Clinical spectrum of Niemann-Pick disease type C

A Case Series on Genotype and Outcome of Liver Transplantation in Children with Niemann-Pick Disease Type C

BACKGROUND

To report on clinical presentation and outcomes of children who underwent liver transplantation (LTx) and were subsequently diagnosed to have Niemann-Pick type C (NPC).

METHODS

Retrospective, descriptive, multi-centre review of children diagnosed with NPC who underwent LTx (2003-2018). Diagnosis was made by filipin skin test or genetic testing.

RESULTS

Nine children were identified (six centres). Neonatal acute liver failure was the most common indication for LTx (seven children). Median age at first presentation: 7 days (range: 0-37). The most prevalent presenting symptoms: jaundice (8/9), hepatosplenomegaly (8/9) and ascites (6/9). 8/9 children had a LTx before the diagnosis of NPC. Genetic testing revealed mutations in NPC1 correlating with a severe biochemical phenotype in 5 patients. All 9 children survived beyond early infancy. Seven children are still alive (median follow-up time of 9 (range: 6-13) years). Neurological symptoms developed in 4/7 (57%) patients at median 9 (range: 5-13) years following LTx.

CONCLUSION

Early diagnosis of NPC continues to be a challenge and a definitive diagnosis is often made only after LTx. Neurological disease is not prevented in the majority of patients. Genotype does not appear to predict neurological outcome after LTx. LTx still remains controversial in NPC.

Molecular basis for a new bovine model of Niemann-Pick type C disease

Niemann-Pick type C disease is a lysosomal storage disease affecting primarily the nervous system that results in premature death. Here we present the first report and investigation of Niemann-Pick type C disease in Australian Angus/Angus-cross calves. After a preliminary diagnosis of Niemann-Pick type C, samples from two affected calves and two obligate carriers were analysed using single nucleotide polymorphism genotyping and homozygosity mapping, and NPC1 was considered as a positional candidate gene. A likely causal missense variant on chromosome 24 in the NPC1 gene (NM_174758.2:c.2969C>G) was identified by Sanger sequencing of cDNA. SIFT analysis, protein alignment and protein modelling predicted the variant to be deleterious to protein function. Segregation of the variant with disease was confirmed in two additional affected calves and two obligate carrier dams. Genotyping of 403 animals from the original herd identified an estimated allele frequency of 3.5%. The Niemann-Pick type C phenotype was additionally confirmed via biochemical analysis of Lysotracker Green, cholesterol, sphingosine and glycosphingolipids in fibroblast cell cultures originating from two affected calves. The identification of a novel missense variant for Niemann-Pick type C disease in Angus/Angus-cross cattle will enable improved breeding and management of this disease in at-risk populations. The results from this study offer a unique opportunity to further the knowledge of human Niemann-Pick type C disease through the potential availability of a bovine model of disease.

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.

Insights into the Molecular Mechanisms of Cholesterol Binding to the NPC1 and NPC2 Proteins

In recent years, a growing number of studies have implicated the coordinated action of NPC1 and NPC2 in intralysosomal transport and efflux of cholesterol. Our current understanding of this process developed with just over two decades of research. Since the cloning of the genes encoding the NPC1 and NPC2 proteins, studies of the biochemical defects observed when either gene is mutated along with computational and structural studies have unraveled key steps in the underlying mechanism. Here, we summarize the major contributions to our understanding of the proposed cholesterol transport controlled by NPC1 and NPC2, and briefly discuss recent findings of cholesterol binding and transport proteins beyond NPC1 and NPC2. We conclude with key questions and major challenges for future research on cholesterol transport by the NPC1 and NPC2 proteins.

Adult Niemann-Pick disease type C in France: clinical phenotypes and long-term miglustat treatment effect

Background

Niemann-Pick disease type C (NP-C) is a neurodegenerative lysosomal lipid storage disease caused by autosomal recessive mutations in the NPC1 or NPC2 genes. The clinical presentation and evolution of NP-C and the effect of miglustat treatment are described in the largest cohort of patients with adolescent/adult-onset NP-C studied to date.

Methods

Observational study based on clinical chart data from adult patients with NP-C (> 18 year old) diagnosed in France between 1990 and 2015. Retrospective data from patients at diagnosis, onset of miglustat therapy (if applicable), and last follow up were analysed.

Results

In France, patients with an adolescent-adult neurological form constituted approximately 25% of all NP-C cases diagnosed during the study period. Forty-seven patients (46 with NP-C1 and one with NP-C2; 53% female) were included. Mean ± SD (range) ages at neurological onset and diagnosis were 23.9 ± 12.5 (8–56) years and 34 ± 13.5 (15–65) years, respectively. At presentation, patients mainly had 1) impaired gait due to cerebellar ataxia and/or dystonia, 2) and/or cognitive/behavioural manifestations, 3) and/or psychotic signs. Initially, almost half of patients had only one of the above three neuro-psychiatric manifestations. Vertical supranuclear gaze palsy, usually occurring without patient complaint, was only detected on careful clinical examination and was recorded in most patients (93%) at the time of diagnosis, several years after neurological onset. Thirty-seven patients (79%) received miglustat, among whom seventeen (46%) continued beyond 2 years (at last follow up) to a maximum of 9.8 years. Eight patients (22%) discontinued treatment early due to side effects (n = 3) or perceived lack of efficacy (n = 5).Miglustat treatment duration correlated significantly with reduced neurological worsening (p < 0.001). Treatment for≥2 years was associated with improved patient survival (p = 0.029). Good responses to miglustat were associated with less severe neurological disability at the start of miglustat treatment (p = 0.02).

Conclusion

The proportion of adolescent/adult-onset NP-C cases diagnosed in France increased 2.5-fold since 2009 compared with the 2000–2008 period due to improved awareness. Adolescent/adult-onset NP-C frequently presented initially with a non-specific isolated neuro-psychiatric manifestation (motor, cognitive or psychotic). Patients with less severe neurological disability responded better to miglustat therapy.

Electronic supplementary material

The online version of this article (10.1186/s13023-018-0913-4) contains supplementary material, which is available to authorized users.

In Vivo Assessment of Neurodegeneration in Type C Niemann-Pick Disease by IDEAL-IQ

Objective

To noninvasively assess the neurodegenerative changes in the brain of patients with Niemann-Pick type C (NPC) disease by measuring the lesion tissue with the iterative decomposition of water and fat with echo asymmetry and least square estimation-iron quantification (IDEAL-IQ).

Materials and Methods

Routine brain MRI, IDEAL-IQ and ¹H-proton magnetic resonance spectroscopy (¹H-MRS, served as control) were performed on 12 patients with type C Niemann-Pick disease (4 males and 8 females; age range, 15–61 years; mean age, 36 years) and 20 healthy subjects (10 males and 10 females; age range, 20–65 years; mean age, 38 years). The regions with lesion and the normal appearing regions (NARs) of patients were measured and analyzed based on the fat/water signal intensity on IDEAL-IQ and the lipid peak on ¹H-MRS.

Results

Niemann-Pick type C patients showed a higher fat/water signal intensity ratio with IDEAL-IQ on T2 hyperintensity lesions and NARs (3.7–4.9%, p < 0.05 and 1.8–3.0%, p < 0.05, respectively), as compared to healthy controls (HCs) (1.2–2.3%). After treatment, the fat/water signal intensity ratio decreased (2.2–3.4%), but remained higher than in the HCs (p < 0.05). The results of the ¹H-MRS measurements showed increased lipid peaks in the same lesion regions, and the micro-lipid storage disorder of NARs in NPC patients was detectable by IDEAL-IQ instead of ¹H-MRS.

