striatal precursor neurons (ISPNs), which recapitulated phenotypes of the parental iPSCs including expression of MAP2/DARPP32 (Akimov et al, 2021). The ISPNs can be differentiated to mature neurons in 2 weeks. To further characterize this human HD striatal neuronal model, we investigated the neuronal maturation process in control (21Q and 33Q) and HD (77Q, 109Q, and 180Q) ISPNs. We found that HD ISPNs have more cells at the dividing phase than controls by cell cycle study and their energy sources shift towards glycolysis based on seahorse assays. Electrophysiological analysis showed that 180Q SPNs are functionally less mature, rarely firing action potentials compared to 33Q controls. To explore the pathways involved in maturation of the ISPNs, we compared the proteomics data of ISPNs before and after maturation. We found about 17% of proteins are significantly up- or down-regulated during the maturation stage in the control cells. In the 180Q cells, however, 30-40% of these proteins are unchanged upon differentiation. SNAP91, a synaptic marker, was significantly decreased in matured HD ISPNs compared to controls. Isoxazole-9 upregulated SNAP91 and promoted neuronal maturation and survival in the 180Q ISPNs. Our data suggests that ISPNs derived from HD iPSCs appear to constitute a useful cellular model platform for neurodevelopment study and disease-modifying therapeutics in HD. <h3>Support</h3> This work was supported by NINDS R21/R33 1R21NS104320-01A1/R33, NIH R01 NS086452-06, and HD PMCOE (HD Precision Medicine Center of Excellent) at Johns Hopkins University School of Medicine (C.A.R.); NINDS R01A1 NS129563 (M.J.).