Multiple Sulfatase Deficiency: A Disease Comprising Mucopolysaccharidosis, Sphingolipidosis, and More Caused by a Defect in Posttranslational Modification

Multiple sulfatase deficiency (MSD, MIM #272200) is an ultra-rare disease comprising pathophysiology and clinical features of mucopolysaccharidosis, sphingolipidosis and other sulfatase deficiencies. MSD is caused by impaired posttranslational activation of sulfatases through the formylglycine generating enzyme (FGE) encoded by the sulfatase modifying factor 1 (SUMF1) gene, which is mutated in MSD. FGE is a highly conserved, non-redundant ER protein that activates all cellular sulfatases by oxidizing a conserved cysteine in the active site of sulfatases that is necessary for full catalytic activity. SUMF1 mutations result in unstable, degradation-prone FGE that demonstrates reduced or absent catalytic activity, leading to decreased activity of all sulfatases. As the majority of sulfatases are localized to the lysosome, loss of sulfatase activity induces lysosomal storage of glycosaminoglycans and sulfatides and subsequent cellular pathology. MSD patients combine clinical features of all single sulfatase deficiencies in a systemic disease. Disease severity classifications distinguish cases based on age of onset and disease progression. A genotype- phenotype correlation has been proposed, biomarkers like excreted storage material and residual sulfatase activities do not correlate well with disease severity. The diagnosis of MSD is based on reduced sulfatase activities and detection of mutations in SUMF1. No therapy exists for MSD yet. This review summarizes the unique FGE/ sulfatase physiology, pathophysiology and clinical aspects in patients and their care and outlines future perspectives in MSD.

Sustained activation of sphingomyelin synthase by 2-hydroxyoleic acid induces sphingolipidosis in tumor cells

The mechanism of action of 2-hydroxyoleic acid (2OHOA), a potent antitumor drug, involves the rapid and specific activation of sphingomyelin synthase (SMS), leading to a 4-fold increase in SM mass in tumor cells. In the present study, we investigated the source of the ceramides required to sustain this dramatic increase in SM. Through radioactive and fluorescent labeling, we demonstrated that sphingolipid metabolism was altered by a 24 h exposure to 2OHOA, and we observed a consistent increase in the number of lysosomes and the presence of unidentified storage materials in treated cells. Mass spectroscopy revealed that different sphingolipid classes accumulated in human glioma U118 cells after exposure to 2OHOA, demonstrating a specific effect on C16-, C20-, and C22-containing sphingolipids. Based on these findings, we propose that the demand for ceramides required to sustain the SMS activation (ca. 200-fold higher than the basal level) profoundly modifies both sphingolipid and phospholipid metabolism. As the treatment is prolonged, tumor cells fail to adequately metabolize sphingolipids, leading to a situation resembling sphingolipidosis, whereby cell viability is compromised.

My journey into the world of sphingolipids and sphingolipidoses

Analysis of lipid storage in postmortem brains of patients with amaurotic idiocy led to the recognition of five lysosomal ganglioside storage diseases and identification of their inherited metabolic blocks. Purification of lysosomal acid sphingomyelinase and ceramidase and analysis of their gene structures were the prerequisites for the clarification of Niemann-Pick and Farber disease. For lipid catabolism, intraendosomal vesicles are formed during the endocytotic pathway. They are subjected to lipid sorting processes and were identified as luminal platforms for cellular lipid and membrane degradation. Lipid binding glycoproteins solubilize lipids from these cholesterol poor membranes and present them to water-soluble hydrolases for digestion. Biosynthesis and intracellular trafficking of lysosomal hydrolases (hexosaminidases, acid sphingomyelinase and ceramidase) and lipid binding and transfer proteins (GM2 activator, saposins) were analyzed to identify the molecular and metabolic basis of several sphingolipidoses. Studies on the biosynthesis of glycosphingolipids yielded the scheme of Combinatorial Ganglioside Biosynthesis involving promiscuous glycosyltransferases. Their defects in mutagenized mice impair brain development and function.

Clinical and mutational characterization of three patients with multiple sulfatase deficiency: report of a new splicing mutation

Multiple sulfatase deficiency (MSD) is a rare autosomal recessive lysosomal storage disease characterized by impaired activity of all known sulfatases. The gene SUMF1, recently identified, encodes the enzyme responsible for post-translational modification of a cysteine residue, which is essential for the activity of sulfatases. Fewer than 30 MSD patients have been reported to date and 23 different mutations in the SUMF1 gene have been identified. Here, we present the characterization of the mutant alleles of two Spanish and one Argentinean MSD patients. While the two Spanish patients were homozygous for the previously described mutations, c.463T>C (p.S155P) and c.1033C>T (p.R345C), the Argentinean patient was homozygous for the new mutation IVS7+5 G>T. A minigene approach was used to analyze the effect of the splice site mutation identified, due to the lack of sample from the patient. This experiment showed that this change altered the normal splicing of the RNA, which strongly suggests that this is the molecular cause of the disease in this patient.

The pathogenesis of glycosphingolipid storage disorders

Glycosphingolipid storage disorders are inborn errors of metabolism caused by the defective activity of degradative enzymes in lysosomes. In this review, we summarize studies performed over the past few years attempting to define the secondary and down-stream biochemical and cellular pathways affected in GSL storage disorders that are responsible for neuronal dysfunction, a characteristic of most of these disorders. We focus mainly on the regulation of intracellular calcium homeostasis and phospholipid biosynthesis. These studies may help unravel new roles for glycosphingolipids in the regulation of normal cell physiology, as well as suggest potential new therapeutic options in the glycosphingolipid and other lysosomal storage disorders.

