Prenatal Diagnosis Of Tay-Sachs Disease Research Articles

Analysis of polymorphic markers located in the HEXA gene region associated with Tay-Sachs disease

Tay-Sachs Disease (TSD) is a genetic disorder resulting from mutations in the HEXA gene. Linkage analysis of polymorphic markers such as single nucleotide polymorphism (SNP) has been used in heterozygous carrier detection and prenatal diagnosis of the disease in families with an affected individual. A large number of SNP markers have been introduced for the HEXA gene in the databases. In the present study, the genotype and informative degree of rs2288258 and rs4777507genetic markers of HEXA gene region were investigated. This study has been conducted using Tetra-primer ARMS PCR and usual ARMS PCR in 148 healthy unrelated control individuals and 10 families in the Iranian population. The allele frequency, degree of heterozygosity and Hardy-Weinberg equilibrium (HWE) was estimated using the GENEPOP program. Also, the estimation of haplotype frequency and linkage disequilibrium for the unrelated individuals was performed using the PowerMmarker software. Based on the obtained results, the observed degree of heterozygosity for rs2288258 and rs4777507 were 18.24 and 27.70, respectively. The allele frequency of rs2288258 was 90.88% for allele A and 9.12% for allele G. Also, the allele frequency of rs4777507 was 84.8% and 15.2% for A and G allele respectively. The results showed two markers, rs2288258-rs4777507, were in linkage disequilibrium together. Consequently, A/A, A/G and G/G informative haplotypes in population level and A/A, A/G and G/A informative haplotypes in family level were identified by using a combination of these two markers. These haplotypes can serve as appropriate tools for linkage analysis and identification of heterozygous carriers and prenatal diagnosis of TSD in the Iranian families with affected children.

Prenatal diagnosis of Tay-Sachs disease: our institutional experience

Tay-Sachs disease (TSD) is the second most common storage disease after Guacher disease in the group of lipid storage disorders in India. In absence of any therapeutic option, prenatal diagnosis is the only way to prevent the disease burden.

First trimester prenatal diagnosis of tay-sachs disease using the sulfated synthetic substrate for hexosaminidase A

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.

Use of 4-methylumbelliferyl-6-sulpho-2-acetamido-2-deoxy-beta- D-glucopyranoside for prenatal diagnosis of Tay-Sachs disease using chorionic villi.

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.

Prenatal diagnosis of Tay-Sachs disease. Reflectometry of hexosaminidase A, B, and C/S bands on zymograms.

Hexosaminidase (Hex) A, B, and C/S were electrophoretically separated from cultured amniotic fluid cells, fetal brain, and white blood cells. Photographs of cellulose acetate zymograms were evaluated by reflectometric scanning. The usefulness and limitations of this rapid method were shown. Hex A was completely absent in the amniotic fluid cells of one out of three pregnancies at risk for Tay-Sachs disease, but Hex C/S was present in this case. The prenatal diagnosis of Tay-Sachs disease was made, and confirmed with the fetal material after abortion. Hex C/S was distinguishable from a residual or "heterozygous" Hex A activity. In the two other risk pregnancies, reflectometric Hex A activities were found to be 50 and 34% of control; the heterozygous stage was presumed for the fetuses.

Prenatal diagnosis of Tay-Sachs disease with heat-labile β-hexosaminidase B

Two consecutive pregnancies at risk for Tay-Sachs disease with heat-labile β-hexosaminidase B were monitored. Differential isozyme detection of β-hexosaminidase in cell free amniotic fluid by DEAE cellulose column chromatography and cellulose acetate paper electrophoresis showed an affected fetus in the first pregnancy and an unaffected in the second. These results were confirmed in the aborted fetus and in a newborn baby, respectively.

Prenatal diagnosis of Tay-Sachs disease: Studies on the reliability of hexosaminidase levels in amniotic fluid

Measurement of hexosaminidase A activity in amniotic fluid was found to be a reliable diagnostic test in the prenatal diagnosis of Tay-Sachs disease. Including normal control specimens, analysis of 39 amniotic fluid samples have correctly predicted the condition of the fetus or, in pregnancies not yet come to term, have been in agreement with results from cultured cell extracts. In each case where both fluid and cultured cell extracts were analyzed, the results were in agreement. Analyses were performed by means of Cellogel, starch gel electrophoresis, polyacrylamide gel electrophoresis, or heat inactivation.

