Glucocerebrosidase mutations are not found in association with LRRK2 G2019S in subjects with parkinsonism

Alteration G2019S in the leucine-rich repeat kinase 2 gene (LRRK2) has been identified in several populations of patients with parkinsonism, including Ashkenazi Jewish subjects with Parkinson disease. Mutations in glucocerebrosidase (GBA), the enzyme deficient in Gaucher disease, are also identified at an increased frequency among Parkinson probands, including those of Ashkenazi Jewish ancestry. A Taqman Assay-by-Design SNP genotyping strategy was utilized to establish whether G2019S was found in association with GBA mutations. Among 37 subjects with parkinsonism who were heterozygous for a GBA mutation, none carried G2019S. Furthermore, G2019S was not found in 18 patients with Gaucher disease who developed parkinsonian manifestations and 11 other Gaucher probands with parkinsonism in a first degree relative. Among 45 patients with Gaucher disease without a history of parkinsonism, one G2019S carrier was found. These findings suggest that GBA and LRRK2 mutations are discrete risk factors for parkinsonism in both Ashkenazi Jewish and non-Jewish subjects.

Homozygosity for the double D409H+H255Q allele in type II Gaucher disease

Homozygosity for D409H has been associated with a unique type III subtype of the disease with a phenotype dominated by severe cardiovascular involvement, whereas neurological findings, if present, are restricted to oculomotor apraxia and features such as visceromegaly are either minimal or absent. Using PCR amplification followed by restriction enzyme analysis, 3 patients (1 Greek, 2 Albanians) were IDentified with the D409H/D409H genotype. All shared a very severe early-onset neurological phenotype that classified them as type II. Amplification and sequencing of the full coding region of the GBA gene revealed that all three patients were homozygous not only for D409H but also for H255Q. Both mutations were present on the same allele, as shown by analysis of the parental DNA. The double D409H+H255Q allele was found in heterozygosity in Greek, Bulgarian and Argentinian patients but was not IDentified in any Spanish patients carrying the D409H mutation.

Upregulation of proinflammatory cytokines in the fetal brain of the Gaucher mouse

Gaucher disease is caused by a deficiency of glucocerebrosidase. Patients with Gaucher disease are divided into three major phenotypes: chronic nonneuronopathic, acute neuronopathic, and chronic neuronopathic, based on symptoms of the nervous system, the severity of symptoms, and the age of disease onset. The characteristics of patients with acute neuronopathic- and chronic neuronopathic-type Gaucher disease include oculomotor abnormalities, bulbar signs, limb rigidity, seizures and occasional choreoathetoid movements, and neuronal loss. However, the mechanisms leading to the neurodegeneration of this disorder remain unknown. To investigate brain dysfunction in Gaucher disease, we studied the possible role of inflammation in neurodegeneration during development of Gaucher disease in a mouse model. Elevated levels of the proinflammatory cytokines, IL-1alpha, IL-1beta, IL-6, and TNF-alpha, were detected in the fetal brains of Gaucher mice. Moreover, the levels of secreted nitric oxide and reactive oxygen species in the brains of Gaucher mice were higher than in wild-type mice. Thus, accumulated glucocerebroside or glucosylsphingosine, caused by glucocerebrosidase deficiency, may mediate brain inflammation in the Gaucher mouse via the elevation of proinflammatory cytokines, nitric oxide, and reactive oxygen species.

AAV8-mediated expression of glucocerebrosidase ameliorates the storage pathology in the visceral organs of a mouse model of Gaucher disease

BACKGROUND

Gaucher disease is the most common of the lysosomal storage disorders. The primary manifestation is the accumulation of glucosylceramide (GL-1) in the macrophages of liver and spleen (Gaucher cells), due to a deficiency in the lysosomal hydrolase glucocerebrosidase (GC). A Gaucher mouse model (D409V/null) exhibiting reduced GC activity and accumulation of GL-1 was used to evaluate adeno-associated viral (AAV)-mediated gene therapy.

METHODS

A recombinant AAV8 serotype vector bearing human GC (hGC) was administered intravenously to the mice. The levels of hGC in blood and tissues were determined, as were the effects of gene transfer on the levels of GL-1. Histopathological evaluation was performed on liver, spleen and lungs.

RESULTS

Vector administration to pre-symptomatic Gaucher mice resulted in sustained hepatic secretion of hGC at levels that prevented GL-1 accumulation and the appearance of Gaucher cells in the liver, spleen and lungs. AAV administration to older mice with established disease resulted in normalization of GL-1 levels in the spleen and liver and partially reduced that in the lung. Analysis of the bronchoalveolar lavage fluid (BALF) from treated mice showed significant correction of the abnormal cellularity and cell differentials. No antibodies to the expressed hGC were detected following a challenge with recombinant enzyme suggesting the animals were tolerized to human enzyme.

CONCLUSIONS

These data demonstrate the effectiveness of AAV-mediated gene therapy at preventing and correcting the biochemical and pathological abnormalities in a Gaucher mouse model, and thus support the continued consideration of this vector as an alternative approach to treating Gaucher disease.

Phenotype variations in Gaucher disease

The Gaucher phenotype is very complex and it cannot be simply evaluated on the basis of blood counts or splenomegaly, but by the analysis of all disease compartments. To establish the diagnosis of Gaucher disease, biochemical assay of glucocerebrosidase activity is the most reliable method. However, it can be supplemented by molecular diagnosis, which may be helpful to predict the severity and the rate of progression of clinical manifestations. The genotype-phenotype correlations are very complex with a high inter-individual variability in the severity of clinical manifestations within a same genotype. Genetic modifiers may play an important role in determining the eventual Gaucher phenotype. Despite of some devastating complications, which can arise with advancing age, Gaucher disease worsen progressively in the majority of patients homozygous for the N370S mutation. The analysis of the data of the International Collaborative Gaucher Group registry should provide a better understanding of the natural history of the Gaucher disease.

Therapeutic goals in Gaucher disease

Evidence-based therapeutic goals have been developed by several European and American experts in Gaucher disease in order to attempt to reverse the entire Type 1 Gaucher phenotype, prevent complications, improve quality of life and prevent life-threatening complications. Patients with Gaucher disease will benefit by maximum enzyme replacement treatment (ERT) efficiency if it is given at the optimal time i.e. generally during the asymptomatic phase of the disease. Currently, Cerezyme is the standard of care for all severities of type 1 Gaucher disease due to its high efficiency at ameliorating bleeding tendencies, reversing organomegaly and part of skeletal damages and eliminating bone crises. ERT has also demonstrated a remarkable safety profile with tolerability at 3 years greater than 99%. Treatment of Gaucher disease is a long-life treatment that the patient should not interrupt without a careful monitoring of the disease evolution.

