A method for rapid prenatal diagnosis of glycogenosis II (Pompe's disease)

Intravenous Injection of an AAV-PHP.B Vector Encoding Human Acid α-Glucosidase Rescues Both Muscle and CNS Defects in Murine Pompe Disease

Pompe disease, a severe and often fatal neuromuscular disorder, is caused by a deficiency of the lysosomal enzyme acid alpha-glucosidase (GAA). The disease is characterized by the accumulation of excess glycogen in the heart, skeletal muscle, and CNS. Currently approved enzyme replacement therapy or experimental adeno-associated virus (AAV)-mediated gene therapy has little effect on CNS correction. Here we demonstrate that a newly developed AAV-PHP.B vector can robustly transduce both the CNS and skeletal muscles in GAA-knockout (GAAKO) mice. A single intravenous injection of an AAV-PHP.B vector expressing human GAA under the control of cytomegalovirus (CMV) enhancer-chicken β-actin (CB) promoter into 2-week-old GAAKO mice resulted in widespread GAA expression in the affected tissues. Glycogen contents were reduced to wild-type levels in the brain and heart, and they were significantly decreased in skeletal muscle by the AAV treatment. The histological assay showed no visible glycogen in any region of the brain and spinal cord of AAV-treated mice. In this study, we describe a set of behavioral tests that can detect early neurological deficits linked to extensive lysosomal glycogen accumulation in the CNS of untreated GAAKO mice. Furthermore, we demonstrate that the therapy can help prevent the development of these abnormalities.

Reduction of Autophagic Accumulation in Pompe Disease Mouse Model Following Gene Therapy

BACKGROUND

Pompe disease is a fatal neuromuscular disorder caused by a deficiency in acid α-glucosidase, an enzyme responsible for glycogen degradation in the lysosome. Currently, the only approved treatment for Pompe disease is enzyme replacement therapy (ERT), which increases patient survival, but does not fully correct the skeletal muscle pathology. Skeletal muscle pathology is not corrected with ERT because low cation-independent mannose-6-phosphate receptor abundance and autophagic accumulation inhibits the enzyme from reaching the lysosome. Thus, a therapy that more efficiently targets skeletal muscle pathology, such as adeno-associated virus (AAV), is needed for Pompe disease.

OBJECTIVE

The goal of this project was to deliver a rAAV9-coGAA vector driven by a tissue restrictive promoter will efficiently transduce skeletal muscle and correct autophagic accumulation.

METHODS

Thus, rAAV9-coGAA was intravenously delivered at three doses to 12-week old Gaa-/- mice. 1 month after injection, skeletal muscles were biochemically and histologically analyzed for autophagy-related markers.

RESULTS

At the highest dose, GAA enzyme activity and vacuolization scores achieved therapeutic levels. In addition, resolution of autophagosome (AP) accumulation was seen by immunofluorescence and western blot analysis of autophagy-related proteins. Finally, mice treated at birth demonstrated persistence of GAA expression and resolution of lysosomes and APs compared to those treated at 3 months.

CONCLUSION

In conclusion, a single systemic injection of rAAV9-coGAA ameliorates vacuolar accumulation and prevents autophagic dysregulation.

Long-term exposure to Myozyme results in a decrease of anti-drug antibodies in late-onset Pompe disease patients

Immunogenicity of recombinant human acid-alpha glucosidase (rhGAA) in enzyme replacement therapy (ERT) is a safety and efficacy concern in the management of late-onset Pompe disease (LOPD). However, long-term effects of ERT on humoral and cellular responses to rhGAA are still poorly understood. To better understand the impact of immunogenicity of rhGAA on the efficacy of ERT, clinical data and blood samples from LOPD patients undergoing ERT for >4 years (n = 28) or untreated (n = 10) were collected and analyzed. In treated LOPD patients, anti-rhGAA antibodies peaked within the first 1000 days of ERT, while long-term exposure to rhGAA resulted in clearance of antibodies with residual production of non-neutralizing IgG. Analysis of  T cell responses to rhGAA showed detectable T cell reactivity only after in vitro restimulation. Upregulation of several cytokines and chemokines was detectable in both treated and untreated LOPD subjects, while IL2 secretion was detectable only in subjects who received ERT. These results indicate that long-term ERT in LOPD patients results in a decrease in antibody titers and residual production of non-inhibitory IgGs. Immune responses to GAA following long-term ERT do not seem to affect efficacy of ERT and are consistent with an immunomodulatory effect possibly mediated by regulatory T cells.

