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Adult Sandhoff's disease: R505Q and I207V substitutions in the HEXB gene of the first Japanese case.

We describe a 31-year-old Japanese man with adult Sandhoff s disease presenting as spinocerebellar degeneration. There was a marked cerebellar atrophy on MRI, and proliferation of abundant PAS-positive foamy macrophages in the rectal mucosa. The activities of total beta-Hex, beta-Hex A, and beta-Hex B in leucocytes of the patient were 14%, 15%, and 6% of control values, respectively. However, oligosacchariduria or ultrastructural storage materials in liver tissue were nil. Direct sequencing of cDNA and genomic DNA, and restriction digestion revealed two different homozygous base substitutions in the HEXB gene: the G1514-->A substitution (R505Q) and the A619-->G substitution (1207V). The parents were consanguineous. His healthy mother, an enzymatic heterozygous carrier, was homozygous for 1207V, but heterozygous for R505Q mutation. Thus, the patient is probably homozygous for both base substitutions and a R505Q mutation may be linked to the phenotype of adult Sandhoff's disease.

Adult↗

Sandhoff disease in the Turkish population.

Eighteen cases affected by Sandhoff disease were investigated by an enzymatic study of serum and leukocytes during the period 1988-1996, the clinical expression and enzymatic study were reported and discussed. An indirect minimum disease incidence was calculated in the Turkish population. Hexosaminidase activity in serum and leukocytes was severely deficient when measured by synthetic substrate 4-MU-N-acetylglucosaminide using the thermolabile fractionation procedure. Fractionation of hexosaminidase revealed different levels of isoenzymes A and B. Clinically, organomegaly was not found in 11 out of 18 infantile Sandhoff disease patients, while the remaining seven had mild organomegaly. Organomegaly was not found in patients with relatively high % hexosaminidase B activities. These results suggested that patients with different percent heat-stable enzyme activity may have a different type of mutation which is related to the underlying molecular heterogeneity in the Turkish population where 21% of marriages are found to be consanguineous.

Consanguinity↗

Elevation of lung surfactant phosphatidylcholine in mouse models of Sandhoff and of Niemann-Pick A disease.

Sandhoff disease is caused by the defective activity of the lysosomal enzyme beta-hexosaminidase, resulting in accumulation of the glycolipids, GA2 and GM2. Niemann-Pick A/B disease is caused by the defective activity of lysosomal acid sphingomyelinase resulting in sphingomyelin accumulation. Pulmonary complications have been observed in both diseases. We now demonstrate changes in phospholipid levels in pulmonary surfactant in mouse models of these diseases. In the Hexb mouse, a model of Sandhoff disease, lipid phosphate levels were elevated in surfactant from 3- and 4-month-old mice, which was mainly due to elevated levels of phosphatidylcholine. In the ASM mouse, a model of Niemann-Pick A disease, levels of the primary storage material, sphingomyelin, were elevated as expected, and levels of phosphatidylcholine and two other phospholipids were also significantly elevated in pulmonary surfactant and in lung tissue from 5-, 6- and 7-month-old mice. These results suggest that changes in phospholipid levels and composition in lung surfactant might be a general feature of sphingolipid storage diseases, which may be in part responsible for the increased susceptibility of these patients to respiratory infections and lung pathology, often the main reason for the death of these patients.

Animals↗

Development of infertility at young adult age in a mouse model of human Sandhoff disease.

