Secondary sphingolipid accumulation in a macrophage model of Gaucher disease

Glucosylceramide (GC) is a metabolic intermediate derived from the cellular turnover of membrane gangliosides and globosides. The catabolism of GC is impaired in Gaucher disease (GD) and consequently GC accumulates in affected cells leading to clinical manifestations of GD. The primary cell type affected in GD is the macrophage, and we investigated what effect excess GC has on the spatial coordination of other sphingolipids and phospholipids in a macrophage model of GD. A THP-1 macrophage model of GD was established by supplementation of the culture media with conduritol B epoxide, a specific irreversible inhibitor of acid beta-glucosidase. This cell model accumulated up to 12-fold more GC compared with untreated cells. Sub-cellular fractionation showed that, initially, the primary site of GC accumulation was the lysosome but as more GC accumulated it distributed relatively evenly across the cell and was present in all sub-cellular fractions. We also observed secondary elevations in the concentrations of ceramide, di- and trihexosylceramide and phosphatidylglycerol, which all had similar sub-cellular distributions to that of GC, initially increasing in the lysosome and then throughout the sub-cellular compartments. Our results suggest that with excess GC accumulation, the pathway trafficking GC to the lysosome becomes saturated and GC as well as other sphingolipids are shunted to other parts of the cell. The presence of these sphingolipids at non-physiological concentrations is likely to interfere with other biochemical pathways outside the lysosome, leading to cell dysfunction and ultimately pathological mechanisms apparent in GD, such as macrophage activation.

Outcome of type III Gaucher disease on enzyme replacement therapy: review of 55 cases

The European Task Force for Neuronopathic Gaucher Disease (NGD) met in 2006 to review its 2001 guidelines. Fifty-five patients from five European countries were reviewed; 29 were male and 26 female. The majority of the patients were homozygous for the L444P mutation. All had been on enzyme replacement therapy (ERT). However, there was considerable variation in the dose of ERT, as well as an uneven distribution of risk factors. Thus, the oldest patients were on the lowest doses, and several had had a total splenectomy, while the youngest patients had a high proportion of compound heterozygosity and were on the highest doses, and very few had had a splenectomy. This heterogeneity rendered analysis very difficult. However, some observations were possible. The older patients appeared to remain relatively stable despite a low dose of ERT. In the younger patients, there was no clear effect of high-dose ERT. However, the period of follow-up was too short in many patients to draw valid conclusions. These data will be used to draw up revised guidelines.

[Biochemical and molecular diagnosis of Gaucher disease in Tunisia]

Our study was carried out at a family from the Sahel (Tunisia). The father (index case) and his two children (son and daughter). The father beta-glucocerebrosidase (GCB) activity showing a deficit. These biochemical analyses are supplemented by molecular studies: enzymatic digestion and the direct sequencing. Two mutations were analysed, the p.Asn 370 Ser and the p.Leu 444 Pro. The DNA sequencing confirmed the presence of the homozygous genotype of this p.Asn 370 Ser in the father DNA and the heterozygous one in the two children DNA. It has no detection of the 55 pb deletion in exon 9 among all the specimens of DNA treated. The mutation p.Asn 370 Ser is associated with Gaucher disease type 1 correlated of a total absence of neurological involvements.

Molecular characterization of type 3 (neuronopathic) Gaucher disease in Thai patients

Gaucher disease is an autosomal recessive lysosomal storage disorder due to deficiency of the lysosomal enzyme glucocerebrosidase. Three clinical phenotypes, type 1, nonneuronopathic; and types 2 and 3, acute and subacute neuronopathic are recognized. The incidence of Gaucher disease in the Thai population is unknown, but likely under-diagnosed. We performed molecular analysis in four patients, from three sibships, with type 3 Gaucher disease. Four mutant glucocerebrosidase (GBA) alleles were identified including two novel splice site mutations, IVS6-1G>C and IVS9-3C>G; both are predicted to result in truncated protein products, p.F255fsX256, and p.K464fsX487 and p.S463fsX480, respectively. One patient, homozygous for the L444P point mutation, had a "Norbottnian-like" phenotype, with more severe visceral involvement, kyphosis, barreled chest, and no neurological involvement other than supranuclear gaze palsy. These molecular studies of neuronopathic Gaucher disease will provide additional genotype-phenotype correlation particularly in non-Caucasian population.

Carrier screening for Gaucher disease: lessons for low-penetrance, treatable diseases

CONTEXT

The aim of carrier screening is to prevent severe, untreatable genetic disease by identifying couples at risk before the birth of an affected child, and providing such couples with options for reproductive outcomes for affected pregnancies. Gaucher disease (GD) is an autosomal recessive storage disorder, relatively frequent in Ashkenazi Jews. Carrier screening for GD is controversial because common type 1 GD is often asymptomatic and effective treatment exists. However, screening is offered to Ashkenazi Jews worldwide and has been offered in Israel since 1995.

OBJECTIVE

To examine the scope and outcomes of nationwide GD screening.

DESIGN, SETTING, AND PARTICIPANTS

All Israeli genetic centers provided data on the number of individuals screened for GD, the number of carriers identified, the number of carrier couples identified, and the mutations identified in these couples between January 1, 1995, and March 31, 2003. Carrier couples were interviewed via telephone between January 21, 2003, and August 31, 2004, using a structured questionnaire for relevant outcome measures.

MAIN OUTCOME MEASURES

Screening scope (number of testing centers, tested individuals, and carrier couples), screening process (type of pretest and posttest consultations), and screening outcomes (utilization of prenatal diagnosis and pregnancy terminations).

RESULTS

Between January 1, 1995, and March 31, 2003, 10 of 12 Israeli genetic centers (83.3%) offered carrier screening. Carrier frequency was 5.7%, and 83 carrier couples were identified among an estimated 28,893 individuals screened. There were 82 couples at risk for offspring with type 1 GD. Seventy of 82 couples (85%) were at risk for asymptomatic or mildly affected offspring and 12 of 82 couples (15%) were at risk for moderately affected offspring. At postscreening, 65 interviewed couples had 90 pregnancies, and prenatal diagnosis was performed in 68 pregnancies (76%), detecting 16 fetuses with GD (24%). Pregnancies were terminated in 2 of 13 fetuses (15%) predicted to be asymptomatic or mildly affected and 2 of 3 fetuses (67%) with predicted moderate disease. There were significantly fewer pregnancy terminations in couples who in addition to genetic counseling had medical counseling with a GD expert (1 of 13 [8%] vs 3 of 3 with no medical counseling [100%], P = .007).

CONCLUSIONS

In this study of GD screening among Ashkenazi Jewish couples in Israel, most couples did not terminate affected pregnancies, although screening was associated with a few pregnancy terminations. The main possible benefit was providing couples with knowledge and control. The divergence of these outcomes from stated goals of screening programs is likely to confront carrier screening programs for low-penetrance diseases.

