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.

Npc1 gene mutation abnormally activates the classical Wnt signalling pathway in mouse kidneys and promotes renal fibrosis.

Niemann-Pick disease type C1 (NPC1) is a lysosomal lipid storage disease caused by NPC1 gene mutation. Our previous study found that, compared with wild-type (Npc1+/+ ) mice, the renal volume and weight of Npc1 gene mutant (Npc1-/- ) mice were significantly reduced. We speculate that Npc1 gene mutations may affect the basic structure of the kidneys of Npc1-/- mice, and thus affect their function. Therefore, we randomly selected postnatal Day 28 (P28) and P56 Npc1+/+ and Npc1-/- mice, and observed the renal structure and pathological changes by haematoxylin-eosin staining. The level of renal fibrosis was detected by immunofluorescence histochemical techniques, and western blotting was used to detect the expression levels of apoptosis-related proteins and canonical Wnt signalling pathway related proteins. The results showed that compared with Npc1+/+ mice, the kidneys of P28 and P56 Npc1-/- mice underwent apoptosis and fibrosis; furthermore, there were obvious vacuoles in the cytoplasm of renal tubular epithelial cells of P56 Npc1-/- mice, the cell bodies were loose and foam-like, and the canonical Wnt signalling pathway was abnormally activated. These results showed that Npc1 gene mutation can cause pathological changes in the kidneys of mice. As age increased, vacuoles developed in the cytoplasm of renal tubular epithelial cells, and apoptosis of renal cells, abnormal activation of the Wnt signalling pathway, and promotion of renal fibrosis increased.

Possible genotype-phenotype correlations in Niemann-Pick type C patients and miglustat treatment.

BACKGROUND AND PURPOSE: Niemann-Pick type C is a rare lysosomal storage disease caused by impaired intracellular cholesterol transport. The autosomal recessive disease is caused by mutations in NPC1 or NPC2 genes. METHODS: Clinical-laboratory features, genotype-phenotype correlation and miglustat treatment response of our patients diagnosed with early infantile Niemann-Pick type C were evaluated. RESULTS: In this article, four Niemann-Pick type C patients diagnosed in the early infantile period are presented. Common features of our patients were hepatomegaly, splenomegaly, cholestasis and retardation in motor development. Patients 1 and 2 are twins, with homozygous mutation c.2776G>A p.(Ala926Thr) in NPC1 gene and severe lung involvement. Lung involvement, which is mostly associated with NPC2 gene mutation in the literature, was severe in our patients and they died early. In patients 3 and 4, there were respectively c.2972del p.(Gln991Argfs*6) mutation in NPC1 gene and c.133C>T p.(Gln45*) homozygous mutation in NPC2 gene. In these two patients, improvement in neurological findings were observed with treatment of miglustat. CONCLUSION: In our twin patients, severe lung involvement was observed. Two of our four early infantile Niemann-Pick type C patients exhibited neurological gains with miglustat treatment.

Ultrastructure of spinal anterior horn cells in human Niemann-Pick type C (NPC) patient and mouse model of NPC with retroposon insertion in NPC1 genes.

Niemann-Pick disease type C (NPC) is a neurovisceral lipid-storage disease. Although NPC patients show lipid storage in anterior horn cells of the spinal cord, little information is available regarding the electron microscopic analyses of the morphologies of intra-endosomal lipid like-materials in the anterior horn cells of NPC patients. In this study, we elucidated the intra-endosomal ultrastructures in spinal anterior horn cells in an NPC patient, as well as in mutant BALB/c NPC1-/- mice with a retroposon insertion in the NPC1 gene. These morphologies were classified into four types: vesicle, multiple concentric sphere (MCS), membrane, and rose flower. The percentages of the composition in the NPC patient and NPC1-/- mice were: vesicle (55.5% and 14.9%), MCS (15.7% and 3.4%), membrane (23.6% and 57.1%), and rose flower (5.2% and 24.6%), respectively. Formation of the intra-endosomal structures could proceed as follows: (i) a vesicle or MCS buds off the endosome into the lumen; (ii) when a vesicle breaks down, a membrane is formed; and (iii) after an MCS breaks down, a rose flower structure is formed. Our new finding in this study is that ultrastructural morphology is the same between the NPC patient and NPC1-/- mice, although there are differences in the composition.

Diagnostic tests for Niemann-Pick disease type C (NP-C): A critical review.