Sandhoff disease is a human lysosomal storage disease. In a knockout mouse model of Sandhoff disease, which lacks the beta-subunit of beta-hexosaminidase A (Hex A, alphabeta subunits) and B (Hex B, betabeta subunits), the mutant homozygous mice (Hexb(-/-)) are healthy until 15 weeks of age when they develop neurodegenerative symptoms. This study was designed to analyse the fertility profile of male and female Hexb(-/-) mice. Mating behaviour of Hexb(-/-) mice was assessed at different ages. The ovarian function of Hexb(-/-) females was determined by superovulation studies. The quality of spermatozoa and ova was assessed by an in vitro fertilization (IVF) procedure. Hexb(-/-) mice were fertile at a young age. Males were fertile up to the age of 69.3 +/- 6.3 days (mean +/- SD) and females were fertile up to the age of 56-63 days. Since both the Hexb (-/-) sexes showed fertility, the results indicate that Hex A and Hex B (major isozymes of beta-hexosaminidase) may not be required for sperm-ovum interactions, in contrast to the widely accepted belief. On the other hand, young adult Hexb(-/-) males showed a reduction in mating behaviour at the age of 84.8 +/- 2.2 days and an absence of mating behaviour at 94.2 +/- 2.0 days. Spermatozoa from Hexb(-/-) mice (aged 109.2 +/- 1.8 days) showed a lower IVF rate. Among Hexb (-/-) females aged 85.6 +/- 2.1 days, no mice became pregnant although they were positive for a vaginal plug when caged with fertile males. The number of ova recovered from Hexb(-/-) females (aged 111.0 +/- 3.1 days) and the IVF rate of ova were lower than those of controls. In conclusion, Hex A and Hex B may not be required for sperm-ovum interactions. Mice lacking Hex A and Hex B activities develop infertility at a young adult age in an age-dependent manner.

Aging↗

Delayed symptom onset and increased life expectancy in Sandhoff disease mice treated with N-butyldeoxynojirimycin.

Sandhoff disease is a neurodegenerative disorder resulting from the autosomal recessive inheritance of mutations in the HEXB gene, which encodes the beta-subunit of beta-hexosaminidase. GM2 ganglioside fails to be degraded and accumulates within lysosomes in cells of the periphery and the central nervous system (CNS). There are currently no therapies for the glycosphingolipid lysosomal storage diseases that involve CNS pathology, including the GM2 gangliosidoses. One strategy for treating this and related diseases is substrate deprivation. This would utilize an inhibitor of glycosphingolipid biosynthesis to balance synthesis with the impaired rate of catabolism, thus preventing storage. One such inhibitor is N-butyldeoxynojirimycin, which currently is in clinical trials for the potential treatment of type 1 Gaucher disease, a related disease that involves glycosphingolipid storage in peripheral tissues, but not in the CNS. In this study, we have evaluated whether this drug also could be applied to the treatment of diseases with CNS storage and pathology. We therefore have treated a mouse model of Sandhoff disease with the inhibitor N-butyldeoxynojirimycin. The treated mice have delayed symptom onset, reduced storage in the brain and peripheral tissues, and increased life expectancy. Substrate deprivation therefore offers a potentially general therapy for this family of lysosomal storage diseases, including those with CNS disease.

1-Deoxynojirimycin↗

Inhibition of calcium uptake via the sarco/endoplasmic reticulum Ca2+-ATPase in a mouse model of Sandhoff disease and prevention by treatment with N-butyldeoxynojirimycin.

Gangliosides are found at high levels in neuronal tissues where they play a variety of important functions. In the gangliosidoses, gangliosides accumulate because of defective activity of the lysosomal proteins responsible for their degradation, usually resulting in a rapidly progressive neurodegenerative disease. However, the molecular mechanism(s) leading from ganglioside accumulation to neurodegeneration is not known. We now examine the effect of ganglioside GM2 accumulation in a mouse model of Sandhoff disease (one of the GM2 gangliosidoses), the Hexb-/- mouse. Microsomes from Hexb-/- mouse brain showed a significant reduction in the rate of Ca2+-uptake via the sarco/endoplasmic reticulum Ca2+-ATPase (SERCA), which was prevented by feeding Hexb-/- mice with N-butyldeoxynojirimycin (NB-DNJ), an inhibitor of glycolipid synthesis that reduces GM2 storage. Changes in SERCA activity were not due to transcriptional regulation but rather because of a decrease in Vmax. Moreover, exogenously added GM2 had a similar effect on SERCA activity. The functional significance of these findings was established by the enhanced sensitivity of neurons cultured from embryonic Hexb-/- mice to cell death induced by thapsigargin, a specific SERCA inhibitor, and by the enhanced sensitivity of Hexb-/- microsomes to calcium-induced calcium release. This study suggests a mechanistic link among GM2 accumulation, reduced SERCA activity, and neuronal cell death, which may be of significance for delineating the neuropathophysiology of Sandhoff disease.