Chemical chaperones and permissive temperatures alter localization of Gaucher disease associated glucocerebrosidase variants

Point mutations in the lysosomal hydrolase, glucocerebrosidase (GC), can cause Gaucher disease, a common lysosomal storage disease. Several clinically important GC mutations impede folding in the endoplasmic reticulum (ER) and target these enzymes for ER-associated degradation (ERAD). The removal of these misfolded proteins decreases the lysosomal concentration of GC, which results in glucosylceramide accumulation. The most common GC variant, N370S, and other clinically relevant variants, G202R and L444P, exhibit different cellular localization patterns in patient-derived fibroblasts. We show that these distributions can be altered by manipulation of the ER folding environment, either by chemical chaperones or by temperature shifts. N370S, L444P, and G202R GC are destabilized in the neutral pH environment of the ER, rendering them prone to ERAD. Fibroblasts harboring the G202R and L444P GC mutations grown at 30 degrees C localize the mutant proteins to the lysosome, and this increases total GC activity. Both of these temperature-sensitive mutants appear to be stable at 37 degrees C once they are trafficked to the low pH environment of the lysosome. Chemical chaperones correct the ER instability and significant ER retention of G202R GC. N370S is also destabilized under ER simulating conditions, a deficiency that is corrected by chemical chaperone binding. These data clearly show manipulating the ER environment with chemical chaperones increases the lysosomal concentration of partially active GC variants and suggest that small molecules could be used to treat Gaucher disease.

Characterization of neuronopathic Gaucher disease among ethnic Poles

PURPOSE

Gaucher disease is a common lysosomal storage disease that results from inherited mutations in the gene (GBA) encoding acid beta-glucosidase (GCase). Here, the clinical and molecular findings of the subacute neuronopathic variant are delineated among ethnic Poles.

METHODS

Longitudinal studies of visceral, bony, and central nervous system involvement are delineated clinically. Complete gene GBA sequencing was used to characterize the mutations and haplotypes in this population.

RESULTS

A greater frequency of subacute neuronopathic Gaucher disease (type 3) is present among ethnic Poles compared with other European countries. Two type 3 phenotypes were found: The first was an early-onset variant with massive visceral disease, progressive kyphoscoliosis, mild cognitive deficits, and survival for three or more decades. This variant resembles the "Norrbottnian" Swedish phenotype. The other variant had more severe progressive central nervous system disease, milder visceral involvement, and absence of kyphoscoliosis. Myoclonus was present in some patients. Neither variant had bone crises and/or pain as major components. The L444P/L444P genotype was most common, but on several different haplotype backgrounds. Other alleles encoded D409H, V305L, and E326K/A446P on various haplotypes.

CONCLUSIONS

These studies provide additional expansion of the type 3 genotypes with some commonalities with and differences from other reported variants. Also, such phenotypic expansion should be expected in the other variants of Gaucher disease as the spectrum of ethnic variation becomes more fully delineated.

Serum levels of osteoprotegerin and osteoprotegerin polymorphisms in Gaucher disease

Bone involvement in Gaucher disease causes disability and reduced quality of life; loss of function and pain are important indications for enzyme replacement therapy. The purpose of this study was to ascertain whether osteoprotegerin (OPG), which decreases osteoclast activity, is indicative of incipient bone involvement by comparing OPG serum levels to Gaucher disease severity (SSI) and bone mineral density (BMD), and to correlate bone and disease markers to OPG polymorphisms: OPG1-2(A163G), OPG3-4(T129C) and OPG5-6(C1217T). Of 554 patients, 173 Ashkenazi Jewish patients with non-neuronopathic Gaucher disease were enrolled and 32 healthy Ashkenazi Jews served as controls. Serum OPG levels were detected by enzyme-linked immunosorbent assay and BMD was obtained by dual X-ray absorptiometry. OPG polymorphisms were determined in 63 randomly chosen patients. Serum OPG values for patients were not greater than in controls, but showed a statistically significant trend to increase with age (P = 0.057). No correlation existed between OPG levels and BMD or with genotype or other disease markers. A significant correlation was noted between OPG5-6 genotype and SSI. A significant difference was found between the allele distributions of each OPG polymorphism when compared with Caucasians and Ashkenazi Jews. OPG levels probably do not predict BMD in Gaucher disease and hence are not indicative of osteoporosis in Gaucher disease.

Increased incidence of Parkinson disease among relatives of patients with Gaucher disease

In a previous study of 99 Ashkenazi Jewish patients with Parkinson disease from Israel who were tested for the six most common mutations for Gaucher disease, 31.3% had at least one Gaucher disease mutation, implying that carrier status per se my be a risk for Parkinson disease. The purpose of this survey was to ascertain the presence of Parkinson disease among Ashkenazi Jewish obligate carriers of Gaucher disease relative to its incidence in a comparable cohort of Ashkenazi Jews who are putatively non-carriers. There was no statistically significant difference in gender or age between the groups (n>100). Among patients, 27.3% reported having a relative with Parkinson disease while among the controls there was a reported 12.3% which was statistically significant (P=0.05). While based completely on subjective reports in a paper-base questionnaire, the results of this survey implicate a high rate of Parkinson disease among individuals with Gaucher disease mutations.

Divergent phenotypes in Gaucher disease implicate the role of modifiers

BACKGROUND

Gaucher disease is classified into neuronopathic and non-neuronopathic forms with wide phenotypic variation among patients sharing the same genotype. While homozygosity for the common L444P allele usually correlates with the neuronopathic forms, how a defined genotype leads to a phenotype remains unknown.

METHODS

The genetic and epigenetic factors causing phenotypic differences were approached by a clinical association study in 32 children homozygous for the point mutation L444P. Direct sequencing and Southern blots were utilised to establish the genotype and exclude recombinant alleles. Glucocerebrosidase activity was measured in lymphoblast and fibroblast cell lines.

RESULTS

Residual enzyme activity was highly variable and did not correlate with the observed clinical course. There was also a wide spectrum of phenotypes. Average age at diagnosis was 15 months, and slowed saccadic eye movements were the most prevalent finding. The most severe systemic complications and highest mortality occurred in splenectomised patients before the advent of enzyme replacement therapy (ERT). On ERT, as morbidity and mortality decreased, developmental and language deficits emerged as a major issue. Some trends related to ethnic background were observed.

CONCLUSION

The wide clinical spectrum observed in the L444P homozygotes implicates the contribution of genetic modifiers in defining the phenotype in Gaucher disease.

