The E326K mutation and Gaucher disease: mutation or polymorphism?

Gaucher disease is caused by mutations in the gene for human glucocerebrosidase, a lysosomal enzyme involved in the intracellular hydrolysis of glucosylceramide. While over 150 different glucocerebrosidase mutations have been identified in patients with Gaucher disease, not all reported mutations have been fully characterized as being causative. One such mutation is the E326K mutation, which results from a G to A nucleotide substitution at genomic position 6195 and has been identified in patients with type 1, type 2 and type 3 Gaucher disease. However, in each instance, the E326K mutation was found on the same allele with another glucocerebrosidase mutation. Utilizing polymerase chain reaction (PCR) screening and restriction digestions of both patients with Gaucher disease and normal controls, we identified the E326K allele in both groups. Of the 310 alleles screened from patients with Gaucher disease, the E326K mutation was detected in four alleles (1.3%). In addition, screening for the E326K mutation among normal controls from a random population revealed that three alleles among 316 screened (0.9%) also carried the E326K mutation. In the normal controls with the E326K allele, the glucocerebrosidase gene was completely sequenced, but no additional mutations were found. Because the E326K mutation may be a polymorphism, we caution that a careful examination of any allele with this mutation should be performed to check for the presence of other glucocerebrosidase mutations.     

Recurrence of the D409H mutation in Spanish Gaucher disease patients: description of a new homozygous patient and haplotype analysis.

Gaucher disease results, in most patients, from mutations in the gene encoding glucocerebrosidase. Mutation D409H is the third most frequent in Spanish patients, accounting for 5.7% of all mutated alleles. This allele is associated mainly with the neurological forms of the disease. Recently, homozygosity for the D409H mutation has been associated with a particular phenotype, including specific cardiovascular symptoms. Here we report a second Spanish patient bearing the D409H/D409H genotype with a very early manifestation of the disease. The patient started enzyme replacement therapy at 3 months of age. A common origin for the Spanish D409H alleles was ruled out by haplotype analysis using an internal polymorphism of the glucocerebrosidase gene and two external microsatellite markers.     

Identification of two novel and four uncommon missense mutations among Chinese Gaucher disease patients

Gaucher disease is the most prevalent lysosomal storage disease. It is panethnic and results from an inherited deficiency of glucocerebrosidase. Most mutations to date have been identified among Jewish and non-Jewish Caucasian patients; mutations in Chinese patients are largely unknown. We have performed nucleotide sequence analysis of PCR-amplified glucocerebrosidase genomic DNA from five unrelated Chinese patients affected with type 1 (non-neuropathic) Gaucher disease. A novel heterozygous C → T mutation at cDNA nucleotide position 475 (R120W) was detected in a patient who is also heterozygous for a C → T transition at cDNA nucleotide position 259 (R48W). In a second patient, a novel, heterozygous T → G transversion at cDNA 226 (F37V) was detected. Mutation 1448 (L444P), the most prevalent mutation among non-Jewish Caucasian Gaucher patients, was found in the heterozygous form in four patients. The mutations in the second Gaucher allele in the other three patients are mutations 254 (G46E), 680 (N188S), and 754 (F213I), which were recently reported in Korean, Arab, and Chinese (Taiwanese) patients. We have developed screening methods that utilize PCR amplification of glucocerebrosidase genomic DNA and Eco571, Nci1, Hinc11, BsaJ1, and Bsr1 restriction endonuclease analyses for the detection of each of these mutations. The population genetics of some of these Gaucher alleles and their implications in genotype/phenotype correlation are discussed. Am. J. Med. Genet. 71:172–178, 1997. © 1997 Wiley-Liss, Inc.     

