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![Cerebellar/Purkinje cell neuropathology of Npc1 I1061 mice. A, Temporal progress of patterned Purkinje cell loss (brown, calbindin D; Nissl nuclear counterstain). B, Purkinje cell density evaluated in cerebellarzones[schematicallycorrespondingto(60)].C,RT-qPCRquantificationofcalbindinDmRNAinthebrainsofWTandNpc1 I1061T miceagesP28,P63,andP105(n4pergroup).D,Exampleofregressive changes in a lobule V Purkinje cell (green), reduction and dystrophy of a dendritic tree, and formation of axonal spheroids (arrows), likely affecting both the main axon and axonal collateral. Extensive microglial pathology(purple,CD68)isobservedinmolecular,Purkinjecell,andgranularcelllayers.TheimageisaMIPofa16.2-m-thickZstack.E,StorageofcholesterolandGM2gangliosideisshowninlobuleXPurkinje cells.F,UltrastructuralappearanceofpolymembranouscytoplasmicstoragebodiesinalobuleXPurkinjecell(cytoplasmicmembraneoutlined)ofanNpc1 I1061T mousecomparedwithNpc1 / mice(equivalent magnification of lobule X Purkinje cell cytoplasm). ML, Molecular layer; PCL, Purkinje cell layer; GCL, granule cell layer. **p 0.001. Scale bars: A, 1 mm; D, 50 m; E, F, 5 m.](profile/Nina-Pipalia/publication/277409846/figure/fig1/AS:614389489086492@1523493277551/Cerebellar-Purkinje-cell-neuropathology-of-Npc1-I1061-mice-A-Temporal-progress-of.png)
Cerebellar/Purkinje cell neuropathology of Npc1 I1061 mice. A, Temporal progress of patterned Purkinje cell loss (brown, calbindin D; Nissl nuclear counterstain). B, Purkinje cell density evaluated in cerebellarzones[schematicallycorrespondingto(60)].C,RT-qPCRquantificationofcalbindinDmRNAinthebrainsofWTandNpc1 I1061T miceagesP28,P63,andP105(n4pergroup).D,Exampleofregressive changes in a lobule V Purkinje cell (green), reduction and dystrophy of a dendritic tree, and formation of axonal spheroids (arrows), likely affecting both the main axon and axonal collateral. Extensive microglial pathology(purple,CD68)isobservedinmolecular,Purkinjecell,andgranularcelllayers.TheimageisaMIPofa16.2-m-thickZstack.E,StorageofcholesterolandGM2gangliosideisshowninlobuleXPurkinje cells.F,UltrastructuralappearanceofpolymembranouscytoplasmicstoragebodiesinalobuleXPurkinjecell(cytoplasmicmembraneoutlined)ofanNpc1 I1061T mousecomparedwithNpc1 / mice(equivalent magnification of lobule X Purkinje cell cytoplasm). ML, Molecular layer; PCL, Purkinje cell layer; GCL, granule cell layer. **p 0.001. Scale bars: A, 1 mm; D, 50 m; E, F, 5 m.
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Niemann-Pick Type C1 (NPC1) disease is a rare neurovisceral, cholesterol-sphingolipid lysosomal storage disorder characterized by ataxia, motor impairment, progressive intellectual decline, and dementia. The most prevalent mutation, NPC1(I1061T), encodes a misfolded protein with a reduced half-life caused by ER-associated degradation. Therapies dir...
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... we performed cal- bindin D immunohistochemistry to visualize these neurons in parasagittal cerebellar sections from P28, P63, and P105 mice. In contrast to WT littermates, cerebella from Npc1 I1061T mice showed progressive, age-dependent loss of calbindin D staining, predominantly in the anterior lobules, indicating loss of Purkinje cells (Fig. 3 A, B). The progressive Purkinje cell degeneration was also reflected in the age-dependent reduction in calbindin D mRNA expression (Fig. 3C). In the cerebella of P63 and P105 mice, there was a significant loss of Purkinje cells in anterior (P63, 58% reduction, p 0.01; P105, 91% reduction, p 0.001), cen- tral (P105, 80% reduction, p 0.001), ...