Conclusion

The findings of this study suggested that IDEAL-IQ may be useful as a noninvasive and objective method in the evaluation of patients with NPC; additionally, IDEAL-IQ can be used to quantitatively measure the brain parenchymal adipose content and monitor patient follow-up after treatment of NPC.

Advantages of Structure-Based Drug Design Approaches in Neurological Disorders

OBJECTIVE

The purpose of the review is to portray the theoretical concept on neurological disorders from research data.

BACKGROUND

The freak changes in chemical response of nerve impulse causes neurological disorders. The research evidence of the effort done in the older history suggests that the biological drug targets and their effective feature with responsive drugs could be valuable in promoting the future development of health statistics structure for improved treatment for curing the nervous disorders.

METHODS

In this review, we summarized the most iterative theoretical concept of structure based drug design approaches in various neurological disorders to unfathomable understanding of reported information for future drug design and development.

RESULTS

On the premise of reported information we analyzed the model of theoretical drug designing process for understanding the mechanism and pathology of the neurological diseases which covers the development of potentially effective inhibitors against the biological drug targets. Finally, it also suggests the management and implementation of the current treatment in improving the human health system behaviors.

CONCLUSION

With the survey of reported information we concluded the development strategies of diagnosis and treatment against neurological diseases which leads to supportive progress in the drug discovery.

Niemann-Pick disease, type C and Roscoe Brady

The Niemann-Pick family of diseases was poorly understood until Roscoe Brady and his colleagues began their investigations in the 1960s. Following Brady's discovery of the defect in acid sphingomyelinase in Niemann-Pick disease, types A and B, Peter Pentchev, a senior scientist in the group, launched a series of investigations of an unusual lipid storage disease in a spontaneous mouse model. These led initially to identification of the cholesterol trafficking defect in the mouse, and then in human Niemann-Pick disease, type C (NPC). This discovery formed the basis of the standard diagnostic test for NPC for the next three decades. Subsequently, an international collaboration was established, based at the Brady lab at NIH, which culminated in discovery of the NPC1 gene. Roscoe Brady, Peter Pentchev and their colleagues defined and refined the clinical biochemical and pathological phenotypes of NPC in a series of elegant parallel studies. They also identified abnormal oxysterols in NPC; later work has proved such compounds to be sensitive biomarkers of the disease. The dedication of the Brady lab to NPC, and the discoveries that flowed therefrom, provided critical foundations for the current explosion of progress in this disease.

Disorders in the initial steps of steroid hormone synthesis

Steroidogenesis begins with cellular internalization of low-density lipoprotein particles and subsequent intracellular processing of cholesterol. Disorders in these steps include Adrenoleukodystrophy, Wolman Disease and its milder variant Cholesterol Ester Storage Disease, and Niemann-Pick Type C Disease, all of which may present with adrenal insufficiency. The means by which cholesterol is directed to steroidogenic mitochondria remains incompletely understood. Once cholesterol reaches the outer mitochondrial membrane, its delivery to the inner mitochondrial membrane is regulated by the steroidogenic acute regulatory protein (StAR). Severe StAR mutations cause classic congenital lipoid adrenal hyperplasia, characterized by lipid accumulation in the adrenal, adrenal insufficiency, and disordered sexual development in 46,XY individuals. The lipoid CAH phenotype, including spontaneous puberty in 46,XX females, is explained by a two-hit model. StAR mutations that retain partial function cause a milder, non-classic disease characterized by glucocorticoid deficiency, with lesser disorders of mineralocorticoid and sex steroid synthesis. Once inside the mitochondria, cholesterol is converted to pregnenolone by the cholesterol side-chain cleavage enzyme, P450scc, encoded by the CYP11A1 gene. Rare patients with mutations of P450scc are clinically and hormonally indistinguishable from those with lipoid CAH, and may also present as milder non-classic disease. Patients with P450scc defects do not have the massive adrenal hyperplasia that characterizes lipoid CAH, but adrenal imaging may occasionally fail to distinguish these, necessitating DNA sequencing.

1H NMR-Linked Metabolomics Analysis of Liver from a Mouse Model of NP-C1 Disease

Clinical manifestations of Niemann-Pick type C1 (NP-C1) disease include neonatal hepatosplenomegaly and in some patients progressive liver dysfunction and failure. This study involved a ¹H NMR-linked metabolomics analysis of liver samples collected from a NP-C1 disease mutant mouse model in order to explore time-dependent imbalances in metabolic pathways associated with NP-C1 liver dysfunction, including fibrosis. NP-C1 mutant (Npc1^-/-; NP-C1), control (Npc1^+/+; WT), and NP-C1 heterozygous mice (Npc1^+/-; HET) were generated from heterozygote matings. Aqueous extracts of these liver samples collected at time points of 3, 6, 9, and 11 weeks were subjected to high-resolution NMR analysis, and multivariate (MV) metabolomics analyses of data sets acquired were performed. A MV random forests (RFs) model effectively discriminated between NP-C1 and a combined WT/HET hepatic NMR profiles with very high predictive accuracy and reliability. Key distinguishing features included significant upregulations in the hepatic concentrations of phenylalanine, tyrosine, glutamate, lysine/ornithine, valine, threonine, and hypotaurine/methionine, and diminished levels of nicotinate/niacinamide, inosine, phosphoenolpyruvate, and 3-hydroxyphenylacetate. Quantitative pathway topological analysis confirmed that imbalances in tyrosine biosynthesis, and hepatic phenylalanine, tyrosine, glutamate/glutamine, and nicotinate/niacinamide metabolism were involved in the pathogenesis of NP-C1 disease-associated liver dysfunction/damage. ¹H NMR-linked metabolomics analysis provides valuable biomarker information regarding hepatic dysfunction or damage in NP-C1 disease.

Gene Therapy for the Treatment of Neurological Disorders: Metabolic Disorders

Metabolic disorders comprise a large group of heterogeneous diseases ranging from very prevalent diseases such as diabetes mellitus to rare genetic disorders like Canavan Disease. Whether either of these diseases is amendable by gene therapy depends to a large degree on the knowledge of their pathomechanism, availability of the therapeutic gene, vector selection, and availability of suitable animal models. In this book chapter, we review three metabolic disorders of the central nervous system (CNS; Canavan Disease, Niemann-Pick disease and Phenylketonuria) to give examples for primary and secondary metabolic disorders of the brain and the attempts that have been made to use adeno-associated virus (AAV) based gene therapy for treatment. Finally, we highlight commonalities and obstacles in the development of gene therapy for metabolic disorders of the CNS exemplified by those three diseases.

Stimulation of adenosine A2A receptors reduces intracellular cholesterol accumulation and rescues mitochondrial abnormalities in human neural cell models of Niemann-Pick C1

Niemann Pick C 1 (NPC1) disease is an incurable, devastating lysosomal-lipid storage disorder characterized by hepatosplenomegaly, progressive neurological impairment and early death. Current treatments are very limited and the research of new therapeutic targets is thus mandatory. We recently showed that the stimulation of adenosine A2A receptors (A2ARs) rescues the abnormal phenotype of fibroblasts from NPC1 patients suggesting that A2AR agonists could represent a therapeutic option for this disease. However, since all NPC1 patients develop severe neurological symptoms which can be ascribed to the complex pathology occurring in both neurons and oligodendrocytes, in the present paper we tested the effects of the A2AR agonist CGS21680 in human neuronal and oligodendroglial NPC1 cell lines (i.e. neuroblastoma SH-SY5Y and oligodendroglial MO3.13 transiently transfected with NPC1 small interfering RNA). The down-regulation of the NPC1 protein effectively resulted in intracellular cholesterol accumulation and altered mitochondrial membrane potential. Both effects were significantly attenuated by CGS21680 (500 nM). The protective effects of CGS were prevented by the selective A2AR antagonist ZM241385 (500 nM). The involvement of calcium modulation was demonstrated by the ability of Bapta-AM (5-7 μM) in reverting the effect of CGS. The A2A-dependent activity was prevented by the PKA-inhibitor KT5720, thus showing the involvement of the cAMP/PKA signaling. These findings provide a clear in vitro proof of concept that A2AR agonists are promising potential drugs for NPC disease.