[Distribution of mutations of acid beta-D-glucosidase gene (GBA) among 68 Russian patients with Gaucher's disease]

Gaucher disease (GD) is the most frequent lysosomal storage disease presenting in all populations. Mutations in the acid beta-D-glucosidase gene (GBA) cause development of GD, resulting in a decrease or full loss of activity of this enzyme. We report here the results of the molecular-genetic analysis in 68 Russian GD patients from 65 families with the three types of the disease. We have identified 126 mutation alleles from 136 investigate alleles. In addition to known mutations p.N370S, c.1263-1317del (del55), p.L444P, p.R463C, Rec NciI, we identified rare mutations p.R120W, p.R170C, p.W184R, p.G202R, Rec C, presenting in other populations and mutations p.P236T, p.L249Q, p.L288P, p.P319S, p.V352M, p.W381X, p.A384D which are had not been described before.

Type 1 Gaucher disease: null and hypomorphic novel chitotriosidase mutations-implications for diagnosis and therapeutic monitoring

Human plasma chitotriosidase (Chito) is a useful diagnostic and therapeutic biomarker for Type 1 Gaucher disease (GD). However, approximately 40% of Caucasians are heterozygous or homozygous for a common null mutation, c.1049_1072dup24 (dup24) in the chitotriosidase gene (chitinase 1, CHIT1), that complicates interpretation for heterozygotes and precludes use for null homozygotes. 320 Type 1 GD patients were screened for CHIT1 genotype and plasma Chito enzyme levels; 37% were heterozygous and 4% were homozygous for the CHIT1 dup24 allele. Four patients who had no or very low plasma Chito activities had wild-type (wt)/dup24 or wt/wt CHIT1 genotypes, suggesting the presence of other mutations. Sequencing their CHIT1 genes revealed three novel mutations: p.E74K (E74K), p.G102S (G102S), and a complex exon 10 lesion (c.[1060G>A; 1155G>A; 1156+5_1156+8delGTAA], p.[G354R; L385L; missplicing], designated "complex E/I-10"). The G102S mutation was common in Type 1 GD patients and controls ( approximately 30% of alleles). In contrast, the E74K mutation was rare, present only in three Type 1 GD patients ( approximately 1% of alleles), all of Ashkenazi Jewish (AJ) descent, but it was not found in normal controls. The complex E/I-10 mutation occurred in two Caribbean Hispanic/African Type 1 GD patients and was present in 0 to 6% of alleles among normal controls from different populations. In vitro expression demonstrated that the E74K and G102S alleles had approximately 51% and approximately 23% of wild-type Chito catalytic efficiency, respectively. Expression of the G354R allele alone or with the L385L silent substitution did not produce detectable Chito activity or protein. RNA studies indicated that the complex E/I-10 allele also caused missplicing. Recognition of these mutations, particularly G102S, will facilitate the use and interpretation of plasma Chito activities for disease diagnosis, estimating disease severity, and monitoring therapeutic efficacy in GD.

Production of glucocerebrosidase with terminal mannose glycans for enzyme replacement therapy of Gaucher's disease using a plant cell system

Gaucher's disease, a lysosomal storage disorder caused by mutations in the gene encoding glucocerebrosidase (GCD), is currently treated by enzyme replacement therapy using recombinant GCD (Cerezyme) expressed in Chinese hamster ovary (CHO) cells. As complex glycans in mammalian cells do not terminate in mannose residues, which are essential for the biological uptake of GCD via macrophage mannose receptors in human patients with Gaucher's disease, an in vitro glycan modification is required in order to expose the mannose residues on the glycans of Cerezyme. In this report, the production of a recombinant human GCD in a carrot cell suspension culture is described. The recombinant plant-derived GCD (prGCD) is targeted to the storage vacuoles, using a plant-specific C-terminal sorting signal. Notably, the recombinant human GCD expressed in the carrot cells naturally contains terminal mannose residues on its complex glycans, apparently as a result of the activity of a special vacuolar enzyme that modifies complex glycans. Hence, the plant-produced recombinant human GCD does not require exposure of mannose residues in vitro, which is a requirement for the production of Cerezyme. prGCD also displays a level of biological activity similar to that of Cerezyme produced in CHO cells, as well as a highly homologous high-resolution three-dimensional structure, determined by X-ray crystallography. A single-dose toxicity study with prGCD in mice demonstrated the absence of treatment-related adverse reactions or clinical findings, indicating the potential safety of prGCD. prGCD is currently undergoing clinical studies, and may offer a new and alternative therapeutic option for Gaucher's disease.

Movement and mood disorder in two brothers with Gaucher disease

Gaucher disease (GD) is a lysosomal storage disorder with a wide spectrum of phenotypic presentations. We report the case histories of two adult brothers with GD who developed both parkinsonism and psychiatric symptoms. Direct sequencing and real-time polymerase chain reaction were used to establish that the patients were homozygous for mutation L444P. While parkinsonism has been described previously in GD, these patients had atypical features, including a complicated mood disorder. The comorbidity of GD and a mood disorder is a new finding, as psychiatric manifestations of GD have been described rarely. The etiology of the mental illness could be related to the processes contributing to the development of parkinsonism.

Pseudo-Gaucher cell proliferation associated with myelodysplastic syndrome

We report an extremely rare case of pseudo-Gaucher cell proliferation with myelodysplastic syndrome (MDS). A 77-year old Japanese man was referred to our hospital with splenomegaly and thrombocytopenia, and subsequent bone marrow aspiration revealed infiltrates of foamy vacuolated macrophages without any evidence of other morphologic abnormalities. A karyotype analysis showed the presence of 46,XY,del(20)(q11) in 20 of 20 examined bone marrow cells. We performed a splenectomy, and the resulting pathologic findings revealed massive infiltration of foamy vacuolated macrophages, which were morphologically compatible with Gaucher cells. The activities of beta-glucosidase and acid sphingomyelinase were within normal ranges; therefore, the foamy vacuolated macrophages were considered pseudo-Gaucher cells. A diagnosis of MDS, subclassified as refractory anemia, was then made according to World Health Organization classification guidelines. Pseudo-Gaucher cell proliferation and infiltration might therefore be observed in other patients presenting with MDS.

Gaucher disease: different clinical manifestations associated with a rare mutation (R48W) in a Lebanese family

Gaucher disease (GD) is the most frequently encountered lysosomal storage disease, caused by autosomal recessive inborn defects in the glucocerebrosidase gene (GBA) at 1q21. The disease is most common in the Ashkenazi Jewish population. GD can present with a vast phenotypic heterogeneity, which can be predicted to some extent from the underlying mutation. In this report, we describe a Lebanese Arab family with multigenerational incidence of GD caused by a heterozygous genotype of a rare mutation, R48W, and a common one, L444P. Our patients' clinical course is described. We also review the English literature for patients with this rare mutation.

Gaucher disease

Although Gaucher disease is a rare disorder, recent developments in novel means for therapeutic intervention have invigorated both academic research and pharmaceutical industry discovery programmes. The common mutations found in the lysosomal enzyme deficient in Gaucher disease, beta-glucocerebrosidase, earmark these proteins for destruction by the endoplasmic reticulum-localised protein folding machinery, resulting in enzyme insufficiency, lysosomal glycolipid storage and subsequent pathology. However, many of these mutants can be rescued from global misfolding to preserve glycolipid substrate binding and eventual catalysis in the lysosome, by the addition of subinhibitory concentrations of pharmacologically active small molecules. This novel, chaperon-mediated approach has benefited from insights into the molecular understanding of beta-glucocerebrosidase structure, drug design and development in cellular models for disease.