Mutation analysis of the M6b gene in patients with Pelizaeus-Merzbacher-like syndrome

"Pelizaeus-Merzbacher-like syndrome" is an undetermined leukodystrophy disorder of diffuse hypomyelination. The patients' clinical phenotype is indistinguishable from classical Pelizaeus-Merzbacher disease (PMD), but the patients lack PLP1 gene duplications or mutations. They represent about 20% of all cases with a clinical PMD phenotype. The M6b gene has been localized to Xp22.2. The encoded M6B protein is a member of a novel proteolipid family that also includes other major brain myelin components like the proteolipid protein (PLP). Recent cotransfection experiments suggest a protein-protein interaction of M6B and mutant PLP1 that may contribute to oligodendrocyte dysfunction in PMD. Therefore, M6b has been considered a good candidate gene for Pelizaeus-Merzbacher-like syndrome. However, our molecular analyses in eight thoroughly characterized patients make it unlikely that mutations in this gene are involved in this subgroup of human hypomyelination disorders.

Use of Rab GTPases to study lipid trafficking in normal and sphingolipid storage disease fibroblasts

We describe methods for studying lipid transport in normal and sphingolipid storage disease fibroblasts. These techniques include endocytic assays with fluorescent sphingolipid analogs, expression of dominant negative (DN) Rab GTPases, and methods of manipulating cholesterol levels in intact cells and isolated cell membranes. These methods should be useful in future studies of lipid trafficking in normal and disease cell types.

[Pigmented form of orthochromatic leukodystrophy]

The pigmentary type of orthochromatic leukodystrophy (van Bogaert-Nyssen disease) is a hardly known neurological disorder usually with late onset that is very difficult to diagnose in vivo. Neuropathologically, the disorder features noninflammatory demyelination and the presence of pigmented macrophages and astrocytes that may contain iron. Clinically, van Bogaert-Nyssen disease can lead to death within a few years and is characterized by dementia, psychiatric abnormalities, epileptic seizures, spastic pareses, and occasionally extrapyramidal motor symptoms. This report presents a typical case and an overview of the literature. Furthermore, galactocerebroside could be documented in remaining macrophages and astrocytes by immunohistochemistry. This possibly indicates a dysfunction in sphingolipid breakdown and could relate the pigmented form of orthochromatic leukodystrophy to the genetically defined globoid cell leukodystrophy (Krabbe's disease). Thus, the rather heterogeneous pool of orthochromatic leukodystrophies could be further narrowed.

Cerebral glycolipidoses: clinical characteristics of 41 pediatric patients

A retrospective clinical and biochemical analysis of 41 pediatric patients with cerebral lipidoses seen between 1995 to 2003 was performed at a tertiary referral center for neurologic disorders in southern India. Enzyme assays in serum and leukocytes, including histopathology, neuroimaging, and neurophysiology studies, were performed. There were 20 cases of metachromatic leukodystrophy (infantile,14; juvenile, 6), 12 cases of Tay-Sachs disease (infantile, 9; late G(M2-M3) gangliosidoses, 3), 8 cases of Sandhoff's disease, and 1 male case with multiple sulfatase deficiency. Consanguinity was present in 51.2% of cases. The male-to-female ratio was 23:17. Similar illness in the families was noted in 24.4%. The prominent clinical features in sulfatide lipidoses were regression of motor and mental milestones, seizures, and speech impairment, and in G(M2) gangliosidoses, the features were delayed milestones, startle myoclonus, seizures, and the presence of cherry-red spots. The case with multiple sulfatase deficiency had low levels of arylsulfatase A and B. This study indicates that these autosomal recessive inherited disorders are indeed prevalent in India.

The latest on leukodystrophies

PURPOSE OF REVIEW

Important advances in our understanding of genetic disorders of the white matter have been made and are discussed here.

RECENT FINDINGS

It has recently been discovered that mutations in the genes encoding the five subunits of eukaryocytic initiation factor 2B (eIF2B) are the cause of vanishing white-matter disease/childhood ataxia with central hypomyelination syndrome. The extension of the clinical features of the eIF2B-related disorders to encompass both infant- and adult-onset disorders is discussed. New clinico-imaging syndromes such as hypomyelination with atrophy of the basal ganglia and cerebellum and leukoencephalopathy with brain-stem and spinal cord involvement and elevated white-matter lactate are described. Recent findings include evidence that mitochondrial fat-oxidation abnormalities may be important in the pathogenesis of adrenoleukodystrophy, and that a mutant myelin protein can cause maldistribution of other myelin proteins, causing dysmyelination, axonal damage, or both.

SUMMARY

This review focuses on advances in the understanding of the role of eIF2B as a cause of a common leukodystrophy syndrome. eIF2B-related disorders have a clinical spectrum ranging from a severe, rapidly progressive congenital or early infantile encephalopathy to a slowly progressive cognitive and motor deterioration often associated with premature ovarian failure. Two newly recognized leukodystrophy syndromes are described: hypomyelination with atrophy of the basal ganglia and cerebellum, and leukoencephalopathy with brain-stem and spinal cord involvement and elevated white-matter lactate. An update is also given for adrenoleukodystrophy and myelin-protein-related disorders. This update demonstrates that an increasing number of genetic defects are being identified that may cause primary white-matter disorders.

Endocytosis and sorting of glycosphingolipids in sphingolipid storage disease

Recent studies on the endocytic itinerary of glycosphingolipids (GSLs) in sphingolipid storage disease (SLSD) fibroblasts have yielded new insights into the mechanisms underlying the endocytosis and intracellular sorting of lipids in normal and disease cells. Here we highlight new data on clathrin-independent endocytosis of GSLs, the involvement of sphingolipid-cholesterol interactions in perturbation of endocytic trafficking, and potential roles for rab proteins in regulation of GSL transport in SLSDs.