Auditory phenotype of Niemann-Pick disease, type C1

OBJECTIVES

The aim of this study was to comprehensively evaluate the auditory phenotype in Niemann-Pick disease, type C1 (NPC1), to understand better the natural history of this complex, heterogeneous disorder, and to define further the baseline auditory deficits associated with NPC1 so that use of potentially ototoxic interventions (e.g., 2-hydroxypropyl-ß-cyclodextrin) may be more appropriately monitored and understood.

DESIGN

Fifty patients with NPC1 ranging in age from 4 months to 21 years (mean = 9.3 years) enrolled in a natural history/observational study at the National Institutes of Health. The auditory test battery included, when possible, immittance audiometry, pure-tone and speech audiometry, otoacoustic emission testing, and a neurotologic auditory brainstem response study. Longitudinal data were collected on a subset of patients.

RESULTS

Over half of the cohort exhibited hearing loss involving the high frequencies ranging from a slight to moderate degree, and 74% of patients presented with clinically significant hearing loss involving the frequencies most important to speech understanding (0.5, 1, 2, 4 kHz). Despite the heterogeneity of the sample, results among patients were sufficiently consistent to implicate retrocochlear dysfunction in the majority (66%) of individuals, with (22%) or without (44%) accompanying cochlear involvement. Some patients (10%) presented with a profile for auditory neuropathy spectrum disorder. The combination of cross-sectional and longitudinal data indicates these patients are at risk for a progressive decline in auditory function.

CONCLUSIONS

This is the largest cohort of patients with NPC1 evaluated comprehensively for auditory dysfunction, and results implicate the pathological processes of NPC1 in the manifestation of hearing loss. Patients with NPC1 should be monitored audiologically throughout their lives, beginning at the time of diagnosis. Clinicians and researchers should be aware of this historically overlooked aspect of the phenotype.

Hearing loss is an early consequence of Npc1 gene deletion in the mouse model of Niemann-Pick disease, type C

Niemann-Pick disease, type C1 (NPC1) is a rare lysosomal lipidosis that is most often the result of biallelic mutations in NPC1, and is characterized by a fatal neurological degeneration. The pathophysiology is complex, and the natural history of the disease is poorly understood. Recent findings from patients with NPC1 and hearing loss suggest that multiple steps along the auditory pathway are affected. The current study was undertaken to determine the auditory phenotype in the Npc1 (nih) mutant mouse model, to extend analyses to histologic evaluation of the inner ear, and to compare our findings to those reported from human patients. Auditory testing revealed a progressive high-frequency hearing loss in Npc1 (-/-) mice that is present as early as postnatal day 20 (P20), well before the onset of overt neurological symptoms, with evidence of abnormalities involving the cochlea, auditory nerve, and brainstem auditory centers. Distortion product otoacoustic emission amplitude and auditory brainstem response latency data provided evidence for a disruption in maturational development of the auditory system in Npc1 (-/-) mice. Anatomical study demonstrated accumulation of lysosomes in neurons, hair cells, and supporting cells of the inner ear in P30 Npc1 (-/-) mice, as well as increased numbers of inclusion bodies, myelin figures, and swollen nerve endings in older (P50-P70) mutant animals. These findings add unique perspective to the pathophysiology of NPC disease and suggest that hearing loss is an early and sensitive marker of disease progression.

Niemann-Pick type C: a potentially treatable disorder?

Niemann-Pick disease refers to a group of autosomal recessive lipid storage disorders associated with a variable degree of neurological manifestations in addition to other organ involvement. Niemann-Pick disease is divided into types A-C. Of interest to neurologists is Niemann-Pick type C because of the association with neurological manifestations that are not confined to childhood. The clinical presentation of Niemann-Pick type C is variable, depending on age at onset. Neurological symptoms vary with age: hypotonia, delay in developmental motor milestones, falls, seizures, learning difficulties, ataxia with cognitive deficits and psychosis. The definitive diagnosis of Niemann-Pick type C requires demonstration of abnormal intracellular cholesterol trafficking using the filipin test. Therapeutic interventions are few but one that is of interest is miglustat, which has been approved for specific treatment of the neurological manifestations. It showed improvement in horizontal saccadic eye movement and a trend towards improvement or stabilisation in swallowing, hearing and walking. Niemann-Pick type C should be considered in patients with early-onset ataxia associated with progressive learning/cognitive difficulties even in the absence of vertical gaze palsy.

Bone-marrow-derived mesenchymal stem cells promote proliferation and neuronal differentiation of Niemann-Pick type C mouse neural stem cells by upregulation and secretion of CCL2

Niemann-Pick type C (NP-C) disease is a neurodegenerative disorder characterized neuropathologically by ballooned neurons distended with lipid storage and widespread neuronal loss. Neural stem cells (NSC) derived from NP-C disease models have decreased ability for self-renewal and neuronal differentiation. Investigation of neurogenesis in the adult brain has suggested that NP-C disease can be overcome, or at least ameliorated, by the generation of new neurons. Bone-marrow-derived mesenchymal stem cells (BM-MSCs) are regarded as potential candidates for use in the treatment of neurodegenerative disorders because of their ability to promote neurogenesis. The underlying mechanisms of BM-MSC-induced promotion of neurogenesis, however, have not been resolved. The aim of the present study was to examine the mechanism of neurogenesis by BM-MSCs in NP-C disease. Coculture of embryonic NSCs from NP-C mice that exhibit impaired ability for self-renewal and decreased rates of neuronal differentiation with BM-MSCs resulted in an enhanced capacity for self-renewal and an increased ability for differentiation into neurons or oligodendrocytes. In addition, results of in vivo studies have demonstrated that transplantation of intracerebral BM-MSCs resulted in stimulated proliferation and neuronal differentiation of NSCs within the subventricular zone. Of particular interest, enhanced proliferation and neuronal differentiation of endogenous NP-C mouse NSCs showed an association with elevated release of the chemokine (C-C motif) ligand 2 (CCL2) from BM-MSCs. These effects suggest that soluble CCL2 derived from BM-MSCs can modulate endogenous NP-C NSCs, resulting in their improved proliferation and neuronal differentiation in mice.

Neuroimaging findings in a brain with Niemann-Pick type C disease

Niemann-Pick type C disease (NPC) is a rare autosomal recessive lipid storage disorder caused by impaired cellular functions in processing and transporting low-density lipoprotein-cholesterol. In this report, we present magnetic resonance imaging (MRI), magnetic resonance spectrography (MRS) and 18-fluoro-2-deoxyglucose positron emission tomography (PET) imaging results for a 22-year-old male NPC patient. The patient's two MRI studies (at age 19 years and 22 years) demonstrated progressive changes of brain atrophy that were more prominent at the frontal lobes, and hyperintense signals in bilateral parietal-occipital periventricular white matter. MRS (at age 19 years) revealed no significant decrease in N-acetyl aspartate/choline ratio in the left frontal central white matter. PET (at age 22 years) showed significant bilateral hypometabolism in the prefrontal cortex and dorsomedial thalamus, and hypermetabolism in the parietal-occipital white matter, lenticular nucleus of the basal ganglia, cerebellum and pons. The imaging findings noted by MRI, MRS and 18-fluoro-2-deoxyglucose PET offered a possible supplementary explanation for the clinical neurological symptoms of this NPC patient.