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... mice. In contrast to WT littermates, cerebella from Npc1 I1061T mice showed progressive, age-dependent loss of calbindin D staining, predominantly in the anterior lobules, indicating loss of Purkinje cells (Fig. 3 A, B). The progressive Purkinje cell degeneration was also reflected in the age-dependent reduction in calbindin D mRNA expression (Fig. 3C). In the cerebella of P63 and P105 mice, there was a significant loss of Purkinje cells in anterior (P63, 58% reduction, p 0.01; P105, 91% reduction, p 0.001), cen- tral (P105, 80% reduction, p 0.001), posterior (P105, 65% reduction, p 0.001), and nodular (P105, 41% reduction, p 0.001) zones but no appreciable Purkinje cell loss in ...
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... significant loss of Purkinje cells in anterior (P63, 58% reduction, p 0.01; P105, 91% reduction, p 0.001), cen- tral (P105, 80% reduction, p 0.001), posterior (P105, 65% reduction, p 0.001), and nodular (P105, 41% reduction, p 0.001) zones but no appreciable Purkinje cell loss in lobule X, which is generally preserved even in end-stage disease ( Fig. 3B; Langmade et al., 2006;Davidson et al., 2009). Loss of Purkinje cell bodies was accompanied by axonal spheroid formation, dystro- phic dendritic abnormalities, and microglial and astrocytic changes in affected cerebellar areas (Fig. 3D). Although the dis- tribution of Purkinje cell loss in the Npc1 I1061T mice was similar to that ...
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... zones but no appreciable Purkinje cell loss in lobule X, which is generally preserved even in end-stage disease ( Fig. 3B; Langmade et al., 2006;Davidson et al., 2009). Loss of Purkinje cell bodies was accompanied by axonal spheroid formation, dystro- phic dendritic abnormalities, and microglial and astrocytic changes in affected cerebellar areas (Fig. 3D). Although the dis- tribution of Purkinje cell loss in the Npc1 I1061T mice was similar to that observed in the Npc1 / model, the degree of Purkinje cell loss at P63 was less severe than in similarly aged Npc1 / mice, findings consistent with delayed onset of impaired motor coor- dination in the knock-in compared with the knock-out ...
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... cells from Npc1 I1061T mice displayed the well characterized subcellular abnormalities of NPC1 disease ( Higashi et al., 1993). Immunofluorescence staining of cerebellar sections revealed subcellular storage of cho- lesterol and ganglioside GM2 in Purkinje neurons from P63 Npc1 I1061T mice, similar to the pattern observed in the Npc1 / model (Fig. 3E). We also observed subcellular ultrastructural pa- thology in these animals, with the presence of polymembranous storage bodies in Purkinje cells from P63 Npc1 I1061T mice ( Fig. 3F; Higashi et al., 1993). In addition, Npc1 I1061T mice exhibited cho- lesterol storage in CD68-positive macrophages (Fig. 4A) and in hepatocytes (Fig. 4B), ...
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... revealed subcellular storage of cho- lesterol and ganglioside GM2 in Purkinje neurons from P63 Npc1 I1061T mice, similar to the pattern observed in the Npc1 / model (Fig. 3E). We also observed subcellular ultrastructural pa- thology in these animals, with the presence of polymembranous storage bodies in Purkinje cells from P63 Npc1 I1061T mice ( Fig. 3F; Higashi et al., 1993). In addition, Npc1 I1061T mice exhibited cho- lesterol storage in CD68-positive macrophages (Fig. 4A) and in hepatocytes (Fig. 4B), cell types critically associated with the pro- gression of the liver disease ( Lopez et al., 2012). Electron micros- copy similarly revealed the presence of polymembranous storage ...
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... P105 (for P63 and P105, p 0.05), consistent with glial activation known to occur in response to neuronal cell death in NPC1 disease ( Fig. 8A; Baudry et al., 2003). This was accompanied by a dramatic increase in expression of cytokines (TNF and MIP1) and markers of microglial activation (CD68 and CD11c), particularly late in dis- ease progression (Figs. 3D, 5C, 8B). A similar pattern of induction of inflammatory gene expression was present in liver tissue (Fig. 8C). With the exception of apoE expression, no significant changes in cholesterol homeostatic gene expression were observed in either brain (Fig. 8A) or liver (data not shown) ...