A model for PKC involvement in the pathogenesis of inborn errors of metabolism

A model for the possible involvement of Protein Kinase C (PKC) in the pathogenesis of inborn errors of metabolism has been proposed. According to this model, perturbation of PKC activity by the accumulation of naturally occurring compounds serves as a unifying functional link between genotype and phenotype. Recent reports regarding an increasing number of modulating metabolites, specific PKC-subtypes activities, their effect on transcription factors and gene expression in various diseases and additional PKC-substrates expand the model. A re-examination of the proposed model in view of these reports and, vice versa, a review of these reports in the context of the proposed model reveal some common phenotypic outcomes in inborn errors of fatty acid-, cholesterol- and homocystine-metabolism as well as lysosomal and peroxisomal diseases.

Application of delayed extraction matrix-assisted laser desorption ionization time-of-flight mass spectrometry for analysis of sphingolipids in cultured skin fibroblasts from sphingolipidosis patients

Sphingolipidoses are caused by defects of enzymes involved in the hydrolysis of sphingolipids. Using delayed extraction matrix-assisted laser desorption ionization time-of-flight mass spectrometry (DE MALDI-TOF-MS), we analyzed sphingolipids in cultured skin fibroblasts from patients with sphingolipidoses, including: (a) Farber disease (FD, acid ceramidase deficiency); (b) Gaucher disease (GD); (c) Niemann-Pick disease type C (NPDC); and (d) GM1-gangliosidosis (GM1G). Crude lipids were extracted from about 50 mg wet weight of cultured skin fibroblasts. After mild alkaline treatment, a sphingolipid fraction was prepared from the crude lipids and analyzed by DE MALDI-TOF-MS. The results were as follows: (a) in fibroblasts from the FD patient, the ceramide/sphingomyelin and ceramide/monohexosylceramide ratios were both significantly high; (b) in the GD patient, the glucosylceramide/sphingomyelin ratio was increased; on the other hand; (c) in the NPDC patient, the monohexosylceramide/sphingomyelin ratio was within normal range; and (d) in the GM1G patient, no specific data were obtained. Sphingolipids in cultured fibroblasts can be evaluated by DE MALDI-TOF-MS, whereas GM1-ganglioside or its asialo derivatives are not detectable. With this DE MALDI-TOF-MS method, ceramide or monohexosylceramide accumulating in cultured fibroblasts from cases of sphingolipidoses, such as FD and GD, respectively, can be easily detected.

[Non specific leukodystrophy. A new case of vacuolizing leukoencephalopathy with megalencephaly]

INTRODUCTION

Amongst the conditions affecting the white matter, the disorders of myelinization, including the leukodystrophies, are important in the field of paediatric neurology. Although classically they have been classified according to whether the metabolic defect was known or not, at the present time great advances in neuroimaging have clarified many genetic disorders involving the white matter and new classifications have been devised. The group of unknown aetiology includes the so called non specific leukodystrophies, characterized by their onset in infancy with a usually more moderate clinical course, and neuro imaging (computerized tomography CT magnetic resonance MR ) with alteration of the signal from the white matter which is symmetrical, bilateral and diffuse. Study and investigation of the patterns of MR has permitted isolation of two new clinical conditions of the non specific leukodystrophies group: leukodystrophy with megalencephaly and temporal cysts (Van der Knaap, 1995) for which currently the term vacuolizing leukoencephalopathy with megalencephaly is preferred and the CASH syndrome (childhood ataxia with central hypomyelinization or vanishing white matter disease) (Van der Knaap, 1997).

DEVELOPMENT

We present a review of nine cases of non specific leukodystrophies with an average course of 13 years. They were studied using the protocol of the European working party on demyelinating diseases. One of these fulfilled clinical and radiological criteria for the diagnosis of vacuolizing leukoencephalopathy with megalencephayl: onset in early childhood, macrocephaly, normal metabolic studies, moderate progression and alteration of the white matter signal which was bilateral, symmetrical and diffuse with the presence of oedema and temporal subcortical cysts. We discuss the most relevant articles currently published on this condition.

The SOX10 transcription factor: evaluation as a candidate gene for central and peripheral hereditary myelin disorders

The SOX10 transcription factor is involved in development of neural crest derivatives and fate determination in glial cells. SOX10 mutations have been found in patients with intestinal aganglionosis and depigmentation with deafness (Waardenburg-Hirschsprung). Associated neurological signs have been reported in some cases, including a patient exhibiting a central and peripheral myelin deficiency. Therefore, we screened for SOX10 mutations in a large cohort of patients with peripheral and central myelin disorders. 56 were affected by classical demyelinating Charcot-Marie-Tooth disease without identified mutations in the genes encoding PNS myelin proteins (PMP22, P0), connexin 32 and the zinc-finger transcription factor, EGR2. 88 patients with undetermined leukodystrophy were selected from a large European prospective study. Associated clinical, magnetic resonance imaging and electrophysiological signs were consistent with a defect in CNS myelination in 83 and with an active degeneration of the CNS myelin in 5. No abnormalities in the proteolipid protein gene (PLP) were found. The absence of SOX100 mutation in this large cohort of patients suggests that this gene is not frequently involved in peripheral or central inherited myelin disorders.

