Fostering collaborative research for rare genetic disease: The example of Niemann-Pick type C disease

Rare disease represents one of the most significant issues facing the medical community and health care providers worldwide, yet the majority of these disorders never emerge from their obscurity, drawing little attention from the medical community or the pharmaceutical industry. The challenge therefore is how best to mobilize rare disease stakeholders to enhance basic, translational and clinical research to advance understanding of pathogenesis and accelerate therapy development. Here we describe a rare, fatal brain disorder known as Niemann-Pick type C (NPC) and an innovative research collaborative known as Support of Accelerated Research for NPC (SOAR-NPC) which illustrates one pathway through which knowledge of a rare disease and its possible treatments are being successfully advanced. Use of the “SOAR” mechanism, we believe, offers a blueprint for similar advancement for many other rare disorders

Global Analysis of Predicted G Protein-Coupled Receptor Genes in the Filamentous Fungus, Neurospora crassa.

G protein-coupled receptors (GPCRs) regulate facets of growth, development, and environmental sensing in eukaryotes, including filamentous fungi. The largest predicted GPCR class in these organisms is the Pth11-related, with members similar to a protein required for disease in the plant pathogen Magnaporthe oryzae. However, the Pth11-related class has not been functionally studied in any filamentous fungal species. Here, we analyze phenotypes in available mutants for 36 GPCR genes, including 20 Pth11-related, in the model filamentous fungus Neurospora crassa. We also investigate patterns of gene expression for all 43 predicted GPCR genes in available datasets. A total of 17 mutants (47%) possessed at least one growth or developmental phenotype. We identified 18 mutants (56%) with chemical sensitivity or nutritional phenotypes (11 uniquely), bringing the total number of mutants with at least one defect to 28 (78%), including 15 mutants (75%) in the Pth11-related class. Gene expression trends for GPCR genes correlated with the phenotypes observed for many mutants and also suggested overlapping functions for several groups of co-transcribed genes. Several members of the Pth11-related class have phenotypes and/or are differentially expressed on cellulose, suggesting a possible role for this gene family in plant cell wall sensing or utilization

Niemann-Pick C1 Is Essential for Ebolavirus Replication and Pathogenesis In Vivo

ABSTRACT Recent work demonstrated that the Niemann-Pick C1 (NPC1) protein is an essential entry receptor for filoviruses. While previous studies focused on filovirus entry requirements of NPC1 in vitro, its roles in filovirus replication and pathogenesis in vivo remain unclear. Here, we evaluated the importance of NPC1, and its partner in cholesterol transport, NPC2, by using a mouse model of Ebolavirus (EBOV) disease. We found that, whereas wild-type mice had high viral loads and succumbed to EBOV infection, Npc1−/− mice were entirely free of viral replication and completely protected from EBOV disease. Interestingly, Npc1+/− mice transiently developed high levels of viremia, but were nevertheless substantially protected from EBOV challenge. We also found Npc2−/− mice to be fully susceptible to EBOV infection, while Npc1−/− mice treated to deplete stored lysosomal cholesterol remained completely resistant to EBOV infection. These results provide mechanistic evidence that NPC1 is directly required for EBOV infection in vivo, with little or no role for NPC1/NPC2-dependent cholesterol transport. Finally, we assessed the in vivo antiviral efficacies of three compounds known to inhibit NPC1 function or NPC1-glycoprotein binding in vitro. Two compounds reduced viral titers in vivo and provided a modest, albeit not statistically significant, degree of protection. Taken together, our results show that NPC1 is critical for replication and pathogenesis in animals and is a bona fide target for development of antifilovirus therapeutics. Additionally, our findings with Npc1+/− mice raise the possibility that individuals heterozygous for NPC1 may have a survival advantage in the face of EBOV infection

X-linked Angelman-like syndrome caused by Slc9a6 knockout in mice exhibits evidence of endosomal–lysosomal dysfunction

Mutations in solute carrier family 9 isoform 6 on chromosome Xq26.3 encoding sodium–hydrogen exchanger 6, a protein mainly expressed in early and recycling endosomes are known to cause a complex and slowly progressive degenerative human neurological disease. Three resulting phenotypes have so far been reported: an X-linked Angelman syndrome-like condition, Christianson syndrome and corticobasal degeneration with tau deposition, with each characterized by severe intellectual disability, epilepsy, autistic behaviour and ataxia. Hypothesizing that a sodium–hydrogen exchanger 6 deficiency would most likely disrupt the endosomal–lysosomal system of neurons, we examined Slc9a6 knockout mice with tissue staining and related techniques commonly used to study lysosomal storage disorders. As a result, we found that sodium–hydrogen exchanger 6 depletion leads to abnormal accumulation of GM2 ganglioside and unesterified cholesterol within late endosomes and lysosomes of neurons in selective brain regions, most notably the basolateral nuclei of the amygdala, the CA3 and CA4 regions and dentate gyrus of the hippocampus and some areas of cerebral cortex. In these select neuronal populations, histochemical staining for β-hexosaminidase activity, a lysosomal enzyme involved in the degradation of GM2 ganglioside, was undetectable. Neuroaxonal dystrophy similar to that observed in lysosomal disease was observed in the cerebellum and was accompanied by a marked and progressive loss of Purkinje cells, particularly in those lacking the expression of Zebrin II. On behavioural testing, Slc9a6 knockout mice displayed a discrete clinical phenotype attributable to motor hyperactivity and cerebellar dysfunction. Importantly, these findings show that sodium–hydrogen exchanger 6 loss of function in the Slc9a6-targeted mouse model leads to compromise of endosomal–lysosomal function similar to lysosomal disease and to conspicuous neuronal abnormalities in specific brain regions, which in concert could provide a unified explanation for the cellular and clinical phenotypes in humans with SLC9A6 mutations