Niemann-Pick disease type C (NP-C) is a neurovisceral lysosomal cholesterol trafficking and lipid storage disorder caused by mutations in one of the two genes, NPC1 or NPC2. Diagnosis has often been a difficult task, due to the wide range in age of onset of NP-C and clinical presentation of the disease, combined with the complexity of the cell biology (filipin) laboratory testing, even in combination with genetic testing. This has led to substantial delays in diagnosis, largely depending on the access to specialist centres and the level of knowledge about NP-C of the physician in the area. In recent years, advances in mass spectrometry has allowed identification of several sensitive plasma biomarkers elevated in NP-C (e.g. cholestane-3ß,5α,6ß-triol, lysosphingomyelin isoforms and bile acid metabolites), which, together with the concomitant progress in molecular genetic technology, have greatly impacted the strategy of laboratory testing. Specificity of the biomarkers is currently under investigation and other pathologies are being found to also result in elevations. Molecular genetic testing also has its limitations, notably with unidentified mutations and the classification of new variants. This review is intended to increase awareness on the currently available approaches to laboratory diagnosis of NP-C, to provide an up to date, comprehensive and critical evaluation of the various techniques (cell biology, biochemical biomarkers and molecular genetics), and to briefly discuss ongoing/future developments. The use of current tests in proper combination enables a rapid and correct diagnosis in a large majority of cases. However, even with recent progress, definitive diagnosis remains challenging in some patients, for whom combined genetic/biochemical/cytochemical markers do not provide a clear answer. Expertise and reference laboratories thus remain essential, and further work is still required to fulfill unmet needs.

Niemann-Pick disease type C1 predominantly involving the frontotemporal region, with cortical and brainstem Lewy bodies: an autopsy case.

Niemann-Pick disease type C (NPC) is an autosomal recessive neurovisceral lipid storage disorder. Two disease-causing genes (NPC1 and NPC2) have been identified. NPC is characterized by neuronal and glial lipid storage and NFTs. Here, we report a man with juvenile-onset progressive neurological deficits, including pyramidal signs, ataxia, bulbar palsy, vertical supranuclear ophthalmoplegia, and psychiatric symptoms; death occurred at age 37 before definitive clinical diagnosis. Post mortem gross examination revealed a unique distribution of brain atrophy, predominantly in the frontal and temporal lobes. Microscopically, lipid storage in neurons and widely distributed NFTs were observed. Lipid storage cells appeared in systemic organs and filipin staining indicated intracellular cholesterol accumulation in hepatic macrophages. Electron microscopy revealed accumulation of lipids and characteristic oligolamellar inclusions. These findings suggested an NPC diagnosis. Neuronal loss and gliosis were frequently accompanied by NFTs and occurred in the frontal and temporal cortices, hippocampus, amygdala, basal forebrain, basal ganglia, thalamus, substantia nigra and brain stem nuclei. Lewy bodies (LBs) were observed in most, but not all, regions where NFTs were evident. In contrast, neuronal lipid storage occurred in more widespread areas, including the parietal and occipital cortices where neurodegeneration with either NFTs or LBs was minimal. Molecular genetic analysis demonstrated that the patient had compound heterozygous mutations in the cysteine-rich loop (A1017T and Y1088C) of the NPC1 gene. To our knowledge there has been no previous report of the A1017T mutation. The pathological features of this patient support the notion that NPC has an aspect of α-synucleinopathy, and long-term survivors of NPC may develop a frontotemporal-predominant distribution of brain atrophy.

Clinical presentation and molecular genetics of Iranian patients with Niemann-pick type C disease and report of 6 NPC1 gene novel variants: A case series.

Niemann Pick Type C disease is a rare and progressive neurodegenerative lysosomal storage disorder caused by autosomal recessive mutations in the NPC1 and NPC2 genes. It is characterized by the accumulation of multiple lipid species in the endolysosomal compartment, leading to neurodegeneration and involvement of the liver, spleen, and lungs. Niemann Pick Type C has a wide range of presentations and severities at different ages with different progression rates. According to the Human Gene Mutation Database, to date, 486 disease-causing mutations in the highly polymorphic NPC1 gene and >20 mutations in the NPC2 have been reported. In the present study, we described the clinical, biochemical, and molecular profiles of 18 Iranian patients with Niemann-Pick Type C disease. Also, we describe six novel variants of the NPC1 gene, to our knowledge, not reported to date.

