Cross-seeding of wild-type and hereditary variant-type amyloid beta-proteins in the presence of gangliosides.

We investigated the molecular mechanism underlying the ganglioside-induced initiation of the assembly of wild and hereditary variant-type amyloid beta-proteins, including Arctic-, Dutch-, and Flemish-type amyloid beta-proteins. We monitored the assembly of amyloid beta-protein by thioflavin-T assay, western blotting and electron microscopy. We also examined how externally added amyloid beta-protein assembles in a cell culture. The assembly of wild-, Arctic-, Dutch-, and Flemish-type amyloid beta-proteins were accelerated in the presence of GM1, GM1, GM3 and GD3 gangliosides. Notably, all of these amyloid beta-proteins accelerated the assembly of different type of amyloid beta-protein, following prior binding to a specific ganglioside. A specific-ganglioside-bound form of variant-type amyloid beta-protein was recognized by the antibody (4396C) specific to the GM1-ganglioside-induced altered conformation of wild-type amyloid beta-protein. Moreover, the assembly of these amyloid beta-proteins in the presence of a specific ganglioside was markedly suppressed by coincubation with 4396C. This study suggests that cross-seeding can occur between wild and hereditary variant-type amyloid beta-proteins despite differences in their amino acid sequences.

Isolation and characterization of major urinary oligosaccharides excreted by a patient with type 3 GM1 gangliosidosis.

Two major oligosaccharides were isolated from the urine of a patient with type 3 GM1 gangliosidosis. From structural studies including compositional sugar analysis, fast-atom bombardment mass spectrometry, direct-inlet chemical ionization mass spectrometry, methylation analysis, chromium trioxide oxidation, and proton magnetic resonance spectroscopy, their structures were deduced to be as follows: [formula: see text] Both oligosaccharides have beta-linked galactose at the non-reducing ends. Oligosaccharide 1 is one of the most common urinary oligosaccharides found in type 1 and type 2 GM1 gangliosidosis. Oligosaccharide 2, lacto-N-difucohexaose II, has not been described in the urine of GM1 gangliosidosis patients. Excretion of oligosaccharide 1 in the type 3 patient was much less than that of a type 2 patient. Thin-layer chromatographic analysis revealed that the excretion of oligosaccharides with higher molecular weight than that of oligosaccharide 1 (octasaccharide) in the type 3 patient was much less than that of a type 2 patient, raising the possibility that the mutant beta-galactosidase of type 3 GM1 gangliosidosis can still act to some extent on higher molecular weight oligosaccharides containing beta-linked galactose at the non-reducing end.

The clinical aspects of adult hexosaminidase deficiencies.

The authors describe the clinical phenotypes of hexosaminidase deficiencies (GM2 gangliosidosis). The symptoms, differently combined, include cerebellar ataxia, motor neuron disease, dystonia, psychosis, neurovegetative troubles with different severity. Morphological changes are evident in rectal, muscle or nerve biopsies. Minor clinical changes are described in carriers from a family. A chronic GM2 gangliosidosis has to be suspected in any atypical case with the above-mentioned symptoms with autosomal-recessive inheritance.

Molecular and clinical heterogeneity of adult GM2 gangliosidosis.

Adult GM2 gangliosidosis is a rare autosomal recessive disease with widely varying neurological and psychiatric manifestations. It is caused by marked deficiency, but not total absence, of beta-hexosaminidase (Hex) A, due to a single base change in the alpha-subunit gene of Hex, resulting in a substitution of Ser for Gly at position 269 in the alpha-subunit of the enzyme. The same mutation was identified in all investigated patients, most of whom are Ashkenazi Jews. Among previously studied non-Jewish patients of unrelated families this mutation appears either homozygously or in compound heterozygosity with an unidentified alpha-subunit mutation, whereas all Ashkenazi patients are compound heterozygotes. In all but one of them the other mutation is one of the Ashkenazi infantile Tay-Sachs alleles, while in one 76-year-old woman with very mild neurological symptoms, it is an unidentified alpha-subunit mutation. At present, the little correlation that seems to exist between these different genotypes and the severity of the disease poses a serious dilemma for genetic counselors.

Biochemical and molecular aspects of late-onset GM2-gangliosidosis: B1 variant as a prototype.

