Monitoring estrogenic activities of waste and surface waters using a novel in vivo zebrafish embryonic (EASZY) assay: Comparison with in vitro cell-based assays and determination of effect-based trigger values

This study reports the use of the recently developed EASZY assay that uses transgenic cyp19a1b-GFP zebrafish (Danio rerio) embryos to assess in vivo estrogenic activity of 33 surface (SW) and waste water (WW) samples collected across Europe that were previously well-characterized for estrogen hormones and in vitro estrogenic activity. We showed that 18 out of the 33 SW and WW samples induced estrogenic responses in the EASZY assay leading to a significant and concentration-dependent up-regulation of the ER-regulated cyp19a1b gene expression in the developing brain. The in vivo 17β-estradiol-equivalents (EEQs) were highly correlated with, both, the chemical analytical risk quotient (RQ) based on steroidal estrogen concentrations and EEQs reported from five different in vitro reporter gene assays. Regression analyses between the vitro and in vivo effect concentrations allowed us to determine an optimal cut-off value for each in vitro assay, above which in vivo responses were observed. These in vitro assay-specific effect-based trigger values (EBTs), ranging from 0.28 to 0.58 ng EEQ/L define the sensitivity and specificity of the individual in vitro assays for predicting a risk associated with substances acting through the same mode of action in water samples. Altogether, this study demonstrates the toxicological relevance of in vitro-based assessment of estrogenic activity and recommends the use of such in vitro/in vivo comparative approach to refine and validate EBTs for mechanism-based bioassays.

Effect-based trigger values for in vitro and in vivo bioassays performed on surface water extracts supporting the environmental quality standards (EQS) of the European Water Framework Directive

Effect-based methods including cell-based bioassays, reporter gene assays and whole-organism assays have been applied for decades in water quality monitoring and testing of enriched solid-phase extracts. There is no common EU-wide agreement on what level of bioassay response in water extracts is acceptable. At present, bioassay results are only benchmarked against each other but not against a consented measure of chemical water quality. The EU environmental quality standards (EQS) differentiate between acceptable and unacceptable surface water concentrations for individual chemicals but cannot capture the thousands of chemicals in water and their biological action as mixtures. We developed a method that reads across from existing EQS and includes additional mixture considerations with the goal that the derived effect-based trigger values (EBT) indicate acceptable risk for complex mixtures as they occur in surface water. Advantages and limitations of various approaches to read across from EQS are discussed and distilled to an algorithm that translates EQS into their corresponding bioanalytical equivalent concentrations (BEQ). The proposed EBT derivation method was applied to 48 in vitro bioassays with 32 of them having sufficient information to yield preliminary EBTs. To assess the practicability and robustness of the proposed approach, we compared the tentative EBTs with observed environmental effects. The proposed method only gives guidance on how to derive EBTs but does not propose final EBTs for implementation. The EBTs for some bioassays such as those for estrogenicity are already mature and could be implemented into regulation in the near future, while for others it will still take a few iterations until we can be confident of the power of the proposed EBTs to differentiate good from poor water quality with respect to chemical contamination.

In Vitro Study of Encapsulation Therapy for Fabry Disease Using Genetically Engineered CHO Cell Line

Fabry disease is an X-linked recessive disorder caused by a deficiency of the lysosomal hydrolase α-galac-tosidase A (α-gal). The deficiency of this enzyme leads to the systemic deposition of ceramide trihexoside (CTH) in various tissues and organs. Enzyme replacement using IV doses of recombinant human α-gal produced in CHO cells or in human fibroblasts is currently being evaluated in clinical trials as a potential therapy for this disease. However, it requires lifelong therapy involving a large amount of purified α-gal. As a novel approach for treatment of Fabry disease we used polymer encapsulated Chinese hamster ovary (CHO) cells genetically modified to express α-gal. The secreted high levels of α-gal passed through the semipermeable polymeric membrane. Using coculture system with Fabry fibroblasts, the secreted enzyme was taken up in cells, resulting in reduced accumulation of CTH in Fabry fibroblasts. This in vitro study demonstrated that an encapsulated α-gal-secreting cell line can be used to treat Fabry mice by transplantation in vivo. Judging from the protection against immune rejection by a semipermeable synthetic membrane, this novel approach may be applied to treat patients with Fabry disease and other lysosomal storage diseases.

Towards the review of the European Union Water Framework Directive: Recommendations for more efficient assessment and management of chemical contamination in European surface water resources

Water is a vital resource for natural ecosystems and human life, and assuring a high quality of water and protecting it from chemical contamination is a major societal goal in the European Union. The Water Framework Directive (WFD) and its daughter directives are the major body of legislation for the protection and sustainable use of European freshwater resources. The practical implementation of the WFD with regard to chemical pollution has faced some challenges. In support of the upcoming WFD review in 2019 the research project SOLUTIONS and the European monitoring network NORMAN has analyzed these challenges, evaluated the state-of-the-art of the science and suggested possible solutions. We give 10 recommendations to improve monitoring and to strengthen comprehensive prioritization, to foster consistent assessment and to support solution-oriented management of surface waters. The integration of effect-based tools, the application of passive sampling for bioaccumulative chemicals and an integrated strategy for prioritization of contaminants, accounting for knowledge gaps, are seen as important approaches to advance monitoring. Including all relevant chemical contaminants in more holistic "chemical status" assessment, using effect-based trigger values to address priority mixtures of chemicals, to better consider historical burdens accumulated in sediments and to use models to fill data gaps are recommended for a consistent assessment of contamination. Solution-oriented management should apply a tiered approach in investigative monitoring to identify toxicity drivers, strengthen consistent legislative frameworks and apply solutions-oriented approaches that explore risk reduction scenarios before and along with risk assessment.

CRED: Criteria for reporting and evaluating ecotoxicity data

Predicted-no-effect concentrations (PNECs) and environmental quality standards (EQSs) are derived in a large number of legal frameworks worldwide. When deriving these safe concentrations, it is necessary to evaluate the reliability and relevance of ecotoxicity studies. Such evaluation is often subject to expert judgment, which may introduce bias and decrease consistency when risk assessors evaluate the same study. The Criteria for Reporting and Evaluating Ecotoxicity Data (CRED) project attempts to address this problem. It aims to improve the reproducibility, transparency, and consistency of reliability and relevance evaluations of aquatic ecotoxicity studies among regulatory frameworks, countries, institutes, and individual assessors. In the present study, the CRED evaluation method is presented. It includes a set of 20 reliability and 13 relevance criteria, accompanied by extensive guidance. Risk assessors who participated in the CRED ring test evaluated the CRED evaluation method to be more accurate, applicable, consistent, and transparent than the often-used Klimisch method. The CRED evaluation method is accompanied by reporting recommendations for aquatic ecotoxicity studies, with 50 specific criteria divided into 6 categories: general information, test design, test substance, test organism, exposure conditions, and statistical design and biological response. An ecotoxicity study in which all important information is reported is more likely to be considered for regulatory use, and proper reporting may also help in the peer-review process.