Prenatal panel screening considerations for non-neuronopathic Gaucher disease in the Ashkenazi-Jewish population

The Ashkenazi-Jewish population is at increased risk for several recessively inherited disorders. While some of the disorders have severe or fatal symptom manifestations, others, such as non-neuronopathic Gaucher disease, do not usually pose a serious, life-threatening illness. Many healthcare centers in Israel offer prenatal panel screening. Controversy exists over the inclusion of Gaucher disease in the panel screening, especially since Gaucher disease screening lacks prognostic reliability. Most screening participants do not discriminate between the specific tests in the panel and are unable to discern between severe, life-threatening diseases and those that are less severe and even treatable. By including screening for Gaucher in the panel screening program, there is risk of a "panel effect," leading to termination of a pregnancy positive for Gaucher disease, without sufficient knowledge and understanding of the disease. Increasing medical and public awareness and knowledge of the disease, its prognosis and treatment options may reduce the rate of under-informed abortions associated with prenatal screening for Gaucher disease.

Short-term effect of miglustat in every day clinical use in treatment-naïve or previously treated patients with type 1 Gaucher's disease

In a prospective, open-label study, 25 patients with mild-to-moderate type 1 Gaucher's disease (GD1) were treated with miglustat (Zavesca), an oral glucosylceramide synthase inhibitor, over 12 months. Of the 25 patients, 10 were therapy-naïve and 15 had previously received enzyme replacement therapy (ERT). Clinical status, blood parameters, biomarkers, and organomegaly were assessed at baseline at 6 months and at 12 months. At 6 months the previously untreated patients showed a mean increase in hemoglobin of 0.77 g/dL, platelet counts improved or remaining stable, chitotriosidase and CCL18 decreased. These results were similar to those observed in 40 Spanish GD1 patients on ERT. Bone marrow infiltration cleared at 12 months. In the previously treated group, clinical and hematologic parameters and biomarkers were maintained/ improved at 12 months. Miglustat was well tolerated. The efficacy of miglustat treatment after 6 months was comparable to that of ERT.

Mouse models of human lysosomal diseases

Genetically authentic animal models of human lysosomal diseases occur spontaneously in many mammalian species. However, most are among larger domestic or farm animals with only two well-defined genetic lysosomal diseases known among rodents. This status changed dramatically in recent years with the advent of the combined homologous recombination and embryonic stem cell technology, which allows directed generation of mouse models that are genetically equivalent to human diseases. Almost all known human sphingolipidoses, two mucopolysaccharidoses and aspartylglycosaminuria have so far been duplicated in mice and more are expected in the near future. This technology also allows generation of mouse mutants that are not known or are highly unlikely to exist in humans, such as "double-knockouts." These animal models will play an important role in studies of the pathogenesis and treatment of these disorders. While the utility of these mouse models is obvious, species differences in brain development and metabolic pathways must be always remembered, if the ultimate goal of the study is application to human patients.

Substrate reduction therapy of glycosphingolipid storage disorders

In the last 15 years enormous progress has been made regarding therapy of type I Gaucher disease, a severely disabling disorder characterized by intralysosomal storage of glucosylceramide in tissue macrophages. Effective enzyme replacement therapy of type I Gaucher disease, based on chronic intravenous administration of mannose-terminated recombinant human glucocerebrosidase, has been available since 1990 and has been applied in several thousand patients without serious adverse effects. An alternative therapeutic approach, so-called substrate reduction therapy, is based on partial reduction of the synthesis of glucosylceramide and hence of subsequent metabolites. Oral administration of an inhibitor of glucosylceramide synthesis (N-butyldeoxynojirimycin, registered in Europe since 2002 as miglustat (Zavesca)), is effective in reversing clinical symptoms in type I Gaucher patients with mild to moderate disease manifestations. The growing long-term experience with substrate reduction therapy indicates that this treatment is also without major adverse effects. Substrate reduction therapy, in conjunction with enzyme replacement therapy, may play an important role in the future clinical management of patients suffering from type I Gaucher disease. Clinical trials are under way that should reveal the value of substrate reduction for maintenance therapy of type I Gaucher disease and for treatment of neuronopathic variants of Gaucher disease, Niemann-Pick disease type C, late-onset Tay-Sachs disease and Sandhoff disease.

Secretion of human glucocerebrosidase from stable transformed insect cells using native signal sequences

The lysosomal hydrolase, glucocerebrosidase (GBA), catalyses the penultimate step in the breakdown of membrane glycosphingolipids. An inherited deficiency of this enzyme activity leads to the onset of Gaucher disease, the most common lysosomal storage disorder. Affected individuals range from adults with hepatosplenomegaly, haematological complications, and bone pain (type 1 disease) to children and neonates with severe neuronopathy leading to neurological degradation and premature death (type 2 and type 3 disease). Enzyme replacement therapy has become the standard of treatment for type I Gaucher disease but remains an expensive option, in part because of the cost of recombinant enzyme production using mammalian cell culture. Using a nonlytic integrative plasmid expression system, we have successfully produced active human GBA in stable transformed Sf9 (Spodoptera frugiperda) cells. Both the 39 and 19 amino acid native GBA signal sequences were capable of endoplasmic reticulum targeting, which led to secretion of the recombinant protein, although approximately 30% more enzyme was produced using the longer signal sequence. The secreted product was purified to apparent electrophoretic homogeneity using hydrophobic interaction chromatography and found to be produced in a fully glycosylated and a hypoglycosylated form, both of which cross-reacted with a human GBA-specific monoclonal antibody. The pH optimum (at pH 5.5) for activity of the recombinant enzyme was as expected for human GBA using the artificial substrate 4-methyl-umbelliferyl-β-D-glycopyranoside. With initial nonoptimized expression levels estimated at 10–15 mg/L using small-scale batch cultures, stable transformed insect cells could provide a viable alternative system for the heterologous production of human GBA when grown under optimized perfusion culture conditions.Key words: Gaucher disease, glucocerebrosidase, protein expression, enzyme purification, Sf9 cells.

Therapeutic strategies to ameliorate lysosomal storage disorders – a focus on Gaucher disease

The lysosomal storage disorders encompass more than 40 distinct diseases, most of which are caused by the deficient activity of a lysosomal hydrolase leading to the progressive, intralysosomal accumulation of substrates such as sphingolipids, mucopolysaccharides, and oligosaccharides. Here, we primarily focus on Gaucher disease, one of the most prevalent lysosomal storage disorders, which is caused by an impaired activity of glucocerebrosidase, resulting in the accumulation of the glycosphingolipid glucosylceramide in the lysosomes. Enzyme replacement and substrate reduction therapies have proven effective for Gaucher disease cases without central nervous system involvement. We discuss the promise of chemical chaperone therapy to complement established therapeutic strategies for Gaucher disease. Chemical chaperones are small molecules that bind to the active site of glucocerebrosidase variants stabilizing their three-dimensional structure in the endoplasmic reticulum, likely preventing their endoplasmic reticulum-associated degradation and allowing their proper trafficking to the lysosome where they can degrade accumulated substrate to effectively ameliorate Gaucher disease.

