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GM2-gangliosidosis, AB variant: clinico-pathological study of a case.

Clinical and neuropathological studies of a case of AB variant GM2-gangliosidosis have been presented. The patient was a 14 months old black female infant who had "black cherry spot" in the retinas. The total activities of beta-galactosidase and N-acetyl-beta-hexosaminidase, as well as the proportion of hexosaminidase A and B components in her serum and leukocytes were normal when the assays were carried out with artificial fluorogenic substrate. Diagnosis of GM2-gangliosidosis AB variant was established by an abnormal increase of GM2-ganglioside in the biopsied brain tissue, similar to classical Tay-Sachs disease. Her clinical manifestation appeared to be similar but somewhat milder than those of classical Tay-Sachs disease. Light microscopic features of the cerebral biopsy were also closely similar to Tay-Sachs disease and Sandhoff disease but gliosis and neuronal loss were less pronounced. Electron microscopic study revealed numerous membranous cytoplasmic bodies (MCB) and zebra bodies in neurons. In addition, varieties of large intracytoplasmic inclusions in astrocytes, a feature distinctly different from classical Tay-Sachs disease, were observed. Numerous cytoplasmic inclusions were also present in oligodendroglia, pericytes and microglial cells.

Acetylglucosaminidase↗

Diagnosis and prevention of lysosomal storage diseases in Russia.

A special programme for the diagnosis and prevention of lysosomal storage diseases (LSD) was developed in the former USSR. All the patients from 814 families at risk were investigated using biochemical techniques. In total, 363 patients with mucopolysaccharidoses (MPS), mucolipidoses, glycoproteinoses, sphingolipidoses and other LSD were diagnosed; 55 families at risk sought prenatal diagnosis and 67 fetuses were investigated for MPS (types I, II, IIIA and IIIB, VI), Tay-Sachs disease, Sandhoff disease, GM1-gangliosidosis, metachromatic leukodystrophy, mannosidosis, Gaucher disease and multiple sulphatidosis; 17 affected fetuses were diagnosed and aborted. There was an ethnic distribution of different lysosomal storage diseases in the former USSR.

Amniotic Fluid↗

[Chance and discovery in research on the cause of infantile amaurotic idiocy].

Infantile amaurotic idiocy-the classical type known as "Tay-Sachs disease" -is the consequence of the accumulation of a ganglioside and a closely related derivation in the human brain. The accumulation of both substances is due to a genetically induced deficiency of their common catabolic enzyme system. K. Sandhoff discovered three enzymic variants of the disease, which, taken together, did not reveal any apparent causal relationship between enzymic defect and substrate accumulation. The role of chance and discovery in finding the three variants as well as in the elucidation of their causes is described.

Acetylglucosaminidase↗

Chorionic villus sampling: diagnostic uses and limitations of enzyme assays.

Control ranges for enzymes in uncultured chorionic villi were established, based on: (1) 21 of 22 enzymes (mainly lysosomal) in villi had similar properties to the enzyme in cultured fibroblasts; (2) isoenzyme patterns in villi were similar to those in fibroblasts for five lysosomal enzymes but different for aryl sulphatases; (3) control ranges were determined for 12 enzymes in abortion villi and for 21 enzymes in biopsy villi, values tending to be higher in the latter for those enzymes studied in both types of sample; (4) storage of samples under various conditions revealed no major changes in activity of seven lysosomal enzymes. A number of potential pitfalls in the use of chorionic villus samples for diagnosis of metabolic disorders by enzyme assay are described: (1) the presence of aryl sulphatase C in chorionic villi, an isoenzyme which may interfere in assays of aryl sulphatase A; (2) the presence of maternal enzyme in chorionic villus material illustrated by the detection of the A isoenzyme of B-hexosaminidase in chorionic villus from a pregnancy affected with Sandhoff's disease; (3) the finding of falsely normal levels of alpha-iduronidase in chorionic villus samples from a pregnancy affected with Hurler's disease, probably due to contamination with maternal tissue which has relatively high levels of this enzyme compared with fetal chorionic material: (4) the inadequacy of indirect assays of incorporation of radiolabel into macromolecules using chorionic villi, for example [14C]propionate incorporation for prenatal diagnosis of methylmalonic aciduria. Provided that such pitfalls are recognized and great care is taken in selection of villus samples and interpretation of results, chorionic villus sampling allows reliable prenatal diagnosis of a large number of disorders using enzyme assays.

Chorionic Villi Sampling↗

Prevalence of different types of lysosomal storage diseases in Saudi Arabia.

