Single Cell Transcriptome Analysis of Niemann–Pick Disease, Type C1 Cerebella

Abstract

Niemann–Pick disease, type C1 (NPC1) is a lysosomal disease characterized by endolysosomal storage of unesterified cholesterol and decreased cellular cholesterol bioavailability. A cardinal symptom of NPC1 is cerebellar ataxia due to Purkinje neuron loss. To gain an understanding of the cerebellar neuropathology we obtained single cell transcriptome data from control (Npc1+/+) and both three-week-old presymptomatic and seven-week-old symptomatic mutant (Npc1−/−) mice. In seven-week-old Npc1−/− mice, differential expression data was obtained for neuronal, glial, vascular, and myeloid cells. As anticipated, we observed microglial activation and increased expression of innate immunity genes. We also observed increased expression of innate immunity genes by other cerebellar cell types, including Purkinje neurons. Whereas neuroinflammation mediated by microglia may have both neuroprotective and neurotoxic components, the contribution of increased expression of these genes by non-immune cells to NPC1 pathology is not known. It is possible that dysregulated expression of innate immunity genes by non-immune cells is neurotoxic. We did not anticipate a general lack of transcriptomic changes in cells other than microglia from presymptomatic three-week-old Npc1−/− mice. This observation suggests that microglia activation precedes neuronal dysfunction. The data presented in this paper will be useful for generating testable hypotheses related to disease progression and Purkinje neurons loss as well as providing insight into potential novel therapeutic interventions.

Toll-like receptor mediated lysozyme expression in Niemann-pick disease, type C1

“…As part of the NPC cerebellar inflammation signature, lysozyme, a highly conserved antibacterial hydrolase, is overexpressed [2][3][4][5]. Using single-cell RNAseq we found that Lyz2 was not only upregulated in microglia, as expected, but expression was also significantly increased in Npc1 −/− glial cells and neurons [6]. We proposed that elevated expression of lysozyme protein may functionally contribute to Purkinje neurons loss.…”

Ferroptosis-Related Genes in Neurodevelopment and Central Nervous System

“…To fully comprehend the genetic background of this association, future studies are warranted and scrutinizing the constitutive roles of genes—in particular, the 10 genes we identified—implicated in ferroptosis may help us understand the pathogenesis of many neurological diseases. Also, we expect that integrating single cell data in neurodegenerative disease models such as Niemann–Pick Disease, Type C1 [ 139 ] into this analysis will unveil ferroptosis genetic hallmarks under the neurological disease condition.…”

Understanding and Treating Niemann–Pick Type C Disease: Models Matter

“…This will require a combination of preparations allowing to study the same type of cells in vivo, ex vivo, and in vitro (Figure 4) as well as new approaches to analyze mRNA, protein, and lipid content of defined cell types replacing transcriptomic, proteomic, and lipidomic studies of entire organs or tissues. As an example, acutely isolated cells combined with single cell transcriptomics [231] represent a first step that needs to be refined and extended with a focus on vulnerable cells in most affected organs, including the brain, liver, and lung. Cells differentiated from induced pluripotent stem cells represent an alternative although with caveats [397].…”

“…In mice, the outcome of a given mutation varies with the genetic background of strains [37,135,[215][216][217][218]. Numerous double mutant mice have been created to test whether and how specific candidate genes impact the disease [163,173,177,190,191,[219][220][221][222][223][224][225][226][227][228][229][230][231][232][233][234][235]. Sex-dependent differences in behavior [236], life span [37,134], and responses to immune activation [237] and to potential therapies [171,238] were reported in some NPC1 mutant mice, raising the question of whether sex is a modifying factor in NPC disease [37] as in other cholesterol-related pathologies [239][240][241][242] and normal cholesterol homeostasis [243,244].…”