Mutation analysis of Gaucher disease patients in Taiwan: high prevalence of the RecNciI and L444P mutations

Gaucher disease, the most prevalent lysosomal storage disease characterized by a remarkable degree of clinical variability, results from deleterious mutations in the beta-glucosidase gene. Although >200 mutations in the gene for human beta-glucosidase have been described, most genotype/phenotype studies have focused on screening for a few common mutations. In the present study, whole gene sequencing analysis was performed. We sequenced eight patients with type 1, five patients with type 2, and six patients with type 3 Gaucher disease in Taiwan. A total of 37 Gaucher chromosome were identified. The detection rate is 97%. For types 1 and 3 Gaucher disease, 1448 T > C (L444P) account for 53.5% Gaucher chromosome and the recombinant allele [1448 T > C, 1483 T > G, 1497 G > C] (RecNciI) has 25% prevalence rate among those patients. For type 2 Gaucher disease, all five patients carry L444P mutation, and RecNciI is found in two of the six patients. Because L444P is also present in the RecNciI mutation, all the patients in this study have a L444P mutation in their Gaucher chromosomes. The third most common mutation of type 1 Gaucher disease is 475 C > T (R120W). L444P homozygote and R120W/RecNciI genotypes are associated with non-neuronopathic Gaucher disease. RecNciI is related to neuronopathic disease, while R120W is represented as a mild mutation in Taiwan. The mutation profile of Gaucher disease in Taiwan is limited. Only four different alleles were identified in types 1 and 3 as well as in type 2 Gaucher disease.

Clinical aspects of early-stage neurological forms of Gaucher disease

Pooling and in-depth analysis of cases taken from the literature and from French experience of patients suffering from early-stage neurological forms of Gaucher disease have made it possible to demonstrate the existence of more than two neurological forms which differ in terms of their natural history, clinical picture and response to enzyme therapy. The perinatal, lethal form is characterised by foetal and placental ânasarca, foetal death, prematurity or life-threatening distress at birth. The specific clinical signs include ichtyosis, muscle and tendon retraction and facial dysmorphism. Type 2 Gaucher disease affects infants and leads to death before the age of 2 years. Organ damage is characterised by the severity of pneumopathy. Neurological signs are of particular importance and include hyperextension of the neck and disorders affecting oculomotricity, sucking and swallowing. Most patients also develop episodes of apnoea which become increasingly lengthy and frequent as the disease progresses. Myoclonic epilepsy, which appears to be scarcely susceptible to enzyme therapy, and psychomotor regression are less common and are mainly seen in the rare cases of prolonged survival and in type 3 Gaucher disease.

Identification and functional characterization of five novel mutant alleles in 58 Italian patients with Gaucher disease type 1

Gaucher disease (GD) is the most frequent lysosomal glycolipid storage disorder due to an autosomal recessive deficiency of acid beta-glucosidase characterized by the accumulation of glucocerebroside. In this work we carried out the molecular analysis of the glucocerebrosidase gene (GBA) in 58 unrelated patients with GD type 1. We identified five novel genetic alterations: three missense changes c.187G>A (p.D63N), c.473T>G (p.I158S), c.689T>A (p.V230E), a gene-pseudogene recombinant allele and a non-pseudogene-derived complex allele [c.1379G>A;c.1469A>G] encoding [p.G460D;p.H490R]. All mutant alleles were present as compound heterozygotes in association with c.1226A>G (p.N409S), the most common mutation in GD1. The missense mutant proteins were expressed in vitro in COS-1 cells and analyzed by enzyme activity, protein processing and intracellular localization. Functional studies also included the c.662C>T (p.P221L) mutation recently reported in the Spanish GD population (Montfort et al., 2004). The missense mutant alleles retained an extremely low residual enzyme activity with respect to wild type; the complex allele expressed no activity. Processing of the mutant proteins was unaltered except for c.473T>G which was differently glycosylated due to the exposition of an additional glycosylation site. Immunofluorescence studies showed that protein trafficking into the lysosomes was unaffected in all cases. Finally, the characterization of the novel recombinant allele identified a crossover involving the GBA gene and pseudogene between intron 5 and exon 7.

Perinatal lethal phenotype with generalized ichthyosis in a type 2 Gaucher disease patient with the [L444P;E326K]/P182L genotype: effect of the E326K change in neonatal and classic forms of the disease

Gaucher disease, the most common lysosomal storage disorder, encompasses a wide spectrum of clinical symptoms. The perinatal lethal form is very rare and is considered a distinct form of classic type 2 Gaucher disease. Prominent features of the severe perinatal form are hepatosplenomegaly variable, associated with hydrops fetalis and ichthyosis. Here, we describe a child who presented generalized ichthyosis and died at 25 days of age. Genotype analysis revealed compound heterozygosity for the complex allele [L444P;E326K] and mutation P182L, described for the first time in this patient. Mutations E326K and L444P were on the same chromosome. Expression studies of mutant glucocerebrosidases showed that the double mutant allele had lower activity, 8.5% of wild type, in contrast to the activity of individual E326K and L444P mutant enzymes, 42.7% and 14.1%, respectively. The P182L mutant enzyme showed no glucocerebrosidase activity. A revision of the genotypes identified in a series of Spanish patients with type 2 Gaucher disease showed that the complex allele [L444P;E326K] accounted for 19.2% of patient alleles and that homozygosity for this allele or its heterozygosity with mutation L444P, or another severe mutation such as P182L, was associated with the perinatal lethal presentation of the disease. In contrast, the [L444P;E326K] allele was not detected in patients with classic type 2 diagnosed when several months old. The high frequency of the E326K substitution observed in patients with type 2 as compared to the general population (0.5%) suggests that this change may have a modulating negative effect on the clinical condition of these Gaucher disease patients when present in combination with mutation L444P. The relatively high prevalence of the double mutant allele in Spanish patients prompted us to perform a haplotype analysis, using four polymorphic markers, which suggest a common origin for this allele. During the mutational analysis of the series of type 2 patients, a novel mutation, I260T (c.896T>C), was identified.