Protein replacement therapy partially corrects the cholesterol-storage phenotype in a mouse model of Niemann-Pick type C2 disease

Niemann-Pick type C2 (NPC2) disease is a fatal autosomal recessive neurovisceral degenerative disorder characterized by late endosomal-lysosomal sequestration of low-density lipoprotein derived cholesterol. The breach in intracellular cholesterol homeostasis is caused by deficiency of functional NPC2, a soluble sterol binding protein targeted to the lysosomes by binding the mannose-6-phosphate receptor. As currently there is no effective treatment for the disorder, we have investigated the efficacy of NPC2 replacement therapy in a murine gene-trap model of NPC2-disease generated on the 129P2/OlaHsd genetic background. NPC2 was purified from bovine milk and its functional competence assured in NPC2-deficient fibroblasts using the specific cholesterol fluorescent probe filipin. For evaluation of phenotype correction in vivo, three-week-old NPC2^−/− mice received two weekly intravenous injections of 5 mg/kg NPC2 until trial termination 66 days later. Whereas the saline treated NPC2^−/− mice exhibited massive visceral cholesterol storage as compared to their wild-type littermates, administration of NPC2 caused a marked reduction in cholesterol build up. The histological findings, indicating an amelioration of the disease pathology in liver, spleen, and lungs, corroborated the biochemical results. Little or no difference in the overall cholesterol levels was observed in the kidneys, blood, cerebral cortex and hippocampus when comparing NPC2^−/− and wild type mice. However, cerebellum cholesterol was increased about two fold in NPC2^−/− mice compared with wild-type littermates. Weight gain performance was slightly improved as a result of the NPC2 treatment but significant motor coordination deficits were still observed. Accordingly, ultrastructural cerebellar abnormalities were detected in both saline treated and NPC2 treated NPC2^−/− animals 87 days post partum. Our data indicate that protein replacement may be a beneficial therapeutic approach in the treatment of the visceral manifestations in NPC2 disease and further suggest that neurodegeneration is not secondary to visceral dysfunction.

Spectrum of phenotypic variability in Niemann-Pick type C disease: A cause of delayed diagnosis

BACKGROUND

Niemann-Pick type C (NP-C) disease exhibits marked heterogeneity in its phenotype. This can pose diagnostic dilemmas and even delayed recognition of this condition.

OBJECTIVE

To highlight the phenotypic variations and distinctive pathological and biochemical findings in this disorder.

DESIGN

Descriptive case studies.

SETTING

Tertiary care children's hospital and clinic.

POPULATION STUDIED

Three cases of NP-C disease where diagnosis was delayed.

RESULTS

In each of the three cases the clinical presentation was varied, one as neonatal hepatitis, the second with megaloblastic anemia, chronic hepatitis and short stature, and the third with neonatal hepatitis and chronic respiratory failure. Definitive diagnosis was established in each case by demonstration of defective cholesterol esterification in skin fibroblasts.

CONCLUSIONS

In the clinical setting of neonatal hepatitis, hepatosplenomegaly and undiagnosed neurological symptoms, NP-C disease should be considered in the differential diagnosis. Electron microscopic examination of skin biopsy is an effective screening test, although the definitive diagnosis should be made by the cholesterol esterification assay and filipin staining.

Anatomically defined neuron-based rescue of neurodegenerative Niemann-Pick type C disorder

Niemann-Pick type C disease is a fatal lysosomal storage disorder caused by loss of NPC1 function. The disorder severely affects multiple body systems, particularly the nervous system. To test whether rescue of NPC1 activity in neurons, astrocytes, or other cell types can correct the neurological defects, a Tet-inducible Npc1-YFP transgene was introduced into Npc1(-/-) mice for the cell type-specific rescue of NPC1 loss. NPC1-YFP produced in neurons prevented neuron degeneration, slowed reactive glial activity, and ameliorated the disease. NPC1-YFP produced in astrocytes or in cells of visceral tissue did not. These results suggest that loss of NPC1 activity from neurons is the primary cause of the neuropathology and that rescue of NPC1 function in neurons is sufficient to mitigate the disease. The ability of neurons to survive and function in a cell-autonomous fashion allowed the use of this newly engineered rescue system to further define the brain regions or neuron populations required to ameliorate a neurological symptom. NPC1-YFP produced specifically in cerebellar Purkinje neurons reduced ataxia, increased weight, and prolonged life, but it did not prevent the eventual decline and premature death of Npc1(-/-) mice. Significant increase in lifespan correlated with sustained reduction of inflammation in the thalamus. Neuron rescue of other forebrain areas provided little benefit. Future work targeting increasingly discrete neuronal networks should reveal which CNS areas are critical for survival. This work may have broad implications for understanding the anatomical and cellular basis of neurological signs and symptoms of other neurodegenerative and lysosomal disorders.

Decreased purinergic inhibition of synaptic activity in a mouse model of Niemann-Pick disease type C

Niemann-Pick disease type C (NPC) is a progressive neurodegenerative disorder characterized by accumulation of free cholesterol in lysosomes, mainly due to a mutation in the NPC1 gene. The pathophysiological basis of the neural disorders in NPC, however, is not well understood. We found that the hippocampal field excitatory postsynaptic potential (fEPSP) was enhanced in NPC1 mutant mice. A1-receptor antagonist or adenosine degrading enzyme enhanced the fEPSP in both types of mice, but had a much weaker effect in the mutant mice, suggesting less tonic inhibition of synaptic transmission by endogenous adenosine in the mutant. Further evidence showed impaired hippocampal long term potentiation (LTP) in mutant mice. Supplement of A1 agonist N6-Cyclopentyladenosine (CPA) partially rescued the impaired LTP in mutant mice. Moreover, adenosine release from hippocampal slices was significantly decreased in the mutant. The enhanced excitatory synaptic transmission and the decreased synaptic plasticity due to the decreased adenosine release in NPC brain may partially contribute to the neural disorders of NPC disease, such as seizures, neurodegeneration, and dementia.

Nonprimary dystonias

Dystonias can be classified as primary or secondary, as dystonia-plus syndromes, and as heredodegenerative dystonias. Their prevalence is difficult to determine. In our experience 80-90% of all dystonias are primary. About 20-30% of those have a genetic background; 10-20% are secondary, with tardive dystonia and dystonia in cerebral palsy being the most common forms. If dystonia in spastic conditions is accepted as secondary dystonia, this is the most common form of all dystonia. In primary dystonias, the dystonic movements are the only symptoms. In secondary dystonias, dystonic movements result from exogenous processes directly or indirectly affecting brain parenchyma. They may be caused by focal and diffuse brain damage, drugs, chemical agents, physical interactions with the central nervous system, and indirect central nervous system effects. Dystonia-plus syndromes describe brain parenchyma processes producing predominantly dystonia together with other movement disorders. They include dopa-responsive dystonia and myoclonus-dystonia. Heredodegenerative dystonias are dystonic movements occurring in the context of other heredodegenerative disorders. They may be caused by impaired energy metabolism, impaired systemic metabolism, storage of noxious substances, oligonucleotid repeats and other processes. Pseudodystonias mimic dystonia and include psychogenic dystonia and various orthopedic, ophthalmologic, vestibular, and traumatic conditions. Unusual manifestations, unusual age of onset, suspect family history, suspect medical history, and additional signs may indicate nonprimary dystonia. If they are suspected, etiological clarification becomes necessary. Unfortunately, potential etiologies are legion. Diagnostic algorithms can be helpful. Treatment of nonprimary dystonias, with few exceptions, does not differ from treatment of primary dystonias. The most effective treatment for focal and segmental dystonias is local botulinum toxin injections. Deep brain stimulation of the globus pallidus internus is effective for generalized dystonia. Antidystonic drugs, including anticholinergics, tetrabenazine, clozapine, and gamma-aminobutyric acid receptor agonists, are less effective and often produce adverse effects. Dopamine is extremely effective in dopa-responsive dystonia. The Bertrand procedure can be effective in cervical dystonia. Other peripheral surgery, including myotomy, myectomy, neurotomy, rhizotomy, ramizectomy, and accessory nerve neurolysis, has largely been abandoned. Central surgery other than deep brain stimulation is obsolete. Adjuvant therapies, including orthoses, physiotherapy, ergotherapy, behavioral therapy, social support, and support groups, may be helpful. Analgesics should also be considered where appropriate.