Imiglucerase (Cerezyme) improves quality of life in patients with skeletal manifestations of Gaucher disease

Health-related quality of life (HRQOL) can be diminished in patients with type 1 Gaucher disease (GD) owing to the debilitating clinical manifestations of this chronic disease. This study investigates the impact of imiglucerase treatment on HRQOL of patients with type 1 GD and bone involvement. Thirty-two previously untreated type 1 GD patients with skeletal manifestations including bone pain, medullary infarctions, avascular necrosis, and lytic lesions received biweekly imiglucerase (at 60 U/kg). The Short Form-36 Health Survey (SF-36) was administered at regular intervals to assess HRQOL. Mean baseline SF-36 physical component summary (PCS) scores were diminished relative to US general population norms. Low PCS scores were more common in patients with medullary infarction, lytic lesions, and higher bone pain severity scores. Statistically significant improvements were observed for all eight SF-36 subscales after 2 years of treatment. Mean PCS and mental component summary (MCS) scores increased to within the normal range after 2 years of treatment and were maintained through year 4. Large HRQOL gains were observed even in patients with the most advanced disease and lowest baseline PCS scores. Imiglucerase treatment has a significant positive impact on HRQOL of type 1 GD patients with skeletal disease, including those with bone infarctions, lytic lesions, and avascular necrosis.

Changes in macrophage morphology in a Gaucher disease model are dependent on CTP:phosphocholine cytidylyltransferase α

We have recently shown that phosphatidylcholine (PC) metabolism is altered in a macrophage model of Gaucher disease. We now demonstrate that treatment of macrophages with conduritol-B-epoxide (CBE), a glucocerebrosidase inhibitor, results in elevated activity of CTP:phosphocholine cytidylyltransferase (CCT), the rate-limiting enzyme in the pathway of PC biosynthesis. Furthermore, we provide evidence for a role for CCT in Gaucher macrophage growth by using macrophages derived from a genetically modified mouse which lacks a specific CCT isoform, CCTalpha, in macrophages. Upon CBE-treatment, macrophage size, analyzed by microscopy and by FACS, was significantly increased in macrophages from control mice, but did not increase, or increased to a much lower extent, in CCTalpha-/- macrophages. Together, these results suggest that the increase in PC biosynthesis is mediated via CCTalpha, and suggests a possible role for macrophage CCTalpha in Gaucher disease pathology.

[Detection of the frequencies of GBA gene major mutations in patients with Gaucher disease in Ukraine]

The molecular diagnostics of 27 from 26 Ukrainian families has been performed. The common mutations in GBA gene (N370S, L444P and 84GG) accounted for up to 58% of all cases: mutation N370S was detected in 42.3% alleles, mutation L444P was observed in 15.4% alleles and mutation 84GG was not found at all. The other mutations were: P178S, W184R and Rec Nci I (in compounds with N370S) in the patients with nonneuronopathic form of Gaucher disease, and the genotypes G377S/c 999G --> A and D409H/R120W/G202R were detected in patients with chronic neuronopathic form of Gaucher disease. The data analysis of the genotype and disease progression in the patients allows confirming the known genotype-phenotype correlation.

Genetic and clinical features of patients with Gaucher disease in Hungary

The aim of this study was to identify mutations in the gene encoding for lysosomal beta-glucocerebrosidase (GBA; gene symbol, GBA) in Hungarian patients with Gaucher disease (GD), and to study genotype-phenotype relationships. Genotypes and allele variations in 27 patients with type I GD of 25 unrelated families were studied. Of the 54 mutant alleles, we detected 38 frequent (N370S, 22/54; RecNciI, 8/54; L444P, 8/54) and 9 rare (N188S, R257Q, R285C, G377S, R120W, T323I, 84GG, 1263-1317del and 1263-1317del/RecTL) mutations. In addition, we identified two novel mutations. The N370S/RecNciI genotype found in 8 patients and the N370S/L444P genotype found in 5 patients were the most frequent genotypes in this cohort. In 22 patients the mutations occurred in heterozygosity with the N370S sequence variant, and one patient was homozygous for the L444P mutation. These data suggest that N370S, RecNciI, and L444P are the most prevalent mutations in Hungarian patients with GD. This mutation profile is characteristic for a Caucasian (non-Jewish) population. The c.260G>A and c.999G>A missense mutations are described here for the first time in GD patients contributing to the panel of reported GBA mutations.

Monitoring of Gaucher patients with a novel chitotriosidase assay

BACKGROUND

Chitotriosidase (CT) is a surrogate plasma marker for Gaucher disease. The enzyme is released by storage cells and is on average thousand fold elevated in serum of Gaucher patients. Plasma CT level is measured with the substrate 4-methylumbelliferyl (4MU)-chitotriose or 4MU-chitobiose. Given the limitations associated with the use of these substrates, a novel substrate, 4MU-deoxychitobiose, has recently been conceived.

METHODS

Chitotriosidase activity was measured with all three substrates in serum samples from 91 type 1 Gaucher patients. Glucocerebrosidase and chitotriosidase genotypes were determined as well as disease parameters.

RESULTS

Chitotriosidase activity when measured with 4MU-deoxychitobiose gave higher values and was proportional to enzyme concentration over a much larger range as compared to the other two substrates. Patients that were carrier for the common CT mutation showed on average half the activity of those with wild type CT genotype. Plasma CT levels correlated best with combined liver and spleen volume: r=0.53 (p<0.001).

CONCLUSIONS

The use of 4MU-deoxychitobiose as substrate renders a substantial improved CT activity assay and may further facilitate accurate laboratory monitoring of Gaucher patients.

Chitotriosidase levels in healthy elderly subjects

Chitotriosidase (CHIT) belongs to the family of glycosylhydrolases and is highly homologous to chitinases from lower organisms. The enzyme CHIT is of interest for clinical reasons, because it is selectively expressed in chronically activated tissue macrophages. In most ethnic groups, approximately 6% of all individuals are homozygous for CHIT deficiency. Pathological tissue macrophages in several disease conditions massively express CHIT. A shared feature of such cells in the different conditions is the accumulation of lipid material in the lysosomal apparatus. Serum CHIT activity is significantly increased in individuals suffering from atherosclerosis disease and is related to the severity of the atherosclerotic lesion, suggesting a possible role as atherosclerotic extent marker. Our objective is to determine the levels of serum CHIT activity in healthy elderly subjects. Healthy 90 (between 65-94 years old) elderly people and 69 (between 20-44 years old) young people were chosen. Serum CHIT enzymatic activity was determined with the flurometric enzyme activity assay using artificial 4-MU substrate. We found CHIT activity 270 +/- 21 (nmol/mL/h) (values are mean +/- SD) in elderly people and 136 +/- 17 in young people. There are statistical differences between elderly and young subjects.

