Neuron-specific changes in gene expression caused by NPC1 deficiency. Mus musculus

Background: Niemann-Pick type C is a rare autosomal recessive lysosomal storage disorder presenting aggravating neurologic symptoms due degeneration of specific types of CNS neurons. At present, it is not well understood how neurons react to NPC1 deficiency and why some neuronal cell types are more vulnerable than others. Purpose: We took aimed to uncover how a specific type of CNS neuron that can be highly purified reacts to NPC1 deficiency based on changes in gene expression. Methods: Retinal ganglion cells were purified from individual one-week old Balb/c mice homozygous for a mutant NPC1 allele (NPC1m1N) and wildtype littermates (n = 4 mice each genotype) using immunopanning. Total RNA was isolated from acutely isolated neurons and subjected to RNAseq using 4 biological replicates for each genotype. Results: Our analysis revealed a strong downregulation of transcripts known to be decreased in mutant mice including Npc1 and Calb1 thus validating our approach. We observed a strong upregulation of genes for cellular cholesterol accretion and the downregulation of those for cholesterol release. Other changes including downregulation genes involved in the immune response and synaptic components. Conclusions: The observed changes suggest that neurons already at one week of age sense a cholesterol deficit because lipids accumulate in the endosomal-lysosomal system and cannot be redistributed intracellularly. Overall design: Gene expression analysis by RNAseq in retinal ganglion cells acutely purified from eight-days-old NPC1-deficient mice and wildtype littermates