hymecromone and Tay-Sachs-Disease

Tay-Sachs disease is an autosomal recessive storage disease caused by the impaired activity of the lysosomal enzyme hexosaminidase A. In this fatal disease, the sphingolipid GM2 ganglioside accumulates in the neurons. Due to high carrier rates and the severity of the disease, population screening and prenatal diagnosis of Tay-Sachs disease are routinely carried out in Israel. Laboratory diagnosis of Tay-Sachs is carried out with biochemical and DNA-based methods in peripheral and umbilical cord blood, amniotic fluid, and chorionic villi samples. The assay of hexosaminidase A (Hex A) activity is carried out with synthetic substrates, 4-methylumbelliferyl-6-sulfo-N-acetyl-beta-glucosaminide (4-MUGS) and 4-methylumbelliferil-N-acetyl-beta-glucosamine (4-MUG), and the DNA-based analysis involves testing for the presence of specific known mutations in the alpha-subunit gene of Hex A. Prenatal diagnosis of Tay-Sachs disease is accomplished within 24-48 h from sampling. The preferred strategy is to simultaneously carry out enzymatic analysis in the amniotic fluid supernatant or in chorionic villi and molecular DNA-based testing in an amniotic fluid cell-pellet or in chorionic villi.

Topics: Acetylglucosamine; Amniocentesis; Amniotic Fluid; beta-Hexosaminidase alpha Chain; Biological Assay; Chorionic Villi; Chorionic Villi Sampling; DNA Mutational Analysis; Female; Fetal Blood; Gene Expression Regulation, Developmental; Genetic Testing; Humans; Hymecromone; Mutation; Polymerase Chain Reaction; Predictive Value of Tests; Pregnancy; Prenatal Diagnosis; Reproducibility of Results; Substrate Specificity; Tay-Sachs Disease; Time Factors

Tay-Sachs and Sandhoff diseases are lysosomal storage disorders that result from an inherited deficiency of beta-hexosaminidase A (alphabeta). Whereas the acute forms are associated with a total absence of hexosaminidase A and early death, the chronic adult forms exist with activity and protein levels of approximately 5%, and unaffected individuals have been found with only 10% of normal levels. Surprisingly, almost all disease-associated missense mutations do not affect the active site of the enzyme but, rather, inhibit its ability to obtain and/or retain its native fold in the endoplasmic reticulum, resulting in its retention and accelerated degradation. By growing adult Tay-Sachs fibroblasts in culture medium containing known inhibitors of hexosaminidase we have raised the residual protein and activity levels of intralysosomal hexosaminidase A well above the critical 10% of normal levels. A similar effect was observed in fibroblasts from an adult Sandhoff patient. We propose that these hexosaminidase inhibitors function as pharmacological chaperones, enhancing the stability of the native conformation of the enzyme, increasing the amount of hexosaminidase A capable of exiting the endoplasmic reticulum for transport to the lysosome. Therefore, pharmacological chaperones could provide a novel approach to the treatment of adult Tay-Sachs and possibly Sandhoff diseases.

Topics: Adult; beta-N-Acetylhexosaminidases; Cell Line; Enzyme Activation; Enzyme Inhibitors; Female; Fibroblasts; Hexosaminidase A; Hot Temperature; Humans; Hymecromone; In Vitro Techniques; Lysosomes; Molecular Chaperones; Mutation; Protein Folding; Sandhoff Disease; Tay-Sachs Disease

We have adapted two methods to evaluate the beta-hexosaminidase (HEX) enzymatic activity in cultured cells, based on the use of (i) the fluorogenic substrate 4-methylumbelliferyl-6-sulfo-2-acetamido-2- deoxy-beta-D-glucopyranoside (MU-GlcNAc-6-SO4) and (ii) the naphthol AS-BI-N-acetyl-beta-D-glucosaminide and hexazotized pararosaniline. We demonstrate that both methods could be used for the HEX isoenzymes by comparing wild-type and mutant human fibroblast cell lines, deficient for either an alpha or beta subunit from Tay-Sachs and Sandhoff patients. This in situ cytochemical assessment of HEX activity offers a rapid evaluation to study the expression of this enzyme in a heterogeneous cell population such as in gene transfer experiments.