A novel mutation in the coding region of the prosaposin gene leads to a complete deficiency of prosaposin and saposins, and is associated with a complex sphingolipidosis dominated by lactosylceramide accumulation

A fatal infantile storage disorder with hepatosplenomegaly and severe neurological disease is described. Sphingolipids, including monohexosylceramides (mainly glucosylceramide), dihexosylceramides (mainly lactosylceramide), globotriaosyl ceramide, sulphatides, ceramides and globotetraosyl ceramide, were stored in the tissues. In general, cholesterol and sphingomyelin levels were unaltered. The storage process was generalized and affected a number of cell types, with histiocytes, which infiltrated a number of visceral organs and the brain, especially involved. The ultrastructure of the storage lysosomes was membranous with oligolamellar, mainly vesicular, profiles. Infrequently, there were Gaucher-like lysosomes in histiocytes. The neuropathology was severe and featured neuronal storage and loss with a massive depopulation of cortical neurons and pronounced fibrillary astrocytosis. There was a paucity of myelin and stainable axons in the white matter with signs of active demyelination. Immunohistochemical investigations indicated that saposins A, B, C and D were all deficient. The patient was homozygous for a 1 bp deletion (c.803delG) within the SAP-B domain of the prosaposin gene which leads to a frameshift and premature stop codon. In the heterozygous parents, mutant cDNA was detected by amplification refractory mutation analysis in the nuclear, but not the cytoplasmic, fraction of fibroblast RNA, indicating that the mutant mRNA was rapidly degraded. The storage process in the proband resembled that of a published case from an unrelated family. Saposins were also deficient in this case, leading to its reclassification as prosaposin deficiency, and her mother was found to be a carrier for the same c.803delG mutation. Both of the investigated families came from the same district of eastern Slovakia.

Remyelinating the demyelinated CNS

The CNS has an inherent capacity to generate remyelinating cells following episodes of myelin loss. However, persistent demyelination is the major pathology of multiple sclerosis and the leucodystrophies, and is also a feature of spinal cord trauma. There are potentially two approaches for achieving remyelination in situations where it fails; enhancement of the inherent remyelinating capacity of the CNS, or transplantation of an exogenous source of myelin forming cells. In experimental animals it is possible to remyelinate demyelinated CNS axons by transplanting cultures containing central or peripheral myelinogenic cells. Glial cell transplantation may thus provide a therapeutic strategy for remyelinating areas of chronic demyelination as well as for stimulating axon regeneration. This presentation will review four issues that have to be addressed before glial transplantation can be undertaken in humans: is the procedure safe, what cells would be used, where would the cells come from and can we predict how much remyelination will be achieved? It concludes that the most promising approach will be to use multipotent neural precursor cells that have been committed to oligodendrocyte lineage differentiation prior to implantation. However, even with such preparations, which have considerable myelinating potential, the extent of remyelination that would be achieved can not yet be predicted with any degree of certainty.

Gaucher disease: understanding the molecular pathogenesis of sphingolipidoses

Gaucher disease is a typical lysosomal storage disease, resulting from an inborn deficiency of glucocerebrosidase. This leads to the accumulation of glycolipids in macrophages, particularly those in the liver, bone marrow, spleen and lung. In addition, disease of the nervous system can arise as a result of the accumulation of endogenous glycosphingolipid metabolites in brain tissue. About 150 mutations of the glucocerebrosidase gene have been identified in patients with Gaucher disease, some of which are predictive of phenotype. However, even patients and siblings with the same mutation, including monozygotic twins, may exhibit marked variability in disease expression and severity, illustrating our lack of understanding of the phenotype-genotype relationship in the sphingolipidoses. Massive organomegaly, particularly of the spleen, is a frequent feature of the disease. Although the liver and spleen may increase greatly in size, the amount of pathological lipid stored in the affected macrophages (Gaucher cells) accounts for less than 2% of the additional tissue mass. It is therefore clear that an inflammatory response occurs in affected individuals and that the clinical phenotype is due to an effect of macrophage storage beyond the physical presence of the Gaucher cells. Factors released by Gaucher cells, including pro-inflammatory cytokines and perhaps cathepsins, provide a mechanistic link between lysosomal storage and the diverse clinical manifestations of Gaucher disease. Emerging proteomic technology and gene expression profiling should not only improve our understanding of pathogenesis but also offer the prospect of identifying novel biomarkers that can be used as surrogate measures of disease activity and responses to treatment.

Broad screening test for sphingolipid-storage diseases

BACKGROUND

Lipid-storage diseases are collectively important because they cause substantial morbidity and mortality, and because they may present as dementia, major psychiatric illness, developmental delay, or cerebral palsy. At present, no single assay can be used as an initial general screen for lipid-storage diseases.

METHODS

We used a fluorescent analogue of lactosylceramide, called N-[5-(5,7-dimethylborondipyrromethenedifluoride)-1-pentanoyl]D- lactosylsphingosine (BODIPY-LacCer), the emission of which changes from green to red wavelengths with increasing concentrations in membranes, to examine the intracellular distribution of the lipid within living cells.

FINDINGS

During a brief pulse-chase experiment, the fluorescent lipid accumulated in the lysosomes of fibroblasts from patients with Fabry's disease, GM1 gangliosidosis, GM2 gangliosidosis (Tay-Sachs and Sandhoff forms), metachromatic leucodystrophy, mucolipidosis type IV, Niemann-Pick disease (types A, B, and C), and sphingolipid-activator-protein-precursor (prosaposin) deficiency. In control cells, the lipid was mainly confined to the Golgi complex. In a masked study, replicate samples of 25 of 26 unique cell lines representing ten different lipid-storage diseases, and 18 of 20 unique cell lines representing controls were correctly identified; the sensitivity was 96.2% (95% CI 80.4-99.9) and the specificity 90.0% (68.3-98.8).

INTERPRETATION

This method may be useful as an initial general screen for lipid-storage diseases, and, with modification, could be used for large-scale automated screening of drugs to abrogate lysosomal storage in various lipidoses. The unexpected accumulation of BODIPY-LacCer in several biochemically distinct diseases raises important questions about common mechanisms of cellular dysfunction in these disorders.