Prenatal diagnosis of Tay-Sachs disease in cell-free amniotic fluid.

The diagnosis of 6 known Tay-Sachs cases was confirmed by isoelectric focusing of the cell-free amniotic fluid. The presence of an additional--hitherto unknown--heatstable, acid hexosaminidase X in normal and pathological amniotic fluids must be taken into account especially when the heat denaturation method of detecting Tay-Sachs disease is applied. Hexosaminidase X shows some properties similar to those of hexosaminidase B.

A modified method for prenatal diagnosis of Tay-Sachs disease in cell-free amniotic fluid.

A modified method for prenatal diagnosis of Tay-Sachs disease in cell-free amniotic fluid.

Tay-Sachs disease: to screen or not to screen?

lo a Jewish iamily awaiting a physicians health report on their newborn there are no words more devastating than "your :hild has Tay-Sachs1 disease." Because this congenital disorder2 is fatal in the early years of a child's life coupled with the statis tical studies showing that it strikes primarily Jewish families of East European heritage an increasing awareness and concern has been voiced3 by the Jewish community with regard to the de tection and cure of this genetic disease. Lately,4 the medical and tialakhic aspects of screening large segments of the Jewish popu lation for the carrier state of Tay-Sachs disease and the perform ance of amniocentesis for the pre-natal detection have been dis cussed and debated. This essay will deal with the moral, ethical, social, psychological and religious indications and contraindica tions to amniocentesis for the pre-natal diagnosis of Tay-Sachs disease.

Prenatal diagnosis and fetal pathology of Tay-Sachs disease.

In 6 cases of high risk pregnancies for Tay-Sachs disease, prenatal diagnosis was successfully carried out by examining hexosaminidase A activity in the supernatant of amniotic fluid and the uncultured and cultured amniotic fluid cells. In 5 out of 6 cases, the activity of hexosaminidase A was found to be within normal or heterozygous levels. They continued their pregnancies and were delivered of healthy children. In the remaining 1 case, the activity was undetected. Her pregnancy was terminated at the 23rd week of gestation. There was no activity of hexosamindase A in the brain and liver from the aborted fetus. A moderate increase in GM2 ganglioside was found in the brain. Electron-microscopic findings revealed membranous cytoplasmic bodies in the spinal ganglion cells as well as in the nerve cells of the retina. These biochemical and histological findings of Tay-Sachs fetus suggest that the disease proceeds early in fetal period. It was found that the cultured amniotic fluid cells was the most reliable material for the prenatal diagnosis of Tay-Sachs disease, because the values of hexoxaminidase A in the cultured cells were well in accord with those in serum from the consequently bord children. Hexosaminidase pattern in the supernatant of amniotic fluid on DEAE-cellulose columnchromatogram showed a distinct difference between homozygote, heterozygote and normal. This procedure also may be useful for prenatal diagnosis of Tay-Sachs disease.

Carrier Detection and Prenatal Diagnosis of Tay-Sachs Disease

Carrier Detection and Prenatal Diagnosis of Tay-Sachs Disease

Amniocentesis in Tay-Sachs Disease

To the Editor.— Tay-Sachs disease is an inborn metabolic disorder, essentially peculiar to Jews, consisting of deficiency or absence of hexosaminidase A. The disease is invariably fatal, usually before 2 or 3 years of age. The carrier or heterozygous state occurs in approximately 1 in 30 Ashkenazi Jews, and is a harmless condition. If two carriers marry, the statistical probability is that one quarter of the offspring will have the full-blown fatal disease, one half will be carriers like the parents, and one quarter will be totally free of the Tay-Sachs gene, according to simple Mendelian genetics. Widespread screening for the carrier state has been undertaken in the United States1and the United Kingdom.2Many laboratories are now offering to carry out tests for the prenatal diagnosis of Tay-Sachs disease by the application of amniocentesis. If the fetus is determined to have Tay-Sachs disease, an abortion is then

Confirmatory studies in the prenatal diagnosis of sphingolipidoses.