Glycogenosis type II: a juvenile-specific mutation with an unusual splicing pattern and a shared mutation in African Americans

The recessively inherited deficiency of acid alpha-glucosidase (GAA) called Glycogenosis Type II is expressed as three different phenotypes: infantile, juvenile, and adult. At the molecular level, infantile and adult forms of the disease have been extensively studied, but little is known regarding the genetic defects associated with the juvenile form. We describe a novel mutation that defines the intermediate juvenile phenotype in a compound heterozygous patient. A transversion of t to g in intron 6 at position -22 creates a cryptic acceptor site and results in unusual splicing abnormality: insertion of 21 nucleotides of the intronic sequence into mRNA and removal of exon 6 without disruption of the reading frame. The second mutation, Arg854Stop in exon 18, had been previously identified in another African-American patient (Hermans et al., 1993a). Family study indicates that a silent allele harboring the Arg854Stop mutation in our patient is inherited from the patient's father, who is also African-American, thus suggesting a common mutation in this population.

Fatal familial infantile glycogen storage disease: multisystem phosphofructokinase deficiency

An infant girl of consanguinous Bedouin parents suffered from fatal early onset of progressive generalized muscle weakness. Her older brother suffered from similar weakness and cardiomyopathy, which led to his death at the age of 21 months. A muscle biopsy performed on the propositus at the age of 9 months was PAS-negative, and showed nonspecific myopathic changes. A second muscle biopsy, performed at 21 months of age, a few days before her death, and postmortem study of heart and liver, disclosed excessive extralysosomal glycogen storage and reduced phosphofructokinase-1 (PFK-1) activity. Because the genes encoded for PFK-1 in liver and muscle are located on separate chromosomes, the reduced enzyme activity in both tissues could not be related to a single mutation for this enzyme. Activity of 6-phosphofructose-2-kinase (PFK-2), a recently discovered physiological activator to all PFK-1 isozymes, was normal in the liver. The possibility that this multisystem PFK-1 deficiency may be related to the absence of a yet unknown activator, common to all PFK-1 isozymes, is discussed.

The biochemical diagnosis of lysosomal storage diseases--a review of five years experience

The inherited lysosomal storage diseases are a distinct group of inborn errors of metabolism characterised by deficiencies in specific lysosomal enzymes. As many as 40 such disorders have now been described in man. We have measured the activities of up to 16 lysosomal acid hydrolases in plasma and/or extracts of leucocytes and cultured skin fibroblasts from 198 patients referred from throughout Ireland. These 16 assays allowed the biochemical diagnosis of 20 lysosomal storage diseases. Activities were compared with reference ranges to determine homozygotes and heterozygotes. Of the 44 patients with positive results, 15 were diagnosed as being homozygous for a specific lysosomal enzyme deficiency, 4 were identified as having multiple enzyme deficiencies (mucolipidosis Type II/I-cell disease) and 25 had heterozygote (carrier) enzyme levels. Of the latter, 24 were either parents (obligate heterozygotes) or siblings of homozygotes and one was a heterozygote for the X-linked recessively inherited Fabry's disease.

Prevalence of different types of lysosomal storage diseases in Saudi Arabia

The frequency of different types of lysosomal storage diseases in 125 referred cases, collected over three years, was compared to the occurrence elsewhere. The data suggest that mucopolysaccharidosis (MPS) type IVA (Morquio disease), multiple sulphatase deficiency, Niemann-Pick disease type B, GM2 gangliosidosis type '0' (Sandhoff disease), and ceroid lipofuscinosis (Jansky-Bielschowsky and Batten-Spielmeyer-Vogt syndromes) are encountered frequently in Saudi Arabia, as compared to other storage diseases. In contrast, some other diseases such as the adult variant of Gaucher's disease were not observed. Half of the GM2 gangliosidosis type '0' cases originated from one large tribe in the country. Other conditions did not show tribal predilection. The ceroid lipofuscinosis cases in Saudi Arabia originated from four large families. Consanguineous marriages taking place within tribal boundaries probably account for the pattern observed.