1-Deoxynojirimycin↗

Molecular pathophysiology in Tay-Sachs and Sandhoff diseases as revealed by gene expression profiling.

Tay-Sachs and Sandhoff diseases are lysosomal storage disorders characterized by the absence of beta-hexosaminidase activity and the accumulation of GM2 ganglioside in neurons. In each disorder, a virtually identical course of neurodegeneration begins in infancy and leads to demise generally by 4-6 years of age. Through serial analysis of gene expression (SAGE), we determined gene expression profiles in cerebral cortex from a Tay-Sachs patient, a Sandhoff disease patient and a pediatric control. Examination of genes that showed altered expression in both patients revealed molecular details of the pathophysiology of the disorders relating to neuronal dysfunction and loss. A large fraction of the elevated genes in the patients could be attributed to activated macrophages/microglia and astrocytes, and included class II histocompatability antigens, the pro-inflammatory cytokine osteopontin, complement components, proteinases and inhibitors, galectins, osteonectin/SPARC, and prostaglandin D2 synthase. The results are consistent with a model of neurodegeneration that includes inflammation as a factor leading to the precipitous loss of neurons in individuals with these disorders.

Cerebral Cortex↗

Specific induction of macrophage inflammatory protein 1-alpha in glial cells of Sandhoff disease model mice associated with accumulation of N-acetylhexosaminyl glycoconjugates.

Sandhoff disease is a lysosomal storage disease caused by simultaneous deficiencies of beta-hexosaminidase A (HexA; alphabeta) and B (HexB; betabeta), due to a primary defect of the beta-subunit gene (HEXB) associated with excessive accumulation of GM2 ganglioside (GM2) and oligosaccharides with N-acetylhexosamine residues at their non-reducing termini, and with neurosomatic manifestations. To elucidate the neuroinflammatory mechanisms involved in its pathogenesis, we analyzed the expression of chemokines in Sandhoff disease model mice (SD mice) produced by disruption of the murine Hex beta-subunit gene allele (Hexb-/-). We demonstrated that chemokine macrophage inflammatory protein-1 alpha (MIP-1alpha) was induced in brain regions, including the cerebral cortex, brain stem and cerebellum, of SD mice from an early stage of the pathogenesis but not in other systemic organs. On the other hand, little changes in other chemokine mRNAs, including those of RANTES (regulated upon activation, normal T expressed and secreted), MCP-1 (monocyte chemotactic protein-1), SLC (secondary lymphoid-tissue chemokine), fractalkine and SDF-1 (stromal derived factor-1), were detected. Significant up-regulation of MIP-1alpha mRNA and protein in the above-mentioned brain regions was observed in parallel with the accumulation of natural substrates of HexA and HexB. Immunohistochemical analysis revealed that MIP-1alpha-immunoreactivity (IR) in the above-mentioned brain regions of SD mice was co-localized in Iba1-IR-positive microglial cells and partly in glial fibrillary acidic protein (GFAP)-IR-positive astrocytes, in which marked accumulation of N-acetylglucosaminyl (GlcNAc)-oligosaccharides was observed from the presymptomatic stage of the disease. In contrast, little MIP-1alpha-IR was observed in neurons in which GM2 accumulated predominantly. These results suggest that specific induction of MIP-1alpha might coincide with the accumulation of GlcNAc-oligosaccharides due to a HexB deficiency in resident microglia and astrocytes in the brains of SD mice causing their activation and acceleration of the progressive neurodegeneration in SD mice.

Acetylglucosamine↗

Metabolic correction in microglia derived from Sandhoff disease model mice.