Erratum to: Criteria for Reporting and Evaluating ecotoxicity Data (CRED): comparison and perception of the Klimisch and CRED methods for evaluating reliability and relevance of ecotoxicity studies

[This corrects the article DOI: 10.1186/s12302-016-0073-x.].

Criteria for Reporting and Evaluating ecotoxicity Data (CRED): comparison and perception of the Klimisch and CRED methods for evaluating reliability and relevance of ecotoxicity studies

BACKGROUND

The regulatory evaluation of ecotoxicity studies for environmental risk and/or hazard assessment of chemicals is often performed using the method established by Klimisch and colleagues in 1997. The method was, at that time, an important step toward improved evaluation of study reliability, but lately it has been criticized for lack of detail and guidance, and for not ensuring sufficient consistency among risk assessors.

RESULTS

A new evaluation method was thus developed: Criteria for Reporting and Evaluating ecotoxicity Data (CRED). The CRED evaluation method aims at strengthening consistency and transparency of hazard and risk assessment of chemicals by providing criteria and guidance for reliability and relevance evaluation of aquatic ecotoxicity studies. A two-phased ring test was conducted to compare and characterize the differences between the CRED and Klimisch evaluation methods. A total of 75 risk assessors from 12 countries participated. Results show that the CRED evaluation method provides a more detailed and transparent evaluation of reliability and relevance than the Klimisch method. Ring test participants perceived it to be less dependent on expert judgement, more accurate and consistent, and practical regarding the use of criteria and time needed for performing an evaluation.

CONCLUSIONS

We conclude that the CRED evaluation method is a suitable replacement for the Klimisch method, and that its use may contribute to an improved harmonization of hazard and risk assessments of chemicals across different regulatory frameworks.

Impact of environmental estrogens on Yfish considering the diversity of estrogen signaling

Research on endocrine disruption in fish has been dominated by studies on estrogen-active compounds which act as mimics of the natural estrogen, 17β-estradiol (E2), and generally exert their biological actions by binding to and activation of estrogen receptors (ERs). Estrogens play central roles in reproductive physiology and regulate (female) sexual differentiation. In line with this, most adverse effects reported for fish exposed to environmental estrogens relate to sexual differentiation and reproduction. E2, however, utilizes a variety of signaling mechanisms, has multifaceted functions and targets, and therefore the toxicological and ecological effects of environmental estrogens in fish will extend beyond those associated with the reproduction. This review first describes the diversity of estrogen receptor signaling in fish, including both genomic and non-genomic mechanisms, and receptor crosstalk. It then considers the range of non-reproductive physiological processes in fish that are known to be responsive to estrogens, including sensory systems, the brain, the immune system, growth, specifically through the growth hormone/insulin-like growth factor system, and osmoregulation. The diversity in estrogen responses between fish species is then addressed, framed within evolutionary and ecological contexts, and we make assessments on their relevance for toxicological sensitivity as well as ecological vulnerability. The diversity of estrogen actions raises questions whether current risk assessment strategies, which focus on reproductive endpoints, and a few model fish species only, are protective of the wider potential health effects of estrogens. Available - although limited - evidence nevertheless suggests that quantitative environmental threshold concentrations for environmental protection derived from reproductive tests with model fish species are protective for non-reproductive effects as well. The diversity of actions of estrogens across divergent physiological systems, however, may lead to and underestimation of impacts on fish populations as their effects are generally considered on one functional process only and this may underrepresent the impact on the different physiological processes collectively.

Integral assessment of estrogenic potentials in sediment-associated samples: Part 2: Study of estrogen and anti-estrogen receptor-binding potentials of sediment-associated chemicals under different salinity conditions using the salinity-adapted enzyme-linked receptor assay

BACKGROUND, AIM, AND SCOPE

The enzyme-linked receptor assay (ELRA) detects estrogenic and anti-estrogenic effects at the molecular level of receptor binding and is a useful tool for the integrative assessment of ecotoxicological potentials caused by hormonally active agents (HAA) and endocrine disrupting compounds (EDC). The main advantage of the ELRA is its high sample throughput and its robustness against cytotoxicity and microbial contamination. After a methodological adaptation to salinity of the ELRA, according to the first part of this study, which increased its salinity tolerance and sensitivity for 17-beta-estradiol, the optimised ELRA was used to investigate 13 native sediments characterised by different levels of salinity and chemical contamination. The applicability of the ELRA for routine analysis in environmental assessment was evaluated. Salinity is often a critical factor for bioassays in ecotoxicological sediment assessment. Therefore, salinity of the samples was additionally adjusted to different levels to characterise its influence on elution and binding processes of receptor-binding substances.

MATERIALS AND METHODS

The ELRA was carried out with the human estrogen receptor alpha (ER) in a 96-well microplate format using the experimental setup known from the competitive immunoassay based on ligand-protein interaction. It is an important improvement that a physiologically relevant receptor was used as a linking protein instead of an antibody. The microplates were coated with a 17-beta-estradiol-BSA conjugate, and dilution series of estradiol and of native sediment samples were added and incubated with the ER. After a washing step, a biotinylated mouse anti-ER antibody was added to each well. Receptor binding to estradiol, agonistic and antagonistic receptor binding, were determined by a streptavidin-POD-biotin complex with subsequent measurement of the peroxidase activity at the wavelength of 450 nm using a commercial ELISA multiplate reader. The sediment elutriates and pore water samples of sediments were tested in a dilution series to evaluate at which dilution step the receptor-binding potential ends. In the elution process (see Section 2.1 to 2.2), a method was developed to adjust the salinity to the levels of the reference testings, which offers an appropriate option to adjust the salinity in both directions. Statistical evaluation was made with a combination of the Mann-Whitney U test and the pT-method.

RESULTS

This part of the study characterised the environmental factor 'salinity' for prospective applications of the ELRA. Using reference substances such as 17-beta-estradiol, the ELRA showed sigmoid concentration-effect relations over a broad range from 0.05 mug/l to 100 mug/l under physiological conditions. After methodological optimisation, both sensitivity and tolerance of the assay against salinity could be significantly raised, and the ELRA became applicable under salinity conditions up to concentrations of 20.5 per thousand. The mean relative inter-test error (n = 3) was around 11% with reference substances and below 5% for single sediments elutriates in three replicates each. For sediment testings, the pore water and different salinity-adjusted elutriates of 13 sediments were used. A clear differentiation of the receptor-binding potential could be reached by application of the pT-method. Thereby, pT-values from one to six could be assigned to the sediments, and the deviation caused by the different salinity conditions was one pT-value. The mean standard deviation in the salinity adaptation procedure of the elutriates was below 5%.