High frequency of mutation G377S in Brazilian type 3 Gaucher disease patients

Gaucher disease (GD), the most prevalent lysosome storage disorder, presents an autosomal recessive mode of inheritance. It is a paradigm for therapeutic intervention in medical genetics due to the existence of effective enzyme replacement therapy. We report here the analysis of GD in 262 unrelated Brazilian patients, carried out in order to establish the frequency of the most common mutations and to provide prognostic information based on genotype-phenotype correlations. Among 247 type 1 GD patients, mutation N370S was detected in 47% of all the alleles, but N370S/N370S homozygosity was found in only 10% of the patients, a much lower frequency than expected, suggesting that most individuals presenting this genotype may not receive medical attention. Recombinant alleles were detected at a high frequency: 44% of the chromosomes bearing mutation L444P had other mutations derived from the pseudogene sequence, present in 25% of patients. Three neuronopathic type 2 patients were homozygous for L444P, all presenting additional mutations (E326K or recombinant alleles) that probably lead to the more severe phenotypes. Six children, classified as type 1 GD patients, had a L444P/L444P genotype, showing that neuronopathic symptoms may only manifest later in life. This would indicate the need for a higher treatment dose during enzyme replacement therapy. Finally, mutation G377S was present in 4 homozygous type 1 patients and also in compound heterozygosity in 5 (42%) type 3 patients. These findings indicate that G377S cannot be unambiguously classified as mild and suggest an allele-dose effect for this mutation.

Enzyme enhancement activity of N-octyl-β-valienamine on β-glucosidase mutants associated with Gaucher disease

Gaucher disease (GD), caused by a defect of beta-glucosidase (beta-Glu), is the most common form of sphingolipidosis. We have previously shown that a carbohydrate mimic N-octyl-beta-valienamine (NOV), an inhibitor of beta-Glu, could increase the protein level and enzyme activity of F213I mutant beta-Glu in cultured GD fibroblasts, suggesting that NOV acted as a pharmacological chaperone to accelerate transport and maturation of this mutant enzyme. In the current study, NOV effects were evaluated in GD fibroblasts with various beta-Glu mutations and in COS cells transiently expressing recombinant mutant proteins. In addition to F213I, NOV was effective on N188S, G202R and N370S mutant forms of beta-Glu, whereas it was ineffective on G193W, D409H and L444P mutants. When expressed in COS cells, the mutant proteins as well as the wild-type protein were localized predominantly in the endoplasmic reticulum and were sensitive to Endo-H treatment. NOV did not alter this localization or Endo-H sensitivity, suggesting that it acted in the endoplasmic reticulum. Profiling of N-alkyl-beta-valienamines with various lengths of the acyl chain showed that N-dodecyl-beta-valienamine was as effective as NOV. These results suggest a potential therapeutic value of NOV and related compounds for GD with a broad range of beta-Glu mutations.

Gaucher disease among Chinese patients: Review on genotype/phenotype correlation from 29 patients and identification of novel and rare alleles

Gaucher disease, the most prevalent lysosomal storage disease, results from an inherited deficiency in the enzyme glucocerebrosidase. Three clinical forms of Gaucher disease have been described: Type 1 non-neuronopathic, Type 2 acute neuronopathic, and Type 3 subacute neuronopathic. Although Gaucher disease is panethnic, its presentation reveals some ethnic-specific characteristics. The Type 1 form is most common among Caucasian patients. In contrast, the majority of Chinese Gaucher disease patients have early age of onset, severe hematological and skeletal complications, and often neurological involvement, resulting in early childhood death. In this report, we review 29 cases of Gaucher disease from 23 unrelated patients and 6 patients from 3 non-consanguineous families. Among these patients, 13 were diagnosed as Type 1, 10 as Type 2, and 6 as Type 3. A novel mutation, del 205-209ACCTT, was identified in the heterozygous form with mutation R353W (c.1174C>T) by DNA sequence analysis in 2 Type 1 patients who are sibs. Mutation R353W was also found in the heterozygous form in 3 other Type 1 patients, with mutation L444P in 2 sibs and a second unknown Gaucher allele in the third patient. The Gaucher genotypes of the remaining Type 1 patients were F37V/L444P, G46E/L444P, R48W/R120W, N188S/L444P, Y205C/L444P, N370S/L444P, and L444P/unknown. It was noted that mutation N370S in the patient was linked to the pv1.1(-)(1) haplotype present in Jewish patients. Among the Type 2 patients, L444P was present in the heterozygous form with mutation F213I, L385P, or the complex allele (RecNci) in 5 patients. The second most common mutation, F213I, was found in the heterozygous form in 6 patients with mutations N382K, L383R, or L444P. The other mutations found in the Type 2 patients were P122L, V375L, Y363C, M416V, and 383-400del. The genotypes of the 6 Type 3 patients identified were D409H/D409H, D409H/G202R, G46E/N188S, N188S/unknown, and L444P/L444P. While D409H has been reported as being associated with cardiovascular/ocular involvements in Gaucher disease, there have been no such complications in these patients. As noted, the majority of the Gaucher mutations we identified in the Chinese patients were either rare or absent in other populations. With the exception of N370S and R353W found only in the Type 1 form, the majority of these mutations are severe ones that result in poor prognosis and often Types 2 and 3 Gaucher disease.

Congenital Gaucher disease with nonimmune hydrops/erythroblastosis, infantile arterial calcification, and neonatal hepatitis/fibrosis. Clinicopathologic report with enzymatic and genetic analysis

The findings in a stillborn female fetus of 31 weeks' gestation with congenital Gaucher disease, nonimmune hydrops/erythroblastosis, infantile arterial calcification, and neonatal hepatitis/fibrosis are presented, the first report of this complete constellation. Prior reports describe two similar patients. One lacked the hepatocellular features of giant cell hepatitis although manifesting hepatic fibrosis; the second lacked hepatic pathology. The diagnosis of Gaucher disease herein was established by microscopic examination of the proband, enzymatic analysis of trophoblast, and enzymatic and genetic study of the parents. The father was heterozygous for a recombinant glucocerebrosidase gene; the mother demonstrated a unique frame shift mutation. Thus the fetus is a compound heterozygote for a null and a severe mutation. Studies of parental DNA were negative for the D409H mutation of type IIIc Gaucher disease. Genetic studies were not performed of the ENPP1 gene, mutations of which are associated with idiopathic infantile arterial calcification.

Mutation analysis and genotype/phenotype relationships of Gaucher disease patients in Spain

Mutations in the glucocerebrosidase (GBA) gene cause Gaucher disease (GD). The aim of this study was to characterise the GBA mutations and analyze genotype/phenotype relationships in 193 unrelated patients from the Spanish GD Registry. We have identified 98.7% of the mutated GBA alleles, finding 56 different GBA mutations and 66 genotypes causing GD in Spain: 47 previously described mutations and 9 novel mutations (4 missense R395C, R463H, W312R and V398I, 1 nonsense R359X, 4 frameshift c.708delC, c.1214-1215delGC, c.1439-1445del7 and c.42-65del24). The most prevalent mutations were N370S and L444P, accounting for 68.7% of the mutated alleles. A wide phenotypic difference was observed within each genotypic group, and 9% of diagnosed type 1 patients developed neurological involvement including parkisonism, tremor, hypoacusia and eye movements. All of these findings indicate that there is a significant genotypic heterogeneity that explains the huge phenotypic variation among Spanish GD patients.