Sandhoff disease is an autosomal recessive lysosomal storage disease caused by a defect of the beta-subunit gene (HEXB) associated with simultaneous deficiencies of beta-hexosaminidase A (HexA; alphabeta) and B (HexB; betabeta), and excessive accumulation of GM2 ganglioside (GM2) and oligosaccharides with N-acetylglucosamine (GlcNAc) residues at their non-reducing termini. Recent studies have shown the involvement of microglial activation in neuroinflammation and neurodegeneration of this disease. We isolated primary microglial cells from the neonatal brains of Sandhoff disease model mice (SD mice) produced by disruption of the murine Hex beta-subunit gene allele (Hexb-/-). The cells expressed microglial cell-specific ionized calcium binding adaptor molecule 1 (Iba1)-immunoreactivity (IR) and antigen recognized by Ricinus communis agglutinin lectin-120 (RCA120), but not glial fibrillary acidic protein (GFAP)-IR specific for astrocytes. They also demonstrated significant intracellular accumulation of GM2 and GlcNAc-oligosaccharides. We produced a lentiviral vector encoding for the murine Hex beta-subunit and transduced it into the microglia from SD mice with the recombinant lentivirus, causing elimination of the intracellularly accumulated GM2 and GlcNAc-oligosaccharides and secretion of Hex isozyme activities from the transduced SD microglial cells. Recomibinant HexA isozyme isolated from the conditioned medium of a Chinese hamster ovary (CHO) cell line simultaneously expressing the human HEXA (alpha-subunit) and HEXB genes was also found to be incorporated into the SD microglia via cell surface cation-independent mannose 6-phosphate receptor and mannose receptor to degrade the intracellularly accumulated GM2 and GlcNAc-oligosaccharides. These results suggest the therapeutic potential of recombinant lentivirus encoding the murine Hex beta-subunit and the human HexA isozyme (alphabeta heterodimer) for metabolic cross-correction in microglial cells involved in progressive neurodegeneration in SD mice.

Animals↗

Impaired neurite outgrowth in the retina of a murine model of Sandhoff disease.

PURPOSE: To investigate the effects of lysosomal storage on the morphologic appearance and the neurite outgrowth capability of the retina in a mouse model of G(M2) gangliosidosis (Sandhoff disease). METHODS: Histopathologic appearances of retinas in Sandhoff (SD) mice at 3 and 4 months of age were examined by light and electron microscopy. Retinas of SD mice and wild-type (WT) mice at 1, 2, and 4 months of age were cultured in collagen gel in the presence or absence of brain-derived neurotrophic factor (BDNF), and neurite outgrowth was examined. RESULTS: Morphologic studies revealed accumulation of G(M2) ganglioside in the retinal ganglion cells of SD mice in a time-dependent manner. The number of neurites from the retinal explants after 7 and 10 days in culture were significantly lower in 2- and 4-month-old SD mice than in the age-matched WT mice. The application of BDNF significantly improved neurite outgrowth from the retina in both SD and WT mice at 2 months of age. At 4 months of age, BDNF was much less effective at stimulating neurite outgrowth in the retina of SD mice than in retina of WT mice. CONCLUSIONS: These results indicate that lysosomal storage of G(M2) ganglioside impairs the capability of neurite outgrowth in retinal ganglion cells in culture and that BDNF is effective at diminishing this impairment during the early stage of the disease.

Animals↗

Inefficiency in GM2 ganglioside elimination by human lysosomal beta-hexosaminidase beta-subunit gene transfer to fibroblastic cell line derived from Sandhoff disease model mice.

