NPC Animal Models
NPC1 Feline Model
NPC Murine Models
NPC murine models are numerous. The most utilized models are listed below, although the relative ease of manipulating mouse genetics allows rapid generation of new models, typically with a specific purpose/scientific question in mind. Many of these models are available at the Jackson Laboratory (jax.org/mouse-search?searchTerm=NPC1). The following list does not provide all mouse models and interested parties are encouraged to explore the Jackson Laboratory website and the numerous publications on different Npc1 models.
- Npc1m1Nmice(BALB/cNctr-Npc1m1n/J, aka Npc1nih; https://www.jax.org/strain/003092) are the most commonly used model and provide a rapid onset and disease progression similar to the early infantile onset in patients. These mice harbor a spontaneous mutation in which an insertion leads to truncation of 11 of the 13 transmembrane domains.
- Npc1m1Nmice(B6.C-Npc1m1n/GarvJ, aka C57BL/6J Npc1m1N; https://www.jax.org/strain/030097) are similar to the Npc1m1Nmice but on a Bl/6 background, which leads to an earlier onset of disease and more severe phenotype.
- Npc1tm1Dsomice(B6.129-Npc1tm1Dso/J, aka Npc1I1061T; https://www.jax.org/strain/027704) were generated with a point mutation (I1061T) which is the most commonly occurring mutation in NPC1 patients. These mice present with a slightly delayed, though still rapidly progressing, disease course. PraggastisM et al 2015(PMID:26019327, DOI: 10.1523/JNEUROSCI.4173-14.2015) characterizes this model.
- Npc1nmf164mice(C57BL/6J-Npc1nmf164/J;https://www.jax.org/strain/004817) have a point mutation (D1005G) and the resulting phenotype is slightly delayed compared to the Npc1m1Nmice, likely because residual protein levels remain.
- Npc1spmmice(C57BLKS/J-Npc1spm/J;https://www.jax.org/strain/002760) result from a spontaneous mutation which leads to frameshift and premature stop codon. Disease progression is similar to the Npc1m1Nmodel albeit modestly longer lifespan even in the presence of faster Purkinje neuron loss in the cerebellum.
- Npc2-/-mice() were generated by targeted genetic disruption. This model shares the phenotype and pathological manifestations observed in the Npc1m1Nmodel, albeit with a slightly protracted disease course. SleatDE et al 2004 (PMID: 15071184, DOI: 10.1073/pnas.0308456101) provide characterization of this model.
NPC1 Zebrafish (Danio rerio)
The zebrafish offers an in vivo model suitable for high throughput screening. Two independent labs have generated NPC1 zebrafish lines using CRISPR/Cas9-mediated gene targeting.
- PMID: 29897878, DOI: 10.1515/hsz-2018-0118 (LinY et al, 2018)
- PMID: 30135069, DOI: 10.1242/dmm.034165 (TsengWC et al, 2018)
NPC Fruit Flies (Drosophila melanogaster)
NPC1 Roundworm (Caenorhabditis elegans)
The world of “-omics”
Genomics is the study of a genome, or all gene within an organism. The National Human Genome Research Institute provides a nice overview of genomics: https://www.genome.gov/about-genomics/fact-sheets/A-Brief-Guide-to-Genomics
Recent NPC Genomic Publications
Lipidomics queries the multitude of different lipids within an organism, or the lipidome. Mass spectrometry, nuclear magnetic resonance spectroscopy, fluorescence spectroscopy, and other techniques are employed in lipidomics.
Metabolomics involves the study of small molecules produced during metabolism, aka metabolites, in a biological system. Frequently used techniques in this field are mass spectrometry and NMR spectroscopy. Washington University in St. Louis has a well-respected Metabolomics Facility where much of the pioneering work in biomarker development occurred. The group, led by Xuntian Jiang at WashU, is intimately familiar with NPC disease. https://research.wustl.edu/core-facilities/metabolomics-facility/In addition to metabolomics, this core also performs lipidomic analyses.
Proteomics focuses on the proteome and their functions within an organism. The proteome consists of all proteins in the organism. Important technologies employed in proteomics are protein purification and mass spectrometry. Two well-known NPC investigators have focused their careers on proteomics: Drs. William Balch (Scripps Research Institute – https://www.scripps.edu/balch/) and Stephanie Cologna (University of Illinois at Chicago – https://chem.uic.edu/profiles/stephanie-m-cologna/).
NPC Biomarkers & Disease Progression Analysis
NPC Severity Score
The NPC Clinical severity score is a linear scale that quantifies the major symptoms of NPC disease and is utilized to quantify disease progression. The scale includes clinical signs and symptoms in nine major categories; ambulation, cognition, eye movement, fine motor, hearing, memory, seizures, speech, swallowing, and eight minor categories; auditory brainstem response, behavior, gelastic cataplexy, hyperreflexia, incontinence, narcolepsy, psychiatric, respiratory problems. The scale is the primary method used to evaluate disease progression in patients. Other information for disease progression include: full scale IQ, verbal IQ, and non-verbal IQ.
Annual Severity Increment Score (ASIS)
ASIS measures rate of disease progression and is stable over several years and can be used to stratify patients for clinical trials. It achieves greater homogeneity of the study cohort relative to age-based inclusion and provides an evidence-based approach for establishing inclusion/exclusion criteria.
Active Biomarker Projects
- Calbindin D is elevated in NPC1 cats and normalizes after treatment with2-hydroxypropyl-b-cyclodextrin. Additionally, analysis of CFS from patients with NPC disease were significantly higher than patients that were unaffected. (Bradbury et al 2016)
- FABP3 showed decreased expression in CSF in miglustat treated groups vs. untreated. Additionally, FABP3 levels decreased in patients when treated 2-hydroxypropyl-b-cyclodextrin vs. untreated. (Ory et al 2017)
- GPNMB was shown to be upregulated in NPC mice and patients (Bradbury et al 2016) . It is now being investigated as part of a multi-omic approach to address the genetic architecture of NPC1 disease. The Pavan group completed a transcriptome analysis using 43 primary NPC1 patient-derived fibroblasts from an NIH-cohort study where extensive clinical data was obtained regarding the natural history of the disease. Initial transcriptome analysis of this dataset demonstrated a set of 107 genes that were significantly upregulated in patient samples and subsequently downregulated in response to 2-hydroxypropyl-b-cyclodextrin treatment. From this, screen the Pavan group identified GPNMB, glycoprotein nonmetastatic melanoma protein B also known as DC-Hil/Osteoactivin. They also demonstrated that it is associated with lysosomal dysfunction in the context of NPC disease in a mouse model.
- Previous studies have shown that abnormal accumulation and recycling of glycosphingolipids, glycoproteins, and oligosaccharides were well established in NPC disease. Using targeted metabolomic screening, they found that six complex oligosaccharides were significantly elevated in cerebral spinal fluid (CSF) from NPC1 patients.
- Please submit additional ongoing projects to Sean Kassen.
Additional Potential Biomarkers
Other Potential Biomarkersthat have been identified but have yet to show their effectiveness as a reliable biomarker:
- Tau protein
- glutathione S-transferase
- superoxide dismutase
- fatty acid binding protein 3
- interleukin (IL)-3
- chemokine ligand 5,
- chemokine ligand 3
- cathepsin D
- lipids including monohexosylceramides ceramides, sphingoid bases, GM1 and GM3 gangliosides