The frequency of different types of lysosomal storage diseases in 125 referred cases, collected over three years, was compared to the occurrence elsewhere. The data suggest that mucopolysaccharidosis (MPS) type IVA (Morquio disease), multiple sulphatase deficiency, Niemann-Pick disease type B, GM2 gangliosidosis type '0' (Sandhoff disease), and ceroid lipofuscinosis (Jansky-Bielschowsky and Batten-Spielmeyer-Vogt syndromes) are encountered frequently in Saudi Arabia, as compared to other storage diseases. In contrast, some other diseases such as the adult variant of Gaucher's disease were not observed. Half of the GM2 gangliosidosis type '0' cases originated from one large tribe in the country. Other conditions did not show tribal predilection. The ceroid lipofuscinosis cases in Saudi Arabia originated from four large families. Consanguineous marriages taking place within tribal boundaries probably account for the pattern observed.

Child, Preschool↗

Inclusions in novel perivascular macrophages (Mato's fluorescent granular perithelial cells) and neurons in the cerebral cortex of Hex A- and Hex B-deficient mice.

Beta-hexosaminidases are important enzymes for lipid and saccharide metabolism in the brain. In mice deficient in these enzymes, indigestible metabolic intermediates deposit in neurons. Inclusions such as membranous cytoplasmic bodies (MCB) and zebra bodies were seen in neurons of Tay-Sachs (TS) model mice, Sandhoff's disease (SD) model mice, and double knockout (DKO) mice. However, the cerebral perivascular macrophages discovered by Mato are active in the uptake of waste products and regarded as scavenger cells under steady-state conditions. We observed that indigestible components derived from neurons were taken up by the perivascular macrophages of TS mice by pinocytosis, but those of SD and DKO mice contained only pale inclusions and had marked vacuolations, and pinocytosis was rarely observed. Histochemically, the inclusions in the perivascular macrophages of TS mice were positive for the PAS stain, but those of SD and DKO mice were negative. In addition, the perivascular cells of TS mice expressed clear positive immunoreactivity against BM-8 and F4/80, but those of DKO mice had very weak BM-8 and F4/80 immunoreactivity. These differences between TS, SD, and DKO mice are based on their metabolism of oligosaccharides and glycosaminoglycans (GAG). Thus, hexosaminidase B is more important for keeping normal morphology and function of perivascular macrophages than hexosaminidase A. The foamy cells that appeared along the cerebral microvessels in lipidosis and saccharidosis were identified as perivascular macrophages (Mato's fluorescent granular perithelial cells: FGP cells).

Animals↗

Substrate reduction therapy of glycosphingolipid storage disorders.

In the last 15 years enormous progress has been made regarding therapy of type I Gaucher disease, a severely disabling disorder characterized by intralysosomal storage of glucosylceramide in tissue macrophages. Effective enzyme replacement therapy of type I Gaucher disease, based on chronic intravenous administration of mannose-terminated recombinant human glucocerebrosidase, has been available since 1990 and has been applied in several thousand patients without serious adverse effects. An alternative therapeutic approach, so-called substrate reduction therapy, is based on partial reduction of the synthesis of glucosylceramide and hence of subsequent metabolites. Oral administration of an inhibitor of glucosylceramide synthesis (N-butyldeoxynojirimycin, registered in Europe since 2002 as miglustat (Zavesca)), is effective in reversing clinical symptoms in type I Gaucher patients with mild to moderate disease manifestations. The growing long-term experience with substrate reduction therapy indicates that this treatment is also without major adverse effects. Substrate reduction therapy, in conjunction with enzyme replacement therapy, may play an important role in the future clinical management of patients suffering from type I Gaucher disease. Clinical trials are under way that should reveal the value of substrate reduction for maintenance therapy of type I Gaucher disease and for treatment of neuronopathic variants of Gaucher disease, Niemann-Pick disease type C, late-onset Tay-Sachs disease and Sandhoff disease.

1-Deoxynojirimycin↗

Two variant hexosaminidase beta-chain alleles segregating in a South African family.

A family is described in which alleles for two different hexosaminidase beta-chain variants are segregating. When they co-exist in the same individual Sandhoff disease results. In the heterozygous state one of the variant alleles results in the production of an unstable Hex B and a Hex A with an altered Km for the substrate 4-MU-acetamido-2-deoxy-beta-D-galactopyranoside. The other allele when heterozygous with a normal allele does not produce unstable isozymes with altered kinetics. Like many rare recessive diseases the affected children in this family would appear to have been compound heterozygotes and not true homozygotes.