Sandhoff disease (SD) is an autosomal recessive GM2 gangliosidosis caused by the defect of lysosomal beta-hexosaminidase (Hex) beta-subunit gene associated with neurosomatic manifestations. Therapeutic effects of Hex subunit gene transduction have been examined on Sandhoff disease model mice (SD mice) produced by the allelic disruption of Hexb gene encoding the murine beta-subunit. We demonstrate here that elimination of GM2 ganglioside (GM2) accumulated in the fibroblastic cell line derived from SD mice (FSD) did not occur when the HEXB gene only was transfected. In contrast, a significant increase in the HexB (betabeta homodimer) activity toward neutral substrates, including GA2 (asialo-GM2) and oligosaccharides carrying the terminal N-acetylglucosamine residues at their non-reducing ends (GlcNAc-oligosaccharides) was observed. Immunoblotting with anti-human HexA (alphabeta heterodimer) serum after native polyacrylamide gel electrophoresis (Native-PAGE) revealed that the human HEXB gene product could hardly form the chimeric HexA through associating with the murine alpha-subunit. However, co-introduction of the HEXA encoding the human alpha-subunit and HEXB genes caused significant corrective effect on the GM2 degradation by producing the human HexA. These results indicate that the recombinant human HexA could interspeciesly associate with the murine GM2 activator protein to degrade GM2 accumulated in the FSD cells. Thus, therapeutic effects of the recombinant human HexA isozyme but not human HEXB gene product could be evaluated by using the SD mice.

Animals↗

Sandhoff disease--a case report of 3 siblings and a review of potential therapies.

INTRODUCTION: Sandhoff disease is a GM2 gangliosidosis that may present within the first 6 months of life with developmental regression. This is the first report of a pedigree from Southeast Asia. CLINICAL PICTURE: All the affected siblings presented in the first year of life with developmental regression, spasticity, seizures and loss of vision. The diagnosis was confirmed by an enzymatic deficiency in both beta-hexosaminidase A and B. CONCLUSION: As the disorder is autosomal recessive, and no curative therapy is currently available, genetic counselling is necessary to prevent the burden of this devastating disease. We review the potential strategies of treatment for Sandhoff disease.

Child, Preschool↗

GM2-gangliosidosis variant 0 (Sandhoff-like disease) in a family of Japanese domestic cats.

A five-month-old, female Japanese domestic shorthair cat with proportionate dwarfism developed neurological disorders, including ataxia, decreased postural responses and generalised body and head tremors, at between two and five months of age. Leucocytosis due to lymphocytosis with abnormal cytoplasmic vacuolations was observed. The concentration of G(M2)-ganglioside in its cerebrospinal fluid was markedly higher than in normal cats, and the activities of beta-hexosaminidases A and B in its leucocytes were markedly reduced. On the basis of these biochemical data, the cat was diagnosed antemortem with G(M2)-gangliosidosis variant 0 (Sandhoff-like disease). The neurological signs became more severe and the cat died at 10 months of age. Histopathologically, neurons throughout the central nervous system were distended, and an ultrastructural study revealed membranous cytoplasmic bodies in these distended neurons. The compound which accumulated in the brain was identified as G(M2)-ganglioside, confirming G(M2)-gangliosidosis. A family study revealed that there were probable heterozygous carriers in which the activities of leucocyte beta-hexosaminidases A and B were less than half the normal value. The Sandhoff-like disease observed in this family of Japanese domestic cats is the first occurrence reported in Japan.

Animals↗

[Sandhoff's and Tay-Sachs disease--based on our own cases].

The authors described two infant with Sandhoff's and Tay-Sachs disease. Tay-Sachs disease is well-known inherited disease leading to an accumulation of gangliosides in the brain and retina. Sandhoffs disease (GM2 gangliosidosis type 0) was diagnosed in an infant, in whom a progressive neurological disorder and cherry-red foveal spots were developed. In addition, to the general clinical examination, indirect ophthalnoscopy, blood white cells enzymatic examination are used to make definitive diagnosis. In this cases, the early eye fundus examination allowed us to make the proper diagnosis. The fundus change is characterized by the "cherry-red spot" in the central area.

Humans↗

[A case of juvenile Sandhoff disease].