Citations
... T. Kataura et al. a knock-in mouse carrying Npc1 I1061T , the most common diseaseassociated mutation (Fig. S1a) [24]. Re-expression of wild-type NPC1 was sufficient to rescue the autophagy and cell death phenotypes in Npc1 -/-MEFs, thus validating the loss of NPC1 protein as the cause of autophagy deficit and subsequent cell death (Fig. 1a-c). ...
... Immortalized Npc1 +/+ and Npc1 -/-MEFs (gift from Peter Lobel) [21], p62luciferase expressing Npc1 -/-MEFs [29], Atg5 +/+ and Atg5 -/-MEFs (gift from Noboru Mizushima) [56] and primary Npc1 WT and Npc1 I1061T (gift from Daniel Ory) [24] MEFs were maintained in DMEM supplemented with 10% foetal bovine serum (FBS), 100 U/mL penicillin/streptomycin and 2 mM L-glutamine (all from Sigma-Aldrich) at 37°C, and 5% CO 2 in a humidified incubator. 293FT cells (Invitrogen, R70007) were cultured as above in a medium supplemented with 1X MEM non-essential amino acids (Gibco). ...
Impairment of autophagy leads to an accumulation of misfolded proteins and damaged organelles and has been implicated in plethora of human diseases. Loss of autophagy in actively respiring cells has also been shown to trigger metabolic collapse mediated by the depletion of nicotinamide adenine dinucleotide (NAD) pools, resulting in cell death. Here we found that the deficit in the autophagy-NAD axis underpins the loss of viability in cell models of a neurodegenerative lysosomal storage disorder, Niemann-Pick type C1 (NPC1) disease. Defective autophagic flux in NPC1 cells resulted in mitochondrial dysfunction due to impairment of mitophagy, leading to the depletion of both the reduced and oxidised forms of NAD as identified via metabolic profiling. Consequently, exhaustion of the NAD pools triggered mitochondrial depolarisation and apoptotic cell death. Our chemical screening identified two FDA-approved drugs, celecoxib and memantine, as autophagy activators which effectively restored autophagic flux, NAD levels, and cell viability of NPC1 cells. Of biomedical relevance, either pharmacological rescue of the autophagy deficiency or NAD precursor supplementation restored NAD levels and improved the viability of NPC1 patient fibroblasts and induced pluripotent stem cell (iPSC)-derived cortical neurons. Together, our findings identify the autophagy-NAD axis as a mechanism of cell death and a target for therapeutic interventions in NPC1 disease, with a potential relevance to other neurodegenerative disorders.
... Consistent with earlier research demonstrating that in addition to cholesterol, sphingolipids also accumulate in NPC1 patients, animal models of NPC1, as well as in NPC1 mutant primary fibroblasts (5,6,19,23), we also found that levels of ceramide and complex sphingolipids were elevated in NPC1-deleted HeLa cells (NPC1-KO) (Fig. 1A-E). Additionally, the level of sphingosine was increased by almost 3-fold in NPC1-KO cells (Fig. 1B). ...
Niemann-Pick type C1 (NPC1) disease is a rare neurodegenerative cholesterol and sphingolipid storage disorder primarily due to mutations in the cholesterol-trafficking protein NPC1. In addition to catabolic-derived sphingolipids, NPC1 dysfunction also leads to an increase in de novo sphingolipid biosynthesis, yet little is known about the cellular mechanism involved. Although deletion of NPC1 or inhibition of the NPC1 sterol binding domain enhanced de novo sphingolipid biosynthesis, sur- prisingly levels of the ORMDLs, the regulatory subunits of serine palmitoyltransferase (SPT), the rate-limiting step in sphingolipid biosynthesis, were also greatly increased. Nevertheless, less ORMDL was bound in the SPT-ORMDL complex despite elevated ceramide levels. Instead, ORMDL colocalized with p62, the selective autophagy receptor, and accumu- lated in stalled autophagosomes due to defective autophagy in NPC1 disease cells. Restoration of autophagic flux with N-acetyl-L-leucine in NPC1 deleted cells decreased ORMDL accumulation in autophagosomes and reduced de novo sphingolipid biosynthesis and their accumulation. This study revealed a previously unknown link between de novo sphingolipid biosynthesis, ORMDL, and autophagic defects present in NCP1 disease. In addition, we provide further evidence and mechanistic insight for the beneficial role of N-acetyl-L-leucine treatment for NPC1 disease which is presently awaiting approval from the Food and Drug Administration and the European Medicines Agency.