Effects of N-hydroxyethyl-1-deoxynojirimycin (BAY m 1099) on the activity of neutral- and acid alpha-glucosidases in human fibroblasts and HepG2 cells

The effect of the glucose analogue N-hydroxyethyl-1-deoxynojirimycin (BAY m 1099) on the activity of alpha-glucosidases was studied in human fibroblasts and HepG2 cells. BAY m 1099 inhibits neutral and acid alpha-glucosidase activities of both cell types in a dosage-dependent and reversible manner. Inhibition of endoplasmic reticulum glucosidases I and/or II is suggested by delayed processing of lysosomal (acid) alpha-glucosidase. Competitive inhibition of mature acid alpha-glucosidase leads to lysosomal accumulation of glycogen as in glycogenosis type II. There seems to be little risk, however, of inducing this storage disorder when using the drug in a dose of 50 mg per os for treatment of type II diabetes. In high doses, the drug may prove useful for studying the pathogenesis of glycogenosis type II in vitro or in animal models.

The urine from patients with peritonitis as a rich source for purifying human acid sphingomyelinase and other lysosomal enzymes

Milligram amounts of human acid sphingomyelinase (EC 3.1.4.12) were purified to 95% homogeneity using urine from patients with acute peritonitis. The activity of this enzyme is elevated more than 200-times in the urine of these patients. To a lesser extent, levels of some other lysosomal hydrolases are also elevated.

Juvenile acid maltase deficiency presenting as paravertebral pseudotumour

In addition to the infantile lethal form of glycogen storage disease with cardiomyopathy (GSD Type IIa, Pompe disease) 1,4 glucosidase or acid maltase deficiency has been reported in a few children and adults (GSD Type IIb or IIc) erroneously thought to have muscular dystrophies. The clinical heterogeneity of the muscle involvement in these latter cases is illustrated in a 12-year-old boy presenting with a right lumbar mass, growth retardation, muscular weakness including difficulty in walking, and marked elevations of muscle and liver enzymes. Light- and electron-microscopic examination of specimens from the lumbar mass, apparently normal skeletal muscle and liver, showed typical changes consistent with the biochemical and enzymatic features of acid maltase deficiency. GSD Type IIb and IIc are more frequent than suspected, may present as local pseudohypertrophy and should be considered in patients with progressive muscle disease and abnormal serum enzymes.

First trimester diagnosis of Pompe's disease (glycogenosis type II) with normal outcome: assay of acid alpha-glucosidase in chorionic villous biopsy using antibodies

Prenatal diagnosis of glycogenosis type II was performed by direct assay of acid alpha-glucosidase (EC 3.2.1.20) in chorionic villous biopsy obtained by transcervical cannula aspiration from a pregnancy at risk in the 10th week of gestation. The exact value of the enzyme activity estimated by the use of antibody preparations for purified human liver acid alpha-glucosidase was in the heterozygous range, and so the homozygous enzyme deficiency could be excluded. The subsequent analysis of cells cultured from amniocentesis sampling in the 18th week of gestation resulted in a similar outcome. The study with antibodies showed that in 23 control chorionic villi obtained during gestational ages between 7-13 weeks, 1-15% of the total alpha-glucosidase activity at pH 4.0 were due to renal or neutral enzyme. This indicates that it may be important to employ antibodies for prenatal diagnosis using chorionic villous sampling. A healthy and unaffected boy was born. The biochemical values obtained from an umbilical blood specimen were in accordance with the results of the prenatal diagnosis.

Synthesis and intracellular localization of chick acid alpha-glucosidase in chick erythrocyte-human fibroblast heterokaryons. A model system for the study of lysosomal enzyme synthesis

The synthesis and localization of chick acid alpha-glucosidase has been studied in chick erythrocyte-human fibroblast heterokaryons. Monospecific antibodies raised against purified chick liver acid alpha-glucosidase were used. It was found that the acid alpha-glucosidase in the heterokaryons is of chick origin, and is localized in the same lysosomes as the human lysosomal enzymes. It is concluded that chick erythrocyte-human fibroblast heterokaryons provide a useful model system for the study of lysosomal enzyme synthesis and routing.

Monoclonal antibody to human lysosomal alpha-glucosidase in immunocytochemistry: unexpected reactivity with cytoskeletal structures

A well-characterized monoclonal antibody against human lysosomal alpha-glucosidase has been used for the immunohistochemical localization of the enzyme in cultured human skin fibroblasts. Under conditions that are routinely used for the preparation of cells for immunocytochemistry, this monoclonal antibody does not react with acid alpha-glucosidase but in contrast with components of the cytoskeleton. Double-labelling experiments with the monoclonal antibody and rabbit anti-vimentin antiserum identified the cytoskeletal components as intermediate filaments. The implications of this observation for the use of monoclonal antibodies in immunocytochemistry in general are discussed.