Long-term miglustat therapy in children with Niemann-Pick disease type C

Niemann-Pick disease type C is a rare, genetic disease associated with impaired intracellular lipid trafficking and progressive neurological symptoms. Miglustat slowed disease progression in a 12-month randomized trial in juveniles and adults with Niemann-Pick disease type C, and in a parallel, noncontrolled study in affected children. Here, the authors report the open-label extension to the pediatric study. Patients aged 4 to 12 years received open-label miglustat (dose adjusted for body surface area) for an initial 12 months, during a further 12-month extension, and a long-term, continued extension phase. Efficacy assessments included horizontal saccadic eye movement, swallowing, and ambulation. Ten children completed 24 months' treatment. Horizontal saccadic eye movement, ambulation, and swallowing were stabilized at 24 months. Analysis of key parameters of disease progression showed disease stability in 8 of 10 patients (80%). Miglustat stabilized neurological disease progression in pediatric patients with Niemann-Pick disease type C, with comparable safety and tolerability to that observed in adults and juveniles.

Spiral analysis in Niemann-Pick disease type C

Spiral analysis is a computerized method of analyzing upper limb motor physiology through the quantification of spiral drawing. The objective of this study was to determine whether spirals drawn by patients with Niemann-Pick disease type C (NPC) could be distinguished from those of controls, and to physiologically characterize movement abnormalities in NPC. Spiral data consisting of position, pressure, and time were collected from 14 NPC patients and 14 age-matched controls, and were analyzed by the Mann-Whitney U test. NPC spirals were characterized by: lower speed (2.67 vs. 9.56 cm/s, P < 0.001) and acceleration (0.10 vs. 2.04 cm/s(2), P < 0.001), higher loop width variability (0.88 vs. 0.28, P < 0.001), tremor (5/10 vs. 0/10 trials in the dominant hand, P < 0.001), and poor overall spiral rating (2.53 vs. 0.70, P < 0.005). NPC spirals also exhibited sustained drawing pressure profiles that were abnormally invariant with time. Other features, such as the tightness of loop widths, were normal. Our findings reveal that differing aspects of tremor, Parkinsonism, ataxia, and dystonia are quantifiable in NPC patients.

Cholesterol in Niemann-Pick Type C disease

Niemann-Pick Type C (NPC) disease is associated with accumulation of cholesterol and other lipids in late endosomes/lysosomes in virtually every organ; however, neurodegeneration represents the fatal cause for the disease. Genetic analysis has identified loss-of-function mutations in NPC1 and NPC2 genes as the molecular triggers for the disease. Although the precise function of these proteins has not yet been clarified, recent research suggests that they orchestrate cholesterol efflux from late endosomes/lysosomes. NPC protein deficits result in impairment in intracellular cholesterol trafficking and dysregulation of cholesterol biosynthesis. Disruption of cholesterol homeostasis is also associated with deregulation of autophagic activity and early-onset neuroinflammation, which may contribute to the pathogenesis of NPC disease. This chapter reviews recent achievements in the investigation of disruption of cholesterol homeostasis-induced neurodegeneration in NPC disease, and provides new insight for developing a potential therapeutic strategy for this disorder.

The National Niemann-Pick Type C1 Disease Database: correlation of lipid profiles, mutations, and biochemical phenotypes

Niemann-Pick type C1 disease (NPC1) is an autosomal recessive lysosomal storage disorder characterized by neonatal jaundice, hepatosplenomegaly, and progressive neurodegeneration. The present study provides the lipid profiles, mutations, and corresponding associations with the biochemical phenotype obtained from NPC1 patients who participated in the National NPC1 Disease Database. Lipid profiles were obtained from 34 patients (39%) in the survey and demonstrated significantly reduced plasma LDL cholesterol (LDL-C) and increased plasma triglycerides in the majority of patients. Reduced plasma HDL cholesterol (HDL-C) was the most consistent lipoprotein abnormality found in male and female NPC1 patients across age groups and occurred independent of changes in plasma triglycerides. A subset of 19 patients for whom the biochemical severity of known NPC1 mutations could be correlated with their lipid profile showed a strong inverse correlation between plasma HDL-C and severity of the biochemical phenotype. Gene mutations were available for 52 patients (59%) in the survey, including 52 different mutations and five novel mutations (Y628C, P887L, I923V, A1151T, and 3741_3744delACTC). Together, these findings provide novel information regarding the plasma lipoprotein changes and mutations in NPC1 disease, and suggest plasma HDL-C represents a potential biomarker of NPC1 disease severity.

Tau deletion exacerbates the phenotype of Niemann-Pick type C mice and implicates autophagy in pathogenesis

Hyperphosphorylation and aggregation of the microtubule-binding protein tau characterize a diverse array of neurodegenerative disorders. Most of these lack mutations in the encoding MAPT gene, and the role of tau in disease pathogenesis remains controversial. Among these tauopathies is Niemann-Pick type C disease (NPC), a lysosomal storage disorder characterized by progressive neurodegeneration and premature death, most often caused by an inherited deficiency in the intracellular lipid trafficking protein NPC1. To determine the extent to which tau affects NPC pathogenesis, we generated Npc1-/- mice deficient in tau. Unexpectedly, NPC1/tau double null mutants are generated in markedly smaller litters, exhibit an enhanced systemic phenotype and die significantly earlier than NPC1 single null mutants. As autophagy is up-regulated in NPC and protein degradation through this pathway depends on movement along microtubules, we knocked down MAPT expression in NPC1-deficient human fibroblasts and examined effects on this pathway. We show that an acute reduction of tau expression in a cellular model of NPC decreases induction and flux through the autophagic pathway. Our data establish that MAPT deletion exacerbates the NPC phenotype through a mechanism independent of tau protein aggregation and identifies a critical role for tau in the regulation of autophagy in NPC1-deficient cells.

Clinical, electrophysiological, and serum biochemical measures of progressive neurological and hepatic dysfunction in feline Niemann-Pick type C disease

Niemann-Pick type C (NP-C) disease is a neurovisceral lysosomal storage disease characterized by neurologic dysfunction, hepatosplenomegaly, and early death. Natural history studies are very difficult to perform due to the low incidence and high heterogeneity of disease in the human population. Sixteen cats with a spontaneously occurring missense mutation in NPC1 were evaluated over time to define the progression of neurologic and hepatic disease. Affected cats had remarkably regular onsets of specific signs of cerebellar and vestibular system dysfunction with progressive severity of dysfunction quantified by postrotatory nystagmus and brain stem auditory evoked response measures. NP-C disease cats also showed increasing serum activity of alanine aminotransferase, asparate aminotransferase, and cholesterol with advancing age. Affected cats lived to a mean age of 20.5 +/- 4.8 wk. CNS and hepatic lesions were similar to those described in human patients. These data are the first to document progressive hepatic disease in the feline model and demonstrate the importance of liver disease as part of the NP-C disease phenotype. Both neurologic and hepatic measures of disease onset and severity can be used as a baseline with which to assess the efficacy of experimental therapies of NP-C disease in the feline model.