Neuronopathic juvenile glucosylceramidosis due to sap-C deficiency: clinical course, neuropathology and brain lipid composition in this Gaucher disease variant

Glucosylceramide lipidosis results from a defective lysosomal degradation of this glycolipid. Lipid degradation is controlled by two components, the enzyme beta-glucocerebrosidase and a sphingolipid activator protein. While most Gaucher cases are due to mutations within the gene that codes for the lysosomal enzyme, only two patients have been described with normal enzyme levels and mutations in the gene for the sphingolipid activator protein C (sap-C). Here we present the detailed neurological manifestations, neuropathological findings and brain lipid composition in one sap-C-deficient patient. The patient was an 8-year-old boy who presented with transient losses of consciousness, myoclonic jerks and generalized seizures resistant to all antiepileptic drugs. He developed progressive horizontal ophthalmoplegia, pyramidal and cerebellar signs, and died at the age of 15.5 years. Neuropathological studies demonstrated neuronal cell loss and neuronophagia, massive intraneuronal lipid storage and lack of perivascular Gaucher cells. Electron microscopy examination showed different types of storage including lipofuscin granules as well as the cytosomes with parallel arrays of bilayers that are assumed to be formed by stored lipids. General brain lipid composition did not show a remarkable increase or loss of any of the major lipid fractions but the glucosylceramide concentration in the cortex of several anatomical regions showed a striking increase. Fatty acid composition of the ceramide moiety clearly suggests that gangliosides are the main precursors in the cerebral cortex, while it implies an additional and distinct source in the cerebellum. Studying the phenotypic consequences of mutant sphingolipid activator proteins is critical to a better understanding of the physiological significance of these proteins.

Sphingolipids and cell signalling

The sphingolipid storage disorders constitute a group of inherited metabolic disorders in which the structure of the stored sphingolipid and the corresponding genetic defect have been established. However, the pathological mechanism(s) behind the disorders has not been fully elucidated. Sphingolipids are known to be recognition molecules involved in intercell communication and altered expression might lead to dyscommunication. The impaired degradation and lysosomal accumulation of specific sphingolipids might influence the metabolism of other molecules and/or intracellular transport, which in turn might alter the distribution of these molecules. However, the progress of these diseases indicates that additional factors, besides the stored sphingolipid itself, might be involved. During the last decade, several sphingolipids have emerged as active participants in intracellular signalling processes such as growth control and apoptosis. Particular interest focused on the sphingolipid metabolites, ceramide and sphingosine, as potential mediators in intracellular events and an altered presence of these metabolites in sphingolipidoses cannot be ruled out. Some sphingolipids have been found to influence cytokine release and thereby might induce immunological processes, which are known to exist in at least one of the sphingolipidoses--Gaucher disease. These processes might already have a pathogenic effect during early development, before significant storage has occurred.

GM2 ganglioside as a regulator of pyramidal neuron dendritogenesis

One of the most profound events in the life of a neuron in the mammalian CNS is the development of a characteristic dendritic tree, yet little is understood about events controlling this process. Pyramidal neurons of the cerebral cortex are known to undergo a single explosive burst of dendritic sprouting immediately after completing migration to the cortical mantle, and following maturation there is no evidence that new, primary dendrites are initiated. Yet in one group of rare genetic diseases--Tay-Sachs disease and related neuronal storage disorders--cortical pyramidal neurons undergo a second period of dendritogenesis. New dendritic membrane is generated principally at the axon hillock and in time is covered with normal-appearing spines and synapses. In our studies of normal brain development and storage diseases we consistently find one feature in common in cortical pyramidal neurons undergoing active dendritogenesis: They exhibit dramatically increased expression of GM2 ganglioside localized to cytoplasmic vacuoles within neuronal perikarya and proximal dendrites. There is also evidence that the increase in GM2 precedes dendritic spouting, and that after dendritic maturation is complete (in normal brain) the GM2 levels in neurons become substantially reduced. These findings are consistent with GM2 ganglioside playing a pivotal role in the regulation of dendritogenesis in cortical pyramidal neurons.

Prosaposin deficiency: further characterization of the sphingolipid activator protein-deficient sibs. Multiple glycolipid elevations (including lactosylceramidosis), partial enzyme deficiencies and ultrastructure of the skin in this generalized sphingolipid storage disease

Sphingolipid activator protein (SAP) deficiency, previously described in two sibs and shown to be caused by the absence of the common saposin precursor (prosaposin), was further characterized by biochemical lipid and enzyme studies and by ultrastructural analysis. The 20-week-old fetal sib had increased concentrations of neutral glycolipids, including mono-, di-, tri- and tetrahexosylceramide, in liver, kidney and cultured skin fibroblasts compared with the controls. Glucosylceramide and lactosylceramide were particularly elevated. The kidney of the affected fetus showed additional increases in the concentration of sulphatide, galactosylceramide and digalactosylceramide. Free ceramide was stored in the liver and kidney, and GM3 and GM2 gangliosides were elevated in the liver, but not the brain, of the fetus. Phospholipids, however, were normal in the affected fetus. In the liver biopsy of the propositus, who later died at 16 weeks of age, only a few lipids could be studied. Glucosylceramide, dihexosylceramide and ceramide were elevated in agreement with our previous study. Enzyme studies were undertaken using detergent-free liposomal substrate preparations and fibroblast extracts. The sibs' beta-glucocerebrosidase and beta-galactocerebrosidase activities were clearly reduced, but their sphingomyelinase activities were normal. The normal activity of the latter enzyme and the almost normal tissue concentration of sphingomyelin in prosaposin deficiency suggest that the prosaposin-derived SAPs are not required for sphingomyelinase activity in vivo. In keeping with the biochemical findings, skin biopsies from the sibs showed massive lysosomal storage with a vesicular and membranous ultrastructure. The function of SAPs in sphingolipid degradation and the role of SAPs for enzyme activity in vitro are discussed. In addition, the similarity in neutral glycolipid accumulations in Niemann-Pick disease type C and in prosaposin deficiency are noted. The phenotype of the prosaposin deficient sibs resembled acute neuronopathic (type 2) Gaucher disease more than Farber disease in several aspects, but their genotype was unique.