Diagnosis of Pompe's disease using pyridylamino-maltooligosaccharides as substrates of alpha-1,4-glucosidase

We have developed a sensitive method for the assay of alpha-1,4-glucosidase in cultured skin fibroblasts and muscle tissue using pyridylamino-maltooligosaccharides as fluorescent substrates. This method is useful for the diagnosis of Pompe's disease.

Biochemical genetics of the Lapland dog model of glycogen storage disease type II (acid alpha-glucosidase deficiency)

A recently described canine model (Lapland dog) of glycogen storage disease type II (GSD II, Pompe disease, acid alpha-glucosidase deficiency) was identified with several biochemical genetic methods. Complementation studies in which fibroblasts from a GSD II dog were fused with fibroblasts derived from control dogs and from human patients with different clinical forms of the disease did not lead to restoration of acid alpha-glucosidase activity in the heterokaryon cell populations. These results indicate that acid alpha-glucosidase deficiency is the primary defect in canine GSD II and that there is a close genetic parallelism with human GSD II. Immunotitration analysis of the residual acid alpha-glucosidase activity in the canine GSD II fibroblasts and liver demonstrated that this residual activity was not due to acid alpha-glucosidase enzyme, in which respect canine GSD II was similar to the infantile form of the human disease. Double immunodiffusion studies showed the presence of catalytically inactive acid alpha-glucosidase enzyme protein in canine GSD II. This is consistent with a structural gene mutation. It is concluded that canine GSD II in the Lapland dog is a homologous model of the infantile form of human GSD II, a conclusion in concordance with clinical and pathological studies.

Myopathy due to juvenile acid maltase deficiency affecting exclusively the type I fibres

The clinical and laboratory findings of a patient with juvenile acid maltase deficiency are presented. The patient died from respiratory muscle weakness at age 31 years. Muscle biopsy shortly prior to his death showed remarkable vacuolation affecting exclusively type I fibres and mild myopathic changes of both types of muscle fibres, while the muscle biopsy at age 26 years had shown no evidence of acid maltase deficiency.

The expression of hex A and hex B isozymes of hexosaminidase in parental and experimental human fibroblast cells and their components

The expression of the two major isozyme forms of hexosaminidase (EC 3.2.1.30), hexosaminidase A and hexosaminidase B, has been examined. The parental cells and/or cellular components of parental cells are individually fused using inactivated Sendai virus with the aid of a micromanipulator. The progeny cells produced from such hybrids are subjected to a microenzymatic assay which allows measurements at the single cell level. The lysosomal-deficient cells used in this study are Tay-Sachs and Sandhoff fibroblasts, and the normal cells used are WI-38 (fetal lung fibroblasts), amniotic fluid cells (GM 473), and JASD3 (normal human foreskin). The results show that the ratio of cell components which are fused to form the experimental cell affects the percentage of hexosaminidase A expressed in the progeny cells. Furthermore, our results imply the presence of a "factor" in the Sandhoff cell's cytoplasm which, together with the Tay-Sachs nucleus, is necessary for hexosaminidase A expression in the experimental cell's progeny.

Pitfalls in the prenatal diagnosis of propionic acidemia

Prenatal diagnosis of propionic acidemia can be performed by two independent methods: measuring an elevated quantity of the metabolite methylcitrate in amniotic fluid; and demonstrating deficient activity of propionyl-CoA carboxylase in amniocytes cultured from the fluid. Discordant results in a pregnancy at risk for propionic acidemia were obtained. Elevated concentration of methylcitrate indicated an affected fetus, but the activity of propionyl-CoA carboxylase was normal. An affected female infant was born. Chromosome variant analysis demonstrated that between passage two and four overgrowth of the female fetal cells by contaminating maternal cells led to the "false negative" results obtained by enzyme assay. This experience demonstrates the value of analysis of abnormal metabolites in amniotic fluid and highlights a problem that could confound the prenatal diagnosis of any condition assessed by enzyme activity.

Microenzymatic assays for lysosomal enzymes in primary amniotic fluid cell cultures

A study of three lysosomal enzymes (hexosaminidase, beta-galactosidase and alpha-galactosidase) in normal primary amniotic fluid cell cultures using a microenzymatic assay is presented. No difference in enzyme activity was found between primary and amniotic cell cultures in passage number one. A progressive change in the proportions of hexosaminidase A and hexosaminidase B with time was demonstrated in culture. The feasibility of this procedure for the early prenatal diagnosis of disorders due to lysosomal enzyme deficiency is discussed.