DISCUSSION

Although the ELRA has already been used for assessments of wastewater, sludge and soil, its applicability for samples to different salinity levels has not been investigated so far. Even if the ELRA is not as sensitive as the E-screen or the YES-assay, with regard to reference substances like 17-beta-estradiol, it is a very useful tool for pre-screening, because it is able to integrate both estrogenic as well as anti-estrogenic receptor-binding effects. According to the results of sediment testing, and given the integrative power to detect different directions of effects, the ELRA shows sufficient sensitivity and salinity tolerance to discriminate receptor-binding potentials in environmental samples.

CONCLUSIONS

The optimised ELRA assay is a fast, cost-effective, reliable and highly reproducible tool that can be used for high-throughput screening in a microplate format in detecting both estrogenic and anti-estrogenic effects. Additionally, the ELRA is robust against microbial contaminations, and is not susceptible towards cytotoxic interferences like the common cell-culture methods. The general applicability and sufficient sensitivity of the ELRA was shown in freshwater environments. Marine and brackish samples can be measured up to salinity levels of 20.5 per thousand.

RECOMMENDATIONS AND PERSPECTIVES

In view of the proven sensitivity, functionality and the fastness of the ELRA, it is recommendable to standardise the test method. At the moment, no adequate in vitro test procedure exists which is standardised to DIN or ISO levels. The E-screen and the yeast estrogen/androgen screens (YES/YAS) sometimes underlie strong cytotoxic effects, as reported in the first part of this study. Further development of an ELRA assay using human androgen receptors appears to be very promising to gain information about androgenic and anti-androgenic effects, too. This would offer a possibility to use the ELRA as a fast and reliable pre-screening tool for the detection of endocrine potentials, thus minimising time and cost-expensive animal experiments.

Integral assessment of estrogenic potentials of sediment-associated samples. Part 1: The influence of salinity on the in vitro tests ELRA, E-Screen and YES

GOAL, SCOPE AND BACKGROUND

Exogenic endocrine-active substances are also called 'Endocrine Disrupting Chemicals' (EDC). They imitate or hinder the function of natural endogenic hormones or disturb the synthesis or the metabolism of hormones or of hormone receptors. The Enzyme-Linked Receptor Assay (ELRA) can detect estrogenic and anti-estrogenic effects at the level of receptor binding and is a useful tool for the integrative detection of contaminant effects. Although the test system has been used repeatedly in sediment assessments, the questions have remained concerning how it responds to variations in the physico-chemical matrix. For some bioassays, the salinity of the sample is a critical factor. This is especially relevant when testing wastewater samples or when sediment-associated samples in the tidal reaches of rivers are tested. Sediments in the tidal reaches of rivers change their salinity several times a day. Against this background, it would be beneficial to have a test procedure of known salinity tolerance. On account of this, the salinity tolerance of the ELRA was tested, assessed with reference substances at several salinity levels, and compared with the E-Screen method and a Yeast Estrogen Screen (YES), which are also frequently applied in environmental testing. The aim of this paper was to explore when the salinity limits within these test procedures are applicable. The trials should reveal the working range to be expected, characterize the salinity-dependent variations in sensitivity of the test, and provide options for methodological adjustments to improve the stability against increased salinity.

METHODS

The ELRA was carried out with the human Estrogen Receptor alpha. (ER) using the same principle like a competitive immunoassay based on ligand-protein interaction. However, an essential difference is the use of a physiologically relevant receptor instead of an antibody as a linking protein. The ELRA measures the competition of sample estrogens and anti-estrogens against estradiol supplied as a BSA-coating conjugate for the binding site of dissolved ER. Estradiol or xeno-estrogen binding is quantified by a biotynilated anti-ER antibody and the subsequent measurement of peroxidase activity by a streptavidin-POD-biotin complex. The E-Screen was performed with the human breast cancer cell line MCF-7, which expresses the estrogen receptor constitutively. Cell proliferation depends on binding of estrogens or xeno-estrogens with the receptor. After incubation, estrogen-dependent cell growth was measured by sulforhodamin B staining. The YES was performed with a recombinant yeast strain, transfected with a receptor and a reporter plasmid bearing the estrogen receptor and a vitellogenin gene fused with the reporter gene lacZ. Estrogen or xeno-estrogen-dependent gene induction was measured indirectly by LacZ activity. The salinity levels were simulated in varying concentrations with NaCl from 0 to 40 per thousand or Artificial Sea Water (ASW) from 0 to 32 per thousand.

RESULTS

The study characterized the factor 'salinity' for the prospective application fields of the ELRA. With reference substances such as 17-beta-estradiol, the ELRA showed classical sigmoidal concentration-effect relations in a range from 0.05 to 100 microg/l under physiological conditions. After a methodological adjustment to compensate decreasing receptor-binding affinity of estrogens and xeno-estrogens at higher salinity levels, the ELRA became applicable under salinity conditions up to concentrations of 20.5 per thousand. In tests, the ELRA reached under the influence of salinity a mean limit of detection of 0.062 microg/l 17-beta-estradiol. The mean relative inter-test error was around 11%. Above concentrations of 20.5 per thousand there is a risk of false negative assessment. Compared with the E-Screen method using the MCF7 cell line and the yeast estrogen test system (YES), the ELRA shows a lower sensitivity to 17-beta-estradiol. In the E-Screen, the cell proliferation was strongly reduced by sodium chloride induced cytotoxicity. In comparison with the E-Screen, the salinity tolerance of the YES and YAS methods is significantly higher.

DISCUSSION

Despite adaption, total salinity tolerance could not be achieved with the ELRA. Freshwater samples were generally appraisable. Higher salinity levels above 20.5 per thousand would tend towards false negative results. The low inter-test error of 11% makes the ELRA suitable for the detection of estrogenic and anti-estrogenic potentials of single substances, substance mixtures, and of environmental samples.

CONCLUSIONS

The ELRA is very fast and reproducible, it can be used for high-throughput screening in a microplate format at low cost, it is robust to microbial contamination, and is less susceptible to cytotoxic interferences than cell culture methods.

RECOMMENDATIONS AND PERSPECTIVES

In their established form, the YES and the E-Screen methods are not applicable for liquid phase testing at higher salinity conditions. The salinity-adapted test version of the ELRA described here shows a broader working range for samples. Native water samples of more or less brackish origin or high-salinity effluent samples are testable. Results of tests with sediment associated samples of different salinity will be subject of a forthcoming publication.