Alleles↗

HPLC analysis of neutral glycolipids: an aid in the diagnosis of lysosomal storage disease.

Concentrations of GL-la (glucocerebroside) (8.36 nmol/ml), GL-2a (lactosylceramide) (4.03 nmol/ml), GL-3a (globotriosylceramide) (2.25 nmol/ml) and GL-4a (globotetraosylceramide) (2.87 nmol/ml) have been determined in normal plasma and compared to concentrations in the plasma from patients with Gaucher, Krabbe, Fabry, Sandhoff and Tay-Sachs diseases as well as with hypercholesterolemia. HPLC analysis of perbenzoylated glycolipid derivatives (isolated and purified by modification of an existing procedure) was performed on samples equivalent to 50 to 100 microliter of plasma. The sensitivity could be readily increased ten-fold. We have employed a novel internal standard-monogalactosyl diglyceride, a plant glycolipid, commercially available in pure form. Analysis was performed on a 5 micron ultrasphere silica column, using a gradient of isopropanol in hexane rather than the more usual dioxane in hexane. Our gradient exhibited an essentially flat baseline precluding the necessity of a reference cell. Recoveries of glycolipids added to plasma (95%), experimental yields (60%) and standard curves are presented and discussed. A method is also presented for the separation of GL-la and monogalactosyl diglyceride derivatives for rapid (8 minute) isocratic analysis of multiple samples from Gaucher patients. The benefits of such a simple, reproducible HPLC technique are discussed.

Chromatography, High Pressure Liquid↗

Expression of lysosomal enzymes in human mutant fibroblast-chick erythrocyte heterokaryons.

The generation of enzymes located in lysosomes, in cytosol or in endoplasmatic reticulum/Golgi complex is studied in heterokaryons in which chick erythrocyte nuclei are reactivated. The lysosomal enzymes, alpha-glucosidase (alpha-glu) and beta-galactosidase (beta-gal), are synthesized in heterokaryons obtained after fusion of chick erythrocytes with human fibroblasts of patients with Pompe's disease (alpha-glu-deficient) and GM1-gangliosidosis (beta-gal-deficient), respectively. The enzymes appear to be of chick origin and their activities can be detected at first around 4 days after fusion, i.e., at a time when the nucleoli in the erythrocyte nuclei have been reactivated. Maximal activities are reached around 15 days after fusion. No generation of the lysosomal enzyme beta-hexosaminidase is detected in the heterokaryons up to 23 days after fusion of chick erythrocyte with either beta-hexosaminidase A- and B-deficient fibroblasts (Sandhoff's disease) or beta-hexosaminidase A-deficient fibroblasts (Tay-Sachs disease). Similarly no expression of the cytosol enzyme glucose-6-phosphate dehydrogenase (G6PD) is fond up to 30 days after fusion, when chick erythrocytes are fused with fibroblasts from two different G6PD-deficient cell strains (residual activities of 4 and 20% respectively). Indirectly we examined N-acetyl-glucosamine-1-phosphate transferase activity, an enzyme located in the endoplasmic reticulum/Golgi region. This enzyme is needed for the phosphorylation of the lysosomal hydrolases and absence of its activity is the cause of the multiple lysosomal enzyme deficiencies in patients with I-cell disease. The retention of both, chick and human beta-galactosidase in the experiments in which I-cell fibroblasts were fused with chick erythrocytes indicates a reactivation of the gene coding for this phosphorylating enzyme. It also implies that this step in the processing of human lysosomal enzymes is not species-specific.

Cell Nucleus↗

beta-N-acetylhexosaminidases in the spleen of a patient with hairy-cell leukaemia.

The spleen from a patient with hairy-cell leukaemia had beta-N-acetylhexosaminidase activity that could be resolved into three isoenzymes by chromatography on phenyl boronate agarose. Two of these were the major forms, A and B, found in normal tissues but, in addition, there was an 'extra' form that accounted for 15% of total activity. The 'extra' form hydrolysed the synthetic substrate 4-methylumbelliferyl-beta-N-acetylglucosamine 6-sulphate, indicating the presence of alpha-subunits. It was more acidic than A, was less heat-stable and showed no generation of B on denaturation under a variety of conditions. These findings and the immunoblot (Western blotting) analysis demonstrate that the 'extra' form is entirely composed of alpha-subunits, and most closely resembles S, the residual activity in Sandhoff's disease.

Blotting, Western↗

Regional assignment of the human acid sphingomyelinase gene (SMPD1) by PCR analysis of somatic cell hybrids and in situ hybridization to 11p15.1----p15.4.

