Gaucher's disease: the best laid schemes of mice and men

The creation of animal models of Gaucher's disease, the inherited deficiency of the enzyme glucocerebrosidase, has led to new clinical insights and to a new appreciation of the complexity of the glucocerebrosidase gene locus. Murine embryonic stem cells with targeted modifications in the glucocerebrosidase gene were used to generate mouse models of Gaucher's disease, the first having a null glucocerebrosidase allele. The resulting knockout mice have no glucocerebrosidase activity and die within 12 hours of birth. Ultrastructural studies of liver, spleen, brain and bone marrow demonstrate the characteristic storage material seen in Gaucher patients. In the nervous system, storage of lipid increased in a rostral-caudal distribution. Analysis of skin from the knockout mice revealed histological, ultrastructural and biochemical abnormalities. The null allele Gaucher mice are analogous to neonates with Type 2 Gaucher's disease who present with hydrops foetalis and/or congenital ichthyosis. Moreover, the epidermal changes seen in Type 2 mice are also found in Type 2 patients and may provide a means to presymptomatically discriminate Type 2 from Type 1 and 3 Gaucher's disease. Another targeted modification in the murine glucocerebrosidase gene locus led to the discovery of a contiguous gene, metaxin. Closer analysis of the glucocerebrosidase gene locus, including sequencing of 75 kb of genomic DNA, reveals that this is a gene-rich region coding for seven genes and two pseudogenes. Further study of these closely arrayed genes may contribute to our understanding of the clinical variation encountered among patients with Gaucher's disease.     

Beta-glucocerebrosidase gene locus as a link for Gaucher's disease and familial hypo-alpha-lipoproteinaemia

BACKGROUND: Gaucher's disease is the most common lysosomal storage disorder, caused by deficiency of glucocerebrosidase resulting from homozygosity for any of several mutations of the glucocerebrosidase gene locus. Affected people have decreased concentrations of LDL cholesterol (LDL-C) and HDL cholesterol (HDL-C). We assessed the association between mutations in the glucocerebrosidase locus and hypo-alpha-lipoproteinaemia. METHODS: We studied 258 people from 43 unrelated Spanish families. 57 participants were affected, 137 were non-affected carriers, and 64 were non-carriers. We determined glucocerebrosidase genotypes and measured plasmid lipids, apolipoproteins A-I, B, and E, and leucocyte glucocerebrosidase activity. FINDINGS: The most common glucocerebrosidase mutations were N370S (45%), L444P (23%), and G377S (5%). Deletions and recombinants accounted for another 5%, and point mutations in exons 5, 6, 9, and 10 were present in 12%. Affected participants had lower LDL-C and HDL-C concentrations than non-affected carriers (p<0.001) and non-carriers (p<0.001). HDL-C values were also significantly different between the non-affected carriers and non-carriers. Mutations at this locus may account for as much as 19.5% of the genetic variability in HDL-C in the population studied. INTERPRETATION: Heterozygosity for these mutations at the glucocerebrosidase locus does not result in clinical expression of Gaucher's disease but can decrease HDL-C concentrations. Given the high frequency of these mutations, the glucocerebrosidase locus might lead to familial low alpha-lipoproteinaemia in up to 2% of the general population and be one of the most common known genetic causes of HDL-C.     

Neuronopathic forms of Gaucher's disease

Neuronopathic Gaucher patients may have a wide variety of clinical manifestations and natural history, and can present with a range of degrees of severity of systemic disease and neurological deficit. The brain pathology of these patients has been well described, but the mechanism by which glucocerebrosidase deficiency leads to neuronal dysfunction is not yet understood. The almost 20 different mutations of the glucocerebrosidase gene that have been described in Type 2 and 3 Gaucher patients poorly predict the phenotype of individual patients. Enzyme replacement therapy (ERT), often at high doses, has been shown to reverse most of the systemic manifestations of this disease, but can rarely reverse the neurological deficits. Therefore, other forms of treatment, such as gene therapy or a more efficient and direct enzyme delivery to neurons, are being devised.     