Topics: Acetylglucosamine; beta-N-Acetylhexosaminidases; Cells, Cultured; Fibroblasts; Glucuronates; Histocytochemistry; Humans; Hymecromone; Isoenzymes; Mutation; Naphthols; Sandhoff Disease; Spectrometry, Fluorescence; Tay-Sachs Disease

The determination of hexosaminidases A and B in most programmes for Tay-Sachs disease carrier detection is based on their different heat sensitivity (hexosaminidase A is the heat labile isoenzyme). This routine cannot be employed for individuals who also possess a thermolabile hexosaminidase B. In Israel, 0.6% of the screened samples have a labile hexosaminidases B (about 110 each year) and the assessment of their hexosaminidase A activity has hitherto been based on isoenzyme separation by ion exchange chromatography. The latter requires relative large serum samples, and the individuals must usually be reappointed. In order to avoid the thermal treatment we have used the alternative technique, which employs two substrates with different specificities for the two isoenzymes: 1. The fluorogenic substance, 4-methylumbelliferyl-N-acetyl-glucopyranoside, which measures total hexosaminidase activity and 2. the derivative, 4-methylumbelliferyl-N-acetyl glucosamine-6-sulphate, which is considerably more specific toward hexosaminidase A. Hexosaminidase A activity was expressed as a ratio of total activities (the ratio of the assay with 4-methylumbelliferyl-N-acetyl glucosamine-6-sulphate to that with 4-methyllumbelliferyl-N-acetyl-glucopyranoside). Using the results from 65 obligate heterozygotes for Tay-Sachs disease, we established our reference ranges for assigning the genotypes with respect to the Tay-Sachs gene. Comparison of the results from 182 unrelated and randomly chosen sera screened by the ratio method and by heat inactivation, showed a very high correlation (r = 0.996). Sixty eight sera with thermolabile hexosaminidase B were tested by ion exchange chromatography and by the double substrate method, and they yielded identical diagnoses with regard to the Tay-Sachs locus.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Acetylglucosamine; beta-N-Acetylhexosaminidases; Chromatography, Ion Exchange; Enzyme Stability; Genetic Carrier Screening; Genetic Testing; Genotype; Hexosaminidase A; Hexosaminidase B; Hot Temperature; Humans; Hymecromone; Jews; Substrate Specificity; Tay-Sachs Disease

GM2-gangliosidosis B1 variant, considered a rare disorder with a wide geographical and ethnic distribution, appears to be exceptionally frequent in Portugal. In order to establish a carrier detection method for this disease we have determined the ratio of enzymatic activities against 4MUGS and 4MUG in urine from B1 variant obligate carriers and controls, using the total extract and the Hex A immunobound to a monoclonal antibody. The Hex A immunoassay was applied to the identification of carriers in B1 variant families and the results obtained were compared with those from DNA analysis. The reliability and feasibility of the Hex A immunoassay make it a suitable method for B1 variant carrier screening, which is particularly important for the prevention of this severe neurological disease in the population at risk.

Topics: Adolescent; Adult; Aged; beta-N-Acetylhexosaminidases; Child; Child, Preschool; Female; Genetic Carrier Screening; Genetic Variation; Hexosaminidase A; Humans; Hymecromone; Male; Middle Aged; Tay-Sachs Disease

We describe late infantile Tay-Sachs disease with high residual hexosaminidase A activity in two siblings of a Syrian Druze family. The patients' leukocytes had 26% of normal hexosaminidase A activity when tested with the conventional fluorogenic substrate 4-methyl-umbelliferyl-2-acetamido-2-deoxy-beta-D-glucopyranoside (4-MUG) and only about 10% when assayed with the sulfated substrate, 4-methyl-umbelliferal- beta-N-acetyl-glucosamine-6-sulfate (4-MUGS). According to the standard procedure of the heterozygote screening program (employing 4-MUG and heat inactivation), the parents were not diagnosed as an at-risk couple since the father was classified as a noncarrier. However, both parents' levels were clearly within the carrier range on the basis of 4-MUGS. The unique catalytic characteristics of the patients' enzyme forward the assumption that the affected sibs are B1 variants. The parents' enzymatic levels, together with their known consanguinity, might indicate that these patients are homozygotes for the rare mutation and not genetic compounds as has been documented for most of the infantile B1 variants. To the best of our knowledge this is the first reported case of B1 variant in a child of that extraction.