Identification of mutation in NPC2 by exome sequencing results in diagnosis of Niemann-Pick disease type C.

We report identification of a homozygous mutation in NPC2 in two Iranian siblings with a neurologic dysfunction whose disease had not been diagnosed prior to our genetic analysis. The mutation was identified by exome sequencing. The finding resulted in diagnosis of Niemann-Pick disease type C (NPC) in the siblings, and initiation of treatment with Miglustat. The clinical features of the patients are presented. It has been suggested that NPC is under diagnosed, particularly when presentations are not very severe, as was the situation in the cases studied here. NPC is a fatal autosomal recessive disorder clinically characterized by hepatosplenomegaly and progressive neurological deterioration. At the cellular level, it causes aberrant cholesterol trafficking and accumulation of unesterified cholesterol in lysosomes. Mutations in NPC1 and NPC2 are cause of disease in respectively, 95% and 5% of NPC patients. The p.Pro120Ser causing mutation in NPC2 observed in the Iranian patients was earlier observed in the only other NPC2 patient reported from the Middle East. The study demonstrates that in addition to greatly facilitating gene discovery, exome sequencing has notable potentials for diagnosis, particularly for diagnosis of atypical cases.

Challenges in the Definitive Diagnosis of Niemann-Pick Type C-Leaky Variants and Alternative Transcripts.

Niemann-Pick type C (NPC, ORPHA: 646) is a neuro-visceral, psychiatric disease caused predominantly by pathogenic variants in the NPC1 gene or seldom in NPC2. The rarity of the disease, and its wide range of clinical phenotypes and ages of onset, turn the diagnosis into a significant challenge. Other than the detailed clinical history, the typical diagnostic work-up for NPC includes the quantification of pathognomonic metabolites. However, the molecular basis diagnosis is still of utmost importance to fully characterize the disorder. Here, the authors provide an overview of splicing variants in the NPC1 and NPC2 genes and propose a new workflow for NPC diagnosis. Splicing variants cover a significant part of the disease-causing variants in NPC. The authors used cDNA analysis to study the impact of such variants, including the collection of data to classify them as leaky or non-leaky pathogenic variants. However, the presence of naturally occurring spliced transcripts can misdiagnose or mask a pathogenic variant and make the analysis even more difficult. Analysis of the NPC1 cDNA in NPC patients in parallel with controls is vital to assess and detect alternatively spliced forms. Moreover, nonsense-mediated mRNA decay (NMD) analysis plays an essential role in evaluating the naturally occurring transcripts during cDNA analysis and distinguishing them from other pathogenic variants' associated transcripts.

Niemann-Pick type C disease with a novel intronic mutation: three Turkish cases from the same family.

OBJECTIVES: Niemann-Pick type C (NPC) disease is a rare progressive neurodegenerative condition that is characterized by the accumulation of cholesterol, glycosphingolipids, and sphingosine in lysosomes. Patients have various systemic and neurological findings depending on their age at onset. This disease is caused by the autosomal recessive transmission of mutations in the NPC1 and NPC2 genes; patients have mutations mainly in the NPC1 gene (95%) and the majority of them are point mutations located in the exonic regions. CASE PRESENTATION: Here, we presented three cousins with hepatosplenomegaly and progressive neurodegeneration who were diagnosed with visceral-neurodegenerative NPC disease. Their parents were relatives, and they had a history of sibling death with similar complaints. Bone marrow smear showed foamy cells in patient 1. Vertical supranuclear gaze palsy was not present in all cases. Sphingomyelinase (SM) activities were almost normal to exclude NPA or NPB. Filipin staining was performed in patient 2 and showed a massive accumulation of unesterified cholesterol The NPC1 gene analysis of the three patients showed a novel homozygous c.1553+5G>A intronic mutation. cDNA analysis was performed from the patient 3 and both parents. It was observed that exon 9 was completely skipped in the homozygous mutant baby. Both the normal and the exon 9-skipped transcripts have been detected in the parents. CONCLUSIONS: When combined with the filipin staining and the patients' clinical outcomes, this mutation is likely to be deleterious. Moreover, cDNA sequencing supports the pathogenicity of this novel variant.

Favorable outcomes following early onset oral miglustat in early infantile Niemann Pick Type C.