In vitro study of encapsulation therapy for Fabry disease using genetically engineered CHO cell line

Fabry disease is an X-linked recessive disorder caused by a deficiency of the lysosomal hydrolase alpha-galactosidase A (alpha-gal). The deficiency of this enzyme leads to the systemic deposition of ceramide trihexoside (CTH) in various tissues and organs. Enzyme replacement using IV doses of recombinant human alpha-gal produced in CHO cells or in human fibroblasts is currently being evaluated in clinical trials as a potential therapy for this disease. However, it requires lifelong therapy involving a large amount of purified alpha-gal. As a novel approach for treatment of Fabry disease we used polymer encapsulated Chinese hamster ovary (CHO) cells genetically modified to express alpha-gal. The secreted high levels of alpha-gal passed through the semipermeable polymeric membrane. Using coculture system with Fabry fibroblasts, the secreted enzyme was taken up in cells, resulting in reduced accumulation of CTH in Fabry fibroblasts. This in vitro study demonstrated that an encapsulated alpha-gal-secreting cell line can be used to treat Fabry mice by transplantation in vivo. Judging from the protection against immune rejection by a semipermeable synthetic membrane, this novel approach may be applied to treat patients with Fabry disease and other lysosomal storage diseases.

Western blotting analysis of the beta-hexosaminidase alpha- and beta-subunits in cultured fibroblasts from cases of various forms of GM2 gangliosidosis

OBJECTIVES

The GM2 gangliosidoses are a group of genetic disorders caused by the accumulation of ganglioside GM2 in neuronal cells. We examined the alpha- and beta-subunits of beta-hexosaminidases by a non-radioisotopes detecting system to evaluate whether it was a useful method for understanding of the pathophysiologies of GM2 gangliosidoses.

MATERIALS AND METHODS

We investigated the alpha- and beta-subunits of beta-hexosaminidases in cultured fibroblasts from cases of various forms of GM2 gangliosidosis by means of Western blotting and a chemiluminescence detection system.

RESULTS

In a patient with infantile Tay-Sachs disease [HEXA genotype, Int5-SA(g-1-->t)/Int5-SA(g-1-->t)], the mature alpha-subunit was undetectable. In a patient with infantile Sandhoff disease (HEXB genotype, C534Y/C534Y), the mature beta-subunit was deficient. However, a small amount of the mature beta-subunit was detected in a patient with adult Sandhoff disease (HEXB genotype, R505Q(+I207V)/R505Q(+I207V)), which may have resulted in the residual enzyme activity and mild clinical course. Normal amounts of alpha- and beta-subunits were detected in a patient with GM2 activator deficiency.

CONCLUSION

This method is easy and sensitive for detecting target proteins, and is useful for clarification of the pathophysiologies of GM2 gangliosidoses.

Characterization of two alpha-galactosidase mutants (Q279E and R301Q) found in an atypical variant of Fabry disease

The mutant products Q279E ((279)Gln to Glu) and R301Q ((301)Arg to Gln) of the X-chromosomal inherited alpha-galactosidase (EC 3.2.1. 22) gene, found in unrelated male patients with variant Fabry disease (late-onset cardiac form) were characterized. In contrast to patients with classic Fabry disease, who have no detectable alpha-galactosidase activity, atypical variants have residual enzyme activity. First, the properties of insect cell-derived recombinant enzymes were studied. The K(m) and V(max) values of Q279E, R301Q, and wild-type alpha-galactosidase toward an artificial substrate, 4-methylumbelliferyl-alpha-D-galactopyranoside, were almost the same. In order to mimic intralysosomal conditions, the degradation of the natural substrate, globotriaosylceramide, by the alpha-galactosidases was analyzed in a detergent-free-liposomal system, in the presence of sphingolipid activator protein B (SAP-B, saposin B). Kinetic analysis revealed that there was no difference in the degradative activity between the mutants and wild-type alpha-galactosidase activity toward the natural substrate. Then, immunotitration studies were carried out to determine the amounts of the mutant gene products naturally occurring in cells. Cultured lymphoblasts, L-57 (Q279E) and L-148 (R301Q), from patients with variant Fabry disease, and L-20 (wild-type) from a normal subject were used. The 50% precipitation doses were 7% (L-57) and 10% (L-148) of that for normal lymphoblast L-20, respectively. The residual alpha-galactosidase activity was 3 and 5% of the normal level in L-57 and L-148, respectively. The quantities of immuno cross-reacting materials roughly correlated with the residual alpha-galactosidase activities in lymphoblast cells from the patients. Compared to normal control cells, fibroblast cells from a patient with variant Fabry disease, Q279E mutation, secreted only small amounts of alpha-galactosidase activity even in the presence of 10 mM NH(4)Cl. It is concluded that Q279E and R301Q substitutions do not significantly affect the enzymatic activity, but the mutant protein levels are decreased presumably in the ER of the cells.

Retrovirus-mediated transfer of human alpha-galactosidase A gene to human CD34+ hematopoietic progenitor cells

Fabry disease, caused by a deficiency of lysosomal enzyme alpha-galactosidase A (alpha-gal A), is one of the inherited disorders potentially treatable by gene transfer to hematopoietic stem cells. In this study, a high-titer amphotropic retroviral producer cell line, MFG-alpha-gal A, was established. CD34+ cells from normal umbilical cord blood were transduced by centrifugal enhancement. The alpha-gal A activity in transduced cells increased 3.6-fold above the activity in nontransduced cells. Transduction efficiency measured by PCR for the integrated alpha-gal A cDNA in CFU-GM colonies was in the range of 42-88% (average, 63%). The expression of functional enzyme in TFI erythroleukemia was sustained for as long as cells remained in culture (84 days) and for 28 days in LTC-IC cultures of CD34+ cells. The ability of the transduced CD34+ cells to secrete the enzyme and to correct enzyme-deficient Fabry fibroblasts was assessed by cocultivation of these cells. The enzyme was secreted into the medium from transduced CD34+ cells and taken up by Fabry fibroblasts through mannose 6-phosphate receptors. These findings suggest that genetically corrected hematopoietic stem/progenitor cells can be an enzymatic source for neighboring enzyme-deficient cells, and can potentially be useful for gene therapy of Fabry disease.

GM2 gangliosidosis AB variant: clinical and biochemical studies of a Japanese patient

OBJECTIVE

To determine the clinical features and biochemical basis of the first Japanese patient with the GM2 gangliosidosis AB variant.

METHODS

The clinical manifestations and laboratory findings in the patient were investigated. Cultured fibroblasts from the patient were analyzed by means of immunofluorescence staining with an anti-GM2 ganglioside monoclonal antibody and thin-layer chromatography and immunostaining. GM1 ganglioside catabolism in cultured cells was analyzed by pulse labeling, and the amount of GM2 activator in cells was determined by Western blot analysis. Gene analysis was performed according to standard protocols.

RESULTS

The patient showed progressive neurologic manifestations of quite early onset. Muscular weakness and hypotonia became evident by 1 month of age, and the patient then developed a startle reaction, severe psychomotor retardation, and myoclonic seizures. Immunocytochemical analysis clearly revealed the accumulation of GM2 ganglioside in cultured fibroblasts from the patient, and thin-layer chromatography confirmed it. Western blot and metabolic studies showed a complete deficiency of GM2 activator. Gene analysis did not reveal any mutations in the protein coding region of the GM2 activator gene.