The change in the pH 4 and pH 6 forms of alpha-glucosidase in cultured amniotic fluid cells and its implication in prenatal diagnosis of Pompe's disease

Activities of two major forms of alpha-glucosidase in cultured amniotic fluid cells have been measured by the 4-methylumbelliferyl-alpha-D-glucoside assay after 3, 6 and 9 weeks of culturing. Activity of the pH 4 forms of alpha-glucosidase, which is deficient in Pompe's disease, was low in early culture but increased rapidly as the culture time was increased. The cells harvested at 3 weeks had a low absolute activity of the pH 4 form as well as low ratio of the pH 4 to pH 6 enzyme. The pH 6 form is not affected in Pompe's disease. The results suggest cautions when attempting early diagnosis by use of microtechniques and re-emphasizes the need for differentiation of these two forms of alpha-glucosidases in prenatal diagnosis of Pompe's disease.

Use of microtechniques for the detection of lysosomal enzyme disorders: Tay-Sachs disease, Gm1-gangliosidosis and Fabry disease

A preliminary report on the use of microtechniques for the detection of three lysosomal storage diseases (Tay-Sachs, GM1-gangliosidosis and Fabry disease) is presented. This microassay method uses from 100 to 300 cultured amniotic fluid cells or skin fibroblasts. A comparison between values for total activity and heat inactivated forms of hexosaminidase (in Tay-Sachs disease) is presented. The feasibility of the use of this microtechnique in prenatal diagnosis is discussed.

Separation of acid and neutral alpha-glucosidase isoenzymes from fetal and adult tissues, cultivated fibroblasts and amniotic fluid cells by DEAE-cellulose and sephadex G-100 column chromatography

Isoenzymes of alpha-glucosidases (EC 3.2.1.20) from various human organs and body fluids from fetuses and adults were separated by DEAE-cellulose column chromatography and gel filtration using Sephadex G-100. A minicolumn (0.35 X 2.5 cm) was used for the DEAE-cellulose column chromatography of extracts from tissues as well as cultivated cells of skin fibroblasts and amniotic fluid. The enzyme activity in the eluates was measured by the use of a methylumbelliferyl derivative as substrate and a very sensitive Microscope fluorimeter. In most tissue samples alpha-glucosidase was eluted mainly as a single peak when monitored at acid pH and as two peaks when the activity was measured at neutral pH in both columns. Another small peak representing alpha-glucosidase was found in fresh extracts of cultured cells on DEAE-cellulose columns. Neutral alpha-glucosidase especially in fibroblasts was extremely sensitive to storage at -20 degrees C. DEAE-cellulose column chromatography of plasma and amniotic fluid showed similar elution patterns of alpha-glucosidase. Differences were noticed in the elution pattern of urine from infants and adults. The tissue distribution and the different characteristics of the enzyme in samples of various origins and ages were discussed.

Lysosomal enzyme activities in different types of amniotic fluid cells measured by microchemical methods, combined with interference microscopy

In primary amniotic fluid cultures, four distinct types of cells were characterized as epithelioid (E I and E II), fibroblast-like (F), And large cells, Small numbers (1-200) of freeze-dried cells were isolated from colonies of each cell type and analyzed for the activity of three lysosomal enzymes: beta-N-acetylglucosaminidase, beta-galactosidase, and alpha-glucosidase. When expressed per cell, the activities for each of the enzymes were not significantly different among the small types of cells (EI, EII, and F). However, 5 to 10-fold higher enzyme activities were found in the large cells. The dry mass of individual large cells, as measured by microinterferometry, was also 5 to 10 times higher than that of the smaller cell types. When expressed per unit of dry mass, the enzyme activities tested, appeared to be independent of the type of amniotic fluid cell. The significance of this observation for the rapid prenatal diagnosis of metabolic diseases is discussed.

