Proteomic signature of NPC1 KO microglia from conditional KO mice

Version 1

Niemann-Pick type C (NPC) disease is a rare neurodegenerative disorder mainly caused by autosomal recessive mutations in Npc1 which result in abnormal late endosomal/lysosomal lipid storage. Although microgliosis is one of the prominent pathological features, consequences of NPC1 loss on microglial function and disease outcome remain largely unknown. Here, we provide an in-depth characterization of microglial proteomic signatures and phenotypes in an NPC1-deficient (Npc1-/-) murine model. We demonstrate that microglial defects, including enhanced phagocytosis and impaired lipid trafficking, occur early in the NPC pathological cascade and precede neuronal death. Compromised microglial function during Npc1-/- mouse development is reflected by enhanced synaptic pruning and deficient turnover of myelin. Accumulation of the undigested myelin occurs mainly within multi-vesicular bodies (MVBs) of Npc1-/- microglia and not within lysosomes. This is in agreement with the impairments in recycling of myelin into lipid droplets. Macrophages of NPC patients displayed similar molecular and functional alterations as murine Npc1-/- microglia, strengthening the role of NPC1 in immune homeostasis. Generated ex vivo assays using patient macrophages are novel promising clinical tools to monitor the progression and therapeutic efficacy in NPC patients.