Miglustat (NB-DNJ) works as a chaperone for mutated acid beta-glucosidase in cells transfected with several Gaucher disease mutations

Gaucher disease (GD) is a disorder of glycosphinglipid metabolism caused by deficiency of lysosomal acid beta-glucosidase (GC), resulting in progressive deposition of glucosylceramide in macrophages. The glucose analogue, N-butyl-deoxynojirimycin (NB-DNJ, Miglustat), is an inhibitor of the ceramide-specific glucosyltransferase (CSG) which catalyzes the first step of glycosphingolipids biosynthesis and is currently approved for the oral treatment of type 1 GD. Using site-directed mutagenesis, we constructed plasmids containing wild-type and several mutations in glucocerebrosidase (GBA) gene. The plasmids were transfected into COS-7 cells and stable transfected cell lines were obtained by geneticin (G418) selection. Cells were cultured during 6 days with medium with or without 10 microM NB-DNJ. The addition of NB-DNJ to COS-7 cell medium leads to 1.3-, 2.1-, 2.3-, 3.6-, and 9.9-fold increase in the activity of S364R, wild-type, N370S, V15M, and M123T GC, respectively. However, no significant changes were observed in the activity of the L444P, L336P, and S465del mutated proteins, but a small decrease in the rare P266L variant was observed. These results suggest that NB-DNJ, in addition to the inhibitory effect on CSG, also works as a "chemical chaperone", increasing the activity of acid beta-glucosidase of wild-type and several GC mutated proteins, including the most frequent N370S mutation. The specific location of the Miglustat binding site in GC is unknown. Potential binding sites in the enzyme have been searched for using computational molecular docking. The searching strategy identified three potential GC binding sites for Miglustat, one being the substrate-binding site of the enzyme, which was the best-ranked site by AutoDock program. Therefore, it is possible that Miglustat exerts its chaperoning activity on acid beta-glucosidase by acting as an inhibitor bound at the active site. This increase on the activity of the acid beta-glucosidase would imply that Miglustat is not only a substrate reducer but also an inhibitor of the GC degradation, with very promising clinical implications for the treatment of GD patients.

A questionnaire study for 128 patients with Gaucher disease

Gaucher disease is an uncommon autosomal recessive disorder characterized by lysosomal storage of glucosyl ceramide, a material released during cell degradation. Patients with Gaucher disease often have significant hematologic, bone structural, and visceral problems which sometimes greatly affect their health and life style. Based on some extraordinary scientific discoveries over the past 45 years, a treatment system has evolved which consists of administration of an enzyme, which destroys the lysosome-stored material and to some extent restores the patients to good health. There are still some problems for these patients; however, and the purpose of the study is to define some of the clinical, sociologic, and psychologic problems with a specially designed questionnaire. Questionnaire data was collected for 128 patients from two institutions with complete anonymity, and the information compared against data from a National Health Interview Survey. The results show that many of the patients still have fairly extensive problems, which could possibly be helped by some alterations in treatment protocols.

Parkinsonism in type I Gaucher's disease

The majority of patients with type I Gaucher's disease never develop neurological signs or symptoms. However, several case reports of Parkinson's disease associated with type I Gaucher's disease have been published, suggesting a genetic link between the two diseases. Hence, detailed clinical investigations are required when the two diseases occur simultaneously, in order to determine whether this is coincidental or whether a true association is present. We present a Japanese man in whom parkinsonism was associated with type I Gaucher's disease. Findings of brain positron tomography (PET) and metaiodobenzylguanidine (MIBG) cardiac scintigraphy are presented.

Analysis of nonsense-mediated mRNA decay in mutant alleles identified in Spanish Gaucher disease patients

Most of the mutations described in the GBA gene as responsible for Gaucher disease are missense mutations. Nevertheless, other alterations, including nonsense and frameshift mutations, have been reported. These mutations generate premature termination codons (PTC) that could trigger the degradation of mRNA through a mechanism known as nonsense-mediated decay (NMD). It has been established that NMD requires the presence of at least one intron downstream of the PTC, and that this PTC should be at least 50-55 nucleotides upstream of the 3'-most exon-exon junction. In this study, we analyse four GBA truncating mutations - c.108G > A (W(-4)X; HGVS recommended nomenclature: p.W36X), c.886C > T (R257X; HGVS: p.R296X), c.1098_1099insA and c.1451_1452delAC - found in Spanish Gaucher disease patients in order to determine whether they undergo mRNA decay and, if so, whether this occurs via the NMD pathway. RT-PCR showed a clear reduction of RNA for three of the alleles: W(-4)X, R257X and c.1098_1099insA. After treatment with cycloheximide (CHX), a known inhibitor of both protein synthesis and NMD, two of the mutant alleles, R257X and c.1098_1099insA, showed a partial recovery of the amount of mRNA. The third mutation, W(-4)X, did not show any significant CHX-induced recovery, while allele c.1451_1452delAC did not show mRNA decay at all. Real-time PCR confirmed these results and allowed the decay and recovery to be quantified. Finally, the protein truncation test was performed to detect the corresponding proteins. Expected products for alleles R257X, c.1451_1452delAC and c.1098_1099insA, but not for W(-4)X, were observed.

Gaucher disease in Colombia: mutation identification and comparison to other Hispanic populations

Gaucher disease is the most common of the lysosomal storage disorders, affecting all ethnic groups. The pathology of this recessively inherited disease arises from the accumulation of glucocerebroside in tissues due to deficient activity of the enzyme glucocerebrosidase (E.C. 3.2.1.45). The glucocerebrosidase (GBA) gene spans a 7.2kb fragment located on locus 1q 21, consisting of 11 exons and 10 introns. Located 16 kb downstream is a highly homologous pseudogene sequence [M. Horowitz, S. Wilder, Z. Horowitz, O. Reiner, T. Gelbart, E. Beutler, The Human Glucocerebrosidase gene and pseudogene: structure and evolution. Genomics 4 (1) (1989) 87-96.]. Fourteen fragments comprising 11 exons of the GBA gene were analyzed in DNA samples from 25 Colombian patients using denaturing High Pressure Liquid Chromatography (DHPLC). Sequencing of abnormal findings led to the discovery of three novel mutations (c.595_596 delCT, c.898 delG and c.1,255 G>C [p.D 419 H] in exons 6, 7, and 9 of the GBA gene) with high prevalence among Colombian patients. We have also found the presence of a double mutation p.L 483 P+p.E 355 K (L 444 P+E 326 K, traditional nomenclature) in two different families classified as Gaucher type 1. This mutation was previously reported in one patient with Gaucher type 2. We have found DHPLC to be a reliable and sensitive method for the detection of mutations and allelic variation in Gaucher patients.

