Neurogenin 2-induced central neurons from iPSC-established patients with NPC display attenuated neurite outgrowth while accumulating cholesterol.

Niemann-Pick disease type C (NPC) is a lysosome disease hallmarked by autosomal recessive mutations in the NPC1 or NPC2 genes. It results in the accumulation of unesterified cholesterol in the late endosome/lysosome compartment, and then induces progressive neurodegeneration in affected individuals. Previous studies have primarily used fibroblasts derived from NPC patients to examine the cellular pathology and test therapeutic agents. However, the neurodegenerative aspect of the disease should be clarified using an in vitro system that recapitulates the cellular mechanisms underlying the neuronal defects. In this study, we generated iPSCs from NPC patients, and differentiated them into neurons to examine the pathological and biological defects in NPC neurons. Five iPSCs (3 NPC and 2 healthy individuals) carrying a doxycycline-inducible NGN2 (iPSCsTetON:NGN2) were generated, and edited cells efficiently differentiated into cortical neurons by 15 days. Although the standard differentiated culture method did not show any phenotypic features in NPC neurons, human-derived low-density lipoprotein (LDL) treatment exhibited cellular pathological features, including the accumulation of unesterified cholesterol and impaired neurite outgrowth. Miglustat, a drug approved for NPC in several countries, promoted neurite outgrowth and reduced unesterified cholesterol accumulation in LDL-treated NPC neurons. Using our model, two drugs among an FDA-approved drug library attenuated the pathological defects by LDL treatment. Collectively, our results indicate that neurons of NPC patients fail neurite extension due to suboptimal cholesterol transport to the membrane. This will be a valuable tool for NPC research to identify the pathological mechanisms of neuronal degeneration and to discover new therapeutics.