... We then assessed connections and common molecular risk factors between AD and DS, NPC, and MPS I. We identified previously unknown genes, pathways that contribute the most to the similarities among the disorders, and identified regulatory gene networks and novel miRNAs as molecular targets. We further extended our comparative genomics approach by comparing frontal cortex transcriptome data from a transgenic NPC1 mutant (Npc1 tm(I1061T)Dso ) mouse model which expresses the most common human mutation found in NPC patients 14 to the AD mouse model 15 and compared their similarities to postmortem human brain samples. Along with phenotypic and chronological and biological aging data, our findings from the disease similarity approach suggest that the NPC1 mut mouse model can be utilized as a unique, short-lived in vivo model for understanding AD mechanisms and identified molecular factors that contribute to brain aging and AD-like pathogenesis. ...
... Animal Studies were conducted in conjunction with the Transgenic Knock-Out Mouse Shared Resource Core at Virginia Commonwealth University (VCU). WT (C57BL/6) and Npc1 tm(I1061T)Dso mutant mice (Strain #027704, The Jackson Laboratory, Bar Harbor, ME, USA) 14 were bred and housed under a protocol approved by the VCU Institutional Animal Care and Use Committee, which has received accreditation from the Association for Assessment and Accreditation of Laboratory Animal Care. All animals were maintained on a 12-hour light/dark cycle and provided food and water ad libitum. ...
... Considering these factors, we aimed to characterize the commonalities in disease phenotypes and molecular mechanisms involved in both NPC and AD pathogenesis. To achieve this, we leveraged the NPC1 mut mouse model (Npc1 tm(I1061T)Dso ), which is a crucial tool in the understanding of the pathobiology of NPC disease 14 . This model, expressing the most common mutation in Npc1 protein seen in juvenile-onset NPC, faithfully . ...
Since its first description in 1906 by Dr. Alois Alzheimer, Alzheimer's disease (AD) has been the most common type of dementia. Initially thought to be caused by age-associated accumulation of plaques, in recent years, research has increasingly associated AD with lysosomal storage and metabolic disorders, and the explanation of its pathogenesis has shifted from amyloid and tau accumulation to oxidative stress and impaired lipid and glucose metabolism aggravated by hypoxic conditions. However, the underlying mechanisms linking those cellular processes and conditions to disease progression have yet to be defined. Here, we applied a disease similarity approach to identify unknown molecular targets of AD by using transcriptomic data from congenital diseases known to increase AD risk, namely Down Syndrome, Niemann Pick Disease Type C (NPC), and Mucopolysaccharidoses I. We uncovered common pathways, hub genes, and miRNAs across in vitro and in vivo models of these diseases as potential molecular targets for neuroprotection and amelioration of AD pathology, many of which have never been associated with AD. We then investigated common molecular alterations in brain samples from an NPC disease mouse model by juxtaposing them with brain samples of both human and mouse models of AD. Detailed phenotypic and molecular analyses revealed NPCmut mouse as a novel, short-lived in vivo model of AD characterized by accelerated brain aging, concluding that NPCmut mouse model can serve as a potential short-lived in vivo model for AD research and for understanding molecular factors affecting brain aging. This research represents the first comprehensive approach to congenital disease association with neurodegeneration and a new perspective on AD research while highlighting shortcomings and lack of correlation in diverse in vitro models. Our findings provide a foundation for future animal and clinical studies and will lead to a better understanding of the molecular mechanisms underpinning the observed association between neurological congenital diseases and AD, thus has the potential to accelerate diagnostic and therapeutic applications against common types of dementia.