A case of Farber disease

We report a case of Farber disease (Farber lipogranulomatosis). The main features were a shrill voice, joint swelling, subcutaneous nodules and retarded psychomotor development. Cytological investigation revealed intracytoplasmic inclusion bodies characteristic of Farber disease. Lipid analysis of liver tissue indicated an accumulation of ceramide containing non-hydroxy fatty acids. It was found that the acid ceramidase activity in the liver was reduced to 31% of the control value. In this patient there was also persistent diarrhea, cholelithiasis, transient proteinuria and increased urinary total sialic acids. These features have not been noted in previously reported cases.

Feline sphingolipidosis resembling Niemann-Pick disease type C

A 9-week old domestic short-hair kitten with progressive neurological dysfunction had histopathological lesions consistent with a lysosomal storage disease. Light microscopy of the brain, spinal cord, and ganglia revealed distention and vacuolation of many neuronal populations, and extensive neuroaxonal dystrophy. Large numbers of foamy macrophages were observed in the liver, spleen, lymph nodes, and lung. Hepatocytes appeared pale and swollen. Ultrastructural examination of all affected tissues and organs revealed heterogeneous membranous inclusions. Lipid analysis of liver revealed an excess of cholesterol, glucosylceramide, lactosylceramide and phospholipids including sphingomyelin. There was some increase in the levels of brain GM2 and GM3 gangliosides. Sphingomyelinase activity in liver was partially deficient or low normal. Skin fibroblasts were cultured from two affected cats from the colony established with littermates of the subject of this report. The cultured skin fibroblasts had partially decreased sphingomyelinase activity and a greatly decreased ability to esterify exogenous cholesterol. Clinical, morphological, and biochemical findings suggest that this cat had sphingolipidosis similar to human Niemann-Pick disease type C, a disease not previously described in the cat. The feline form of this storage disease may provide a useful model for studies on the human disease.

Farber's lipogranulomatosis in siblings: light and electron microscopic studies

Two cases of Farber's lipogranulomatosis in siblings are reported. The clinical features included contractures of the limbs with swelling of the joints and subcutaneous nodules and erythematous infiltrated plaques. On histology there were many large foam cells in the dermis, and electron microscopy showed numerous large cells with round cytoplasmic lamellar and microtubular bodies.

Neurovisceral sphingomyelinosis in a Siamese cat

This report presents the clinical, morphological and biochemical findings on an 11-month-old female Siamese cat with neurovisceral sphingomyelinosis. Gross pathological features and histochemical findings are compared with the human disease counterpart and the previously described animal models. Hepatomegaly was observed while splenomegaly was not. Although sphingomyelin in liver and spleen was biochemically elevated, histochemical results in this case were slightly different from those previously recorded in human and feline Niemann-Pick disease. These results suggest that this feline case might be a different type of animal Niemann-Pick disease to that reported previously.

The contribution of pathology to the study of storage disorders

Our purpose is to illustrate some contributions of pathology to a better knowledge of metabolic disorders affecting the brain and visceral organs. Four groups of diseases are used to that effect. A comparative study of pre- and postnatal examples of mucopolysaccharidoses I, II and III reveals for example that severe neuronal lesions are already found in fetuses and that a rough parallelism exists between the maturation of neurons and the progressive intralysosomal accumulation of undigested metabolites. The study of four patients with I-cell disease shows that the intralysosomal storage occurs nearly exclusively in fibroblasts. Since the enzyme defect has also been found in non-mesenchymal cells, other mechanisms for a proper processing of lysosomal enzymes must be available in the intact cells. Adrenoleukomyeloneuropathy is used to demonstrate that the morphological features witnessing the accumulation of the very long chain fatty acids can be different in the central and in the peripheral nervous system. Finally, juvenile dystonic lipidosis illustrate the heterogeneity of the conditions grouped under the denomination of sphingomyelinoses. These few examples confirm the role of pathology in the diagnosis of metabolic disorders and in the study of their physiopathogenesis.

Cerebellar involvement in murine sphingomyelinosis: a new model of Niemann-Pick disease

Mice with sphingomyelinosis (spm) with a C57BL/KsJ inbred background showed hepatosplenomegaly as early as four weeks (wk) of age and cerebellar signs around seven wk. Almost all animals died by 14 wk. Sudanophilic lipid accumulated in the liver, spleen, and lymph nodes as well as in the brain. The striking neuropathological change was a marked atrophy of the cerebellum, where Purkinje cells were predominantly involved. Loss of Purkinje cells started at the age of six wk before the cerebellar signs had become evident clinically. The cell loss appeared to be more marked in the vermis than in the hemispheres. Cytoplasmic inclusions in most cells consisted of myelin figures composed of concentric membranous lamellae. These inclusions were found mainly in the Purkinje cells at an early stage; thereafter, they were widely distributed in the granule cells, Golgi cells, some glial cells, macrophages and endothelial cells. The neuronal inclusions were frequently located in the vicinity of the Golgi apparatus; there were no unusual mitochondrial configurations. The clinicopathological characteristics of the mutant mice are similar to those of the human Niemann-Pick disease type C.