Niemann-Pick disease Type C (NPC) is a rare autosomal recessive neurovisceral lysosomal disorder. Perinatal and early infantile onset NPC are the most severe types of the disease. Early infantile type is characterized by a rapidly progressive neurodegenerative course, which entails significant morbidity and usually results in death within 5 years. Miglustat, an iminosugar that selectively inhibits the glycosylceramide synthase enzyme, is known to stabilize or delay neurological progression in individuals with NPC, but its impact on affected infants is yet to be elucidated. We present two siblings with early infantile NPC due to the previously reported devastating homozygous mutation c.2279_2281delTCT in NPC1. Their considerably discrepant neurological disease courses were dependent on the timing of initiation of miglustat treatment. The outcomes support the significant role of early treatment with miglustat in the disease course of early infantile NPC and suggest that therapy should be considered even before the occurrence of neurological involvement. Moreover, this report emphasizes the importance of early diagnosis, in light of the availability of a potential disease-modifying medication.

Niemann-Pick Disease Type C: Mutation Spectrum and Novel Sequence Variations in the Human NPC1 Gene.

Niemann-Pick type C (NP-C) is a rare autosomal recessive disorder characterized by storage of unesterified glycolipids and cholesterol in lysosome and/or late endosome due to mutations in either NPC1 or NPC2 gene. This study aims to identify the spectrum of sequence alterations associated to NP-C in individuals with clinical suspicion of this disease. The entire coding region and flanking sequences of both genes associated to NP-C were evaluated in a total of 265 individuals that were referred to our laboratory. Clinical and/or biochemical suspicion of NP-C was confirmed by molecular analysis in 54 subjects. In this cohort, 33 different sequence alterations were identified in NPC1 and one in NPC2. Among those, 5 novel alterations in NPC1 gene were identified as follows: one deletion (p.Lys38_Tyr40del), one frameshift (p.Asn195Lysfs*2), and three missense mutations (p.Cys238Arg, p.Ser365Pro and, p.Val694Met) that are likely to be pathogenic through different approaches, including in silico tools as well as multiple sequence alignment throughout different species. We have also reported main clinical symptoms of patients with novel alterations and distribution of frequent symptoms in the cohort. Findings reported here contribute to the knowledge of mutation spectrum of NP-C, defining frequent mutations as well as novel sequence alterations associated to the disease.

Role of Niemann-Pick Type C Disease Mutations in Dementia.

BACKGROUND: Several neurological and systemic diseases can cause dementia, beyond Alzheimer's disease. Rare genetic causes are often responsible for dementia with atypical features. Recently, mutations causative for Niemann-Pick type C disease (NPC) have also been implicated in neurodegenerative diseases. NPC is an autosomal recessive lipid storage disorder caused by mutations in NPC1 and NPC2 genes. In adults, clinical presentation mimicking other neurodegenerative diseases makes diagnosis difficult. Recent evidence suggests that heterozygous mutations in NPC genes may take on etiological significance. OBJECTIVE: To investigate the presence of NPC1 and NPC2 mutations in adults affected by neurodegenerative dementia plus. METHODS: We performed a genetic screening on 50 patients using a wide clinical and biochemical approach to characterize the phenotype of mutated patients. RESULTS: Sequencing analysis revealed four different and known heterozygous mutations in NPC1 and NPC2 genes. Patient 1 carried the p. F284LfsX26 in NPC1 and was affected by progressive supranuclear palsy-like syndrome. The remaining three patients showed a corticobasal syndrome and harbored the c.441+1G>A variant of NPC2 (patient 2), the missense p.N222 S mutation associated with the c.1947+8G>C variant in the splice region of intron 12 in NPC1 (patient 3), and the p.V30M mutation in NPC2 (patient 4), respectively. Filipin staining was abnormal in patients 1 and 2. mRNA analysis revealed an altered splicing of the NPC2 gene in patient 2. CONCLUSIONS: Heterozygous mutations of NPC1 and NPC2 genes could contribute to dementia plus, at least in a subset of patients. We highlight the occurrence of NPC1 and NPC2 heterozygous variants in dementia-plus as pathological event.

Adult-Onset Niemann-Pick Disease Type C: Rapid Treatment Initiation Advised but Early Diagnosis Remains Difficult.

