Novel NPC1 mutations with different segregation in two related Greek patients with Niemann-Pick type C disease: molecular study in the extended pedigree and clinical correlations

Overview of clinical, molecular, and therapeutic features of Niemann-Pick disease (types A, B, and C): Focus on therapeutic approaches

Niemann-Pick disease (NPD) is another type of metabolic disorder that is classified as lysosomal storage diseases (LSDs). The main cause of the disease is mutation in the SMPD1 (type A and B) or NPC1 or NPC2 (type C) genes, which lead to the accumulation of lipid substrates in the lysosomes of the liver, brain, spleen, lung, and bone marrow cells. This is followed by multiple cell damage, dysfunction of lysosomes, and finally dysfunction of body organs. So far, about 346, 575, and 30 mutations have been reported in SMPD1, NPC1, and NPC2 genes, respectively. Depending on the type of mutation and the clinical symptoms of the disease, the treatment will be different. The general aim of the current study is to review the clinical and molecular characteristics of patients with NPD and study various treatment methods for this disease with a focus on gene therapy approaches.

Novel compound heterozygous mutations of the NPC1 gene associated with Niemann-pick disease type C: a case report and review of the literature

BACKGROUND

Niemann-Pick Disease type C is a fatal autosomal recessive lipid storage disorder caused by NPC1 or NPC2 gene mutations and characterized by progressive, disabling neurological deterioration and hepatosplenomegaly. Herein, we identified a novel compound heterozygous mutations of the NPC1 gene in a Chinese pedigree.

CASE PRESENTATION

This paper describes an 11-year-old boy with aggravated walking instability and slurring of speech who presented as Niemann-Pick Disease type C. He had the maternally inherited c.3452 C > T (p. Ala1151Val) mutation and the paternally inherited c.3557G > A (p. Arg1186His) mutation using next-generation sequencing. The c.3452 C > T (p. Ala1151Val) mutation has not previously been reported.

CONCLUSIONS

This study predicted that the c.3452 C > T (p. Ala1151Val) mutation is pathogenic. This data enriches the NPC1 gene variation spectrum and provides a basis for familial genetic counseling and prenatal diagnosis.

Mass spectrometry-based proteomics in neurodegenerative lysosomal storage disorders

The major function of the lysosome is to degrade unwanted materials such as lipids, proteins, and nucleic acids; therefore, deficits of the lysosomal system can result in improper degradation and trafficking of these biomolecules. Diseases associated with lysosomal failure can be lethal and are termed lysosomal storage disorders (LSDs), which affect 1 in 5000 live births collectively. LSDs are inherited metabolic diseases caused by mutations in single lysosomal and non-lysosomal proteins and resulting in the subsequent accumulation of macromolecules within. Most LSD patients present with neurodegenerative clinical symptoms, as well as damage in other organs. The discovery of new biomarkers is necessary to understand and monitor these diseases and to track therapeutic progress. Over the past ten years, mass spectrometry (MS)-based proteomics has flourished in the biomarker studies in many diseases, including neurodegenerative, and more specifically, LSDs. In this review, biomarkers of disease pathophysiology and monitoring of LSDs revealed by MS-based proteomics are discussed, including examples from Niemann-Pick disease type C, Fabry disease, neuronal ceroid-lipofuscinoses, mucopolysaccharidosis, Krabbe disease, mucolipidosis, and Gaucher disease.

Nutrition management of Niemann Pick disease type C: A case report

Objectives. We aim to report the clinical repercussions of a nutritional approach in a patient diagnosed with Niemann Pick disease type C (NPC) using miglustat as pharmacological therapy. Case report. A 33-year-old woman diagnosed with NPC using miglustat was instructed to look for a dietary management at our nutrition service. Patient's symptoms were weight loss and important gastrointestinal alterations. Our nutritional prescription was a high-calorie and high-protein, lactose- and sucrose-free diet, as well as a daily supplementation of L-glutamine, probiotics, omega 3, and coenzyme Q10. After two months, the patient had weight gain and improvement in the intestinal health. Conclusions. We found that nutritional prescription aided in the treatment of NPC and revealed that nutritional care represents an important strategy in the management of rare genetic diseases.

Niemann-Pick Disease Type C Diagnosed Using Neonatal Cholestasis Gene Panel

Niemann-Pick disease type C (NPC) is a neurovisceral lysosomal storage disorder caused by mutations in the NPC1 and NPC2 genes. These mutations cause the accumulation of unesterified cholesterol and other lipids in the lysosomes. NPC has a broad spectrum of clinical manifestations, depending on the age of onset. A 15-day-old infant presented at the Seoul National University Children's Hospital with neonatal cholestasis and hepatosplenomegaly, with the onset of jaundice at 5 days of age. Despite supportive treatment, the patient was considered for a liver transplant because of progressive liver failure. Unfortunately, the patient died from gastrointestinal bleeding before undergoing the transplant. The neonatal cholestasis gene panel revealed two novel likely pathogenic variants in the NPC1 gene (c.1145C>G [p.Ser382*] and c.2231_2233del [p.Val744del]). The patient was diagnosed with NPC, and both parents were found to be carriers of each variant. In infants presenting with neonatal cholestasis, a gene panel can help diagnose NPC.