Topics: beta-N-Acetylhexosaminidases; Female; Genetic Carrier Screening; Hexosaminidase A; Humans; Hymecromone; Infant, Newborn; Male; Syria; Tay-Sachs Disease

An assay for measuring hexosaminidase A in serum and leucocytes is described in which a centrifugal analyser is used for automation of the enzyme assays after manual heat inactivation. The assay was used in a screening programme to identify heterozygotes for Tay-Sachs disease in Ashkenazi Jewish subjects in the UK. The first results from this programme indicate a carrier frequency of 1 in 27. Automation of an assay for direct measurement of hexosaminidase A in serum using 4-methyl-umbelliferyl-beta-N-acetylglucosamine-6-sulphate as substrate is also described. Comparison of data obtained from 66 control and 30 obligate carrier sera tested by this method and by heat inactivation showed improved discrimination using the sulphated substrate. Results obtained using the sulphated substrate for screening serum during pregnancy are also presented.

Topics: Acetylglucosamine; Automation; beta-N-Acetylhexosaminidases; Cell Separation; Centrifugation; Female; Flow Cytometry; Genetic Carrier Screening; Genetic Testing; Glucosamine; Hexosaminidase A; Hot Temperature; Humans; Hymecromone; Leukocytes; Pregnancy; Prenatal Diagnosis; Tay-Sachs Disease

Uncultured and cultured embryonic trophoblastic tissue obtained by chorionic villus sampling (CVS) displays enzyme activity towards 4-methylumbelliferyl-2-acetamido-2-deoxy-beta-D-glucopyranosyl-6-sulfate (MUGS), a specific substrate for Hexosaminidase A (Hex A), the enzyme deficient in Tay-Sachs disease (TSD). Specific activity is comparable to that found in cultured amniocytes and fibroblasts. The enzyme activity has a pH optimum of 4.1 and an apparent Km of 6 x 10(-4) mol/L. Thirteen pregnancies in eight families at risk for TSD were monitored by CVS using MUGS as the Hex A substrate. Four fetuses were proven affected by enzyme analysis of fetal tissues and cultured fetal fibroblasts obtained at the time of termination of the pregnancies. Nine fetuses were judged to be unaffected. Eight babies were clinically normal while the other pregnancy is continuing. The use of MUGS as substrate for Hex A makes prenatal diagnosis by CVS of families at risk for TSD simple, direct and accurate.

Topics: beta-N-Acetylhexosaminidases; Cells, Cultured; Chorionic Villi; Female; Hexosaminidase A; Humans; Hymecromone; Pregnancy; Pregnancy Trimester, First; Prenatal Diagnosis; Risk Factors; Substrate Specificity; Tay-Sachs Disease

Prenatal diagnosis of Tay-Sachs disease was performed using the sulphated substrate 4-methylumbelliferyl-6-sulpho-2-acetamido-2-deoxy-beta-D-glucopyranoside to detect hexosaminidase A in chorionic villi. The presence or absence of hexosaminidase A in villi was detected by both a quantitative enzyme assay, and by a rapid, novel procedure which permitted visual discrimination between normal and affected villi.