Analyses of variant acid beta-glucosidases: effects of Gaucher disease mutations

Acid beta-glucosidase (GCase) is a 497-amino acid, membrane-associated lysosomal exo-beta-glucosidase whose defective activity leads to the Gaucher disease phenotypes. To move toward a structure/function map for disease mutations, 52 selected single amino acid substitutions were introduced into GCase, expressed in an insect cell system, purified, and characterized for basic kinetic, stability, and activator response properties. The variant GCases from Gaucher disease patients and selected variant GCases from the mouse had decreased relative k(cat) and differential effects on active site binding and/or attachment of mechanism-based covalent (conduritol B epoxide) or reversible (deoxynojirimycin derivatives) inhibitors. A defect in negatively charged phospholipid activation was present in the majority of variant GCases but was increased in two, N370S and V394L. Deficits in saposin C enhancement of k(cat) were present in variant GCases involving residues 48-122, whereas approximately 2-fold increases were obtained with the L264I GCase. About 50% of variant GCases each had wild-type or increased sensitivity to in vitro cathepsin D digestion. Mapping of these properties onto the crystal structures of GCase indicated wide dispersion of functional properties that can affect catalytic function and stability. Site-directed mutagenesis of cysteine residues showed that the disulfide bonds, Cys(4)-Cys(16) and Cys(18)-Cys(23), and a free Cys(342) were essential for activity; the free Cys(126) and Cys(248) were not. Relative k(cat) was highly sensitive to a His substitution at Arg(496) but not at Arg(495). These studies and high phylogenetic conservation indicate localized and general structural effects of Gaucher disease mutations that were not obvious from the nature of the amino acid substitution, including those predicted to be nondisruptive (e.g. Val --> Leu). These results provide initial studies for the engineering of variant GCases and, potentially, molecular chaperones for therapeutic use.

TNF-alpha levels and TNF-alpha gene polymorphism in type I Gaucher disease

The objective of this pilot study was to determine the levels of Tumor Necrosis Factor (TNF)-alpha and TNF-alpha gene polymorphism as a marker of inflammation among patients with type I Gaucher disease as well as to ascertain the relationship between this cytokine and parameters of disease severity and other measures of inflammation. Levels of TNF-alpha and genotyping for the -308 G-->A polymorphism in the promoter of the TNF-alpha gene were performed in 17 patients with type I Gaucher disease. TNF-alpha levels were compared with the promoter gene polymorphism, and with hematological and other clinical parameters of Gaucher disease. Eight patients (47.1%) were homozygotes (A/A) for the TNF-alpha polymorphism, six patients (35.3%) had the wild type (G/G), and three patients (17.6%) were heterozygotes (G/A). A significant correlation was found between serum TNF-alpha levels and TNF-alpha genotypes for homozygotes versus heterozygotes patients (p = 0.02), with patients homozygous for the polymorphism having the lower levels of serum TNF-alpha relative to heterozygotes with the highest levels. No correlation was found between TNF-alpha genotypes and chitotriosidase levels, a putative biochemical marker for Gaucher disease severity. Because a significant correlation was found between homozygosity for a common promoter polymorphism of TNF-alpha and milder expression i.e. non-neuronopathic form, of Gaucher disease (versus the neuronopathic forms), this may be suggestive of an association between genetic variability in TNF-alpha and phenotypic expression in Gaucher disease. Larger studies will be required.

The N370S (Asn370-->Ser) mutation affects the capacity of glucosylceramidase to interact with anionic phospholipid-containing membranes and saposin C

The properties of the endolysosomal enzyme GCase (glucosylceramidase), carrying the most prevalent mutation observed in Gaucher patients, namely substitution of an asparagine residue with a serine at amino acid position 370 [N370S (Asn370-->Ser) GCase], were investigated in the present study. We previously demonstrated that Sap (saposin) C, the physiological GCase activator, promotes the association of GCase with anionic phospholipid-containing membranes, reconstituting in this way the enzyme activity. In the present study, we show that, in the presence of Sap C and membranes containing high levels of anionic phospholipids, both normal and N370S GCases are able to associate with the lipid surface and to express their activity. Conversely, when the amount of anionic phospholipids in the membrane is reduced (approximately 20% of total lipids), Sap C is still able to promote binding and activation of the normal enzyme, but not of N370S GCase. The altered interaction of the mutated enzyme with anionic phospholipid-containing membranes and Sap C was further demonstrated in Gaucher fibroblasts by confocal microscopy, which revealed poor co-localization of N370S GCase with Sap C and lysobisphosphatidic acid, the most abundant anionic phospholipid in endolysosomes. Moreover, we found that N370S Gaucher fibroblasts accumulate endolysosomal free cholesterol, a lipid that might further interfere with the interaction of the enzyme with Sap C and lysobisphosphatidic acid-containing membranes. In summary, our results show that the N370S mutation primarily affects the interaction of GCase with its physiological activators, namely Sap C and anionic phospholipid-containing membranes. We thus propose that the poor contact between N370S GCase and its activators may be responsible for the low activity of the mutant enzyme in vivo.

A Comprehensive Assessment of Renal Function in Patients With Gaucher Disease

BACKGROUND

Gaucher disease (GD) is caused by deficiency of acid beta-glucocerebrosidase and is the most common lysosomal storage disease. Patients may have massive hepatosplenomegaly, severe bone disease, and, occasionally, pulmonary or neurological involvement. Although other storage diseases, such as Fabry disease, frequently affect the kidneys, reports of renal abnormalities in patients with GD are limited to case reports. Our aim was to perform a comprehensive evaluation of renal function in patients with GD.

METHODS

Evaluation was performed at routine clinic visits and included blood pressure recording and renal ultrasound. Serum chemistries, urinalysis, urine electrolytes, total protein, and tubular proteinuria were assessed, and estimated glomerular filtration rate (GFR) was calculated.

RESULTS

One hundred sixty-one patients underwent evaluation, including 26 children. GFR was significantly greater in patients with GD than in age- and sex-matched healthy controls (P = 0.01 in men, P < 0.001 in women, P = 0.003 in children). Subgroups of patients with markers of more severe disease had a greater GFR than other patients. No patient had decreased renal function. Significant proteinuria was found only in patients with such comorbidities as diabetes mellitus or multiple myeloma. No evidence of renal tubular abnormalities was found, and kidney sonographic appearance and size were normal.

CONCLUSION

Despite the multiorgan nature of the disease, a systematic evaluation did not find renal abnormalities in patients with GD. Glomerular hyperfiltration was observed in a proportion of patients, particularly those with markers of more severe disease. This phenomenon does not seem to be associated with a subsequent decline in renal function.