Acid phosphatase isoenzymes in Gaucher's disease

Acid phosphatase (EC 3.1.3.2) isoenzyme profiles of extracts of splenic tissue and serum from patients with Gaucher's disease were measured by a mini-column ion-exchange chromatographic method [Clin. Chem., 23, 000 (1977)]. Diagnosis of Gaucher's disease in the five patients studied was confirmed by demonstrating decreased (2.3 to 4.1% of normal) glucocerebrosidase activity in the spleen. With p-nitrophenyl phosphate as substrate, increased acid phosphatase activity (three-to eight-fold normal) was demonstrated in spleen tissue from Gaucher;s disease patients; isoenzyme profiles by the ion-exchange column technique showed acid phosphatase isoenzyme 5 to be the predominant isoenzyme. Comparison of acid phosphatase isoenzyme profiles from patients with Gaucher's disease and prostatic carcinoma revealed distinct differences in the activities of isoenzymes 2 and 5. The isoenzyme-5 measurement thus appears to provide a diagnostic test for Gaucher's disease that can be done reapidly and easily in the routine clinical chemistry laboratory.     

Therapeutic delivery of proteins to macrophages: implications for treatment of Gaucher's disease

BACKGROUND: The primary defect in Gaucher's disease, a lysosomal disorder affecting macrophages, is in the activity of glucocerebrosidase. Treatment with exogenous enzyme (modified to increase its affinity for macrophage glycoprotein receptors) aims to restore this activity. However, the fate of the exogenous enzyme in vivo is unknown. We used radiolabelled enzyme to assess macrophage receptor activity for mannosylated ligands in vivo. METHODS: We examined the uptake and tissue distribution of radiolabelled enzyme molecules by gamma scintigraphy after bolus injection of iodine-123-labelled recombinant or placental enzyme (imiglucerase and alglucerase, respectively) in eight patients with type 1 Gaucher's disease, and in one healthy individual. The metabolism of the tracer enzyme was followed by scintigraphy and by analysis of blood, urine, and faeces. RESULTS: The tracer enzyme was rapidly cleared from blood (half-life 4.7 min [SD 1.0]). Concomitantly, there was avid uptake by the liver (about 30% of the injected dose), the spleen (about 15%), and the bone marrow. 40-55% of the tracer was cleared rapidly from the viscera (half-life 1-2 h) and 45-60% was cleared slowly (half-life 34-42 h). The half-life in the bone marrow was 14.1 h. Infusion of alglucerase at dose of 5 U/kg bodyweight normalised acid beta-glucosidase activity of splenic Gaucher's cells in vivo. When the enzyme was administered at a seven-fold higher dose (35 U/kg over 1 h), the receptor-mediated uptake in vivo was saturated, as shown by the increase in blood-clearance half-life of tracer enzyme from 4.5 min to 12 min. INTERPRETATION: Avid and saturable uptake of modified glucocerebrosidase was found, which indicates high-affinity targeting to the macrophage system in vivo. The rate of enzyme turnover suggests a rational basis for use of this therapy in treatment of Gaucher's disease.     

Gaucher's disease: molecular, genetic and enzymological aspects

The molecular, genetic and enzymological abnormalities in Gaucher's disease have been delineated during the past decade. Although our understanding of the primary predisposition to the Gaucher's disease phenotypes has improved, the relationships remain poorly understood between the mutant alleles, the resultant enzyme variants, the saposin C (activator protein) locus and phenotypes. Of the more than 100-disease associated alleles, about 8 to 10 have significant frequencies in various ethnic and demographic groups. The N370S(1226G) allele is very frequent in Caucasian populations, but absent in Asian groups. In the Ashkenazi Jewish population, the N370S homozygosity predisposes to Gaucher's disease, but over 50% of such patients escape medical detection because of their mild to absent involvement, i.e. N370S may be a prediposing polymorphic variant. Clarification of genotype/phenotype relationships and the identification of modifier loci that impact on Gaucher's disease phenotypes remain a critical area for research. Greater understanding of these issues will facilitate genetic counselling and appropriate interventive therapy to prevent the morbid long-term manifestations of Gaucher's disease.     

Transferrin is necessary and sufficient for the neural effect on growth in amphibian limb regeneration blastemas