Endogenous and synthetic neurosteroids in treatment of Niemann-Pick Type C disease

The functions for neurosteroids during development and in response to nervous system injury are beginning to be identified. We focused on a mouse model in which we believed neurosteroid production would be altered, and which had a neurodegenerative phenotype. Niemann-Pick Type-C (NP-C) is an autosomal recessive neurodegenerative disease caused by mutations in NPC1 (95%) or NPC2 (5%), resulting in lysosomal accumulation of unesterified cholesterol and glycolipids. The NIH mouse model of NP-C has a mutation in the NPC1 gene, and exhibits several pathological features of the most severe NP-C patients. How lysosomal storage and trafficking defects lead to neurodegeneration is unknown. We found that these mice had normal neurosteroidogenic enzyme activity during development, but lost this activity in the early neonatal period, prior to onset of neurological symptoms. Neurons that expressed P450scc, 3beta HSD, as well as those that expressed 3alpha HSD and 5alpha reductase were lost in adult NP-C brains, resulting in diminished concentrations of allopregnanolone. We treated NP-C mice with allopregnanolone and found that a single dose in the neonatal period resulted in a doubling of life span, substantial delay in onset of neurological symptoms, survival of cerebellar Purkinje and granule cell neurons, and reduction in cholesterol and ganglioside accumulation. The mechanism by which allopregnanolone elicited these effects is unknown. Our in vitro studies showed that Purkinje cell survival promoted by allopregnanolone was lost by treatment with bicuculline, suggesting GABA(A) receptors may play a role. We treated NP-C mice with a synthetic GABA(A) neurosteroid, ganaxolone (3alpha-hydroxy-3beta-methyl-5alpha-pregnan-20-one). Ganaxolone treatment of NP-C mice produced beneficial neurological effects, but these effects were not as robust as those obtained using allopregnanolone. Thus, allopregnanolone may elicit its effects through GABA(A) receptors and through other mechanisms. Additional studies also suggest that allopregnanolone may elicit its effects through pregnane-X-receptors (PXR). Our data suggest that mouse models of neurodegeneration may be beneficial in establishing both physiologic and pharmacologic actions of neurosteroids. These animal models further establish the wide range of functions of these compounds, which may ultimately be useful for treatment of human diseases.

Brainstem neuropathology in a mouse model of Niemann-Pick disease type C

Niemann-Pick disease type C (NPC) is a neurovisceral lipid storage disorder characterized by progressive and widespread neurodegeneration. Although some characteristic symptoms of NPC result from brainstem dysfunction, little information is available about which brainstem structures are affected. In this study, the brainstems of mutant BALB/c NPC1-/- mice with a retroposon insertion in the NPC1 gene were examined for neuropathological changes. In the midbrain, the integrated optic density (IOD) and cell count density of tyrosine-hydroxylase (TH) immunostained neurons were decreased in the substantia nigra. In the pons, TH immunoreactivity in the locus ceruleus (LC) neurons was decreased, while the IOD and the neuronal density of choline acetyltransferase (ChAT)-immunostained neurons in the pedunculopontine tegmental nucleus were preserved. The ChAT immunoreactivity of the hypoglossal nucleus (12N) neurons was not decreased, but Klüver-Barrera staining showed that neuronal density in the nucleus of the solitary tract (NTS) was decreased. Klüver-Barrera and neuronal nuclei (NeuN) staining showed a decrease in neuronal density in the ventral cochlear nucleus, but not in the dorsal cochlear nucleus. Gliosis was widely identified by GFAP staining in various brainstem structures, including the superior and inferior colliculi, the rostral interstitial nucleus of the medial longitudinal fasciculus, the oculomotor complex, the medial geniculate nucleus, the nucleus ambiguus, and the 12N. However, GFAP expression was not augmented in the LC, the cochlear nucleus, or the NTS. These neuropathological findings suggest a basis for the neurological syndromes observed in NPC, such as rigidity, oculomotor symptoms, cataplexy and sleep disturbance, dysphagia, and perceptive deafness.

Gingival enlargement in Niemann-Pick disease: a coincidence or link? Report of a unique case

A case of a 25-year-old man appearing with generalized gingival enlargement is reported here. Niemann-Pick disease (NPD) was provisionally diagnosed by histopathologic analysis of tissue excised by gingivectomy and later confirmed by quantitative enzyme assay. Correlation between clinical features and histopathologic and biochemical analysis enabled the diagnosis of NPD type C.

The National Niemann–Pick C1 disease database: Report of clinical features and health problems

Niemann-Pick type C1 (NPC1) disease is an autosomal recessive disorder characterized clinically by neonatal jaundice, hepatosplenomegaly, vertical gaze palsy, ataxia, dystonia, and progressive neurodegeneration. The present study provides basic clinical and health information from the National Niemann-Pick C1 disease database that was obtained using a clinical questionnaire of 83 questions mailed to families affected by NPC1 disease living in the United States. The study was conducted over a 1-year period, during which time parents/caregivers and physicians completed the clinical questionnaire. Sixty-four percent (87/136) of the questionnaires were returned, with 53% and 47% representing male and female NPC1 patients, respectively. The average age of diagnosis for NPC1 disease was 10.4 years, with one-half of patients being diagnosed before the age of 6.9 years. The average age of death for NPC1 disease was 16.2 years, with one-half of patients dying before the age of 12.5 years. A common clinical symptom reported at birth was neonatal jaundice (52%), followed by enlargement of the spleen (36%) and liver (31%); ascites (19%) and neonatal hypotonia (6%) were much less frequent. With respect to developmental difficulties, the most common findings included clumsiness (87%), learning difficulties (87%), ataxia (83%), dysphagia (80%), and vertical gaze palsy (81%). Together, these findings confirm and extend previous reports investigating the clinical features associated with NPC1 disease.

Kinematic analysis of motor dysfunction in Niemann-Pick type C

OBJECTIVE

To provide the first descriptive analysis of upper limb motor physiology in Niemann-Pick Type C disease (NP-C).

METHODS

Fifteen patients with confirmed NP-C underwent motor physiology testing using accelerometry and surface EMG (sEMG). Tremor amplitude and frequency were quantified using accelerometry, and sEMG was examined for abnormal patterns consistent with various movement disorders.

RESULTS

Forty-seven percent of patients had postural tremor in the upper limbs, generally bilateral, with frequencies ranging from 0.3 to 3 Hz, and an average amplitude of 1.20+/-0.98 mm. Eighty-seven percent of patients had bilateral action tremor with frequencies ranging from 2.0 to 3.7 Hz, and an average amplitude of 5.25+/-3.76 mm. sEMG revealed long but variable duration, variable amplitude muscle burst discharges during action in some patients, as well as short high frequency irregularly timed bursts in others.

CONCLUSIONS

Accelerometric findings correlated with the clinical findings were most consistent with cerebellar outflow tremors. sEMG revealed a mix of dystonic, myoclonic and choreiform movements.

SIGNIFICANCE

These quantitative methods may serve as ancillary measures of disease pathophysiology, markers of change over time, and methods to evaluate efficacy, and side effects, of new treatments as they are developed.

Gender and age differences in expression of GABAA receptor subunits in rat somatosensory thalamus and cortex in an absence epilepsy model

Absence epilepsy is more prevalent in females, but reasons for this gender asymmetry are unknown. We reported previously that perinatal treatment of Long-Evans Hooded rats with the cholesterol synthesis inhibitor (CSI) AY9944 causes a life-long increase in EEG spike-wave discharges (SWDs), correlated with decreased expression of GABA(A) receptor subunit gamma2 protein levels in thalamic reticular and ventrobasal nuclei (SS thalamus) [Li, H., Kraus, A., Wu, J., Huguenard, J.R., Fisher, R.S., 2006. Selective changes in thalamic and cortical GABA(A) receptor subunits in a model of acquired absence epilepsy in the rat. Neuropharmacology 51, 121-128]. In this study, we explored time course and gender different effects of perinatal AY9944 treatment on expression of GABA(A) receptor alpha1 and gamma2 subunits in SS thalamus and SS cortex. Perinatal AY9944 treatment-induced decreases in GABA(A) gamma2 receptor subunits in rat SS thalamus and increases in SS cortex are gender and age specific. The findings suggest a mechanism for the higher prevalence of absence epilepsy in female patients.