Gaucher Disease-Associated Glucocerebrosidases Show Mutation-Dependent Chemical Chaperoning Profiles

Gaucher disease is a lysosomal storage disorder caused by deficient glucocerebrosidase activity. We have previously shown that the cellular activity of the most common Gaucher disease-associated glucocerebrosidase variant, N370S, is increased when patient-derived cells are cultured with the chemical chaperone N-nonyl-deoxynojirimycin. Chemical chaperones stabilize proteins against misfolding, enabling their trafficking from the endoplasmic reticulum. Herein, the generality of this therapeutic strategy is evaluated with other glucocerebrosidase variants and with additional candidate chemical chaperones. Improved chemical chaperones are identified for N370S glucocerebrosidase. Moreover, we demonstrate that G202R, a glucocerebrosidase variant that is known to be retained in the endoplasmic reticulum, is also amenable to chemical chaperoning. The L444P variant is not chaperoned by any of the active site-directed molecules tested, likely because this mutation destabilizes a domain distinct from the catalytic domain.

Impaired trafficking of mutants of lysosomal glucocerebrosidase in Gaucher's disease

Gaucher's disease is the most inherited lysosomal storage disorder. Except for a few cases, the broad phenotypic heterogeneity of Gaucher's disease can be neither predicted from defined mutations nor from differences in residual enzyme activity. Here, we analyse the intracellular trafficking of glucocerebrosidase as an underlying mechanism for the expression of the clinical phenotype. Biosynthetic labeling studies combined with immunofluorescence analyses with fibroblasts from patients with the defined mutations N370S, L444P, D409H and G202R unequivocally demonstrate a retarded transport of glucocerebrosidase carrying the mutation N370S and a transport block in the ER of the enzyme with the mutations G202R, L444P and D409H. We asked whether cellular components in the patients' fibroblasts other than glucocerebrosidase are implicated in the onset of the disease. For this, mutant cDNA's corresponding to the phenotypes N370S, G202R and L444P were expressed in the mouse fibroblasts NIH3T3. Essentially similar biochemical and cellular features were revealed as compared to the patients' fibroblasts strongly suggesting that these mutations are exclusively responsible for the characterized phenotypes. Interestingly, the immunoglobulin binding protein (BiP) binds wild type and the mutant N370S but not the G202R and L444P variants suggesting a discriminatory role played by this chaperone associated with the severity of the disease.

Parkinsonism among Gaucher disease carriers

An association between Gaucher disease and Parkinson disease has been demonstrated by the concurrence of Gaucher disease and parkinsonism in rare patients and the identification of glucocerebrosidase mutations in probands with sporadic Parkinson disease. Using a different and complementary approach, we describe 10 unrelated families of subjects with Gaucher disease where obligate or confirmed carriers of glucocerebrosidase mutations developed parkinsonism. These observations indicate that mutant glucocerebrosidase, even in heterozygotes, may be a risk factor for the development of parkinsonism. Understanding the relationship between altered glucocerebrosidase and the development of parkinsonian manifestations will provide insights into the genetics, pathogenesis, and treatment of Parkinson disease.

Use of fluorescent substrates for characterization of Gaucher disease mutations

Gaucher disease results from impaired activity of the lysosomal enzyme beta-glucocerebrosidase. More than 200 mutations within the glucocerebrosidase gene have been associated with this disease. In this study we tested the effect of several mutations (K157Q, D140H, E326K, D140H+E326K, V394L and R463C) on RNA stability, protein stability and activity toward four different fluorescent substrates (LR-12-GC, Bodipy-12-GC, LR-0-PAP-glucose and 4-MUG), using the vaccinia-derived expression system. The results indicated that the K157Q mutation leads to RNA instability, causing low protein levels and a concomitant reduction in beta-glucocerebrosidase activity. All other tested mutations led to production of glucocerebrosidase RNA and protein with stabilities comparable to those of the normal counterpart. The D140H variant exhibited a high activity toward the tested substrates while the variant enzymes containing either the E326K or D140H and E326k mutations together expressed low beta-glucocerebrosidase activity. The V394L variant exhibited low activity toward the tested substrates, while a higher activity was presented by the R463C containing glucocerebrosidase variant. Our results strongly indicated that the LR-12-GC substrate distinguishes between severities of different mutant glucocerebrosidase variants overexpressed in a heterologous system.

[From gene to disease; Gaucher disease]

Gaucher disease is an autosomal recessive inherited lysosomal storage disorder due to mutations in the glucocerebrosidase gene located on chromosome 1q21. Hepatosplenomegaly and bone disease due to massive accumulation of undegraded glucocerebroside in macrophages found in the liver, spleen and bone marrow dominate the clinical picture in type 1 disease. In rare instances (type 2 and 3 disease) the central nervous system is involved. Phenotype-genotype correlations are poor. Diagnosis is possible by enzyme assay at clinical genetic centres in the Netherlands. The availability of effective therapies emphasizes the need for early recognition of the disease.

Long-term expression of the human glucocerebrosidase gene in vivo after transplantation of bone-marrow-derived cells transformed with a lentivirus vector

BACKGROUND

Gaucher disease is a lysosomal storage disorder resulting from a deficiency of glucocerebrosidase (GC). Recently, lentivirus vectors have been developed for efficient gene transfer into hematopoietic stem cells (HSCs). A recombinant lentivirus vector was used to evaluate the transduction of the human GC gene into murine bone-marrow-derived HSCs and its expression in their progeny.

METHODS

Murine HSCs were transduced with lentivirus vector (lenti-EF-GC; MOI = 10-100). We transplanted female wild-type C57BL/6J mice with genetically modified male HSCs via the tail vein.

RESULTS

We show that intravenous transplantation of transduced HSCs has therapeutic potential. Enzyme activity was increased two- to three-fold in various tissues, especially in the hematopoietic system. Numerous transplanted HSCs survived for 6 months and were shown by PCR to contain the provirus genes; the Y chromosome was identified by FISH analysis in the cells of female mouse recipients.

CONCLUSIONS

The recombinant lentiviral vector transduces HSCs that are capable of long-term gene expression in vivo. This approach is potentially useful for the treatment of patents with Gaucher disease and other lysosomal storage disorders.

Mutations in the glucocerebrosidase gene and Parkinson disease: phenotype-genotype correlation

Mutations in the glucocerebrosidase (GBA) gene have been recently identified as contributory to Parkinson disease (PD) in Ashkenazi Jews. In the present study, the clinical characteristics of Ashkenazi patients with PD with GBA mutations (n = 40) were compared to those of Ashkenazi patients with PD without any known GBA mutation (n = 108). The overall clinical manifestations and age at disease onset did not differ in patients with GBA mutations compared to patients without mutations.

Gaucher mutation N188S is associated with myoclonic epilepsy

The recent article by Montfort et al. [2004] reported a functional analysis of 13 glucocerebrosidase alleles, including mutation N188S, which they considered to be a "very mild mutation" or "modifier variant." Our clinical experience with patients carrying this mutation and preliminary protein modeling data lead us to dispute this conclusion.