CONCLUSION

The clinical features and biochemical basis of this Japanese patient with GM2 gangliosidosis AB variant were determined. Immunocytochemical analysis using cultured fibroblasts as samples is available for the diagnosis of this disease.

Urinary excretion of the vitronectin receptor (integrin alpha V beta 3) in patients with Fabry disease

A renal disorder is one of the important manifestations of Fabry disease, but the details of the pathogenesis have not been clarified yet. We examined the possibility that the vitronectin receptor (VNR, integrin alpha V beta 3), one of the integrins, is involved in the progression of the renal injury in Fabry disease. We measured the urinary excretion of beta 3 originating from VNR in Fabry patients by immunoblotting analysis and enzyme-linked immunosorbent assay (ELISA). Immunofluorescent microscopic analyses for VNR and globotriaosylceramide were performed on urinary sediments from Fabry patients. Furthermore, beta 3 and vitronectin in kidney tissues were analyzed immunohistochemically. Immunoblotting analysis and ELISA showed that the urinary excretion of beta 3 originating from VNR was significantly increased in the Fabry group compared with both the pathological and healthy control groups. Immunofluorescent microscopy revealed the expression of VNR and accumulation of globotriaosylceramide in urinary sediments from the Fabry patients. Increased expression of beta 3 was observed in glomerular epithelial cells, and in Bowman's capsular epithelial layer and tubular cells, and the amount of vitronectin was moderately increased in the kidney tissues from the Fabry patients. The urinary excretion of VNR was increased, and the expression of VNR was observed in Fabry kidney tissues. The expression of VNR may be involved in the progression of the renal injury in this disease.

Alpha-galactosidase transgenic mouse: heterogeneous gene expression and posttranslational glycosylation in tissues

We produced six transgenic mouse lines expressing human alpha-galactosidase (alpha-Gal) in order to evaluate its posttranslational modification. Among them, serum alpha-Gal activity increased 3000-fold in two transgenic mouse lines (TgN2 and TgN51), as compared to that in non-transgenic lines. The heart and liver of the TgN2 mouse expressed a high amount of transcript as well as high alpha-Gal activity. Its gene products in the heart and kidney were sensitive to endoglycosidase H digestion, but those in the spleen and liver were largely resistant. Glycopeptidase F treatment confirmed an identical molecular mass for the peptide moiety of the enzyme. We concluded that heterogeneous molecular mass of the gene products was caused by different degrees of posttranslational glycosylation in murine tissues.

Immunohistochemical characterization of transgenic mice highly expressing human lysosomal alpha-galactosidase

Human lysosomal alpha-galactosidase predominantly hydrolyzes ceramide trihexoside. A transgenic mouse line, C57BL/6CrSIc-TgN(GLA) 1951 Rin, highly expressing human alpha-galactosidase, has been established and investigated biochemically and immunohistochemically in order to clarify the distribution of the expressed enzyme proteins and to evaluate it as a donor model of organ transplantation therapy for Fabry disease caused by a genetic defect of alpha-galactosidase. In these transgenic mice, about five copies of the transgene were integrated, and alpha-galactosidase activity was expressed in liver, kidney, heart, spleen, small intestine, submaxillary gland, skeletal muscle, cerebrum, cerebellum, bone marrow cells and serum. The enzyme activity was about 22 to 11,080-fold higher than that in non-transgenic mice. In liver, heart and kidney tissues, which are important organs for transplantation studies, sufficient amounts of alpha-galactosidase mRNAs were transcribed, and the expressed enzymes, with molecular weights of 54-60 kDa, are abundant in the liver (enzyme activity: 53,965 nmol h-1 mg-1 protein) and heart (39,906 nmol h-1 mg-1 protein), followed by in the kidney tissue (9177 nmol h-1 mg-1 protein), respectively. An immunohistochemical microscopic study clearly demonstrated the distribution of the expressed enzyme proteins in kidney and liver tissues. Highly expressed alpha-galactosidase was detected in glomerular cells, tubular cells and hepatocytes. These transgenic mice will be useful as a donor model for experimental organ transplantation, and also it will enable recurrent biopsies and long-term observation. The organ transplantation data on mice will provide us with important information.

Adult Sandhoff's disease: R505Q and I207V substitutions in the HEXB gene of the first Japanese case

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 beta-Hex, beta-Hex A, and beta-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 (1207V). The parents were consanguineous. His healthy mother, an enzymatic heterozygous carrier, was homozygous for 1207V, 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.

Generation and characterization of transgenic mice expressing a human mutant alpha-galactosidase with an R301Q substitution causing a variant form of Fabry disease

Transgenic mice expressing a human mutant alpha-galactosidase with an R301Q substitution, which was found in a patient with a variant form of Fabry disease, were established. The mice transcribed a sufficient amount of alpha-galactosidase mRNA, but the steady-state levels of the enzyme protein were decreased in liver, kidney and heart, only residual activity being detected in these tissues. The mice will be useful for the clarification of the defective regulation of the structurally altered enzyme protein expressed by the mutant gene at the organ or individual level as well as for the evaluation of drugs that stabilize and/or activate the mutant alpha-galactosidase.

Generation and characterization of mouse monoclonal antibodies specific for N-linked neutral oligosaccharides of glycoproteins

We generated four monoclonal antibodies (MAbs) specific for asparagine-linked neutral oligosaccharides of glycoproteins by immunizing mice with neoglycolipids, which were derived from glycoproteins by conjugation to phosphatidylethanolamine dipalmitoyl. The binding specificity of these MAbs was determined by an enzyme-linked immunosorbent assay and immunostaining on thin-layer chromatography. The four MAbs designated OMB3, OMB4, OMR5, and OMR6 reacted strongly with the neoglycolipids, Gal beta1-4GlcNAc beta1-2Man alpha1-6(Gal beta1-4GlcNAc beta1-2Man alpha1-3)Man beta1-4GlcNAc-PD, GlcNAc beta1-2Man alpha1-6(GlcNAc beta1-2Man alpha1-3)(GlcNAc beta1-4)Man beta1-4GlcNAc beta1-4GlcNAc-PD, Man alpha1-6Man beta1-4GlcNAc beta1-4(Fuc alpha1-6)GlcNAc-PD, and Man alpha1-3Man beta1-4GlcNAc-PD, respectively, that were used as immunogens. All of these MAbs exhibited a high binding specificity. The epitopes of the MAbs OMB3 and OMB4 were suggested to be nonreducing terminal trisaccharides, Gal beta1-4GlcNAc beta1-2Man-, and nonreducing beta-GlcNAc residues, respectively. MAbs OMR5 and OMR6 showed a highly restricted binding specificity, reacting only with the immunizing neoglycolipids. Subsequently, MAbs OMB3 and OMB4 were shown to react strongly with asialo-alpha1-acid-glycoprotein and asialo-agalacto-alpha1-acid-glycoprotein, respectively, by Western blotting. Furthermore, it was shown that these MAbs reacted specifically with the epitope on Chinese hamster ovary cells by an immunofluorescence technique. MAb OMB4 was also shown to detect the accumulated oligosaccharides with nonreducing terminal beta-GlcNAc residues as granular inclusions in the cultured fibroblasts from a classical Sandhoff disease patient.