The usefulness of bone marrow aspiration in the diagnosis of Niemann-Pick disease type C in infantile liver disease

BACKGROUND

Niemann-Pick disease type C (NPC) is a fatal, autosomal recessive lysosomal storage disease which may present in infancy with cholestatic jaundice and/or hepatosplenomegaly. In cholestatic patients with splenomegaly, a bone marrow aspirate has been advocated as a relatively accessible tissue to demonstrate storage phenomena. Typically in patients with NPC, macrophages with abnormal cholesterol storage, so called foam cells, can be detected in the bone marrow.

AIM

To review our experience of bone marrow aspiration in children with NPC presenting with infantile liver disease.

METHODS

A retrospective analysis of 11 consecutive children (8 males) from Birmingham Children's Hospital with NPC presenting with infantile liver disease was undertaken. The diagnosis of NPC was confirmed in all cases by demonstrating undetectable or low rates of cholesterol esterification and positive filipin staining for free cholesterol in cultured fibroblasts.

RESULTS

The median age at presentation was 1.5 months (range 0.5-10). Bone marrow aspirates showed storage cells in only 7/11 cases. Bone marrow aspirates which had storage cells were undertaken at a median age of 11 months while those with no storage cells were undertaken at median age 2.3 months. The overall sensitivity of bone marrow aspirates for detecting storage cells in children presenting with infantile liver disease was 64%; however, for children who had bone marrow aspirates in the first year of life it was only 57%.

CONCLUSIONS

The sensitivity of bone marrow aspirate for the diagnosis of NPC disease in patients presenting with infantile liver disease was lower than previously reported. Where NPC is suspected clinically, definitive investigations should be undertaken promptly. There is a need to develop sensitive screening methods for NPC in children presenting with infantile liver disease.

Lipid dynamics in neurons

Compared with other organs, the brain is highly enriched in cholesterol. Essentially all cholesterol in the brain is synthesized within the brain; the blood-brain barrier prevents the import of plasma lipoproteins into the brain. Consequently, the brain operates an independent lipoprotein transport system in which glial cells produce ApoE (apolipoprotein E)-containing lipoproteins that are thought to deliver cholesterol to neurons for axonal growth and repair. We have shown that ApoE-containing lipoproteins generated by glial cells stimulate axon extension. ApoE associated with lipoprotein particles, and a receptor of the low-density lipoprotein receptor family, are required for stimulation of axon growth. NPC (Niemann-Pick type C) disease is a severe neurological disorder caused by mutations in the NPC1 or NPC2 gene. A hallmark of this disease is impaired transport of cholesterol out of late endosomes/lysosomes and the accumulation of cholesterol in these organelles. Although cholesterol accumulates in cell bodies of neurons from NPC1-deficient mice, the cholesterol content of axons is reduced. The presence of NPC1 in endosomal structures in nerve terminals, and the finding of aberrant synaptic vesicles, suggest that defects in synaptic vesicle recycling contribute to neurological abnormalities characteristic of NPC disease. We have also shown that ApoE-containing lipoproteins produced by glial cells from NCP1-deficient mice are of normal composition and stimulate axon extension.

Recent advances in elucidating Niemann-Pick C disease

Lysosomal sequestration of endocytosed LDL-derived cholesterol, premature and abnormal enrichment of cholesterol in trans Golgi cisternae and accompanying anomalies in intracellular sterol trafficking are the hallmark phenotypic features of the Niemann-Pick C (NPC) lesion. A variable severity of these alterations has been observed, with only partial correlation between clinical and biochemical phenotypes. NPC also affects the metabolism of sphingolipids, and other biochemical abnormalities have been reported. Occurrence of neurofibrillary tangles in the brain of patients with a slowly progressive course is a recent intriguing observation. Genetic heterogeneity was established by cell hybridization and linkage studies. The two complementation groups could not be distinguished from each other by clinical, cellular or biochemical criteria, suggesting that the two gene products may interact or function sequentially. The major (> 90% of patients) NPC1 gene was mapped to 18q11 and recently isolated by positional cloning. The cDNA sequence predicts a 1278-amino acid protein, with 13 to 16 possible transmembrane regions and a putative cholesterol-sensing domain. Two murine models of the disease involving the same gene are known. The murine cDNA and the npc(nih) mutation have been characterized. Described homologies of the NPC1 protein are in line with its putative involvement in cellular cholesterol traffic.

Cholesterol homeostasis in neurons and glial cells

Cholesterol is highly enriched in the brain compared to other tissues. Essentially all cholesterol in the brain is synthesized endogenously since plasma lipoproteins are unable to cross the blood-brain barrier. Cholesterol is transported within the central nervous system in the form of apolipoprotein E-containing lipoprotein particles that are secreted mainly by glial cells. Cholesterol is excreted from the brain in the form of 24-hydroxycholesterol. Apolipoprotein E and cholesterol have been implicated in the formation of amyloid plaques in Alzheimer's disease. In addition, the progressive neurodegenerative disorder Niemann-Pick C disease is characterized by defects in intracellular trafficking of cholesterol.

Troubles psychiatriques révélateurs d’une maladie de Niemann-Pick de type C à l’âge adulte

INTRODUCTION

Niemann-Pick Type C disease (NPC) is an autosomal recessive neurovisceral lysosomal lipid storage disorder.

CASE REPORT

A 31-year-old right-handed woman had suffered from schizophrenia for 13 years. At 25 years of age, she developed a gait disorder with a static and kinetic cerebellar syndrome, dysarthria, vertical supranuclear gaze palsy and cognitive impairment. Brain MRI was normal. Abdominal ultrasonography was performed because of hypercholesterolemia and elevated transaminases and revealed hepatosplenomegaly, which in conjunction with other signs and symptoms, suggested the diagnosis of NPC. The diagnosis was confirmed by demonstration of lysosomal storage of unesterified cholesterol (filipin staining) and of a reduced rate of LDL-induced cholesterol esterification. Implication of the NPC1 gene was assessed by genetic complementation analysis.

DISCUSSION

The phenotypic presentation of NPC is remarkably variable. The rarer adult-onset form has a slowly progressive course. Psychotic manifestations are often prominent and may precede neurologic symptoms. Exposure to neuroleptics delays the diagnosis of NPC.

CONCLUSION

Psychotic manifestations associated with cerebellar syndrome, vertical supranuclear gaze palsy, and splenomegaly are very suggestive of NPC disease which can be reliably diagnosed on cultured skin fibroblasts by filipin staining.

Structure and function of the NPC2 protein

Somatic cell hydridization and linkage studies indicated the implication of a second gene as a cause of Niemann-Pick C disease in a minority (5%) of patients. A study of the lysosomal proteome led to the identification of a previously known gene, HE1, as the NPC2 gene. The mature NPC2/HE1 protein is a ubiquitous soluble small 132-amino-acid glycoprotein, first characterized as a major secretory protein in the human epididymis, but also detected in most tissues. Seventeen families with mutations in the NPC2 gene are known. Good genotype-phenotype correlations were observed. No distinction can be made between the biochemical phenotypes of NPC1 or NPC2 mutants. The NPC2 protein binds cholesterol with submicromolar affinity at neutral and acidic pH. The bovine protein has been crystallized, and the cholesterol-binding site assigned to a hydrophobic loosely packed region. There is strong evidence that the NPC1 and NPC2 proteins must function in a closely related fashion. Current data have led to the hypothesis that NPC2 would bind cholesterol from internal lysosomal membranes, enabling a physical interaction with NPC1 (or another protein) and allowing postlysosomal export of cholesterol. In this model, the activity of NPC1 would depend on that of NPC2. The precise function of the NPC2 protein has, however, not been fully elucidated.