Lipid storage disease: Part III. Ultrastructural evaluation of cultured fibroblasts in sphingolipidoses

For the purpose of evaluating electron microscopy of tissue culture in making the diagnosis of sphingolipidoses, an ultrastructural study was made on the cultured fibroblasts from 23 patients with the disorders. The characteristic cytoplasmic inclusions were observed in the cultured cells of Fabry disease, Tay-Sachs disease, Sandhoff disease, generalized gangliosidosis, Niemann-Pick disease, metachromatic leukodystrophy, and multiple sulfatase deficiency, and differ in fine structure with these diseases. All these cytoplasmic inclusions were surrounded by a single limiting membrane and enzyme cytochemically showed acid phosphatase activity, indicating their lysosomal origin. Ultrastructurally, the cytoplasmic inclusions showed pleomorphic osmiophilic inclusions in Fabry disease, membranous cytoplasmic bodies (MCB) in Tay-Sachs disease and Sandhoff disease, MCB and vacuolar inclusions containing finely reticulogranular materials in generalized gangliosidosis, myelin-like inclusions in Niemann-Pick disease, concentric lamellar inclusions in metachromatic leukodystrophy, and polymorphic cytoplasmic inclusions in multiple sulfatase deficiency. In the heterozygous carriers of Fabry disease, pleomorphic osmiophilic inclusions were also detected. However, any specific inclusions were not detectable in the cultured fibroblasts of Gaucher disease and Krabbe disease. Availability of electron microscopy in the cultured fibroblasts of sphingolipidoses is discussed.

Farber's disease: a fine structural study

A 1-week-old baby boy presented with hepatosplenomegaly, coarse facial features, and cloudy corneas. A metabolic storage disease was considered and he underwent cutaneous and liver biopsy. By light microscopy the skin was normal. Kupffer cells were enlarged and had foamy cytoplasm. Ultrastructural examination of skin and liver demonstrated features compatible with Farber's disease: curvilinear and "banana" bodies, zebra-like structures, and concentric lamellar bodies. A deficiency of lysosomal acid ceramidase was subsequently demonstrated in cultured fibroblasts and in liver tissue corroborating the ultrastructural findings.

Sphingomyelin lipidosis variant with cirrhosis in the pediatric age group

Two children with a variant of sphingomyelin lipidosis had otherwise unexplained cirrhosis that was histologically inactive and appeared to run an indolent course. The primary clinical problems involved the central nervous system, with vertical supranuclear ophthalmoplegia being the most distinctive feature. Biochemical analysis of cultured skin fibroblasts obtained from one of the children revealed that sphingomyelinase activity was 42% of control values. The typical inconspicuous hepatic storage and cirrhosis, coupled with the important morphologic finding of sea-blue histiocytes in the marrow, suggested that in cases of unexplained infantile or childhood cirrhosis the marrow should be closely examined for such histiocytes. Likewise, in cases of sea-blue histiocytes without evident etiology, with or without cirrhosis, this disease should be considered.

Farber's disease in two siblings, sural nerve and subcutaneous biopsies by light and electron microscopy

Two siblings born from consanguineous tunisian parents are reported. They showed a severe form of Farber's disease with prominent involvement of the central and peripheral nervous system: low conduction velocity was noticed in both children. Macular cherry red spots were observed in one of them. The diagnosis for the girl investigated was confirmed by evidence of ceramidase deficiency in cultured fibroblasts. Here we report the pathological findings in the subcutaneous nodules using light and electron microscopy (one case), and in sural nerves using morphometric studies (both cases). Varying morphological aspects of intracellular inclusions, depending on the tissues involved, are described and discussed. A review of all cases reported since Farber's first paper in 1952 is given.

[Farber's lipogranulomatosis. Apropos of a case]

A case of Farber's lipogranulomatosis is described in an 18 month-old girl. There was clinical evidence for diagnosis, which was confirmed by a ceramidase activity assay on cultured fibroblasts. A study of the conjunctiva by electron microscopy was performed. The authors emphasize the clinical and biological characteristics of such cases.

Heritable metabolic storage diseases

During the last decade, examinations of skin biopsies have gained increasing importance in the search for a better understanding and facilitated diagnosis of metabolic storage diseases. In addition to biochemical and tissue culture techniques, light- and electron-microscopic investigations have been recommended in a number of such disorders (1-6). There are, however, a large number of different and inhomogeneous conditions to be identified in this group. At present, approximately 300 diseases can be identified as inborn errors of metabolism by the determination of a biochemically well-established underlying defect. Moreover, a yet undetermined number of pathological conditions is accompanied by the deposition of more or less defined storage materials in cutaneous tissue elements. It appears, therefore, premature to propose a systematic dermatopathology of metabolic storage diseases, and the following contribution should be understood as an attempt to indicate possibilities and chances by quoting some representative examples.

Farber's disease. Light and electron microscopic study of the eye

A 35-month-old girl had Farber's disease (disseminated lipogranulomatosis) manifested clinically by macular cherry-red spots. The pathologic changes consisted of intracellular inclusions of varying morphologic features and density. The most frequently encountered inclusion was 1.2 micron wide and consisted of flattened stacks of osmophilic lamellae (2.1 to 2.3 nm thick, with 4.4-nm periodicity) oriented in parallel or oblique array ("zebra-body" configuration) and enclosed by a focally discontinuous unit membrane. Some of the inclusions contained curved tubular profiles resembling curvilinear tubular bodies. The retinal ganglion cells were grossly distended with inclusions and showed the greatest pathologic changes.