... Genetic background in Npc1 mutant mice can significantly influence the severity of the NPC1 phenotype. Homozygous Npc1 mutant mice on a C57Bl/6J background have a more severe phenotype compared to the same mutant alleles on a Balb/cJ background [24][25][26]. Rodriguez-Gil et al. [25] performed a QTL analysis for lifespan between these two different strains, and found significant evidence for linkage to markers on mouse chromosomes 1 and 7. Similarly, Zhang and Erickson [27] observed evidence of a phenotypic modifier on mouse chromosome 19. Multiple studies have evaluated potential genetic modifiers in double-mutant mice. ...
Niemann-Pick disease type C1 (NPC1) is a lysosomal disorder due to impaired intracellular cholesterol transport out of the endolysosomal compartment.. Marked heterogeneity has been observed in individuals with the same NPC1 genotype, thus suggesting a significant effect of modifier genes. Prior work demonstrated that decreased SOAT1 activity decreased disease severity in an NPC1 mouse model. Thus, we hypothesized that a polymorphism associated with decreased SOAT1 expression might influence the NPC1 phenotype. Phenotyping and genomic sequencing of 117 individuals with NPC1 was performed as part of a Natural History trial. Phenotyping included determination of disease severity and disease burden. Significant clinical heterogeneity is present in individuals homozygous for the NPC1I1061T variant and in siblings. Analysis of the SOAT1 polymorphism, rs1044925 (A>C), showed a significant association of the C-allele with earlier age of neurological onset. The C-allele may be associated with a higher Annualized Severity Index Score as well as increased frequency of liver disease and seizures. A polymorphism associated with decreased expression of SOAT1 appears to be a genetic modifier of the NPC1 phenotype. This finding is consistent with prior data showing decreased phenotypic severity in Npc1-/-:Soat1-/- mice and supports efforts to investigate the potential of SOAT1 inhibitors as a potential therapy for NPC1.
... Npc1 spm mice, which carry another spontaneous NPC1 mutation, recapitulate similar hallmarks of aggressive NPC pathology [28]. In addition to fast-progressing disease models, NPC pathology is also studied in transgenic mice carrying patient NPC1 mutations such as I1061T, which leads to a partial loss of NPC1 function [29]. This mouse model displays a less aggressive phenotype compared with Npc1 −/− mice, with the lethality at the age of 15 weeks. ...
Niemann–Pick type C (NPC) disease is a rare progressive lysosomal lipid storage disorder that manifests with a heterogeneous spectrum of clinical syndromes, including visceral, neurological and psychiatric symptoms. This monogenetic autosomal recessive disease is largely caused by mutations in the NPC1 gene, which controls intracellular lipid homeostasis. Vesicle-mediated endo-lysosomal lipid trafficking and non-vesicular lipid exchange via inter-organelle membrane contact sites are both regulated by the NPC1 protein. Loss of NPC1 function therefore triggers intracellular accumulation of diverse lipid species, including cholesterol, glycosphingolipids, sphingomyelin and sphingosine. The NPC1-mediated dysfunction of lipid transport has severe consequences for all brain cells, leading to neurodegeneration. Besides the cell-autonomous contribution of neuronal NPC1, aberrant NPC1 signalling in other brain cells is critical for the pathology. We discuss here the importance of endo-lysosomal dysfunction and a tight crosstalk between neurons, oligodendrocytes, astrocytes and microglia in NPC pathology. We strongly believe that a cell-specific rescue may not be sufficient to counteract the severity of the NPC pathology, but targeting common mechanisms, such as endo-lysosomal and lipid trafficking dysfunction, may ameliorate NPC pathology.
This article is part of a discussion meeting issue ‘Understanding the endo-lysosomal network in neurodegeneration’.