Human acid sphingomyelinase (SMPD1) is the lysosomal phosphodiesterase that cleaves sphingomyelin to ceramide and phosphocholine. The deficient activity of SMPD1 is the enzymatic defect in Types A and B Niemann-Pick disease. Previously, the gene encoding human SMPD1 was assigned to chromosome 17 by the differential thermostability of human and hamster SMPD1 in somatic cell hybrids. The recent isolation of the human SMPD1 cDNA (L. E. Quintern, E. H. Schuchman, O. Levran, M. Suchi, K. Ferlinz, H. Reinke, K. Sandhoff, and R. J. Desnick, 1989, EMBO J. 8: 2469-2473) permitted the mapping of this gene by molecular techniques. Oligonucleotide primers were synthesized to PCR amplify the human, but not murine, SMPD1 sequences in man-mouse somatic cell hybrids. In a panel of 15 hybrid cell lines, amplification of the human SMPD1 sequence was 100% concordant with the presence of human chromosome 11. For each of the other human chromosomes there were at least 6 discordant hybrid lines. Further analysis of somatic cell hybrids containing only chromosome 11 or chromosome 11 rearrangements localized the human SMPD1 gene to the region 11p15.1----p15.4. To provide an independent regional gene assignment, in situ hybridization was performed using the radiolabeled human SMPD1 cDNA. In the 58 metaphase cells examined, 34% of the 122 hybridization sites scored were located in the distal end of chromosome 11 with the major peak of hybridization at band 11p15. The absence of any other in situ hybridization site indicated the absence of pseudogenes or homologous sequences elsewhere in the genome. In contrast to the previous provisional localization to chromosome 17, these results assign a single locus for human SMPD1 to 11p15.1----p15.4.

Animals↗

Structural organization and complete nucleotide sequence of the gene encoding human acid sphingomyelinase (SMPD1).

Acid sphingomyelinase (ASM; HGMW-approved symbol, SMPD1) is the lysosomal phosphodiesterase that hydrolyzes sphingomyelin to ceramide and phosphocholine. The deficient activity of this enzyme results in Types A and B Niemann-Pick disease (NPD). The full-length cDNA encoding human ASM has been isolated and characterized (E. H. Schuchman, M. Suchi, T. Takahashi, K. Sandhoff, and R. J. Desnick (1991) J. Biol. Chem. 66:8531-8539), and the ASM gene has been localized to chromosomal region 11p15.1-p15.4 (L. V. Pereira, R. J. Desnick, D. Adler, C. M. Disteche, and E. H. Schuchman (1991) Genomics 9:229-234). Using the cDNA as a probe, a genomic clone containing the ASM genomic region was isolated and the complete nucleotide sequence of the human ASM gene, including 1116 and 468 nucleotides upstream and downstream from the ASM coding region, respectively, was determined. This housekeeping gene contained six exons ranging in size from 77 to 773 bp and five introns ranging in size from 153 to 1059 bp. Exon 2 was unusually large and encoded 258 amino acids, or about 44% of the mature ASM polypeptide. The alternatively spliced 172-bp type 1-specific sequence was encoded by exon 3, whereas the type 2-specific sequence was located at the 5' end of intron 2. An analysis of the intron/exon junctions revealed that there was a weak donor splice site (AAA gtgagg) at the exon 3/intron 3 junction which occasionally leads to alternative splicing of exon 3 and the occurrence of the type 2 and 3 ASM transcripts. A single Alu1 element in the reverse orientation was in intron 2, immediately downstream from the type 2-specific sequence.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗

Sphingolipidoses in Turkey.

During the last 5 years 2057 children under the age of 5 with various neurologic symptoms with the suspected diagnosis of lysosomal storage diseases were referred to our hospital from different universities and state hospitals. We were able to separate sphingolipidoses by lysosomal enzyme screening. A total of 300 patients (15%) with sphingolipidoses were diagnosed; there were deficiencies of arylsulfatase A [metachromatic leukodystrophy (MLD)] in 93 (31%), hexosaminidase [Sandhoff disease (SHD)] in 62 (20.7%), hexosaminidase A [Tay-Sachs disease (TSD)] in 15 (5%), beta-galactosidase (GM1 gangliosidosis) in 35 (11.7%), alpha-galactosidase (Fabry disease) in one (0.3%) cerebroside beta-galactosidase (Krabbe disease) in 65 (21.7%) and glucosylceramidase (Gaucher disease) in 29 (9.6%). SHD (20.7%), MLD (31%) and Krabbe disease (21.7%) were common. Prenatal enzymatic diagnosis was made in 70 at risk pregnancies, 64 for TSD and SHD, three for MLD and three for GM1 gangliosidosis by using chorionic villus biopsy in 54, cord blood samples in 12 and cultured amniotic fluid cells in four. Seventeen fetuses were found to be affected. We have calculated the relative frequency and minimum incidence of sphingolipidoses in Turkey. The combined incidence of sphingolipidoses is 4.615 per 100,000 live births. The calculated incidences are 1.43, 0.95, 1, 0.23, 0.54, 0.45, 0.015 per 100,000 live births for MLD, SHD, Krabbe, Gaucher, TSD, GM1 gangliosidosis and Fabry diseases, respectively. The real incidence, which covers all subtypes of this group of diseases, should be greater than this number. The results suggested that, as a group, sphingolipidoses are relatively common and represent an important health problem in Turkey and some rare autosomal recessive diseases of Turkey are due to 'founder effect' created by consanguineous marriages.