Combined saposin C and D deficiencies in mice lead to a neuronopathic phenotype, glucosylceramide and α-hydroxy ceramide accumulation, and altered prosaposin trafficking

Saposins (A, B, C and D) are approximately 80 amino acid stimulators of glycosphingolipid (GSL) hydrolases that derive from a single precursor, prosaposin. In both humans and mice, prosaposin/saposin deficiencies lead to severe neurological deficits. The CD-/- mice with saposin C and D combined deficiencies were produced by introducing genomic point mutations into a critical cysteine in each of these saposins. These mice develop a severe neurological phenotype with ataxia, kyphotic posturing and hind limb paralysis. Relative to prosaposin null mice ( approximately 30 days), CD-/- mice had an extended life span ( approximately 56 days). Loss of Purkinje cells was evident after 6 weeks, and storage bodies were present in neurons of the spinal cord, brain and dorsal root ganglion. Electron microscopy showed well-myelinated fibers and axonal inclusions in the brain and sciatic nerve. Marked accumulations of glucosylceramides and alpha-hydroxy ceramides were present in brain and kidney. Minor storage of lactosylceramide (LacCer) was observed when compared with tissues from the prosaposin null mice, suggesting a compensation in LacCer degradation by saposin B for the saposin C deficiency. Skin fibroblasts and tissues from CD-/- mice showed an increase of intracellular prosaposin, impaired prosaposin secretion, deficiencies of saposins C and D and decreases in saposins A and B. In addition, the deficiency of saposin C in CD-/- mice resulted in cellular decreases of acid beta-glucosidase activity and protein. This CD null mouse model provides a tool to explore the in vivo functional interactions of saposins in GSL metabolism and lysosomal storage diseases, and prosaposin's physiological effects.

Chitotriosidase: the yin and yang

The enzyme chitotriosidase (ChT), the human analogue of chitinases from non-vertebrate species, is one of the most abundant and indicative proteins secreted by activated macrophages. Its enzymatic activity is elevated in serum of patients suffering from Gaucher's disease type 1 and in some other inherited lysosomal storage disorders, as well as in diseases in which macrophages are activated. The last decade has witnessed the appearance of a substantial number of studies attempting to unravel its cellular functions, which have yet not been fully defined. A great deal of progress has been made in the study of the physiological roles of ChT. This review is looks at the key areas of investigations addressed to further illuminate whether ChT activation might have different functional meanings in various diseases.

The biology of the Gaucher cell: the cradle of human chitinases

Gaucher disease (GD) is the most common lysosomal storage disorder and is caused by inherited deficiencies of glucocerebrosidase, the enzyme responsible for the lysosomal breakdown of the lipid glucosylceramide. GD is characterized by the accumulation of pathological, lipid laden macrophages, so-called Gaucher cells. Following the development of enzyme replacement therapy for GD, the search for suitable surrogate disease markers resulted in the identification of a thousand-fold increased chitinase activity in plasma from symptomatic Gaucher patients and that decreases upon successful therapeutic intervention. Biochemical investigations identified a single enzyme, named chitotriosidase, to be responsible for this activity. Chitotriosidase was found to be an excellent marker for lipid laden macrophages in Gaucher patients and is now widely used to assist clinical management of patients. In the wake of the identification of chitotriosidase, the presence of other members of the chitinase family in mammals was discovered. Amongst these is AMCase, an enzyme recently implicated in the pathogenesis of asthma. Chitinases are omnipresent throughout nature and are also produced by vertebrates in which they play important roles in defence against chitin-containing pathogens and in food processing.

Effect of mannose chain length on targeting of glucocerebrosidase for enzyme replacement therapy of Gaucher disease

Recombinant human glucocerebrosidase (imiglucerase, Cerezyme) is used in enzyme replacement therapy for Gaucher disease. Complex oligosaccharides present on Chinese hamster ovary cell-expressed glucocerebrosidase (GCase) are enzymatically remodeled into a mannose core, facilitating mannose receptor-mediated uptake into macrophages. Alternative expression systems could be used to produce GCase containing larger oligomannose structures, offering the possibility of an improvement in targeting to macrophages. A secondary advantage of these expression systems would be to eliminate the need for carbohydrate remodeling. Here, multiple expression systems were used to produce GCase containing primarily terminal oligomannose, from Man2 to Man9. GCase from these multiple expression systems was compared to Cerezyme with respect to affinity for mannose receptor and serum mannose-binding lectin (MBL), macrophage uptake, and intracellular half-life. In vivo studies comparing clearance and targeting of Cerezyme and the Man9 form of GCase were carried out in a Gaucher mouse model (D409V/null). Mannose receptor binding, macrophage uptake, and in vivo targeting were similar for all forms of GCase. Increased MBL binding was observed for all forms of GCase having larger mannose structures than those of Cerezyme, which could influence pharmacokinetic behavior. These studies demonstrate that although alternative cell expression systems are effective for producing oligomannose-terminated glucocerebrosidase, there is no biochemical or pharmacological advantage in producing GCase with an increased number of mannose residues. The display of alternative carbohydrate structures on GCase expressed in these systems also runs the risk of undesirable consequences, such as an increase in MBL binding or a possible increase in immunogenicity due to the presentation of non-mammalian glycans.

Comparison between the biochemical properties of plasma chitotriosidase from normal individuals and from patients with Gaucher disease, GM1-gangliosidosis, Krabbe disease and heterozygotes for Gaucher disease

OBJECTIVES

The aim of the present work was to establish the range of chitotriosidase (CT) activity in normal individuals (controls), patients with Gaucher disease (GD), GM1-gangliosidosis (GM1), Krabbe disease (KD) and heterozygotes for Gaucher disease (HG). The kinetics of the enzyme in the five groups was also investigated.

DESIGN AND METHODS

Plasma CT activity, as well as Km, Vmax, optimum pH and thermal stability of the enzyme was determined in plasma of controls, GM1, KD, GD and HG subjects.

RESULTS

CT activity in GD, GM1 and KD patients was, respectively, around 600-fold, 15-fold and 12-fold greater than in normal individuals. There was no significant difference between CT activity in the HG and the control group. We also demonstrated that all CT kinetic parameters evaluated (optimum pH, Km, Vmax, thermal stability) in plasma of GD, KD and GM1 patients were significantly different from those of normal individuals. Regarding to thermal stability, our results show that CT activity in the control group was more stable than in the other groups.

CONCLUSIONS

Based on the differences found in the biochemical parameters studied, we presume that the parameters analyzed may be useful in the diagnosis of the Lysosomal Storage Diseases.

Simultaneous preimplantation genetic diagnosis for Tay–Sachs and Gaucher disease

Preimplantation genetic diagnosis (PGD) for single gene defects is described for a family in which each parent is a carrier of both Tay-Sachs (TS) and Gaucher disease (GD). A multiplex fluorescent polymerase chain reaction protocol was developed that simultaneously amplified all four familial mutations and 10 informative microsatellite markers. In one PGD cycle, seven blastomeres were analysed, reaching a conclusive diagnosis in six out of seven embryos for TS and in five out of seven embryos for GD. Of the six diagnosed embryos, one was wild type for both TS and GD, and three were wild type for GD and carriers of TS. Two remaining embryos were compound heterozygotes for TS. Two transferable embryos developed into blastocysts (wt/wt and wt GD/carrier TS) and both were transferred on day 5. This single cycle of PGD resulted in a healthy live child. Allele drop-out (ADO) was observed in three of 34 reactions, yielding an 8% ADO rate. The occurrence of ADO in single cell analysis and undetected recombination events are primary causes of misdiagnosis in PGD and emphasize the need to use multiple polymorphic markers. So far as is known, this is the first report of concomitant PGD for two frequent Ashkenazi Jewish recessive disorders.