Pericellular glycosaminoglycans in cultured human cells. A possible source of error in prenatal diagnosis of mucopolysaccharidoses

Normal fibroblasts and amniotic fluid cells, and cells from patients with Mucopolysaccharidosis type I and II, were cultured in the presence of 35SO4. After harvesting by trypsinization, the radioactivity was recovered from the intracellular and pericellular pool of glycosaminoglycans. The amount of incorporated radioactivity in these respective pools was 1 : 2.3 in normal fibroblasts and 1 : 7.2 in control amniotic fluid cells. Incorporation in the pericellular pool was not elevated in cells from patients with Mucopolysaccharidosis type I and II, in contrast to incorporation in the intracellular pool. Studies on different methods of harvesting showed that reliable prenatal analysis can be performed only if the pericellular pool is removed by trypsinization. Amniotic fluid cells from a pregnancy carrying a fetus affected with Hurler's disease revealed the expected increased level of 35SO4 incorporation if the cells were trypsinized, but the intracellular accumulation of glycosaminoglycans was obscured by the pericellular pool if the cells were harvested by scraping.

A sensitive semi-automated kinetic assay of alpha-D-glucosidase for the prenatal diagnosis of type 2 glycogenosis (Pompe's disease)

Prenatal diagnosis of type 2 glycogenosis (Pompe's disease) has been done on cultured amniotic fluid cells, using a semi-automated fluorimetric kinetic assay for alpha-D-glucosidase with 4-methylumbelliferyl-alpha-D-glucoside as substrate. The activity of the enzyme was related to that of beta-D-galactosidase, and found to be absent in cells from an affected fetus. The diagnosis was confirmed in fetal liver, where the same assay was used to show absence of alpha-D-glucosidase activity with normal beta-D-galactosidase activity, and where increased glycogen deposition was demonstrated histologically. This type of assay is generally applicable to lysosomal enzymes, and to other fluorigenic enzyme reactions.

Adult-onset acid maltase deficiency: a postmortem study

In a postmortem study of a patient with adult-onset acid maltase deficiency (AMD), morphological abnormalities were confined to skeletal muscle and consisted of a vacuolar myopathy. Acid maltase activity, however, was approximately 6% of normal in muscle, liver, and brain, and 3% of normal in heart. Kinetic characteristics, and inhibition by antibodies and Zn++, showed that the residual activity was "authentic" acid maltase. Neutral maltase activity was normal in muscle and liver, but decreased in brain (55% of normal) and heart (19% of normal). Although the relative decrease of acid maltase was similar in different tissues, absolute residual activity was lowest in skeletal muscle: this may explain the selective involvement of this tissue in late-onset AMD.

[Microchemical investigation of alpha D-glucosidases using 4-methylumnelliferyl- and 2-naphthyl-alpha-d-glucoside (author's transl)]

In crude homogenates prepared from freeze-dried cryostate sections of various rat organs the Km and Vmax of acid and neutral alpha-glucosidase as well as the effect of the pH, substrate and enzyme concentration and the incubation time on the activity were determined fluorometrically with 4-methylumbelliferyl- and 2-naphthyl alpha-d-glucoside as substrates. On the basis of the biochemical data 2 assays were developed for the microchemical measurement of both alpha-glucosidases in groups of epithelial cells isolated from freeze dried cryostate sections of the epididymis, jejunum, ilium, liver and kidney of suckling and adult rats. The rate of hydrolysis of 2-naphthyl and 4-methylumbelliferyl alpha-d-glucoside differs moderately. However, due to the higher sensitivity of 4-methylumbelliferone the methylumbelliferyl derivative is preferable especially for the evaluation of alpha-d-glucosidases in cells with low enzyme activity.

Rapid prenatal diagnosis of GM1-gangliosidosis using microchemical methods

Prenatal diagnoses were established in 3 pregnancies at risk for GM1-gangliosidosis at 9, 10, and 12 days after amniocentesis. Beta-galactosidase activities in cultured amniotic fluid cells were determined by microchemical assays in cell homogenates and in isolated groups of 10--30 freeze-dried cells. The latter method requires only a few hundred cells growing in one or more clones and will usually allow a diagnosis within 9--12 days after amniocentesis.

The symptomatology, morphology and biochemistry of glycogenosis type II (Pompe) in the adult

The mild, generalized myopathy (glycogenosis type II) of a 23-year-old male, previously thought to have progressive muscular dystrophy, was studied clinically, electro-myographically, biochemically and with light- and electron microscopes. However, the history and clinical aspects, as well as the registration of high frequency discharges in the electromyogram first made the diagnosis uncertain. This kind of spontaneous activity has been found in nearly all cases reported in the literature. Light microscopic and histochemical examinations show vacular degeneration and glycogen storage in muscle fibres. With the electron microscope we found free dispersed glycogen in the cytoplasm and membrane-bound glycogen, glycogen-filled lysosomes. Biochemical measurements of the muscle enzymes, involved in the glycogen breakdown, were normal except for acid alpha-1,4-glucosidase, which was deficient. The evidence of these findings in this abortive form of glycogenosis type II is discussed and compared with the few cases found in the literature.