... To corroborate that increased Ca V 1.2-K V 2.1 complexes occur in intact brain regions, we performed multiplexed immunolabeling on cerebellar tissue of WT and NPC1 I1061T mutant mice (Fig. 4C). The cerebellum was chosen because Purkinje cells represent another highly vulnerable neuronal population in NPC1 disease 64,65 . Like isolated cortical neurons, Ca V 1.2 and K V 2.1 channels showed increased spatial proximity in mouse NPC1 I1061T Purkinje neurons ( Fig. 4C; movie S1). ...
Lysosomes communicate through cholesterol transfer at endoplasmic reticulum (ER) contact sites. At these sites, the Niemann Pick C1 cholesterol transporter (NPC1) facilitates the removal of cholesterol from lysosomes, which is then transferred to the ER for distribution to other cell membranes. Mutations in NPC1 result in cholesterol buildup within lysosomes, leading to Niemann-Pick Type C (NPC) disease, a progressive and fatal neurodegenerative disorder. The molecular mechanisms connecting NPC1 loss to NPC-associated neuropathology remain unknown. Here we show both in vitro and in an animal model of NPC disease that the loss of NPC1 function alters the distribution and activity of voltage-gated calcium channels (CaV). Underlying alterations in calcium channel localization and function are KV2.1 channels whose interactions drive calcium channel clustering to enhance calcium entry and fuel neurotoxic elevations in mitochondrial calcium. Targeted disruption of KV2–CaV interactions rescues aberrant CaV1.2 clustering, elevated mitochondrial calcium, and neurotoxicity in vitro. Our findings provide evidence that NPC is a nanostructural ion channel clustering disease, characterized by altered distribution and activity of ion channels at membrane contacts, which contribute to neurodegeneration.
... Similar to what was reported by the Padilla group, my group in collaboration with Dr. Yuqing Li's lab at the University of Florida raised an NPC1-I1061T-knockin model mouse [57] and discovered that the AP firing frequency in triphasic cerebellar Purkinje neurons was 30% lower in the mutant than that in the wild-type (QXJ, unpublished observations). The decreased cholesterol-content likely activated Kv channel more significantly than the Nav or Cav channels in the Purkinje neurons, leading to a marked inhibitory effect. ...
Eukaryotic cells contain phospholipids and nonphospholipids. The latter lack phosphodiester groups in their head group regions. Lipid-dependent gating of voltage-gated ion channels represents a steady-state energetic effect of nonphospholipids in favoring the resting state of voltage-sensor domains (VSDs) of the channels. It suggests adaptation of ion channels to lipid compositions in their native niche and significant roles of low-to-intermediate affinity lipid-binding sites at the channels. The nonphospholipids include glycoglycerolipids, glycosphingolipids, ceramides, cholesterol or cholesterol esters, diacylglycerol (DAG), fatty acids, cation lipids, etc. Change in relative ratios of phospholipids to nonphospholipids can shift the energetic levels of the VSDs and the gating of these channels, which in turn may alter excitability in certain cells. It is expected that reduced relative abundance of nonphospholipids / phospholipids in plasma membranes may change resting transmembrane potential or gating transitions of voltage-gated Na or K channels. The net results will be a change in action potential firing at least in certain areas of an excitable cell. Such changes in the central nervous system (CNS) are anticipated to affect brain functions and contribute to early-onset neurological phenotypes observed in patients carrying lipid metabolic defects. We will describe the basics of lipid-dependent gating and review its projected links to phenotypes of monogenic lipid metabolic defects and related changes of lipid composition in cell membranes as well as altered neuronal excitability in CNS. However, lack of high-resolution techniques to measure lipid composition around individual channels in cell membranes has been limiting the studies of direct connections between lipid redistribution caused by metabolic defects and altered ion channel activities. Potential solutions will be described for future studies.
... However, we observed a profound change in phenotype after removal of NeoR, with animals having a longer lifespan and reduced visceral pathology. Visceral organs were atrophied in P361R-SMA mice, which we hypothesize is proportional to the loss in body weight observed, as with mouse models of other sphingolipidoses 49,57 . Organomegaly, observed in P361R-Farber mice 36,38 , has been postulated to occur due to massive accumulation of foamy macrophages with storage material, which is not seen in P361R-SMA mice. ...