Blood oxidative stress markers in Gaucher disease patients

BACKGROUND

Gaucher disease (GD) is the most common glycosphingolipidosis resulting in accumulation of glucoceramide. The most effective treatment for this disease is enzyme replacement therapy (ERT) which involves recombinant enzyme infusion. Enzymatic deficiency in GD patients may induce a cascade of events culminating in secondary effects such as the production of reactive oxygen species (ROS). We investigated the relationship between ROS and GD by analyzing blood oxidative stress markers in GD patients submitted to ERT at different stages during the treatment.

METHODS

Blood were collected before and just after enzyme infusion. Red blood cell catalase (CAT), glutathione peroxidase (GPx), superoxide dismutase (SOD) and total glutathione (tGSH), and plasma thiobarbituric acid reactive substances (TBARS) were assayed by spectrophotometry. Homocysteine concentrations and related polymorphisms were also studied. Control individuals matched for sex and age were also analyzed.

RESULTS

Concentrations of homocysteine and TBARS, and GPx enzyme activity were not different in ERT-treated GD patients. CAT activity was higher while SOD was lower in patients compared to controls. No variations in any of these parameters were found before and just after ERT. Regarding tGSH, a significant increase was observed in GD patients after infusion. Genotypic frequencies studied did not differ from controls or other Brazilian samples.

CONCLUSION

ERT-treated GD patients show an improvement in antioxidant capacity, which is further increased just after recombinant enzyme infusion.

Gaucher disease mouse models: point mutations at the acid beta-glucosidase locus combined with low-level prosaposin expression lead to disease variants

Gaucher disease is a common lysosomal storage disease caused by a defect of acid beta-glucosidase (GCase). The optimal in vitro hydrolase activity of GCase requires saposin C, an activator protein that derives from a precursor, prosaposin. To develop additional models of Gaucher disease and to test in vivo effects of saposin deficiencies, mice expressing low levels (4--45% of wild type) of prosaposin and saposins (PS-NA) were backcrossed into mice with specific point mutations (V394L/V394L or D409H/D409H) of GCase. The resultant mice were designated 4L/PS-NA and 9H/PS-NA, respectively. In contrast to PS-NA mice, the 4L/PS-NA and 9H/PS-NA mice displayed large numbers of engorged macrophages and nearly exclusive glucosylceramide (GC) accumulation in the liver, lung, spleen, thymus, and brain. Electron microscopy of the storage cells showed the characteristic tubular storage material of Gaucher cells. Compared with V394L/V394L mice, 4L/PS-NA mice that expressed 4--6% of wild-type prosaposin levels had approximately 25--75% decreases in GCase activity and protein in liver, spleen, and fibroblasts. These results imply that reduced saposin levels increased the instability of V394L or D409H GCases and that these additional decreases led to large accumulations of GC in all tissues. These models mimic a more severe Gaucher disease phenotype and could be useful for therapeutic intervention studies.

Recent clinical progress in Gaucher disease

PURPOSE OF REVIEW

Major clinical advances in Gaucher disease focus on detection, prediction and treatment of variant phenotypes.

RECENT FINDINGS

The advent of efficacious enzyme therapy has emphasized the importance of early diagnosis and intervention to prevent the morbid manifestations of the disease including organomegaly, growth and pubertal retardation, and osteopenia/osteoporosis. Genotype/phenotype correlations provide some guidance for prognosis by categorical distinctions of nonneuronopathic (type 1) and neuronopathic (types 2 and 3) variants. Early detection of children genetically predisposed to severe disease are a management challenge for the pediatrician and metabolic physician. The development of specific therapeutic goals provides a framework for assessments of visceral therapeutic and palliative responses in children with type 1, and types 2 and 3, respectively.

SUMMARY

The pediatrician plays a major role in these clinical and genetically based decisions.

Biochemical properties of beta-glucosidase in leukocytes from patients and obligated heterozygotes for Gaucher disease carriers

BACKGROUND

Gaucher's disease (GD) is a disorder caused by the deficiency of lysosomal beta-glucosidase, an enzyme that participates in the degradation of glycosphingolipids. Deficiency of this enzyme results in the storage of glucocerebrosides in lysosomes of macrophage. No studies are available in the literature comparing biochemical and kinetic behavior of this enzyme in leukocytes and fibroblasts from normal individuals, obligate heterozygotes and patients with GD.

METHODS

The behavior of beta-glu in terms of optimum pH, heat stability, Km and Vmax in leukocytes from patients with GD and obligated heterozygotes with different genotypes and normal individuals were characterized.

RESULTS

Optimum pH was similar in all groups analyzed. In terms of Km and Vmax, several differences among heterozygotes and homozygotes groups and among these groups and normal enzyme were observed. Enzyme from all groups were inactivated when preincubated at 60 degrees C, but some enzymes were more stable than other. Results showed a different behavior of the enzyme in the 3 groups under analysis. Such behavior varied according to individual mutation.

CONCLUSIONS

The catalytic gradient presented by beta-glu allowed the correlation of N370S mutation-which presented more stable biochemical properties-with the non-neurological clinical condition of the disease and the catalytically less stable mutation (D409H), with the neurological clinical condition of GD. This study contributes to a better understanding of the repercussion of the different mutations on the protein function, thus allowing to predict the severity of such complex metabolic disorder and to anticipate the most appropriate intervention for each case specifically.

Perinatal lethal Gaucher disease: a distinct phenotype along the neuronopathic continuum

Gaucher disease, the inherited deficiency of glucocerebrosidase, is characterized by significant genetic and phenotypic heterogeneity. At the extreme end of the phenotypic continuum is the perinatal lethal variant, typically presenting in utero or during the neonatal period as hydrops and/orcongenital ichthyosis, with severe and progressive neurological involvement. Insights from the null-allele Gaucher mouse model contributed to the identification of this distinct phenotype, which has unique epidermal involvement. While multiple mutations are encountered, many affected infants are homozygous for recombinant alleles. The diagnosis is often missed due to the early lethality and the failure to recognize the association between lysosomal disorders and hydrops fetalis. The incidence of severe perinatal Gaucher disease may prove more common than currently appreciated with greater physician awareness of the disorder.

A mutation within the saposin D domain in a Gaucher disease patient with normal glucocerebrosidase activity

Only two Gaucher disease (GD) patients bearing mutations in the prosaposin gene (PSAP), and not in the glucocerebrosidase gene (GBA), have been reported. In both cases, one mutant allele remained unidentified. We report here the identification of the second mutation in one of these patients, being the first complete genotype described so far in a SAP-C-deficient GD patient. This mutation, p.Q430X, is the first one reported in the saposin D domain and probably produces a null allele by nonsense mediated mRNA decay.