Juvenile Sandhoff disease: a Japanese patient carrying a mutation identical to that found earlier in a Canadian patient

doi:10.1016/0022-510X(90)90269-S

Journal of the Neurological Sciences

Volume 98, Issues 2–3, September 1990, Pages 277-286

https://doi.org/10.1016/0022-510X(90)90269-S Get rights and content

Abstract

A 35-year-old Japanese man with juvenile Sandhoff disease is described. He showed progressive neurogenic muscular atrophy, cerebellar ataxia and mental deterioration, beginning at age 10 years. The accumulation of GM₂ ganglioside in the submucosal nerve cell was confirmed by positive immunostaining using anti-GM₂ ganglioside antibody. Biochemical evaluation revealed nearly absent β-hexosaminidase A and B activities in leukocytes and cultured fibroblasts. Hydrolysis of [³H]globoside I in the intact fibroblasts was apparently disturbed but the rate of hydrolysis was higher than those seen in cells from patients with infantile Sandhoff disease. Analysis of the β-hexosaminidase β-subunit gene of the patient disclosed a point mutation (a G-to-A transition) within intron 12. The mutation generates a new splice junction resulting in a 24-base insertion between exons 12 and 13 in the processed mRNA and consequently an 8-amino acid insertion in the translation product. This mutation is identical to that originally found in a Canadian patient with juvenile Sandhoff disease. A possible relationship with the clinical phenotype and the gene abnormality is discussed.

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Cited by (17)