Extract: Chemical and biochemical variables of the sphingolipids were examined in fetal liver, kidney, and brain using saline-aborted (SA) and hysterotomy-aborted (HA) tissues. Brain sphingolipid hexose (BSH) and ganglioside N-acetyl neuraminic acid (NANA) content were similar in each group (BSH/SA, 4.1–5.0 mg/g dry wt and HA, 3.0–6.7 mg/g dry wt; NANA/SA, 1.1–3.3 mg/g dry wt and HA, 1.3–3.1 mg/g dry wt). The distribution of the major gangliosides was also comparable in each group. Sulfatide levels were lower in the hysterotomy group (0.2–0.4 mg/g dry wt) than in the saline group (0.5–0.9 mg/g dry wt), perhaps reflecting the earlier gestational age of this group. Activities of arylsulfatase A (ARA), β-galactosidase, and hexosaminidase A from each tissue were similar, respectively, in saline-and hysterotomy-aborted fetuses. The ARA activity (liver, 23–67; kidney, 13–21; and brain, 1–42 nmol cleaved/mg protein/hr) was about 10–20% of postnatal levels. Utilizing these control values, amniocentesis-derived diagnoses were confirmed in two fetuses with Tay-Sachs disease (TSD) and in another with Gm1 gangliosidosis type I. The disease-specific ganglioside (Gm2 in TSD and Gm1 in Gm1-gangliosidosis) was significantly elevated in brain from each case (TSD, 5–6 times control values and Gm1-gangliodosis, approximately twice control values). In liver and kidney from the affected fetuses the disease-related enzyme activity of hexosaminidase A in TSD and β-galactosidase in Gm1-ganglactosidase) was less than 10% of control values. In liver, kidney, and brain extracts, cellulose-acetate gel electro-phoresis of the disease-specific enzyme revealed no bands of enzyme activity for hexosaminidase A in Tay-Sachs disease or for the relevant, β-galactosidase isoenzymes in Gm1-gangliosidosis.Speculation: The prenatal diagnosis of Tay-Sachs disease, Gm1-gangliosidosis, and other sphingolipidoses may be confirmed in saline-aborted fetal tissues. Since abortion by hysterotomy may jeopardize the possibility of future pregnancy, saline-induced abortion may be preferable. An intriguing observation of this study was the presence of a β-galactosidase isoenzyme in brain from the Gm1 fetus. This isoenzyme was clearly different from the disease-specific enzyme and was not present in fetal Gm1 liver or kidney or in postnatal type I Gm1 brain. This finding may indicate the presence of a tissue and age-specific β-galactosidase isoenzyme.

Hexosaminidases in cell-free amniotic fluid

By heat denaturation at 50° C. serum and amniotic fluid hexosaminidase behave very similarly. pH optima and Michaelis-Menton constants are almost identical for the hexosaminidases from these two sources. The hexosaminidase from amniotic fluid, serum and white blood cells show the same migration on polyacrylamide gel. These studies suggest that amniotic fluid hexosaminidase is the same enzyme as that found in serum and, as such, its determination may be a valuable tool in the rapid prenatal diagnosis of Tay-Sachs disease.

Studies on cerebral lipidosis. Prenatal diagnosis of Tay-Sachs disease.

Summary In the attempt to diagnose TSD, amniotic fluid was obtained by amniocentesis in a mother whose first child was TSD. Amniotic fluid and uncultured amniotic cells showed absence of hexosaminidase A. The fetus was diagnosed as TSD and the pregnancy was terminated through artificial abortion. Hexosaminidase A in the fetal brain and liver was deficient and an increase of ganglioside Gm2 was observed in the brain of the affected fetus.

PRENATAL DIAGNOSIS OF TAY-SACHS DISEASE

Uncultured cells and fluid collected by amniocentesis during the second trimester from a mother of a child with Tay-Sachs disease were shown to have trace amounts of hexosaminidase-A activity. Accordingly the pregnancy was terminated. Biochemical and morphological studies of the aborted fetal tissue confirmed the prenatal diagnosis of Tay-Sachs disease.