A Japanese male with juvenile Sandhoff disease is described. The patient was a product of full-term normal pregnancy from non-consanguineous parents. Since age 10, he developed progressive dysarthria and proximal muscle atrophy and weakness. Mental deterioration and cerebellar ataxia are also noted since the age of 20. On neurological examination at age 35, he showed decreased mentality (IQ 62), marked atrophy and weakness of proximal muscles, cerebellar ataxia and increased deep tendon reflexes. Brain CT scans revealed moderate to marked atrophy of cerebellum. Giant MUP, fasciculation potentials and positive sharp waves were observed on EMG examination. Biopsied sural nerve showed markedly decreased myelinated fibers. Hexosaminidase A and B activities in leukocytes and cultured fibroblasts were about 10% of normal values, while other lysosomal enzyme activities were within normal range. Rectal biopsy demonstrated lamellar inclusion bodies in submucosal ganglion cells. This is the first Japanese patient with juvenile Sandhoff disease presenting symptoms similar to motor neuron disease and cerebellar degeneration.

Adult↗

[Juvenile Sandhoff disease with local panatrophy--a case report].

A case of juvenile Sandhoff disease with Gowers' local panatrophy was reported. A mentally retarded 39 year-old man had been noticed to have localized skin atrophy on the right leg since 7 years of age, and was also aware of the atrophy of his right leg since his junior high school age. His parents were first cousins. He had multiple localized atrophic skin lesions on the right side of his nape, the right side of lower back, and the right thigh. These skin lesions did not show any signs of sclerosis. Although he was mentally retarded (IQ=44), the neurological examination was normal including funduscopy. Histological examination of the atrophic skin le led that the epidermal basal layer was hyperpigmented and that the dermis and subcutaneous fatty tissue were extremely atrophic. The nerves meandered across the dermis and subcutaneous tissue, and had membranous lipid storage cytosomes in the axon and Schwann cells. Biochemical studies revealed marked deficiency fo leukocyte hexosaminidase activity. Total hexosaminidase activity was decreased to 18% of normal controls, and hexosaminidase B activity was completely deficient. Other lysosomal enzymes in leukocytes were normal in activities. Both parent showed intermediate levels of leukocyte hexosaminidase A and B activities. Electron microscopy analysis of a rectal biopsy specimen showed neuronal accumulation of dense osmophilic deposits, as well as membranous cytoplasmic bodies in Meissner's plexus. On the basis of the patient's age at onset and the above findings, the patient was diagnosed to have juvenile Sandhoff disease. The local panatrophy observed in the present case could be the result of the accumulation of GM2-ganglioside in autonomic nervous system, and may well be a new clinical feature of GM2-gangliosidosis.

Adult↗

Ultrastructure of the conjunctiva, skin, and gingiva: a case of Sandhoff's disease in a Jewish patient.

Pleomorphic membranous cytoplasmic bodies that indicated glycolipid storage were found in the conjunctiva, skin, and gingiva of a Jewish patient with Sandhoff's disease. The clinical symptoms were typical of GM2 gangliosidosis. Both hexosaminidase A and hexosaminidase B activities were deficient in the leukocytes and serum. Glycosaminoglycan levels in cultured fibroblasts were elevated. Membranous cytoplasmic bodies were observed in high concentrations in a large proportion of the vascular endothelial cells, pericytes, and Schwann cells and to a somewhat lesser extent in the fibrocytes of all tissues studied. Ultrastructural analysis of the conjunctiva, skin, and gingiva as an aid for the diagnosis of Sandhoff's disease is suggested.

Capillaries↗

Cultured skin fibroblasts in lipidoses. Enzymatic, histochemical, and ultrastructural relationship in Fabry's Tay-Sachs, and Sandhoff's diseases.

Enzymatic, histochemical, and ultrastructural studies were performed on cultured skin fibroblasts from patients with Fabry's disease, Tay-Sach's disease, and Sandhoff's disease and from their families (carriers). alpha-Galactosidase activity was deficient in the proband with Fabry's disease (lower in the homozygotes than in the heterozygote). Levels of hexosaminidase A in the patient with Tay-Sachs disease and hexosaminidase A and B in the patient with Sandhoff's disease were deficient and were lower in her mother than in the control subject. Lysosome-like structures were observed in cultured fibroblasts from the patients with each disease, as well as in the heterozygote with Fabry's disease and the carrier with Tay-Sach's disease. The amount of the accumulating arrays in the lysosome-like structures was related to low level of enzymatic activity.

Cells, Cultured↗