Niemann-Pick type C disease (NP-C) presents with heterogeneous neurological and psychiatric symptoms. Adult onset is rare and possibly underdiagnosed due to frequent lack of specific and obvious key symptoms. For both early and adolescent/adult onset, the available data from studies and case reports describe a positive effect of Miglustat (symptom relief or stabilization). However, due to the low frequency of NP-C, experience with this therapy is still limited. We describe two adult-onset cases of NP-C. In both cases, vertical supranuclear gaze palsy was not recognized at symptom onset. Correct diagnosis was delayed from onset of symptoms by more than 10 years. The video demonstrates the broad spectrum of symptoms in later stages of the disease. Compared with published data, the treatment outcome observed in our cases after delayed initiation of Miglustat therapy was disappointing, with continuing disease progression in both cases. Thus, early treatment initiation could be necessary to achieve a good symptomatic effect. Hence, early biochemical testing for NP-C should be considered in patients suffering from atypical neurological/neuropsychological and psychiatric symptoms, even in cases of uncertainty.

Identification of bovine NPC1 gene cSNPs and their effects on body size traits of Qinchuan cattle.

NPC1 gene is an important gene closely related to the Niemann-Pick type C (NPC). Mutations in the NPC1 gene tend to cause Niemann-Pick type C, a lysosomal storage disorder. Previous studies have shown that NPC1 protein plays an important role in subcellular lipid transport, homeostasis, platelet function and formation, which are basic metabolic activities in the process of development. In this study, to explore the association between the NPC1 gene variation and body size traits in Qinchuan cattle, we detected four novel coding single nucleotide polymorphisms (cSNPs) in the bovine NPC1 gene, including one missense mutation (SNP1) and three synonymous mutations (SNP2, SNP3 and SNP4). Population genetic analyses of 518 individuals and association correlations between cSNPs and bovine body size traits were conducted in this research. A missense mutation at SNP1 locus was found to be significantly related to the heart girth, hip width and body weight (P<0.01 or P<0.05, 3.5-year-old). Two synonymous mutations at SNP2 and SNP3 loci also showed significant effects on hip width (P<0.05, 3.5-year-old). One synonymous mutation at SNP4 locus showed significant effect on body weight (P<0.05, 2.0-year-old). Combined haplotypes H2H6 and H6H6 showed significant effects on body size traits such as heart girth, hip width, and body weight (3.5-year-old, P<0.01 or P<0.05). This study provides evidence that the NPC1 gene might be involved in the regulation of bovine growth and body development, and may be considered as a candidate gene for marker assisted selection (MAS) in beef cattle breeding industry.

Niemann-Pick disease type C: a case series of Brazilian patients / Doenca de Niemann-Pick tipo C: serie de casos de pacientes brasileiros

The aim of the study was to analyze a series of Brazilian patients with Niemann-Pick disease type C (NP-C). Method Correlations between clinical findings, laboratory data, molecular findings and treatment response are presented. Result The sample consisted of 5 patients aged 8 to 26 years. Vertical supranuclear gaze palsy, cerebellar ataxia, dementia, dystonia and dysarthria were present in all cases. Filipin staining showed the “classical” pattern in two patients and a “variant” pattern in three patients. Molecular analysis found mutations in the NPC1 gene in all alleles. Miglustat treatment was administered to 4 patients. Conclusion Although filipin staining should be used to confirm the diagnosis, bone marrow sea-blue histiocytes often help to diagnosis of NP-C. The p.P1007A mutation seems to be correlated with the “variant” pattern in filipin staining. Miglustat treatment response seems to be correlated with the age at disease onset and disability scale score at diagnosis. .

O objetivo desse estudo foi analisar uma série de casos de pacientes brasileiros com doença de Niemann-Pick tipo C (NP-C). Método Correlação entre manifestações clínicas, alterações laboratoriais, estudo molecular e resposta ao tratamento foram realizadas. Resultado A amostra consiste de 5 pacientes com idade entre 8 e 26 anos. Paralisia do olhar vertical supranuclear, ataxia cerebelar, demência, distonia e disartria estavam presentes em todos os casos. Coloração de filipina na cultura de fibroblastos mostrou padrão “clássico” em dois pacientes e padrão “variante” em três casos. O estudo molecular encontrou mutações no gene NPC1 em todos os alelos. O tratamento com miglustate foi realizado em 4 pacientes. Conclusão Embora coloração de filipina seja utilizada para confirmar o diagnóstico, o histiócito azul-marinho no aspirado de medula óssea frequentemente auxilia a confirmar o diagnóstico de NP-C. A mutação p.P1007A está correlacionada com o padrão “ variante” na coloração de filipina. A resposta ao tratamento com miglustate parece estar correlacionada com a idade e escore de desabilidade no momento do diagnóstico. .