High incidence of thrombosis in Fabry's disease

Although a high incidence of thrombotic accidents in Fabry's disease has been postulated, few investigations have been performed. To clarify the incidence of thrombosis in Fabry's disease, we undertook a systematic study on thrombosis in patients with Fabry's disease including hemizygous males and heterozygous females. Sixty patients with Fabry's disease (45 hemizygotes and 15 heterozygotes) from 36 Japanese families were subjected to clinical, biochemical and genetic investigations. We found that seven patients with Fabry's disease (4 hemizygous males and 3 heterozygous females) had experienced thrombotic accidents. Six of these thrombotic patients developed brain infarctions, including one man who had the complication of recurrent thrombophlebitis. The remaining woman showed central retinal artery occlusion and thrombophlebitis. We demonstrated a high incidence of thrombosis in Fabry's disease. Thrombotic accidents occurred not only in hemizygous males but also in heterozygous females. The complication of thrombotic accidents should be taken into account in patients with Fabry's disease.

Clinical manifestations in 105 persons with nevoid basal cell carcinoma syndrome

Nevoid basal cell carcinoma syndrome (NBCC; Gorlin syndrome), an autosomal dominant disorder linked to 9q22.3-q31, and caused by mutations in PTC, the human homologue of the Drosophila patched gene, comprises multiple basal cell carcinomas, keratocysts of the jaw, palmar/plantar pits, spine and rib anomalies and calcification of the falx cerebri. We reviewed the findings on 105 affected individuals examined at the NIH since 1985. The data included 48 males and 57 females ranging in age from 4 months to 87 years. Eighty percent of whites (71/90) and 38% (5/13) of African-Americans had at least one basal cell carcinoma (BCC), with the first tumor occurring at a mean age of 23 (median 20) years and 21 (median 20) years, respectively. Excluding individuals exposed to radiation therapy, the number of BCCs ranged from 1 to > 1,000 (median 8) and 1 to 3 (median 2), respectively, in the 2 groups. Jaw cysts occurred in 78/105 (74%) with the first tumor occurring in 80% by the age of 20 years. The number of total jaw cysts ranged from 1 to 28 (median 3). Palmar pits and plantar pits were seen in 87%. Ovarian fibromas were diagnosed by ultrasound in 9/52 (17%) at a mean age of 30 years. Medulloblastoma occurred in 4 patients at a mean age of 2.3 years. Three patients had cleft lip or palate. Physical findings include "coarse face" in 54%, relative macrocephaly in 50%, hypertelorism in 42%, frontal bossing in 27%, pectus deformity in 13%, and Sprengel deformity in 11%. Important radiological signs included calcification of the falx cerebri in 65%, of the tentorium cerebelli in 20%, bridged sella in 68%, bifid ribs in 26%, hemivertebrae in 15%, fusion of the vertebral bodies in 10%, and flame shaped lucencies of the phalanges, metacarpal, and carpal bones of the hands in 30%. Several traits previously considered components of the syndrome (including short fourth metacarpal, scoliosis, cervical ribs and spina bifida occulta) were not found to be significantly increased in the affected individuals. This study delineates the frequency of the clinical and radiological anomalies in NBCC in a large population of US patients and discusses guidelines for diagnosis and management.

Screening and detection of gene mutations in Japanese patients with Fabry disease by non-radioactive single-stranded conformation polymorphism analysis

We have applied non-radioactive polymerase chain reaction (PCR)-single-stranded conformation polymorphism (SSCP) to the detection of gene mutations causing Fabry disease. Nineteen of 22 known mutations were detected as electrophoretic mobility shifts on PCR-SSCP analysis. Then, DNA from newly diagnosed Japanese patients with the classical form of Fabry disease was subjected to PCR-SSCP analysis, and 4 novel mutations (1 small deletion, 1 nonsense mutation and 2 missense mutations) and 1 neutral polymorphism were identified. Furthermore, identification of an asymptomatic heterozygote and a hemizygote with moderate clinical manifestations was successfully achieved by application of this method to a family with the variant form of Fabry disease. PCR-SSCP is useful for the gene diagnosis of etiologically heterogeneous Fabry disease.

Only sphingolipid activator protein B (SAP-B or saposin B) stimulates the degradation of globotriaosylceramide by recombinant human lysosomal alpha-galactosidase in a detergent-free liposomal system

The degradation of globotriaosylceramide (GbO-se3Cer) by insect-cell derived recombinant human alpha-galactosidase (EC 3.2.1.22) was carried out in a detergent-free liposomal system in order to mimic intralysosomal conditions. GbOse3Cer incorporated into unilamellar liposomes was used as the substrate, and naturally occurring sphingolipid activator proteins, rather than detergents, were used to stimulate the enzyme reaction. The degradation of GbOse3Cer was dependent on the presence of both alpha-galactosidase and sphingolipid activator protein B (SAP-B or saposin B). It proceeded optimally at pH 4.6, and was enhanced by increasing amounts of both alpha-galactosidase (0.24-24 mU/50 microliters assay) and SAP-B (0-5 micrograms/50 microliters assay). The enzyme reaction was not affected by SAP-A, SAP-C, or SAP-D. Therefore, our results indicate that only SAP-B is essential for the degradation of GbOse3Cer by alpha-galactosidase.

Two novel mutations in the alpha-galactosidase gene in Japanese classical hemizygotes with Fabry disease

Four alpha-galactosidase gene mutations were identified in Japanese male patients with Fabry disease who had no detectable alpha-galactosidase activity. Two of them were novel mutations, an 11-bp deletion in exon 2 and a g-1 to t substitution at the 3' end of the splice acceptor site in intron 1. The former caused a frameshift and led to the creation of a new stop codon at codon 118. The latter was predicted to provoke aberrant mRNA splicing followed by accelerated degradation of the mRNA. A nonsense mutation, R301X, and a 2-bp deletion starting at nucleotide position 718, which were reported previously, were also identified in unrelated patients.

Aggregation of the inactive form of human alpha-galactosidase in the endoplasmic reticulum

35S-Labeled mutant alpha-galactosidases (Q279E and R301Q) expressed in COS1 cells were detected as two forms (46-kDa protein and gel-top aggregate) on SDS-polyacrylamide gel electrophoresis under nonreducing conditions. The 46-kDa protein disappeared rapidly, but the aggregate decreased slowly. The accumulation of aggregate was observed in COS1 cells expressing either Q279E or R301Q on Western blot analysis. The aggregate was mainly recovered in the fraction extracted with 1% Triton X-100 and had no catalytic activity. The COS1 cells expressing Q279E were treated with 10 microgram/ml brefeldin A or 5 microM monensin. Treatment with brefeldin A caused a decrease in the alpha-galactosidase activity and an increase in the amount of aggregate, but the amount of aggregate did not change on monensin treatment.