Cerebroside-Sulfatase↗

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.

Antigens, CD↗

[Clinical and electrophysiological aspects of the gangliosidoses (author's transl)].

The gangliosidoses belong to the family of diseases known as the lipidoses and are due to an excess of ganglioside I (GM1) or II (GM2). The illness described by Landing belongs to Group I, whilst Tay-Sachs and Sandhoff's disease are type 2. This study was particularly concerned with the electro-clinical aspects of group 2, and 4 stages have been differentiated: --the first occurs between 4-10 months: the child is apathetic, hypotonic and has occasional audiogenic seizures; fundoscopy revealing the classical cherry red spot on the macula. The diagnosis can be confirmed by biopsy. The EEG is irregular but abnormalities are minor. --the second stage (10 months-2 years) the child spastic and amaurotic, often unresponsive is suffering from frequent seizures. The EEG is of high voltage, with slow and sharp waves. Auditory stimulation does not produce EEG changes. --in the third and 4th stages (after 2 years) the child is in a vegetative state with a progressive reduction in EEG voltage and sharp waves until death aged 3 or 4. Although there is a good correlation between clinical signs and EEG this is of no diagnostic value.

Brain↗

Encephaloneuropathy with lysosomal zebra bodies and GM2 ganglioside storage.

An 11-year-old girl died of a neuronal storage disorder that clinically was characterized by failure to thrive and muscular hypotonia from birth, with the subsequent evolution of motor neuron disease, epilepsy, and dementia. A wide range of metabolic disorders, including all forms of GM2 gangliosidosis, could be excluded. Electron microscopy demonstrated neuronal zebra body inclusions, and immunohistochemistry demonstrated that GM2 ganglioside was a major constituent of the storage material. We suggest that the patient died of a lysosomal storage disease that is clinically and biochemically different from Tay-Sachs disease, Sandhoff disease, and other GM2 gangliosidoses described previously. This case also further demonstrates that significant accumulation of GM2 ganglioside, which is crucial for dendritic formation, may occur in neuronal storage diseases lacking known defects in ganglioside catabolism.

Child↗

A single site in human beta-hexosaminidase A binds both 6-sulfate-groups on hexosamines and the sialic acid moiety of GM2 ganglioside.

Human beta-hexosaminidase A (Hex A) (alphabeta) is composed of two subunits whose primary structures are approximately 60% identical. Deficiency of either subunit results in severe neurological disease due to the storage of GM2 ganglioside; Tay-Sachs disease, alpha deficiency, and Sandhoff disease, beta deficiency. Whereas both subunits contain active sites only the alpha-site can efficiently bind negatively charged 6-sulfated hexosamine substrates and GM2 ganglioside. We have recently identified the alphaArg(424) as playing a critical role in the binding of 6-sulfate-containing substrates, and betaAsp(452) as actively inhibiting their binding. To determine if these same residues affect the binding of the sialic acid moiety of GM2 ganglioside, an alphaArg(424)Gln form of Hex A was expressed and its kinetics analyzed using the GM2 activator protein:[3H]-GM2 ganglioside complex as a substrate. The mutant showed a approximately 3-fold increase in its K(m) for the complex. Next a form of Hex B (betabeta) containing a double mutation, betaAspLeu(453)AsnArg (duplicating the alpha-aligning sequences), was expressed. As compared to the wild type (WT), the mutant exhibited a >30-fold increase in its ability to hydrolyze a 6-sulfated substrate and was now able to hydrolyze GM2 ganglioside when the GM2 activator protein was replaced by sodium taurocholate. Thus, this alpha-site is critical for binding both types of negatively charge substrates.

Binding Sites↗