Consequences of NPC1 and NPC2 loss of function in mammalian neurons

Genetic deficiency of NPC1 or NPC2 results in a devastating cholesterol-glycosphingolipidosis of brain and other organs known as Niemann-Pick type C (NPC) disease. While NPC1 is a transmembrane protein believed involved in retroendocytic shuttling of substrate(s) to the Golgi and possibly elsewhere in cells as part of an essential recycling/homeostatic control mechanism, NPC2 is a soluble lysosomal protein known to bind cholesterol. The precise role(s) of NPC1 and NPC2 in endosomal-lysosomal function remain unclear, nor is it known whether the two proteins directly interact as part of this function. The pathologic features of NPC disease, however, are well documented. Brain cells undergo massive intracellular accumulation of glycosphingolipids (lactosylceramide, glucosylceramide, GM2 and GM3 gangliosides) and cholesterol and concomitant distortion of neuron shape (meganeurite formation). In neurons from humans with NPC disease the metabolic defects and storage often lead to extensive growth of new, ectopic dendrites (possibly linked to ganglioside sequestration) as well as formation of neurofibrillary tangles (NFTs) (possibly linked to dysregulation of cholesterol metabolism). Other features of cellular pathology in NPC disease include fragmentation of the Golgi apparatus and neuroaxonal dystrophy, though reasons for these changes remain largely unknown. As the disease progresses, neurodegeneration is also apparent for neurons in some brain regions, particularly Purkinje cells of the cerebellum, but the basis of this selective neuronal vulnerability is unknown. The NPC1 protein is evolutionarily conserved with homologues reported in yeast to humans; NPC2 is reported in C. elegans to humans. While neurons in mammalian models of NPC1 and NPC2 diseases exhibit many changes that are remarkably similar to those in humans (e.g., endosomal/lysosomal storage, Golgi fragmentation, neuroaxonal dystrophy, neurodegeneration), a reduced degree of ectopic dendritogenesis and an absence of NFTs in these species suggest important differences in the way lower mammalian neurons respond to NPC1/NPC2 loss of function.

Woman with a 26-year history of parkinsonism, supranuclear ophthalmoplegia, and loss of postural reflexes

A woman who had her first serious fall at age 48 years subsequently developed neurological symptoms. Her case is described, differential diagnoses are presented, pathology is discussed, and a final diagnosis is reached.

Niemann-Pick type C disease involves disrupted neurosteroidogenesis and responds to allopregnanolone

Niemann-Pick type C (NP-C) disease is a fatal, autosomal recessive, childhood neurodegenerative disease. The NP-C mouse recapitulates the cholesterol and sphingolipid storage, onset of neurological deficits, histopathological lesions, Purkinje cell loss and early death typical of the most severe form of human NP-C. Neurosteroids, steroids made in the brain, affect neuronal growth and differentiation, and modulate neurotransmitter receptors. Disordered cholesterol trafficking might disrupt neurosteroidogenesis, thereby contributing to the NP-C phenotype. Here we show that NP-C mouse brain contains substantially less neurosteroid than wild-type brain and has an age-related decrease in the ability to synthesize 5alpha-dihydroprogesterone and allopregnanolone. Immunohistochemical assessment confirms a decrease in expression of 5alpha-reductase and 3alpha-hydroxysteroid dehydrogenase, especially in cerebellum. Neonatal administration of allopregnanolone delays the onset of neurological symptoms, increases Purkinje and granule cell survival, reduces cortical GM2 and GM3 ganglioside accumulation and doubles the lifespan of NP-C mice. Earlier administration increases effectiveness of treatment. Decreased production of allopregnanolone apparently contributes to the pathology of NP-C; thus, neurosteroid treatment may be useful in ameliorating progression of the disease.

Niemann-Pick disease type C

Niemann-Pick disease type C (NPC) is an autosomal recessive neurovisceral lipid storage with a wide spectrum of clinical phenotypes. At the cellular level, the disorder is characterized by accumulation of unesterified cholesterol and glycolipids in the lysosomal/late endosomal system. Approximatively 95% of patients have mutations in the NPC1 gene (mapped at 18q11) which encodes a large membrane glycoprotein primarily located to late endosomes. The remainder have mutations in the NPC2 gene (mapped at 14q24.3) which encodes a small soluble lysosomal protein with cholesterol-binding properties. The identical biochemical patterns observed in NPC1 and NPC2 mutants suggest that the two proteins function in a coordinate fashion. Identification of mutations revealed a complex picture of molecular heterogeneity, allowing genotype - phenotype correlations for both genes and providing insights into structure - function relationships for the NPC1 protein. Although a whole body of evidence suggests that the NPC1 and NPC2 proteins are involved in the cellular postlysosomal/late endosomal transport of cholesterol, glycolipids and other cargo, their precise functions and relationship remain unclear and are currently the subject of intense investigation. These studies, conducted in various models, should ultimately lead to a better understanding of the pathophysiology of NPC and new therapeutic approaches.

Frontal lobe atrophy due to a mutation in the cholesterol binding protein HE1/NPC2

This is the first description of slowly progressive Niemann-Pick disease type C (NPC) without the typical lysosomal storage in bone marrow and viscera in two descendants of a group of 17th century French-Canadians. The index patient was a married 43-year-old woman with onset of dementia in her thirties, later followed by the development of ataxia and athetoid movements. Her autopsy disclosed frontal lobe atrophy, neurolysosomal storage with oligolamellar inclusion and tau-positive neurofibrillary tangles. Of the 119 family members screened, only a married 42-year-old sister displayed symptoms of a dementia. Both women displayed vertical supranuclear ophthalmoplegia; expressive aphasia; concrete, stimulus-bound, perseverative behavior; and impaired conceptualization and planning. Cultured fibroblasts showed decreased cholesterol esterification and positive filipin staining, but no mutation was detected in coding or promoter regions of the NPC1 gene using conformation sensitive gel electrophoresis and sequencing. Sequencing showed a homozygous gene mutation that is predicted to result in an amino acid substitution, V39M, in the cholesterol binding protein HE1 (NPC2). Adult-onset NPC2 with lysosomal storage virtually restricted to neurons represents a novel phenotypic and genotypic variant with diffuse cognitive impairment and focal frontal involvement described for the first time.

The significance of opthalmologic evaluation in the early diagnosis of inborn errors of metabolism: the Cretan experience

BACKGROUND

The Inborn Errors of Metabolism (IEM) are far from the rare systemic diseases that mainly affect the neural tissue. There are very few written reports on ocular findings in subjects with IEM, thus it was interesting to study the frequency of ocular findings in the studied population and explore their contribution to the early diagnosis of IEM.

METHODS

Our study involved the evaluation of IEM suspected cases, which had been identified in a rural population in Crete, Greece. Over a period of 3 years, 125 patients, who fulfilled the inclusion criteria of this study, were examined. Analytical physical examination, detailed laboratory investigation as well as a thorough ocular examination were made.

RESULTS

A diagnosis of IEM was established in 23 of the 125 patients (18.4%). Ten (43.5%) of the diagnosed IEM had ocular findings, while 8 of them (34.8%) had findings which were specific for the diagnosed diseases. One patient diagnosed with glycogenosis type 1b presented a rare finding. Of the 102 non-diagnosed patients, 53 (51.96 %) presented various ophthalmic findings, some of which could be related to a metabolic disease and therefore may be very helpful in the future.

CONCLUSIONS

The ocular investigation can be extremely useful for raising the suspicion and the establishment of an early diagnosis of IEM. It could also add new findings related to these diseases. The early management of the ocular symptoms can improve the quality of life to these patients.