Galactose stabilizes various missense mutants of alpha-galactosidase in Fabry disease

The effect of galactose on alpha-galactosidase missense mutants causing Fabry disease was investigated in the COS-1 cell expression system and lymphoblasts. Three mutant enzymes, A156V, L166V and Q279E, showed increases in activity and amount in COS-1 cells cultured with galactose. Another mutant without catalytic activity, C142Y, did not show any changes. In lymphoblasts cultured with galactose, the enzyme activity increased significantly in four classical Fabry patients with the respective mutations, A156V, L166V, G260A and G373S, and in three atypical Fabry patients with the respective mutations, Q279E, R301Q and M296I. Such an increase was not observed in the other four classical Fabry patients, with C142Y, E66Q/R112C, G328R and N320K, respectively. This suggests that many missense mutations in the alpha-galactosidase gene causing Fabry disease allow the expression of catalytically active mutant enzymes regardless of the clinical phenotype, which are rapidly degraded under physiological conditions and stabilized by galactose.

Alpha-galactosidase gene mutations in Fabry disease: heterogeneous expressions of mutant enzyme proteins

Five point mutations were identified in unrelated Japanese Fabry disease hemizygotes: three new missense mutations, C142Y (425 G-->A), A156V (467 C-->T), and L166V (496 C-->G) in exon 3; one new splice site mutation at the 3' end of the consensus sequence in exon 4; one previously reported nonsense mutation, W44X (131 G-->A). C142Y expressed 50% of the normal enzyme protein in COS-1 cells, but catalytic activity was not detected. Both A156V and L166V expressed significant amounts of residual enzyme activity (6.7% and 9.8%) and enzyme proteins (10% each), the latter were more thermolabile at neutral pH than at acid pH, in vitro.

The functional role of glutamine-280 and threonine-282 in human alpha-galactosidase

Our previous study on chimeric mutants of alpha-galactosidase suggested that two peptide regions encoded by exons 1-2 and 6 of the enzyme gene contribute to substrate recognition (Ishii, S. et al. (1994) Biochim. Biophys. Acta 1204, 265-270). In this study, we constructed five single amino acid substitutions for functional analysis of the amino acid residues around glutamine-279, the mutation site detected in an atypical Fabry disease patient. Two mutants, Q280S (Gln280-->Ser; CAA-->TCA) and T282A (Thr282-->Ala; ACT-->GCT), showed increased Km and decreased thermostability as compared with normal enzyme. Circular dichroism spectrum was not modified. An additional chimeric mutation in the exon 1-2 region by substitution with the homologous sequence of alpha-N-acetylgalactosaminidase cDNA restored catalytic activity and thermostability in both mutants. These data indicated the functional significance of glutamine-280 and threonine-282 for expressing the activity and stability of alpha-galactosidase molecule, and also the presence of an intramolecular interaction between the two peptide regions encoded by exons 1-2 and 6.

Protective protein as an endogenous endothelin degradation enzyme in human tissues

An enzyme hydrolyzing the carboxyl terminus of endothelin-1 was detected in control human tissues but was deficient in tissues from a patient with galactosialidosis, a metabolic disease caused by the protective protein gene mutation. It was proportional to the amount of immunologically estimated mature protective protein. An antibody against the lysosomal protective protein/beta-galactosidase complex precipitated the enzyme activity almost completely. Transfection of the human cDNA for protective protein resulted in high expression of the enzyme activity in transformed fibroblasts from a galactosialidosis patient. These results indicated that the mature protective protein is a major soluble endogenous endothelin degradation enzyme in human tissues.

Lysosomal enzyme replacement using alpha 2-macroglobulin as a transport vehicle

Improvement of the delivery of exogenous enzymes is essential to achieve effective enzyme replacement therapy in lysosomal storage diseases. To test whether alpha 2-macroglobulin, an endogenous plasma protein, could serve as a transport vehicle of therapeutic agents to cells, alpha 2-macroglobulin and acid alpha-glucosidase or alpha-galactosidase A were coupled using two heterobifunctional cross-linking reagents. The alpha-glucosidase-alpha 2-macroglobulin conjugate was internalized and transported into lysosomes of acid alpha-glucosidase-deficient fibroblasts. The enzyme activity was stable after being taken up by the cells. Uptake of the conjugate resulted in the degradation of glycogen accumulated in lysosomes. The alpha-galactosidase A-alpha 2-macroglobulin conjugate was also internalized into the lysosomes of alpha-galactosidase A-deficient fibroblasts. Internalized alpha-galactosidase A-conjugate degraded globotriaosylceramide accumulated in lysosomes. The endocytosis of both conjugate was inhibited by alpha 2-macroglobulin-trypsin complex, indicating that the conjugates were endocytosed by an alpha 2-macroglobulin receptor system. These results showed the usefulness of alpha 2-macroglobulin as a transport vehicle of lysosomal enzymes for effective enzyme replacement.

Clinical findings in two African-American families with the nevoid basal cell carcinoma syndrome (NBCC)

The nevoid basal cell carcinoma syndrome (NBCC) is an autosomal dominant multisystem disorder with variable expressivity. We present the clinical findings on 11 African-American NBCC cases from 2 families and a review of the literature of NBCC in African-Americans. The 2 new families, as well as those previously reported, suggest minimal expression of the basal cell carcinomas and full expression of the other components of the syndrome. The 3 most common findings in the 11 cases were jaw cysts, palmar and/or plantar pits, and calcification of the falx cerebri. Only 44% (4/11) of these cases had one or more confirmed basal cell carcinomas. This frequency is substantially less than that observed in whites (90% with basal cell carcinomas). The relative lack of these skin tumors in African-Americans partly reflects ultraviolet radiation protection resulting from increased skin pigmentation. Future research should help identify the specific mutation(s) in blacks as well as other modifying genes and environmental exposures that may contribute to the varied manifestations of the syndrome.