Identification of Brain-Specific Treatment Effects in NPC1 Disease by Focusing on Cellular and Molecular Changes of Sphingosine-1-Phosphate Metabolism

Niemann-Pick type C1 (NPC1) is a lysosomal storage disorder, inherited as an autosomal-recessive trait. Mutations in the Npc1 gene result in malfunction of the NPC1 protein, leading to an accumulation of unesterified cholesterol and glycosphingolipids. Beside visceral symptoms like hepatosplenomegaly, severe neurological symptoms such as ataxia occur. Here, we analyzed the sphingosine-1-phosphate (S1P)/S1P receptor (S1PR) axis in different brain regions of Npc1^-/- mice and evaluated specific effects of treatment with 2-hydroxypropyl-β-cyclodextrin (HPβCD) together with the iminosugar miglustat. Using high-performance thin-layer chromatography (HPTLC), mass spectrometry, quantitative real-time PCR (qRT-PCR) and western blot analyses, we studied lipid metabolism in an NPC1 mouse model and human skin fibroblasts. Lipid analyses showed disrupted S1P metabolism in Npc1^-/- mice in all brain regions, together with distinct changes in S1pr3/S1PR3 and S1pr5/S1PR5 expression. Brains of Npc1^-/- mice showed only weak treatment effects. However, side effects of the treatment were observed in Npc1^+/+ mice. The S1P/S1PR axis seems to be involved in NPC1 pathology, showing only weak treatment effects in mouse brain. S1pr expression appears to be affected in human fibroblasts, induced pluripotent stem cells (iPSCs)-derived neural progenitor and neuronal differentiated cells. Nevertheless, treatment-induced side effects make examination of further treatment strategies indispensable.

Determination of the Pathological Features of NPC1 Variants in a Cellular Complementation Test

Niemann-Pick Type C (NP-C) is a rare disorder of lipid metabolism caused by mutations within the NPC1 and NPC2 genes. NP-C is a neurovisceral disease leading to a heterogeneous, multisystemic spectrum of symptoms in those affected. Until now, there is no investigative tool to demonstrate the significance of single variants within the NPC genes. Hence, the aim of the study was to establish a test that allows for an objective assessment of the pathological potential of NPC1 gene variants. Chinese hamster ovary cells defective in the NPC1 gene accumulate cholesterol in lysosomal storage organelles. The cells were transfected with NPC1-GFP plasmid vectors carrying distinct sequence variants. Filipin staining was used to test for complementation of the phenotype. The known variant p.Ile1061Thr showed a significantly impaired cholesterol clearance after 12 and 24 h compared to the wild type. Among the investigated variants, p.Ser954Leu and p.Glu1273Lys showed decelerated cholesterol clearance as well. The remaining variants p.Gln60His, p.Val494Met, and p.Ile787Val showed a cholesterol clearance indistinguishable from wild type. Further, p.Ile1061Thr acquired an enhanced clearance ability upon 25-hydroxycholesterol treatment. We conclude that the variants that caused an abnormal clearance phenotype are highly likely to be of clinical relevance. Moreover, we present a system that can be utilized to screen for new drugs.

Prevalence of antibodies to ganglioside and Hep 2 in Gaucher, Niemann - Pick type C and Sanfilippo diseases

Lysosomal Storage Diseases (LSDs) are rare genetic diseases, the majority of which are caused by specific lysosomal enzyme deficiencies and all are characterized by malfunctioning lysosomes. Lysosomes are key regulators of many different cellular processes and are vital for the function of the immune system. Several studies have shown the coexistence of LSDs and immune abnormalities. In this study, we investigated the presence of autoantibodies in the plasma of patients with Gaucher disease (GD; n = 6), Sanfilippo Syndrome B (SFB; n = 8) and Niemann - Pick type C disease (NPC; n = 5) before and following Miglustat treatment (n = 3). All were examined for antibodies to antigens of Hep-2 cells and antiganglioside antibodies (AGSA). No autoantibodies were detected in GD patients. 3/8 SFB patients showed only AGSA (2/3 IgM / IgG; 1/3 IgG), 3/8 only anti-Sm E/F and 2/8 showed both IgM / IgG or IgG AGSA and anti-Sm E/F. 3/5 NPC patients showed AGSA (2/3 IgM and IgG, 1/3 IgM) and one anti-Sm E/F and IgM AGSA. Following treatment one patient with no AGSA developed IgM AGSA and two with both IgG and IgM showed only IgG AGSA. In our study, investigating similar numbers of patients, autoantibodies were observed in NPC and SFB patients but not in GD patients. Our findings suggest that, independently of the development of an autoimmune disease in patients with LSDs, there seems to be an autoimmune activation that differs in different disorders. Further studies including more patients, also at different stages of disease and treatment, are needed in order to get further insight into the immune irregularities associated with different LSDs and their significance.