[Generalized GM1 gangliosidosis. Report of a case and review of the literature]

Authors present the case of a child, daughter of non related parents with neurologic progressive affectation, retina and visceral implication with certain pseudogargolic clinical aspect without near familiar antecedents suggestive of this disease. Biochemistry and histologic studies revealed a B-galactosidase enzyme deficiency and lipidic intracellular increase in different viscera. Biochemistry, hystological and clinical aspects exposed are fundamentally differential of another causes of pseudo-Hurler syndrome.

Sphingomyelin lipidosis in a cat: Golgi studies

Alterations in neuronal geometry in a feline model of sphingomyelin lipidosis were evaluated using Golgi staining. Neurons in cerebral cortex, basal ganglia, amygdala, thalamus, and cerebellum were impregnated and many were found to possess conspicuous enlargements at the axon hillock-initial segment region (meganeurites) and/or to sprout secondary neuritic processes from this same area. The latter were sometimes well developed and resembled small dendrites. These changes were cell type specific with distribution limited to certain types of neurons in select brain regions, while others remained normal, or underwent only simple somatic enlargement or generalized degenerative changes. Occasional cortical pyramidal neurons also displayed thinning of dendrites and extensive loss of dendritic spines. These observations add sphingomyelin lipidosis to other neuronal storage disorders in which aberrant neurite growth and meganeurite formation accompany lysosomal enzyme deficiency and the associated metabolic alterations and storage. Although meganeurite-like expansions have been reported to occur in many storage disorders, the appearance of axon hillock-associated neurite growth on morphologically mature neurons has been identified heretofore only in the gangliosidoses, and in feline models of alpha-mannosidosis and mucopolysaccharidosis type 1.

Abnormalities of lysosomes in human diploid fibroblasts from patients with Farber's disease

An accumulation of ceramide associated with the deficiency of acid ceramidase has been demonstrated in cultured diploid skin fibroblasts from a patient with Farber's disease. We extend this observation to investigate the lysosomal localization of accumulated ceramide and the abnormalities of lysosomes caused by this ceramide accumulation in Farber's diseased fibroblasts. We have found that the lysosomal fraction isolated from Farber's diseased fibroblasts by a subcellular fractionation procedure is markedly low in density compared with that of normal fibroblasts and is separated from other subcellular organelles. Ultrastructural studies of the isolated lysosomal fraction from Farber's diseased fibroblasts showed a mixed population of intact and swollen vesicles with a lysosomal appearance. Examination under high magnification clearly demonstrated lysosomal inclusions which contain lamellar and curvilinear membranes and resembled those seen in the intact fibroblasts. Subcellular localization of Farber's fibroblasts showed that the accumulated [3H]ceramide from the culture medium was predominantly localized in the lysosomal fraction with a markedly low density and very little was found to be associated with other cellular membranes. Our finding that ceramide is accumulated in the lysosomal fraction of Farber's fibroblasts and that these cells also show membranous inclusions strongly suggests that the accumulation of ceramide is directly involved in the formation of lysosomal inclusions.

Ovine ceroid-lipofuscinosis: a model of Batten's disease

An inherited neurological disease of sheep was characterized by the intracellular accumulation of autofluorescent lipopigments in neurones and a wide variety of other cells within the body. The staining, fluorescent, ultrastructural and physical characteristics of the storage material were similar to those found in a heterogeneous group of storage diseases of children known as Batten's disease or the ceroid-lipofuscinoses. The ovine disease did not exactly fit any of the main human entities, but had features in common with both the late infantile and juvenile forms. It was concluded that this was a useful model for studying the pathogenesis of this type of storage disease and for therapeutic trials. A flock of sheep is maintained for this purpose.

[Interest of ultrastructural study of skin and muscle biopsies in inborn storage diseases. A report of 18 cases (author's transl)]

Skin and muscle biopsies were performed in 18 patients affected by various inborn storage disorders: mucopolysaccharidosis (MPS), sphingolipidosis, GM1 gangliosidosis, I-cell disease, ceroid-lipofuscinosis (CLF), adrenoleucodystrophy (ALD) and glycogenosis. In most cases, cutaneous and muscle biopsies demonstrate clearly the presence of storage inclusions in different cell types with great reproducibility and sometimes a specificity for a particular disease. Thus, electron microscopic examinations of skin and muscle, often complementary, can given valuable informations at two levels: - either a morphological confirmation depending on the type of the storage disease: e. g. clear, granular and fuzzy inclusions identified with mucopolysaccharidic material, lamellar and pseudomyelinic figures corresponding to lipidic structures are found in different cell types in MPS, gangliosidosis and sphingolipidosis; - or a diagnostic proof of some lysosomal diseases where there are very specific ultrastructural features such as the curvilinear bodies and fingerprint profiles in CLF or the spicular inclusions in ALD. These informations are the more important as the enzymatic defect is unknown in these inherited disorders. We conclude that the ultrastructural examination of a skin and muscle biopsy are an important tool for the diagnosis of a lysosomal storage disease which avoids any more difficult biopsies as brain, kidney, liver.

Electron microscopy of skin and peripheral blood lymphocytes in infantile (Santavuori) neuronal ceroid lipofuscinosis

Skin punch biopsies and peripheral blood lymphocyte preparations from two siblings with early infantile (Santavuori) neuronal ceroid lipofuscinosis have been examined by electron microscopy. In both cases characteristic osmiophilic inclusion bodies were found in various cells in the skin and in lymphocytes. In one case, lymphocyte inclusions were detected before the onset of any symptoms as a result of a family study. This indicates the possibility of screening lymphocytes of siblings of affected patients as a result of a family study. This indicates the possibility of screening lymphocytes of siblings of affected patients with a view to early detection of the disorder.