The striking and apparent specific elevation of the activity of chitotriosidase found in plasma from patients with Gaucher disease (GD) Type 1 (Mc Kusick 230800) is considered a new diagnostic hallmark of GD and should prove useful in assessing clinical manifestations and monitoring enzyme supplementation therapy. Further data have suggested that the increased levels of chitotriosidade activity in plasma from patients with unexplained diseases may be indicative of a lysosomal storage disorder. We present here an experience of the plasmatic chitotriosidase in an Argentinean population consisting of three groups: a) 25 healthy controls; b) subjects related with GD: 3 patients Type 1, 3 obligated heterocygotes and 1 patient with an atypical variant of GD; c) 42 patients with a precise nosologycal definition of inherited error of metabolism (IEM) and 5 patients presumably affected by a lysosomal pathology but without enzymatic confirmation. Methylumbellypheryl-tri-N-acetyl chitotrioside hydrolase activity was markedly increased: the mean activity being > 600 times and > 100 times the mean value in plasma of our healthy control (mean 17 nmol/min/ml, range 6-60.4 nmol/min/ml) in the plasma of the patients of Gaucher Type 1 disease and an atypical variant of GD, respectively. In the two more affected patients the elevated levels of chitotriosidase activity ran parallel to the severity of the disease and also as a response to the supplementation enzymatic therapy with a decrease of 50% of its activity at 10 months of therapy at a dose of 30 u/kg/month. Moreover, no increase of chitotriosidase activity was found in the 3 obligated heterozygotes of Gaucher Type 1 and Type 2 disease or in any other of the IEM. Chitotriosidase activity was absent in plasma of 2 control subjects and in 4 patients with exact diagnosis of an IEM. The physiological role of the human chitinase still has to be established and warrants further investigation and the natural consequence of the high frequency of a genetic deficiency in man. Meanwhile, reports on the purification and characterization of human chitotriosidase with chitinolytic activity toward chitin-containing pathogens and on the cloning of cDNA encoding chitinase will be crucial to obtain a better insight into this new chapter of medical genetics.     

Radiopharmacology of inhaled 133Xe in skeletal sites containing deposits of Gaucher cells

Gaucher's disease is a lysosomal storage disease in which cells of the reticuloendothelial system accumulate the lipid glucocerebroside. It is characterized by slowly progressive visceral and osseous involvement. One of the latter manifestations includes lipid infiltration of bone marrow. We monitored the rate of inhaled 133Xe uptake and wash-out over diseased and normal metaphyseal and epiphyseal areas of the knee. Twenty-two patients (15 adults, 7 children) with various degrees of previously diagnosed Gaucher's disease were positioned supine under a gamma-camera interfaced to a computer system. All patients rebreathed 133Xe gas from a closed system for 10 min followed by 14 min of wash-out. Digitized images of the lung, liver, spleen, bony sites and soft tissue were obtained at 1 min intervals during the wash-in and wash-out phases. Counts for each ROI were normalized per 100 pixels and plotted as a function (time). Maximum uptake was also calculated by relating the counts/ROI/100 pixels to the 10 min integrated lung count during equilibrium (the administered "dose"). There was essentially no 133Xe uptake in liver and spleen involved with Gaucher's disease. Monophasic uptake and biphasic wash-out curves were observed in the limited investigative population. Skeletal Gaucher deposits released the 133Xe at a greater rate relative to soft tissue.     

Simultaneous occurrence of hereditary angioneurotic edema and Crohn disease

Hereditary C1 esterase inhibitor deficiency is often associated with immunpathologic disorders. The authors present a case of the rare coincidence of hereditary angioedema (HAE) and Crohn's disease. The history of the patient is analysed along with the familial occurrence of the disease. Characteristic abdominal manifestations of C1 esterase inhibitor deficiency are compared to the clinical signs of Crohn's disease. Differential diagnostic pitfalls are described along with efficatious therapeutic options.     

Enzyme substitution in Gauscher disease

Gaucher's disease is the most common inherited lysosomal storage disorder, displaying hepato-splenomegaly, thrombocytopenia, anaemia and bone pain as characteristic features. Substitution therapy with a modified enzyme alglucerase has revolutionized the treatment and prognosis of Gaucher's disease. The first Danish patients treated with alglucerase are reported.     

Non-Hodgkin's lymphoma associated with Gaucher's disease

Gaucher's disease is an uncommon disorder which has been reported to be associated with an increased risk of lymphoproliferative disorders, including Non-Hodgkin's lymphoma (NHL). A new instance of such an association is described here. This was a 58 year-old-patient with adult type I Gaucher's disease who, one and a half year after the above diagnosis, presented with supraclavicular lymphadenopathy, massive splenomegaly, prominent retroperitoneal lymphadenopathy and increased serum LDH levels. This led to the diagnosis of large-cell NHL of B-cell type, successfully treated with chemotherapy. The previously published cases of Gaucher's disease associated with NHL as well as the possible mechanisms leading to this association are reviewed here.     

Plasma and metabolic abnormalities in Gaucher's disease

An overview of the most important plasma abnormalities that can be found in Gaucher's disease is presented in this chapter. Attention is focussed on their practical applications and possible clinical relevance. In addition, the result of studies on metabolic alterations in Gaucher's disease are reviewed.     