Integrated multiplex ligation dependent probe amplification (MLPA) assays for the detection of alterations in the HEXB, GM2A and SMARCAL1 genes to support the diagnosis of Morbus Sandhoff, M. Tay-Sachs variant AB and Schimke immuno-osseous dysplasia in humans
2013, Molecular and Cellular Probes
Citation Excerpt :
The M. Sandhoff panel included 73 samples; 23 patient DNAs had undergone conventional HEXB exon sequencing (NM_000521) during a diagnostic assessment. In this group, five published [10,28,34–37], 12 unpublished mutations (Table 2) and gene variants (Table 3). In addition, each of these patients had a second, novel nucleotide exchange in intron 13, c.1614-14C>A (marked red in Table 2).
Multiplex ligation dependent probe amplification (MLPA) assays were designed for the genes HEXB (OMIM: 606873), GM2A (OMIM: 613109) and SMARCAL1 (OMIM: 606622) of humans. Two sets of synthetic MLPA probes for these coding exons were tested. Changes in copy numbers were detected as well as single nucleotide polymorphisms (SNPs) by complementary DNA sequence analyses. The MLPA method was shown to be reliable for mutation detection and identified five published and 12 new mutations. In all cases from a Morbus Sandhoff cohort of patients, exclusively one variation in copy number was observed and linked to a nucleotide alteration called c.1614-14C>A. This deletion comprised exons 1–5. One of these cases is described in detail. Deletions were neither detected in the GM2A nor the SMARCAL1 genes. The MLPA assays complement routine diagnostics for M. Sandhoff (OMIM: 268800), M. Tay-Sachs variant AB (OMIM: 272750) and Schimke immuno-osseous dysplasia (OMIM: 242900).
Compound heterozygosity with two novel mutations in the HEXB gene produces adult Sandhoff disease presenting as a motor neuron disease phenotype
2002, Journal of the Neurological Sciences
Little information is available on molecular defects involved in adult Sandhoff disease presenting as motor neuron disease phenotype. We studied enzyme activities of β-hexosaminidase (Hex) and the HEXB gene encoding the β-subunit of Hex in a family of the Japanese case. Enzyme assay with 4-methylumbelliferyl-2-acetamido-2-deoxy-β-d-glucopyranoside revealed a reduction in Hex A and B activity in proband's leukocytes. Although the activity of both in the mother were intermediate between those of controls and the proband, only Hex B reduction determined with heat inactivation was found in the father. Analysis of HEXB gene demonstrated two novel point mutations. The first mutation, IVS2-1G>A, was located at the 3′-splice acceptor site of intron 2 derived from the mother, causing exon 3 skipping. The resultant mRNA encoded a shorter β-chain, which may not form an active enzyme. The second mutation was a G-to-A transition in exon 13 (c.1598G>A) derived from the father and resulted in arginine-to-histidine substitution at amino acid position 533 (R533H). Expression of R533H mutation in COS-1 cells demonstrated a lack of normal Hex activity, indicating that this mutation is pathological. Compound heterozygosity of these two mutations may trigger the development of adult Sandhoff disease with a motor neuron disease phenotype.
17. Naturally occurring mutations in G<inf>M2</inf> gangliosidosis: A compendium
2001, Advances in Genetics
This chapter includes a discussion on naturally occurring mutations in G_M2 gangliosidois: a compendium. The characterization of complementary DNA clones encoding the subunits of α-hexosaminidase (Hex) set the stage for delineating the mutation basis. Guided by elegant biochemical and genetic studies, these analyses rapidly progressed to other populations and individuals with variant forms of both Tay-Sachs and Sandhoff diseases. Two of the genes, Hex A (αβ) and Hex B (ββ) encode α and β subunits. The third gene, G_M2 A, encodes the G_M2 activator. Only Hex acting on the G_M2 ganglioside–G_M2 activator complex, hydrolyze the terminal N-acetylgalactosamine of G_M2 ganglioside. Mutations in the Hex A gene, leading to deficiency of Hex A activity, cause Tay-Sachs disease or less severely affected variants. Mutations in the Hex B gene, leading to deficiency of both Hex A and Hex B activities, cause Sandhoff disease or its variants. Mutations in the G_M2A gene, leading to defects of the G_M2 activator while retaining functional Hex A and Hex B, result in the AB variant of G_M2 gangliosidosis. Other studies have described genetic and biochemical heterogeneity that has been largely accounted for the discovery of allelic diversity.
Biochemical consequences of mutations causing the GM2 gangliosidoses
1999, Biochimica et Biophysica Acta - Molecular Basis of Disease
The hydrolysis of GM2-ganglioside is unusual in its requirements for the correct synthesis, processing, and ultimate combination of three gene products. Whereas two of these proteins are the α- (HEXA gene) and β- (HEXB) subunits of β-hexosaminidase A, the third is a small glycolipid transport protein, the GM2 activator protein (GM2A), which acts as a substrate specific co-factor for the enzyme. A deficiency of any one of these proteins leads to storage of the ganglioside, primarily in the lysosomes of neuronal cells, and one of the three forms of GM2-gangliosidosis, Tay–Sachs disease, Sandhoff disease or the AB-variant form. Studies of the biochemical impact of naturally occurring mutations associated with the GM2 gangliosidoses on mRNA splicing and stability, and on the intracellular transport and stability of the affected protein have provided some general insights into these complex cellular mechanisms. However, such studies have revealed little in the way of structure–function information on the proteins. It appears that the detrimental effect of most mutations is not specifically on functional elements of the protein, but rather on the proteins’ overall folding and/or intracellular transport. The few exceptions to this generalization are missense mutations at two codons in HEXA, causing the unique biochemical phenotype known as the B1-variant, and one codon in both the HEXB and GM2A genes. Biochemical characterization of these mutations has led to the localization of functional residues and/or domains within each of the encoded proteins.
Adult Sandhoff's disease: R505Q and 1207V substitutions in the HEXB gene of the first Japanese case
1998, Journal of the Neurological Sciences
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 β-Hex, β-Hex A, and β-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 (I207V). The parents were consanguineous. His healthy mother, an enzymatic heterozygous carrier, was homozygous for I207V, 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.
Characterization of two HEXB gene mutations in Argentinean patients with Sandhoff disease
1992, BBA - Molecular Basis of Disease
β-hexosaminidase A ( $β-N- acetyl- d -hexosaminidase$ , EC 3.2.1.52) is a lysosomal hydrolase composed of an α- and a β-subunit. It is responsible for the degradation of G_M2 ganglioside. Mutations in the HEXB gene encoded β-subunit cause a form of G_M2 gangliosidosis known as Sandhoff disease. Although this is a rare disease population, several geographically isolated groups have a high carrier frequency. Most notably, a 1 in 16–29 carrier frequency has been reported for an Argentinean population living in an area contained within a 375-km radius from Córdoba. Analysis of the genomic DNA of two patients from this region revealed that one was homozygous for a G to A substitution at the 5′ donor splice site of intron 2. This mutation completely abolishes normal mRNA splicing. The other patient was a compound of the intron 2 G → A susbtitution and a second allele due to a 4-bp deletion in exon 7. The β-subunit mRNA of this allele is unstable, presumably as a result of an early stop codon introduced by the deletion. Two novel PCR-based assays were developed to detect these mutations. We suggest that one of these assays could be modified and used as a rapid procedure for 5′ donor splice site defects in other genes. These results provide a further example of the genetic heterogeneity that can exist even in a small geographically isolated population.

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Juvenile Sandhoff disease: a Japanese patient carrying a mutation identical to that found earlier in a Canadian patient

Abstract

Cell

Gene

J. Neurol. Sci.

J. Neurol. Sci.

J. Biol. Chem.

Methods Enzymol.

Biochem. Biophys. Res. Commun.

Buffer gradient gels and 35S label as an aid to rapid DNA sequence determination

Partial enzyme deficiencies: residual activities and the development of neurological disorders

Dev. Neurosci.

Ganglioside GM2N-acetyl-β-d-galactosaminidase activity in cultured fibroblasts of late-infantile and adult GM2 gangliosidosis patients and of healthy probands with low hexosaminidase levels

Am. J. Hum. Genet.

Absence of hexosaminidase A and B in a normal adult

New Engl. J. Med.

Characterization of a variant of β-hexosaminidase, “Hexosaminidase Paris”

Am. J. Hum. Genet.

Sensitive enzyme-immunostaining and densitometric determination of ganglio-series gangliosides on thin-layer plate

Biochim. Biophys. Acta

Buffer gradient gels and ³⁵S label as an aid to rapid DNA sequence determination

Ganglioside GM₂ $N- acetyl -β- d -galactosaminidase$ activity in cultured fibroblasts of late-infantile and adult GM₂ gangliosidosis patients and of healthy probands with low hexosaminidase levels