Human alpha-galactosidase gene expression: significance of two peptide regions encoded by exons 1-2 and 6

Two proteins with alpha-galactosidase activity, alpha-galactosidase A (alpha-GalA) and alpha-galactosidase B (alpha-GalB, or alpha-N-acetylgalactosaminidase; alpha-NAGA) have a high homology of amino-acid sequence. Point mutations of the alpha-GalA gene have been reported only in the exons 1, 2 or 6. In this study, the exon 1-2 and/or 6 sequences of alpha-GalA cDNA were partly substituted by the corresponding regions of alpha-GalB cDNA, and three chimeric proteins were prepared by the baculovirus expression system: CMB12 with substitution at the exon 1-2 region, CMB6 at the exon 6 region, and CMB126 at both regions. They all preserved alpha-GalA antigenicity. Their kinetic properties toward 4-methylumbelliferyl alpha-galactopyranoside were compared with those of alpha-GalA. The catalytic activity was slightly low in CMB12, decreased to 1/10 in CMB6, and restored to a significant degree in CMB126. Km was more than 4-fold higher for CMB6 and CMB126 than for alpha-GalA. The pH optimum was 4.0 for both CMB12 and alpha-GalA, 4.8 for CMB6, and 4.6 for CMB126 and alpha-GalB. The catalytic activity was inhibited most by galactosamine in CMB6, and less in alpha-GalB, CMB126, alpha-GalA and CMB12 in decreasing order. The 50% inhibition concentrations of melibiose (Gal alpha 1-6Glc) and methyl alpha-galactopyranoside were 2.5- to 3-fold higher for CMB126 than for alpha-GalA. These results indicate that the low affinity of CMB126 to the substrate was caused by a reduced affinity to terminal alpha-linked galactose. We conclude that (1) the two regions encoded by exons 1-2 and 6 contribute to the alpha-galactosidic cleavage, and (2) an increase in Km of CMB6 or CMB126, with chimeric substitutions at the exon 6 region, was caused by a loss of affinity toward terminal alpha-linked galactose.

Intracellular processing and maturation of mutant gene products in hereditary beta-galactosidase deficiency (beta-galactosidosis)

Heterogeneous patterns of biosynthesis, posttranslational processing, and degradation were demonstrated for mutant enzymes in three clinical forms of beta-galactosidase deficiency (beta-galactosidosis): juvenile GM1-gangliosidosis, adult GM1-gangliosidosis, and Morquio B disease. The precursor of the mutant enzyme in adult GM1-gangliosidosis was not phosphorylated, and only a small portion of the gene product reached the lysosomes. The enzyme in Morquio B disease was normally processed and transported to lysosomes, but its catalytic activity was low. A common gene mutation in juvenile GM1-gangliosidosis (R201C) produced an enzyme protein that did not aggregate with protective protein in the lysosome, and was rapidly degraded by thiol proteases. This abnormal turnover was similar to that for the normal but dissociated beta-galactosidase in galactosialidosis. Protease inhibitors restored the enzyme activity in fibroblasts of this clinical form. A possible therapeutic approach is discussed for this specific type of enzyme deficiency.

Characterization of a mutant alpha-galactosidase gene product for the late-onset cardiac form of Fabry disease

The expression product of a mutant alpha-galactosidase gene, Q279E (279Gln-->Glu), found in an atypical variant (cardiac form) of Fabry disease, was purified and characterized. It had kinetic properties similar to those of normal alpha-galactosidase, but was markedly thermolabile at neutral pH. Galactose and melibiose at high concentrations stabilized the mutant enzyme in vitro. Its catalytic activity was 15% of that for the normal enzyme, when it was expressed in COS-1 cells at 37 degrees C. The activity increased at 30 degrees C or in the presence of galactose at 37 degrees C. An increase was also observed in lymphoblasts from a patient with this mutation in the presence of galactose or melibiose. We conclude that this mutant protein is posttranslationally inactivated under the neutral conditions in the cells. The possibility of a new therapeutic approach is suggested.

Purification and characterization of human lysosomal protective protein expressed in stably transformed Chinese hamster ovary cells

Chinese hamster ovary cells were transfected with a recombinant DNA containing the entire coding sequence of human lysosomal protective protein cDNA under the control of mouse metallothionein I promoter. Neomycin and methotrexate-resistant stably transformed cell lines expressing this protein were isolated. Immunoprecipitation of the product with antiserum against human placental protective protein-beta-galactosidase complex revealed a 52-kDa protective protein precursor, which was then processed to mature form, a heterodimer of 32- and 20-kDa polypeptides. The precursor secreted in the culture medium was taken up by the mannose 6-phosphate receptor system and restored acid carboxypeptidase, beta-galactosidase, and neuraminidase activities in galactosialidosis fibroblasts. The expressed protein showed a granular pattern in intracellular distribution, was fractionated at the density of lysosomes, and had serine esterase activities; acid carboxypeptidase at pH 5.6, esterase at pH 7.0, and carboxyl-terminal deamidase at pH 7.0. They were inhibited simultaneously by phenylmethylsulfonyl fluoride, N-benzyloxycarbonyl-L-phenylalanine chloromethyl ketone, or iodoacetamide. The acid carboxypeptidase activity of the purified monomeric mature protective protein was labile in vitro under the acidic condition. Saposins (sphingolipid activator proteins) stabilized the activity at micromolar level concentrations.

Developmental defects in gorlin syndrome related to a putative tumor suppressor gene on chromosome 9

Gorlin syndrome is an autosomal dominant disorder that predisposes to basal cell carcinomas of the skin, ovarian fibromas, and medulloblastomas. Unlike other hereditary disorders associated with cancer, it features widespread developmental defects. To investigate the possibility that the syndrome is caused by mutation in a tumor suppressor gene, we searched for loss of heterozygosity in 16 sporadic basal cell carcinomas, 2 hereditary basal cell carcinomas, and 1 hereditary ovarian fibroma and performed genetic linkage studies in five Gorlin syndrome kindreds. Eleven sporadic basal cell carcinomas and all 3 hereditary tumors had allelic loss of chromosome 9q31, and all informative kindreds showed tight linkage between the Gorlin syndrome gene and a genetic marker in this region. Loss of heterozygosity at this chromosomal location, particularly in hereditary tumors, implies that the gene is homozygously inactivated and normally functions as a tumor suppressor. In contrast, hemizygous germline mutations lead to multiple congenital anomalies.

Galactosialidosis: simultaneous deficiency of esterase, carboxy-terminal deamidase and acid carboxypeptidase activities

Esterase and deamidase activities at pH 7.0 and carboxypeptidase activity at pH 5.7 were markedly low or deficient in seven galactosialidosis fibroblast strains with deficient activity of "protective protein" for lysosomal beta-galactosidase and neuraminidase. No simultaneous deficiency of these three enzyme activities was observed in other lysosomal disease fibroblasts examined in this study. This result strongly suggests that "protective protein" is identical with a multifunctional protein with esterase/deamidase/carboxypeptidase activities and its mutation in galactosialidosis results in deficiency of these three enzyme activities.

Neutralizing monoclonal antibody specific for alpha-bungarotoxin: preparation and characterization of the antibody, and localization of antigenic region of alpha-bungarotoxin

We prepared an alpha-bungarotoxin-specific monoclonal antibody that neutralizes the biological activity of the toxin in vivo. The antigenic determinant combining specifically with this antibody was determined on the basis of cross-reaction experiments using three other long neurotoxins and peptide fragments of alpha-bungarotoxin. The antigenic determinant was located on the peptide fragment containing S34-S35-R36-G37-K38, which forms a part of the expected site that binds to the acetylcholine receptor proteins.