Murine MPS I: insights into the pathogenesis of Hurler syndrome

Mucopolysaccharidosis type I (MPS I) is an autosomal recessive disease resulting from deficiency of the lysosomal enzyme alpha-L-iduronidase. A murine model which shows complete deficiency in alpha-L-iduronidase activity has been developed and shows phenotypic features similar to severe MPS I in humans. Here we report on the long-term clinical, biochemical, and pathological course of MPS I in mice with emphasis on the skeletal and central nervous system (CNS) manifestations. Affected mice show a progressive clinical course with the development of coarse features, altered growth characteristics and a shortened life span. Progressive lysosomal accumulation is seen in all tissues. Skeletal manifestations represent the earliest clinical finding in MPS I mice with histologic analysis of growth plate and cortical bone revealing evidence that significant early pathology is present. Analysis of the CNS has revealed the novel finding of progressive neuronal loss within the cerebellum. In addition, brain tissue from MPS I mice shows increased levels of GM2 and GM3 gangliosides. This murine model clearly shows phenotypic and pathologic features which mimic those seen in severe human MPS I and should be an invaluable tool for the study of the pathogenesis of generalized storage disorders.     

Lysosomal glycogen storage disease without acid maltase deficiency

Lysosomal glycogen storage disease without acid maltase deficiency is characterized by the triad of clinical manifestations (hypertrophic cardiomyopathy), mental retardation, and mild myopathy), morphologic findings (glycogen storage, glycogenosomes, and autophagic vacuoles), and normal glycolytic enzyme activities. Though most of the patients suffering from the triad were males, family studies often revealed female patients with only cardiomyopathy. So far 27 cases have been reported. The cardiac involvement is progressive and fatal and as severe in females as in males. Many patients of both sexes die in their youth, unexpectedly, because of cardiac failure. The specific biochemical defect causing this disease remains unknown. From abnormal lectin staining patterns on the membrane and preclinical morphologic changes in biopsied skeletal muscle, membranous abnormality is suspected in this disease.     

Subacute combined degeneration: clinical, electrophysiological, and magnetic resonance imaging findings

OBJECTIVE: Vitamin B12 deficiency is a systemic disease that often affects the nervous system. One of the most prevalent manifestations is subacute combined degeneration (SCD) of the spinal cord. To access the clinical, electrophysiological, and structural abnormalities associated with SCD, a study was conducted in nine patients. METHODS: Clinical, electrophysiological (electroneurography, somatosensory and motor evoked potentials), and MRI evaluations were performed in patients before and after treatment. RESULTS: The most prominent clinical and electrophysiological findings in all patients were dysfunctions of the posterior column. Corresponding hyperintense lesions in the posterior column of the spinal cord were found in two patients by T2 weighted MRI. Damage to the central motor pathway was identified in four patients. Demyelinating neuropathy was present in one patient and axonal neuropathy in four. All patients showed improvement of their symptoms after treatment with cobalamin. Abnormalities of the spinal cord on MRI disappeared early in recovery. Motor evoked potentials and median somatosensory evoked potentials typically normalised after treatment, whereas tibial somatosensory evoked potentials remained abnormal in most patients. CONCLUSIONS: Clinical, electrophysiological, and MRI findings associated with SCD in vitamin B12 deficiency are diverse. Thus vitamin B12 deficiency should be considered in the differential diagnosis of all spinal cord, peripheral nerve, and neuropsychiatric disorders.     

Corneal opacities in Gaucher disease

PURPOSE: To describe the corneal findings in a variant of Gaucher disease. METHODS: Case report. In an 18-year-old man, ophthalmic and general clinical evaluation, and enzymatic and molecular genetics studies were performed. RESULTS: Diffuse, well-defined, small, linear, or dotlike corneal opacities were observed through, out the posterior two thirds of the corneal stroma in both eyes. The patient had calcific valvular heart disease. Enzymatic and ultrastructural studies were consistent with Gaucher disease. Analysis of the glucocerebrosidase gene disclosed homozygosity for a D409H mutation. CONCLUSION: Corneal opacities are a distinguishing ocular feature of the variant of Gaucher disease associated with the D409H mutation and with calcific cardiac disease.     