Phenotypic and genotypic heterogeneity in Gaucher disease type 1: a comparison between Brazil and the rest of the world

Type 1 Gaucher disease, the most common lysosomal storage disorder, results from deficiency of glucocerebrosidase causing pathologic accumulation of glucocerebroside. The disease is characterized by marked variation in age of onset and degree of anemia, thrombocytopenia, hepatosplenomegaly, and skeletal disease. Most published data on Gaucher disease come from populations with large proportions of Ashkenazi-Jewish patients, who tend to have less severe disease. We compared selected demographic, clinical, and genetic parameters for Brazilian (N = 221) and rest-of-world (N = 1477) type 1 Gaucher disease patients entered into the ICGG Gaucher Registry since 1991. We also compared Brazilian patients to non-Ashkenazi rest-of-world patients (N = 692) to determine if differences were the result of fewer Brazilian Ashkenazi-Jewish patients (0.5% vs 45.0%). The Brazilian cohort differed significantly (p < 0.05) from the rest-of-world and rest-of-world non-Ashkenazi cohort, respectively, in the following measures: higher proportion of females (59.7% vs 50.4% and 49.7%), lower mean age at diagnosis (17.1 vs 24.1 and 18.8), and higher proportions of patients with anemia (55.5% vs 29.9% and 35.7%), bone pain (57.7% vs 33.7% and 35%), bone crises (16.1% vs 6.5% and 7.4%), and lytic lesions (17.0% vs 7.6% and 7.4%). The most common genotype in Brazil was N370S/L444P (c1448T-->C/c1226A-->C) (46.8% versus 16.3% and 25.7%). These data highlight the genetic and phenotypic heterogeneity among geographic populations of type 1 Gaucher patients and suggest that as a group, Brazilian patients may have a more aggressive form of the disease than rest-of-world patients. The findings also emphasize the need for caution in making generalizations about Gaucher disease across demographic groups.

[Mutation spectrum of Gaucher disease in Tunisia: high frequency of N370S/Rec NciI compound heterozygous]

Gaucher disease is the most common lysosomal storage disorder, it results from the inherited deficiency of the enzyme glucocerebrosidase, the accumulation of its substrate causes many clinical manifestations. Since the discovery of GBA gene, more than 200 different mutations have been identified, but only handful mutations are recurrent (N370S, L444P and c.84insG). In order to determine the mutation spectrum in Tunisia, we performed recurrent mutation screening in ten unrelated Tunisian children with Gaucher disease. Screening of recurrent mutation by PCR/RFLP and direct sequencing, has shown that N370S is the most frequent mutation (6/20 mutant alleles, 30%), followed by recombinant allele (RecNciI) which is found in five patients (5/20 mutant alleles, 25%), the L444P mutation represent 20% (4/20 mutant alleles). Our findings revealed that five among ten studied patients, were compound heterozygous N370S/RecNciI (50%). The screening of these mutations provides a simple tool for molecular diagnosis of Gaucher disease in Tunisian patients and allows also genetic counselling for their family members.

Matched unrelated bone marrow transplantation without splenectomy for a child with Gaucher disease caused by homozygosity of the L444P mutation, who also suffered from schizencephaly

Splenectomy followed by bone marrow transplantation (BMT) has been applied successfully in the treatment of neuronopathic Gaucher disease (GD). GD in combination with schizencephaly has not previously been reported. We describe a girl who presented with hemiparesis and oculomotor apraxia since infancy, and thereafter developed progressive anemia, thrombocytopenia, hepatosplenomegaly, psychomotor retardation, and skeletal abnormalities. GD caused by homozygosity of the L444P mutation was diagnosed, in combination with schizencephaly. The child received enzyme replacement therapy for 3 years, followed by successful matched unrelated BMT without splenectomy. The strategy of BMT without splenectomy after a period of enzyme replacement may be feasible in neuronopathic GD.

Orthopaedic manifestations of Gaucher disease

Gaucher disease is a rare, hereditary disease caused by lack of a lysosomal enzyme. This results in the accumulation of glucocerebroside in the cells of the reticuloendothelial system, including the bone marrow. The orthopaedic manifestations of this disease are important for the orthopaedic surgeon to recognize and understand. Patients with Gaucher disease are at risk for pathologic fracture, abnormal bony remodeling and delayed healing, increased intraoperative bleeding, and infection. Osteomyelitis and avascular necrosis, two common sequelae of the disease, can present in very similar fashions and warrant careful and accurate diagnosis to ensure proper treatment. The impact of Gaucher disease on the musculoskeletal system is reviewed with emphasis on the importance of understanding these effects for the treating orthopaedic surgeon.

Characterization of two novel GBA mutations causing Gaucher disease that lead to aberrant RNA species by using functional splicing assays

The correct identification of disease-causing mutations from the background of harmless nucleotide polymorphisms/substitutions has become a critical issue in the investigation of human genetic diseases. Here, we describe two novel disease-causing splicing mutations in the glucocerebrosidase gene, g.4252C>G and g.4426A>G, that have been found in two patients affected by Gaucher disease. The g.4252C>G substitution occurred in intron 5 and was located 12 nucleotides upstream of exon 6 acceptor site whilst the g.4426A>G mutation was located within this exon, 12 nucleotides upstream of the donor site. An in silico analysis suggested that both mutations could have altered the splicing process of exon 6 by creating a novel acceptor and donor site, respectively. However, because the wild-type acceptor and donor sites of exon 6 were not apparently affected, the severity of both mutations could not be established by simple sequence analysis alone. Nonetheless, the use of minigene functional assays to complement transcript analysis of patient fibroblasts shows that both mutations cause the almost complete switch of splice site usage from the wild-type to the newly-created ones, thus providing a functional explanation for the appearance of disease.

Dopaminergic neuronal dysfunction associated with parkinsonism in both a Gaucher disease patient and a carrier

A clinical association between Gaucher disease and parkinsonism has been demonstrated. We herein report a Japanese patient with type 3 Gaucher disease who was compound heterozygous for F213I and L444P mutations in the glucocerebrosidase gene while his father was heterozygous for the L444P mutation. They both presented with parkinsonism characterized by a predominance of akinetic-rigid signs and a favorable response to anti-Parkinson therapies. We investigated the dopaminergic neuronal function using positron emission tomography (PET) with radioligands, [(11)C] CFT and [(11)C] raclopride. PET studies of both patients demonstrated the [(11)C] CFT uptake to be severely decreased in the putamen and the caudate nucleus, however, the [(11)C] raclopride uptake was normal in the basal ganglia. Although the majority of Gaucher disease patients with parkinsonism tend to be refractory to anti-Parkinson therapies. The clinical features and the findings of the PET studies suggest that patients with parkinsonism associated with the mutation in the glucocerebrosidase gene, even in heterozygosis, may be related to the presynaptic dopaminergic neuronal dysfunction reported in Parkinson's disease. A PET study to evaluate the dopaminergic neuronal function in Gaucher disease would provide both a better understanding of the effects of anti-Parkinson therapies and a help to improve our ability to make an early diagnosis of parkinsonism associated with Gaucher disease.