Clinical phenotypes of GM2-gangliosidosis are complex. In the past 5 years it has become possible to dissect out the phenotypic complexity on the basis of abnormalities on the DNA level. Available data on the 18 disease-causing mutations so far identified in the beta-hexosaminidase alpha-gene allow an oversimplified generalization; mutations that produce no or highly unstable mRNA cause the most severe infantile forms of the disease, while all late-onset forms are due to point mutations within the protein-coding region, which generate stable mRNA and stable mutant protein. The mutation underlying the distinct phenotype of Jewish adult Tay-Sachs disease will be discussed separately by Navon. The prototype of juvenile Tay-Sachs disease is the B1 variant. The disease was first recognized by an apparent discrepancy in the beta-hexosaminidase activities toward the conventional artificial substrates and the natural lipid substrate, GM2-ganglioside. When assayed with the conventional artificial substrates, patients appear reasonably normal while they are severely deficient in hydrolysis of the natural substrate (and more recently the 'sulfated' artificial substrate). The majority of B1 patients fall in the clinical category of juvenile GM2-gangliosidosis. Some of the earlier juvenile patients reported to have partial hexosaminidase A deficiency are likely to be B1 variant. Two point mutations, occurring at a mutation hot spot, CpG, and both affecting the same codon, have been described as the causes of the B1 variant phenotype; G533----A, Arg178----His; and C532----T, Arg178----Cys. The latter mutation has been found so far only in one Czechoslovakian family. In contrast, the former mutation has a wide geographic and ethnic distribution.(ABSTRACT TRUNCATED AT 250 WORDS)

Neuropathology of late onset gangliosidoses. A review.

Neuropathological features of late onset gangliosidoses are reviewed. Although neuropathological studies are carried out on limited numbers of late onset cases, it appears that electron-dense heterogeneous conglomerates of neuronal inclusions increased with age admixed with more typical membranous cytoplasmic inclusions of gangliosidosis. Unlike early onset cases, which show extensive storage in cerebral cortical neurons, cortical neurons are involved less in late onset cases. In chronic (or adult) GM1 gangliosidosis, neuronal storage is almost exclusively limited to the basal ganglia, while in chronic (or adult) GM2 gangliosidosis storage neurons are more widely distributed in the thalamus, substantia nigra and other brainstem nuclei, and cerebellum is significantly affected.

Diagnosis of subtypes of GM1 gangliosidosis in vitro and in vivo--using urinary oligosaccharides as substrates.

In order to delineate clinical subtypes of GM1 gangliosidosis enzymologically, we prepared galactosyl oligosaccharides from the urine of patients, as substrates, and established the method of the galactosyl oligosaccharide beta-galactosidase assay. Galactosyl oligosaccharides beta-galactosidase activities (nmol/mg protein/20 h) in vitro, using substrates without repeating structures were; type 1, 1.0 +/- 0.5 (n = 6), type 2A, 2.1, type 2B, 3.4 +/- 0.7 (n = 5), type 3, 4.9 +/- 0.2 (n = 2). The activities in vitro using substrates with repeating structures were: type 1, 0.3 +/- 0.2 (n = 5), type 2A, 1.2, type 2B, 2.2 +/- 0.5 (n = 4), type 3, 4.2 +/- 0.3 (n = 2). The activities using substrates with and without repeating structures were affected in the fibroblasts of patients, and the residual activities in each subtype were reduced progressively with the increasing severity of the clinical features. The ratio between activities using substrates without repeating structures and activities using substrates with repeating structures indicated that beta-galactosidase activities toward Gal beta 1- of repeating structures were reduced progressively with the increasing severity of the clinical features. The activities in vivo (pmol/mg protein per 24 h) were: type 1, 11.8 +/- 1.8 (n = 2), type 2A, 24.8, type 2B, 40.0 +/- 9.7 (n = 2), type 3, 63.2. The activities in vivo were affected in the fibroblasts of patients and the residual activities were reduced in proportion to the severity of the clinical features. These differences of residual activities among each subtype make it possible to delineate clinical subtypes enzymologically.

Abnormalities of cerebral lipids in GM1-gangliosidoses, infantile, juvenile, and chronic type.

Cerebral lipids of patients with GM1-gangliosidoses, infantile, juvenile, and chronic type which are caused by deficiency of beta-galactosidase, were examined and compared to each other. The infantile type demonstrated abnormal accumulation of GM1 and asialo-GM1 in contrast with marked decrease in such major cerebral lipids as cholesterol, phospholipids, cerebroside, and sulfatide. It was also noted that significant amounts of such unusual lipids as free fatty acids, GlcCer, LacCer, GbOse3Cer, and GbOse-4Cer plus nLcOse4Cer were found in the brain. These findings pointed out that this infantile type might accompany a severe cerebral dysgenesis with poor myelination. The juvenile type also showed marked increase in GM1 and asialo-GM1, but the decrease in cholesterol, phospholipids, cerebroside, and sulfatide was not so much as the infantile type. These findings along with the occurrence of cholesterol ester suggested that the brain caused progressive demyelination after the immature myelin appeared. An autopsized brain tissue of a male patient who was eventually diagnosed as a case of GM1-gangliosidosis chronic type after his death, showed some accumulation of GM1 and asialo-GM1 particularly in the caudate nucleus and putamen, whereas it showed moderate amounts of GM1 in apparently normal gray and white matters. It seemed that there are no abnormal cerebral lipids except for gangliosides and some neutral glycosphingolipids in the chronic type.