Chronic Cyclodextrin Treatment of Murine Niemann-Pick C Disease Ameliorates Neuronal Cholesterol and Glycosphingolipid Storage and Disease Progression

BACKGROUND:Niemann-Pick type C (NPC) disease is a fatal neurodegenerative disorder caused most commonly by a defect in the NPC1 protein and characterized by widespread intracellular accumulation of unesterified cholesterol and glycosphingolipids (GSLs). While current treatment therapies are limited, a few drugs tested in Npc1(-/-) mice have shown partial benefit. During a combination treatment trial using two such compounds, N-butyldeoxynojirimycin (NB-DNJ) and allopregnanolone, we noted increased lifespan for Npc1(-/-) mice receiving only 2-hydroxypropyl-beta-cyclodextrin (CD), the vehicle for allopregnanolone. This finding suggested that administration of CD alone, but with greater frequency, might provide additional benefit. METHODOLOGY/PRINCIPAL FINDINGS:Administration of CD to Npc1(-/-) mice beginning at either P7 or P21 and continuing every other day delayed clinical onset, reduced intraneuronal cholesterol and GSL storage as well as free sphingosine accumulation, reduced markers of neurodegeneration, and led to longer survival than any previous treatment regime. We reasoned that other lysosomal diseases characterized by cholesterol and GSL accumulation, including NPC disease due to NPC2 deficiency, GM1 gangliosidosis and mucopolysaccharidosis (MPS) type IIIA, might likewise benefit from CD treatment. Treated Npc2(-/-) mice showed benefits similar to NPC1 disease, however, mice with GM1 gangliosidosis or MPS IIIA failed to show reduction in storage. CONCLUSIONS/SIGNIFICANCE:Treatment with CD delayed clinical disease onset, reduced intraneuronal storage and secondary markers of neurodegeneration, and significantly increased lifespan of both Npc1(-/-) and Npc2(-/-) mice. In contrast, CD failed to ameliorate cholesterol or glycosphingolipid storage in GM1 gangliosidosis and MPS IIIA disease. Understanding the mechanism(s) by which CD leads to reduced neuronal storage may provide important new opportunities for treatment of NPC and related neurodegenerative diseases characterized by cholesterol dyshomeostasis

Gene therapy for the treatment of Niemann-Pick disease type C1: Comparison of AAV9 to a novel serotype, AAV-PHP.B

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Gene therapy for the treatment of Niemann-Pick disease type C1: Comparison of AAV9 to a novel serotype, AAV-PHP.B

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Seawater carbonate chemistry and macromolecular data of diatoms

Primary production in the Southern Ocean is dominated by diatom-rich phytoplankton assemblages, whose individual physiological characteristics and community composition are strongly shaped by the environment, yet knowledge on how diatoms allocate cellular energy in response to ocean acidification (OA) is limited. Understanding such changes in allocation is integral to determining the nutritional quality of diatoms and the subsequent impacts on the trophic transfer of energy and nutrients. Using synchrotron-based Fourier transform infrared microspectroscopy, we analysed the macromolecular content of selected individual diatom taxa from a natural Antarctic phytoplankton community exposed to a gradient of fCO2 levels (288–1263 µatm). Strong species-specific differences in macromolecular partitioning were observed under OA. Large taxa showed preferential energy allocation towards proteins, while smaller taxa increased both lipid and protein stores at high fCO2. If these changes are representative of future Antarctic diatom physiology, we may expect a shift away from lipid-rich large diatoms towards a community dominated by smaller taxa, but with higher lipid and protein stores than their present-day contemporaries, a response that could have cascading effects on food web dynamics in the Antarctic marine ecosystem

Enhanced Efficacy of Gene Therapy Treatment for Niemann-Pick C1 Disease Using a Novel Serotype, AAV-PHP.B

Accessing the central nervous system (CNS) continues to present a challenge when developing therapies for the treatment of neurological diseases. Overcoming the barrier of gene transfer to brains of animals and patients from systemic circulation has been difficult. Recent advances using Cre recombination-based adeno-associated virus (AAV) targeted evolution (CREATE) has yielded a promising new serotype, AAV-PHP.B, with greater transduction than AAV9 in the adult mouse CNS after systemic delivery. Here we show systemic delivery of a therapeutic AAV-PHP.B vector outperforms the naturally occurring AAV9 in treatment of a murine model of a rare lysosomal storage disorder, Niemann-Pick C1 (NPC1) disease. Approximately 95% of patients have a mutation in NPC1 which results in either absence or a significant reduction in functional NPC1, a lysosomal transmembrane protein involved in cholesterol transport. NPC1 pathology involves lysosomal accumulation of unesterified cholesterol and other lipids. Patients typically present with neurological symptoms and visceral complications including hepatosplenomegaly. Disease progression in the null mouse model of NPC1 (Npc1-/-) is characterized by weight loss, ataxia, and early death. Results: We previously reported that systemic delivery of an AAV9 vector expressing the human NPC1 gene under transcriptional control of a ubiquitous promoter (EF1a) improved lifespan and ameliorated disease phenotype of Npc1-/- mice. Using a similar study design, we find that an otherwise identical AAV-PHP.B vector improved lifespan in Npc1-/- mice more effectively than an AAV9 vector