Mutations in ASAH1 have been linked to two allegedly distinct disorders: Farber disease (FD) and spinal muscular atrophy with progressive myoclonic epilepsy (SMA-PME). We have previously reported FD-like phenotypes in mice harboring a single amino acid substitution in acid ceramidase (ACDase), P361R, known to be pathogenic in humans (P361R-Farber). Here we describe a mouse model with an SMA-PME-like phenotype (P361R-SMA). P361R-SMA mice live 2-3-times longer than P361R-Farber mice and have different phenotypes including progressive ataxia and bladder dysfunction, which suggests neurological dysfunction. We found profound demyelination, loss of axons, and altered sphingolipid levels in P361R-SMA spinal cords; severe pathology was restricted to the white matter. Our model can serve as a tool to study the pathological effects of ACDase deficiency on the central nervous system and to evaluate potential therapies for SMA-PME.
... 33 These Npc1 tm(I1061T)Dso mice develop progressive neurodegeneration and start to show ataxia phenotypes at 9-10 weeks of age. [33][34][35] The Npc1 tm(I1061T)Dso mice were fed at lib with 1.0 g lithium/kg chow starting at 6 weeks of age and continuing until their death. This yielded plasma lithium concentrations of 0.354 G 0.052 mM, which is within the therapeutic range for bipolar disorder treatment in humans. ...
Niemann-Pick disease type C (NP-C) is a genetic lysosomal disorder associated with progressive neurodegenerative phenotypes. Its therapeutic options are very limited. Here, we show that lithium treatment improves ataxia and feeding phenotypes, attenuates cerebellar inflammation and degeneration, and extends survival in Npc1 mouse models. In addition, lithium suppresses STING activation, SREBP2 processing to its mature form and the expression of the target genes in the Npc1 mice and in Npc1-deficient fibroblasts. Lithium impedes STING/SREBP2 transport from the ER to the Golgi, a step required for STING activation and SREBP2 processing, probably by lowering cytosolic calcium concentrations. This effect of lithium on STING/SREBP2 transport provides a mechanistic explanation for lithium’s effects on Npc1 mice. Thus, this study reveals a potential therapeutic option for NP-C patients as well as a strategy to reduce active STING/SREBP2 pathway.
... StARD9 KO mice developed comparable neurodegeneration phenotypes to those of NPC mutant mice, with loss of Purkinje cells (Fig. 6A-E) and the development of tremors, ataxia, loss of grip strength and abnormal walking gait (Table S2). The onset of symptoms was closer to NPC1 (I1061T) mutant mice than NPC1(−/−) mice Praggastis et al., 2015). However, the pattern of phenotype presentation and the progression towards mortality was analogous (Davidson et al., 2009). ...
... Immunohistochemistry was performed as previously described (Praggastis et al., 2015). Cerebella were dissected and placed in 4% paraformaldehyde for 24 h at 4°C. ...
The pathological accumulation of cholesterol is a signature feature of Niemann-Pick type C (NPC) disease, in which excessive lipid levels induce Purkinje cell death in the cerebellum. NPC1 encodes a lysosomal cholesterol-binding protein, and mutations in NPC1 drive cholesterol accumulation in late endosomes and lysosomes (LE/Ls). However, the fundamental role of NPC proteins in LE/L cholesterol transport remains unclear. Here, we demonstrate that NPC1 mutations impair the projection of cholesterol-containing membrane tubules from the surface of LE/Ls. A proteomic survey of purified LE/Ls identified StARD9 as a novel lysosomal kinesin responsible for LE/L tubulation. StARD9 contains an N-terminal kinesin domain, a C-terminal StART domain, and a dileucine signal shared with other lysosome-associated membrane proteins. Depletion of StARD9 disrupts LE/L tubulation, paralyzes bidirectional LE/L motility and induces accumulation of cholesterol in LE/Ls. Finally, a novel StARD9 knock-out mouse recapitulates the progressive loss of Purkinje cells in the cerebellum. Together, these studies identify StARD9 as a microtubule motor protein responsible for LE/L tubulation and provide support for a novel model of LE/L cholesterol transport that becomes impaired in NPC disease.