Neurophysiological studies in GM1, gangliosidosis.

Neurophysiological studies (EEG, ERG, VEP) have been carried out on 8 children with proven GM1 gangliosidosis (3 of Type I and 5 of Type II). All the EEGs were abnormal showing an increasing amount of irregular slow activity as the disease progressed. Around 2 to 3 years of age, Type II patients often showed a fluctuating 4-5 c/s rhythmic activity especially prominent in the temporal regions. Paroxysmal activity was not a conspicuous feature in any of the patients. The ERG was normal in all cases but the VEP was variably altered. The EEG/ERG/VEP findings in GM1 gangliosidosis differ from those seen in most other neurometabolic disorders of childhood.

GM1 gangliosidosis: phenotypic variation in a single family.

Infantile, juvenile, and adult forms of GM1 gangliosidosis have been well characterized. Certain genetic and biochemical studies have suggested that the phenotypic variation found in GM1 gangliosidosis results from different allelic mutations affecting the GM1 ganglioside beta-galactosidase locus and that different combinations of these mutations accounts for the clinical heterogeneity of this illness. A family in which both the infantile and juvenile forms of GM1 gangliosidosis occurred, the children sharing a common mutation of their acid beta-galactosidase activity, supports the allelic nature of these different clinical forms of the disease. From the observations made in this unique family, additional phenotypes of GM1 gangliosidosis might be anticipated.

GM1 gangliosidosis: enzymatic variation in a single family.

Acid beta-galactosidase activity can be separated into multiple molecular forms by isoelectric focusing on cellulose acetate membranes. The residual acid beta-galactosidase in the juvenile form of GM1 gangliosidosis has three bands of enzyme activity with an apparent isoelectric pH (pI) range from 4.9 to 5.2, whereas that in the infantile form has a single band with an apparent pI of 5.2. Separation of residual acid beta-galactosidase into multiple molecular forms by analytical isoelectric focusing demonstrates enzymatic differences that can be correlated with the allelic mutations that affect the GM1 ganglioside beta-galactosidase locus.

[Lysosomal beta-galactosidase properties and the molecular genetics of GM1 gangliosidosis]. / Svoistva lizosomal'noi beta-galaktozidazy i molekuliarnaia generika gangliozidozov GM1.

Review of the data is presented on the hereditary disease gangliosidosis GM1 and on the enzyme beta-galactosidose, deficiency of which is responsible for this disease. Heterogeneity of the disease and existence of various forms of beta-galactosidase are considered. Possible correlation is discussed between the defects of the enzyme forms detected and the type of the disease.

[A case of GM-Gangliosidosis (atypical form of the AB variant)]. / Un caso di gangliosidose GM, cariante AB atipica.

A case of GM-gangliosidosis, variant AB, with some atypical feautres is reported in a male child, who died at the age of 4 years and 3 months. When he was 2 and a half years old, he showed signs of progressive cerebral disease with increasing motor and mental impairment. The clinical signs suggested a form of neurolipidosis; however the data of the enzymatic activities of the peripheral blood leucocytes did not show any deficit related to these forms. More specifically the values of the exosaminides A and B were normal, although the component A was near the lowest limit of the range. The anatomical, histological, histochemical, ultrastructural and chemical studies showed that it was a form of GM-gangliosidosis with visceral involvement. In the crude lipid extracts of various organs there was not only GM-ganglioside, but also a compound not previously demonstrated in these forms of neurolipidosis. Chemically this compound may be considered a phosphoglyco-lipid-and protein complex. From the enzymatic data in the peripheral blood leucocytes, the case may be a variant AB of the Sandhoff and al. classification (1971). However some clinical signs make our case closer to the 3th type of the O'Brien and al, classification while some histopathological aspects are similar to Tay-Sachs disease (i.e. to the variant B of the Sandhoff et al. classification; i.e. to the 1th type of the O'Brien et al. classification). These data, and the presence of an 'unknown compound', not yet demonstrated in the known forms of GM-gangliosidosis, support the hypothesis that our case may be considered as an 'atypical' form of the variant AB of the gangliosidosis GM and that further studies are necessary to reach a final nosography of these entities.

[Globoid cells leukodystrophy apropos of a case of Krabbe's disease]. / Leucodystrophie à cellules globoïdes. A propos d'une observation de la maladie de Krabbe

A case of Krabbe's leucodystrophy is reported after photon and delayed ultrastructural microscopic study. Cerebroside overload within the cerebral globoid cells was shown as well as in the interstitial histiocytic infiltration of the peripheral nerves. Reviewed with the published literature, the characteristics of the inclusions observed seem to be unspecific and, from a morphological standpoint, Krabbe's disease may be related to the gangliosidoses.