Topics: beta-N-Acetylhexosaminidases; Chorionic Villi; Female; Hexosaminidase A; Humans; Hymecromone; Pregnancy; Prenatal Diagnosis; Tay-Sachs Disease; Umbelliferones

Topics: beta-N-Acetylhexosaminidases; Humans; Hymecromone; Infant; Male; Substrate Specificity; Tay-Sachs Disease

Topics: Amniotic Fluid; Female; Hexosaminidases; Humans; Hymecromone; Pregnancy; Prenatal Diagnosis; Sandhoff Disease; Tay-Sachs Disease; Umbelliferones

A non-Jewish child with late onset GM2 gangliosidosis is described. Tissues from the patient had near normal hexosaminidase A (hex A) activity using 4-methylumbelliferyl-2-acetamido-2-deoxy-beta-D-glucopyranoside (MU-glcNAc) as substrate, and deficient activity when assayed with the 6-sulphate derivative of MU-glcNAc (MU-glcNAcS) or GM2 in the presence of activator. We present evidence that this patient is a genetic compound for different alpha-subunit mutations. The father's tissues have hex A activity in the heterozygote range when assayed with MU-glcNAcS, but normal activity using MU-glcNAc; the mother's tissues have activities toward both substrates in the heterozygote range. These results emphasize the pitfalls of using only MU-glcNAc for the diagnosis of unusual variants of GM2 gangliosidosis.

Topics: Acetylglucosamine; Alleles; beta-N-Acetylhexosaminidases; Child, Preschool; Female; Glucosamine; Heterozygote; Hexosaminidase A; Hexosaminidases; Humans; Hymecromone; Mutation; Pedigree; Substrate Specificity; Tay-Sachs Disease

4-Methylumbelliferyl-6-sulfo-2-acetamido-2-deoxy-beta-D-glucopyranoside was synthesized and tested as a substrate for the diagnosis of GM2 gangliosidoses using leukocytes. Less than 2% of normal activity was measured in homogenates from patients with typical Tay-Sachs disease and from a patient with a variant form having 37% Hexosaminidase A by heat denaturation using the usual fluorogenic substrate. An adult patient had 8.5% of normal activity. Three patients with Sandhoff disease were found to have values ranging from 17% to 37% of normal. These values overlap the range found for carriers of Tay-Sachs disease, and suggest that the usefulness of this substrate, while excellent for diagnosing B variants of GM2 gangliosidosis, requires further study. Perhaps when used together with 4-methylumbelliferyl-2-acetamido-2-deoxy-beta-D-glucopyranoside excellent discriminations of patients, carriers and controls will be realized.

Topics: Acetylglucosaminidase; beta-N-Acetylhexosaminidases; Female; Genetic Carrier Screening; Hexosaminidase A; Hexosaminidases; Humans; Hymecromone; Leukocytes; Male; Sandhoff Disease; Substrate Specificity; Tay-Sachs Disease; Umbelliferones

Measurement of hexosaminidase A (Hex A) is an important clinical chemical procedure in the classification of GM2 gangliosidosis genotypes. We have synthesized a new substrate which may be useful in both the biochemical diagnosis of GM2 gangliosidosis and the detection of heterozygotes for the Tay-Sachs disease (TSD) allele. 4-Methylumbelliferyl-beta-D-N-acetylglucosamine-6-sulfate (4MUGS) was synthesized by sulfation of 4MU-beta-D-N-acetylglucosamine (4MUG) with chlorosulfonic acid and purified through gel filtration and ion-exchange chromatography. The structure of 4MUGS was verified by elemental analysis and NMR. Hex A is approximately 100 times more active toward 4MUGS than Hex B. The advantage of this increased specificity is that Hex A can be determined in a one-step procedure which allows separation of normal control serum values from those of obligate heterozygotes. Alternatively, assay values obtained using both substrates can be transformed by application of an empirical equation that allows the calculation of both Hex A and Hex B without the requirement of thermal fractionation. Lower values for % Hex A in serum have been obtained for Tay-Sachs homozygotes using the 4MUGS assay procedure. The results of Hex A assays on fibroblast cell strains obtained from Tay-Sachs homozygotes, variant forms of GM2 gangliosidosis and normal controls are also discussed.

Topics: beta-N-Acetylhexosaminidases; Cell Line; Drug Stability; Fibroblasts; Gangliosidoses; Genetic Carrier Screening; Genotype; Hexosaminidase A; Hexosaminidase B; Hexosaminidases; Homozygote; Hot Temperature; Humans; Hymecromone; Kinetics; Liver; Substrate Specificity; Tay-Sachs Disease; Umbelliferones