A case of pulmonary mesenchymal hamartoma in a 9-year-old child

A 14 years old patient, diagnosed in early childhood of type 1 Gaucher's disease is reported to show his unusual genotype and clinical course. The patient is heterozygous for mutation D409H, that in the homozygous patient determines an aggressive disease accompanied by neurological signs, and for a new mutation, which must be considered of mild effects. Early detection of bone involvement is emphasized as a factor to consider when indicating of enzyme replacement therapy.     

Enzyme replacement therapy for Gaucher's disease: the early Canadian experience

BACKGROUND: The management of severe Gaucher's disease was dramatically improved by the development of enzyme replacement therapy. However, this treatment is very costly (currently about $21,000 per infusion for adults at the starting dose recommended by the manufacturer). The goal of this study was to determine how enzyme replacement therapy was being prescribed and financially supported in various parts of Canada. In addition, demographic and outcome information was elicited. METHODS: Prescribing physicians were identified through professional associations and with the help of the manufacturer of the enzyme preparations used for the treatment of Gaucher's disease. The physicians were surveyed by questionnaire in July 1995. The study included all patients in Canada who had received enzyme replacement therapy for Gaucher's disease before July 1, 1995. RESULTS: A total of 25 patients (15 children and 10 adults) with type 1 Gaucher's disease, the common nonneuronopathic variant of the disease, were receiving enzyme replacement therapy by the end of 1995. The indications for treatment included massive splenomegaly, growth failure, and severe bony, hematologic and pulmonary complications of the disease; no patients with mild disease were receiving treatment. Treatment regimens varied markedly (from 12 to 160 units of enzyme/kg per month). All the patients were reported to have responded well to therapy, based on serial measurements of hematologic indices, liver and spleen volumes, and numbers of bony crises as well as patients' subjective impressions. Financial support for therapy varied markedly from one province to another. None of the reporting physicians was aware of any patients with severe Gaucher's disease who were denied therapy as a result of inability to pay for the medication. Various agencies provided financial support for therapy, including both federal and provincial governments, private insurance carriers and the commercial supplier of the enzyme. In Ontario provincial health care officials accepted the development, by a multidisciplinary panel of medical experts, of formal guidelines for determining eligibility, on the basis of objective medical criteria, for reimbursement for enzyme replacement treatment. INTERPRETATION: Although some differences were found across the country with respect to the details of treatment, the indications for enzyme replacement therapy and the selection of severely affected patients were similar in the various provinces. However, financial support was inconsistent and varied among provinces and patients. This will prove to be a challenge in future, not only with respect to this disease but also for other diseases for which effective, expensive therapy has been developed.     

Cytokine patterns at the site of mycobacterial infection

Distinct patterns of T cell cytokine production have been shown to influence the outcome of infection in mouse models and humans. Th1 or Type 1 cytokines, interleukin-2 (IL-2) and interferon-gamma (IFN-gamma) are generally associated with resistance to infection, whereas Th2 or Type 2 cytokines, IL-4 and IL-10 are associated with progressive disease. Leprosy is a useful model for studying the role of cytokines in modulating T cell responses in human infectious disease. Infection by Mycobacterium leprae results in disease manifestations that encompass an immunological spectrum. Tuberculoid patients are able to restrict the growth of the pathogen and mount strong T cell responses to M. leprae. In contrast, lepromatous patients manifest disseminated infection and their T cells weakly respond to M. leprae. We have found that tuberculoid leprosy lesions have a predominance of CD4+ T cells producing the Type 1 cytokine pattern. Secondly, IL-12 mRNA was expressed at 10-fold higher levels in tuberculoid lesions as compared to lepromatous lesions and that IL-12 promotes the selective expansion of the Type 1 cytokine producing cells. In contrast, lepromatous lesions contain CD8+ IL-4-producing cells that suppress antigen-specific T cell responses and promote the outgrowth of additional suppressor T cells. IL-10, also expressed at higher levels in lepromatous as compared to tuberculoid lesions, was found to be produced by macrophages, effectively inhibiting cytokine production and macrophage activity.     

Antibody-mediated protection against intracellular pathogens

Gaucher disease is an autosomal recessive genetic disorder characterized by a deficiency in the glucocerebrosidase enzyme. Glucocerebroside then accumulates in macrophages (Gaucher cells), causing anemia, thrombocytopenia, organomegaly and major bone problems. Discovery of the enzyme deficiency by Brady in 1964, and subsequent extraction and partial deglycosylation of the native enzyme led to a treatment. 1,600 people out of 5,000 possible worldwide patients benefit from this drug. The 70 French treated patients (out of an estimated 200) show remarkable improvement.