Prenatal diagnosis of genetic disorders

Three hundred and fifty pregnancies were monitored by transabdominal amniocentesis in the fourteenth to sixteenth week of gestation followed by karyotyping or biochemica assays of cultured amniotic fluid cells and analysis of alpha-fetoprotein in the amniotic fluid supernatant. The pregnancy was interrupted in 36 cases (10%) either becasue of a fetal abnormality or the presence of a male fetus in pregnancies at risk for an X-linked disease. Four chromosomal aberrations were found in 87 pregnancies tested because of advanced maternal age. In 101 pregnancies with a recurrence risk of Down's syndrome, 2 fetuses with an abnormal karyotype were detected. In 11 cases, in which 1 parent was a carrier of a balanced translocation, 2 unbalanced fetal karyotypes were found. Fetal chromosome studies in 43 pregancies at risk for an X-linked disease indicated the presence of a male fetus in 21 cases. Prenatal diagnosis of 11 different metabolic diseases was performed in a total of 34 cases. Microchemical techniques were used to allow completion of the diagnosis of seven different enzyme deficiencies within 9 to 22 days after amniocentesis. Alpha-fetoprotein assay in the amniotic fluid supernatant of 47 pregnancies at risk for an open neural tube defect resulted in the detection of 3 anencephalic fetuses during the second half of pregnancy. The safety and reliability of amniocentesis and the possible effects on the outcome of pregnancy are evaluated. Prenatal diagnosis offers a promising alternative for parents who are at risk of having a child with a genetic disease which can be detected in amniotic fluid or in cultured amniotic fluid cells.

Two alpha-glucosidases in cultured amniotic fluid cells and their differentiation in the prenatal diagnosis of Pompe's disease

A sensitive fluorometric assay utilizing 4-methylumbelliferyl-alpha-D-glucopyranoside has been developed for the determination of alpha-glucosidase. The enhanced sensitivity was achieved by increasing the solubility of the substrate with a water miscible organic solvent. With this system, cultured amniotic fluid cells were found to have two major forms of alpha-glucosidase with somewhat overlapping acidic pH optima; one with pH optimum at 4.5 is deficient in Pompe's disease (type II glycogenosis), while one with pH optimum at 6.0 is not affected in this disease. Specificity for the pH 4 form of alpha-glucosidase was achieved by exploiting the greater thermal lability of the pH 6 enzyme. The pH 6 form of the enzyme was also detectable in freshly prepared extracts of cultured fibroblasts. The procedure is direct and simple and has been applied to the prenatal diagnosis in two pregnancies at risk for Pompe's disease.

Amniotic cell 4-methylumbelliferyl-alpha-glucosidase activity for prenatal diagnosis of Pompe's disease

Using a simple fluorometric assay for alpha-glucosidase activity of cultured amniotic cells, we have monitored two pregnancies from families at risk for Pompe's disease. The fetus was judged to be affected in one, the pregnancy being terminated and unaffected in the other. The accuracy of these predictions was confirmed. These results suggest that this assay allows accurate prenatal diagnosis of Pompe's disease, three weeks after diagnostic amniocentesis.

Adult-onset acid maltase deficiency. Morphologic and biochemical abnormalities reproduced in in cultured muscle

We established muscle-tissue cultures from biopsy of a patient with adult-onset acid maltase deficiency. Morphologically and biochemically, the newly grown fibers of the cultured muscle showed the same abnormalities as those of the biopsied muscle. Light microscopy showed multiple vacuoles filled with acid-phosphatase-positive material; on ultrastructural examination there was abnormal accumulation of glycogen in membrane-bound sacs (secondary lysosomes), some of which also contained dark membranous of homogeneous material. Acid maltase (pH 4.0), a lysosomal enzyme, was undetectable in either cultured or biopsied muscle by maltose hydrolysis, whereas acid phosphatase, also a lysosomal enzyme, was increased in both sources of muscle cells. Cultured muscle fibers demonstrate the same morphologic and biochemical abnormalities characteristic of biopsied muscle, supporting the concept of a biochemically distinct primary myopathy in man.