Selective action of the iminosugar isofagomine, a pharmacological chaperone for mutant forms of acid-beta-glucosidase

Gaucher disease is a lysosomal glycolipid storage disorder characterized by defects in acid-beta-glucosidase (GlcCerase), the enzyme responsible for the catabolism of glucosylceramide. We recently demonstrated that isofagomine (IFG), an iminosugar that binds to the active site of GlcCerase, enhances the folding, transport and activity of the N370S mutant form of GlcCerase. In this study we compared the effects of IFG on a number of other glucosidases and glucosyltransferases. We report that IFG has little or no inhibitory activity towards intestinal disaccharidase enzymes, ER alpha-glucosidase II or glucosylceramide synthase at concentrations previously shown to enhance N370S GlcCerase folding and trafficking in Gaucher fibroblasts. Furthermore, treatment of wild type fibroblasts with high doses of IFG did not alter the processing of newly synthesized N-linked oligosaccharides. These findings support further evaluation of IFG as a potential therapeutic agent in the treatment of some forms of Gaucher disease.

Heterozygosity for a Mendelian disorder as a risk factor for complex disease

While genetic diseases are generally classified as being either 'simple' monogenic or 'complex' polygenic, the distinction between Mendelian and complex disorders is becoming increasingly blurred. Mendelian disorders may demonstrate qualities more typical of multifactorial diseases through shared clinical presentations, the effect of genetic modifiers, moonlighting proteins, synergistic heterozygosity, disease manifestations in heterozygotes and situations where heterozygosity for a 'simple' disorder proves to be a risk factor for seemingly unrelated complex diseases. A recent example of the last instance is the observation that mutations in glucocerebrosidase, the enzyme deficient in Gaucher disease, may be a risk factor for the development of Parkinson disease and other synucleinopathies. Insights gleaned from the study of Mendelian disorders may ultimately lead to a better understanding of factors influencing complex diseases.

Detection of 12 new mutations in Gaucher disease Brazilian patients

Gaucher disease is the most frequent lysosome storage disease and presents an autosomal recessive mode of inheritance. It is caused by mutations at the GBA gene leading to deficient activity of the glucocerebrosidase enzyme. This report describes 12 new mutations [c.38A>G (K-27R), c.220G>A (G35S), c.448G>A (E111K), IVS4+1G>A, c.746C>T (A210V), c.776A>G (Y220C), c.793delC (Q226_fs4X), c.1102C>T (R329C), c.1300C>T (R395C), c.1309G>A (V398I), c.1324-1326delATT (delI403) and c.1583T>C (I489T)] and 4 novel silent alterations [c.342C>T (F75), c.528C>T (D137), c.1011C>T (D298) and c.1092G>A (G325)] detected among 40 unrelated Brazilian type 1 Gaucher disease patients by a combination of RFLP, dHPLC and DNA sequencing procedures. The R329C mutation, previously described in a Parkinson's disease patient (A. Lwin, E. Orvisky, O. Goker-Alpan, M.E. LaMarca, E. Sidransky. Glucocerebrosidase mutations in subjects with Parkinsonism. Mol. Genet. Metab. 81 (2004) 70-73), is described here for the first time in a Gaucher disease patient. Several genotype-phenotype correlations could be established, contributing significantly to the panel of reported mutations and conferring predictive value to their detection.

RNAi-mediated inhibition of the glucosylceramide synthase (GCS) gene: A preliminary study towards a therapeutic strategy for Gaucher disease and other glycosphingolipid storage diseases

Small interference RNAs (siRNAs) have recently been used in various experimental settings to silence gene expression. In some of them, chemically synthesized or in vitro transcribed siRNAs have been transfected into cells. In others, siRNAs have been expressed endogenously from siRNA expression vectors. Enzyme replacement and substrate deprivation therapies are currently used to treat Gaucher disease. Although good results have been reported, there are several limitations and side effects that make necessary to search for new alternatives. We present a new approach based on the inhibition of the GCS gene using siRNAs as a potential therapeutic strategy for Gaucher disease. We have designed four siRNAs for the human GCS gene and transfected them into HeLa cells. A clear reduction of GCS RNA levels and enzyme activity was obtained using two of the four siRNAs. Furthermore, a reduction in glucosylceramide synthesis was also observed. Similar results were obtained when plasmids expressing shRNAs (targeting the same sequences) were transfected into the cells. The inhibition of the mouse homolog Ugcg gene was also achieved, using a siRNA that targeted both human and mouse sequences.

Hydrophilic iminosugar active-site-specific chaperones increase residual glucocerebrosidase activity in fibroblasts from Gaucher patients

Gaucher disease is an autosomal recessive lysosomal storage disorder caused by the deficient activity of glucocerebrosidase. Accumulation of glucosylceramide, primarily in the lysosomes of cells of the reticuloendothelial system, leads to hepatosplenomegaly, anemia and skeletal lesions in type I disease, and neurologic manifestations in types II and III disease. We report herein the identification of hydrophilic active-site-specific chaperones that are capable of increasing glucocerebrosidase activity in the cultured fibroblasts of Gaucher patients. Screening of a variety of natural and synthetic alkaloid compounds showed isofagomine, N-dodecyl deoxynojirimycin, calystegines A3, B1, B2 and C1, and 1,5-dideoxy-1,5-iminoxylitol to be potent inhibitors of glucocerebrosidase. Among them, isofagomine was the most potent inhibitor of glucocerebrosidase in vitro, and the most effective active-site-specific chaperone capable of increasing residual glucocerebrosidase activity in fibroblasts established from Gaucher patients with the most prevalent Gaucher disease-causing mutation (N370S). Intracellular enzyme activity increased approximately two-fold after cells had been incubated with isofagomine, and the increase in glucocerebrosidase activity was both dose-dependent and time-dependent. Western blotting demonstrated that there was a substantial increase in glucocerebrosidase protein in cells after isofagomine treatment. Immunocytochemistry revealed an improvement in the glucocerebrosidase trafficking pattern, which overlaps that of lysosome-associated membrane protein 2 in Gaucher fibroblasts cultivated with isofagomine, suggesting that the transport of mutant glucocerebrosidase is at least partially improved in the presence of isofagomine. The hydrophilic active-site-specific chaperones are less toxic to cultured cells. These results indicate that these hydrophilic small molecules are suitable candidates for further drug development for the treatment of Gaucher disease.

Critical assessment of chitotriosidase analysis in the rational laboratory diagnosis of children with Gaucher disease and Niemann-Pick disease type A/B and C

Laboratory diagnosis of lysosomal storage disorders, especially sphingomyelinase deficiency (Niemann-Pick disease type A/B) and Niemann-Pick disease type C (NPC) can be challenging. We therefore aimed to analyse the feasibility of first-step screening with specific chitotriosidase cut-off values in children </= 10 years of age with visceral organomegaly (hepatomegaly, splenomegaly, or hepatosplenomegaly) in whom a storage disorder was suspected. We conducted a retrospective, cross-sectional, referral, single-centre study to assess diagnostic test properties in 106 individuals. Median chitotriosidase activity was 12 655 nmol/h per ml (interquartile range 4693-20982) in Gaucher disease (GD); 780 (465-1298) in SMD (sphingomyelinase deficiency); 925 (319-1215) in NPC and 50 (29-54) in patients with miscellaneous diseases. To restrict the differential diagnosis to GD, SMD or NPC, chitotriosidase activity above 200 nmol/h per ml had a sensitivity of 96%, specificity of 100%, positive predictive value (PPV) of 100%, and negative predictive value (NPV) of 95%. For GD alone, chitotriosidase activity above 4000 nmol/h per ml had a sensitivity of 77%, specificity of 100%, PPV of 100% and NPV of 92%. Of the 44 patients analysed, 4.5% were homozygous and 36.4% heterozygous for chitotriosidase gene duplication. Adjusting for the chitotriosidase genotype, chitotriosidase activities were higher in GD type III than in GD type I. We conclude that, in the above setting, the degree of elevation of chitotriosidase activity can be applied to increase the likelihood of GD, SMD, or NPC and guide the choice of the appropriate confirmatory assay.

Genpolymorphismus bei der verkalkten Aortenklappenstenose

In the Caucasian world calcified and stenosed aortic valves are a common disease. Due to increasing life expectancy prevalence of aortic valve disease will increase dramatically. In order to establish alternative therapeutic approaches to valve replacement, we have to get a better understanding of the pathophysiological process and genetic determinations leading to calcified and stenotic valve disease. Exploring these genetic determinations will open new specific fields of therapeutic modulations of the disease process. In the literature, different gene polymorphisms have been characterized to develop calcifications and further stenosis of the aortic valves.Here, congestive polyvalent aortic valve abnormalities without specific genetic determinations (i. e., DiGeorge syndrome or fragile x syndrome), autosomal inherited alterations leading to congestive aortic valve disease (i. e., Williams-Beuren syndrome, Gaucher's disease, tetralogy of Fallot, genetic aberrations of chromosomes 2 and 4 as well as trisomy 18), X- and Y-chromosomal specific alterations (i. e., Turner syndrome), congestive structure-based aortic valve disease (i. e., bicuspid aortic valve with regard to hand-heart syndromes, tetracuspid aortic valve associated with DiGeorge syndrome) and genetic mutations of specific target genes (i. e., epidermal growth factor receptor, NOTCH-1, elastin, angiotensin I conversion enzyme, beta-glucocerebrosidase, interleukin-10, chemokine receptor 5, connective tissue growth factor, transforming growth factor beta1, vitamin D receptor, estrogen receptor-alpha, apolipoproteins A1, B, and E) are summarized. The roles of gene polymorphism in the development of calcified and stenosed aortic valve appear slowly in the understanding of the process leading to the valve disease and are mainly based on studies of supravalvular and bicuspid aortic valve stenoses. New molecular biological methods enabling broad gene expression analyses demonstrate the similarity in the pathophysiology of atherosclerotic vessel inflammation, bone formation/fibrosis, with the processes leading to stenosed and calcified aortic valves. Based on to-date knowledge, further analyses have to be done and will improve understanding of the pathophysiological processes with regard to the development of new therapeutic drug targets.

[Colombian haplotypes of the Gaucher disease-causing N370S mutation may originate from a possible common ancestral haplotype]

INTRODUCTION

Gaucher disease is a pan-ethnic condition characterised by glucosylceramide accumulation in macrophages due to glucocerebrosidase deficiency. Its gene, GBA, has been mapped to 1q21 and mutation N370S is the main cause of the disease in western populations, including Colombia.

OBJECTIVE

To asses the degree of association between N370S mutation and the alleles of five microsatellites near the mutation site in the GBA locus in nine Colombian Gaucher patients, from the Cundinamarca-Boyacá region.

MATERIALS AND METHODS

DNA from patients bearing the N370S mutation, their closest relatives, and 30 controls was taken to PCR-amplify the markers: D1S305, D1S2624, DIS2777, ITG6.6.2 and 5GC3.2. Allele frequencies were calculated, haplotypes inferred and linkage disequilibrium levels between marker alleles and N370S were also estimated.

RESULTS

Eleven N370S chromosomes were obtained. A consensus N370S haplotype consisting of the alleles: 222-314-260-301-172 (base pairs) was identified. Each allele corresponding to markers 5GC3.2, ITG6.6.2, D1S277, D1S2624 and D1S305, respectively. There was statistically significant linkage disequilibrium between the alleles of 222, 314, 260, 301 base pairs and the N370S mutation.

CONCLUSION

A conserved fraction of the haplotypes suggests that N370S may be present among patients and stem from a single ancestral chromosome for which the ethnic origin is still unclear.

The iminosugar isofagomine increases the activity of N370S mutant acid beta-glucosidase in Gaucher fibroblasts by several mechanisms

Gaucher disease is a lysosomal storage disorder caused by deficiency in lysosomal acid beta-glucosidase (GlcCerase), the enzyme responsible for the catabolism of glucosylceramide. One of the most prevalent disease-causing mutations, N370S, results in an enzyme with lower catalytic activity and impaired exit from the endoplasmic reticulum. Here, we report that the iminosugar isofagomine (IFG), an active-site inhibitor, increases GlcCerase activity 3.0 +/- 0.6-fold in N370S fibroblasts by several mechanisms. A major effect of IFG is to facilitate the folding and transport of newly synthesized GlcCerase in the endoplasmic reticulum, thereby increasing the lysosomal pool of the enzyme. In addition, N370S GlcCerase synthesized in the presence of IFG exhibits a shift in pH optimum from 6.4 to 5.2 and altered sensitivity to SDS. Although IFG fully inhibits GlcCerase in the lysosome in an in situ assay, washout of the drug leads to partial recovery of GlcCerase activity within 4 h and full recovery by 24 h. These findings provide support for the possible use of active-site inhibitors in the treatment of some forms of Gaucher disease.

Polymorphisms in the glucocerebrosidase gene and pseudogene urge caution in clinical analysis of Gaucher disease allele c.1448T>C (L444P)

Background

Gaucher disease is a potentially severe lysosomal storage disorder caused by mutations in the human glucocerebrosidase gene (GBA). We have developed a multiplexed genetic assay for eight diseases prevalent in the Ashkenazi population: Tay-Sachs, Gaucher type I, Niemann-Pick types A and B, mucolipidosis type IV, familial dysautonomia, Canavan, Bloom syndrome, and Fanconi anemia type C. This assay includes an allelic determination for GBA allele c.1448T>C (L444P). The goal of this study was to clinically evaluate this assay.

Methods

Biotinylated, multiplex PCR products were directly hybridized to capture probes immobilized on fluorescently addressed microspheres. After incubation with streptavidin-conjugated fluorophore, the reactions were analyzed by Luminex IS100. Clinical evaluations were conducted using de-identified patient DNA samples.

Results

We evaluated a multiplexed suspension array assay that includes wild-type and mutant genetic determinations for Gaucher disease allele c.1448T>C. Two percent of samples reported to be wild-type by conventional methods were observed to be c.1448T>C heterozygous using our assay. Sequence analysis suggested that this phenomenon was due to co-amplification of the functional gene and a paralogous pseudogene (ΨGBA) due to a polymorphism in the primer-binding site of the latter. Primers for the amplification of this allele were then repositioned to span an upstream deletion in the pseudogene, yielding a much longer amplicon. Although it is widely reported that long amplicons negatively impact amplification or detection efficiency in recently adopted multiplex techniques, this assay design functioned properly and resolved the occurrence of false heterozygosity.

Conclusion

Although previously available sequence information suggested GBA gene/pseudogene discrimination capabilities with a short amplified product, we identified common single-nucleotide polymorphisms in the pseudogene that required amplification of a larger region for effective discrimination.