A novel mutation (V191G) in a German-British type 1 Gaucher disease patient. Mutations in brief no. 131. Online

Gaucher disease results from mutations in the glucocerebrosidase gene located on human chromosome 1q21. Three clinical forms of Gaucher disease have been described: type 1, nonneuropathic; type 2, acute neuropathic; and type 3, subacute neuropathic. We have identified a novel mutation in a German-British patient with type 1 Gaucher disease which results in V191G of the glucocerebrosidase polypeptide. Because the mutation abolishes a HphI cleavage site, its presence was confirmed by HphI RFLP analysis of PCR-amplified genomic DNA. In the second allele of the patient, the mutation identified was g.5841A G(N370S). Sequence analysis of the remainder of the coding region of the gene as well as the exon-intron boundaries showed identity to normal controls. Because mutation N370S has so far been found only in type 1 Gaucher disease and postulated to result in mild clinical presentation, and since the clinical course of this patient has been relatively mild with minimal skeletal involvement, we speculate that the V191G/N370S genotype may also result in good prognosis.     

Type I Gaucher disease due to homozygosity for the 259T mutation in a Bedouin patient

A 26-year-old Bedouin with moderate thrombocytopenia and enlarged spleen and liver was diagnosed as having type I Gaucher disease based on the presence of Gaucher cells in the bone marrow biopsy and enzymatic determination of glucocerebrosidase activity. Molecular analysis excluded 10 common mutations in the glucocerebrosidase gene. Homozygosity for the C → T mutation in nucleotide 259 of the cDNA (1763 genomic) was detected by digestion with restriction enzyme StyI after an amplification of a portion of exon 3 by mismatched primers. This is the first known case of homozygosity for this mutation. The fact that it produces a very mild phenotype, confirms a previous suggestion that 259T can be classified as a “mild” mutation. Association of the 259T mutation with the “Pv 1.1 +” haplotype is consistent with a common origin of the mutated alleles. Am. J. Med. Genet. 72:77–78, 1997. © 1997 Wiley-Liss, Inc.     

A mutation in SCARB2 is a modifier in Gaucher disease

Lysosomal integral membrane protein type 2 (LIMP-2) is responsible for proper sorting and lysosomal targeting of glucocerebrosidase, the enzyme deficient in Gaucher disease (GD). Mutations in the gene for LIMP-2, SCARB2, are implicated in inherited forms of myoclonic epilepsy, and myoclonic epilepsy is part of the phenotypic spectrum associated with GD. We investigated whether SCARB2 mutations impact the Gaucher phenotype focusing on patients with myoclonic epilepsy, including a pair of siblings with GD who were discordant for myoclonic seizures. Sequencing of SCARB2 genomic and cDNA identified a heterozygous, maternally inherited novel mutation, c.1412A>G (p.Glu471Gly), in the brother with GD and myoclonic epilepsy, absent from his sibling and controls. Glucocerebrosidase activity, Western blots, real-time PCR, and immunofluorescence studies demonstrated markedly decreased LIMP-2 and glucocerebrosidase in cells from the sibling with (p.Glu471Gly) LIMP-2, and diminished glucocerebrosidase in lysosomes. The cells secreted highly glycosylated enzyme and showed mistrafficking of glucocerebrosidase. Sequencing of SCARB2 in 13 other subjects with GD and myoclonic epilepsy and 40 controls failed to identify additional mutations. The study provides further evidence for the association of LIMP-2 and myoclonic epilepsy, explains the drastically different phenotypes encountered in the siblings, and demonstrates that LIMP-2 can serve as a modifier in GD.     

DNA mutational analysis of type 1 and type 3 gaucher patients: How well do mutations predict phenotype?

The wide spectrum of clinical manifestations resulting from glucocerebrosidase deficiency complicates genetic counseling for Gaucher disease. The identification of mutations in the glucocerebrosidase gene has enabled studies of genotype–phenotype correlation. However, a genotypic analysis of 60 type 1 and type 3 Gaucher patients reveals that the 5 most common Gaucher mutations, N370S, L444P, R463C, 84insG, and IVS2 + 1 G→A, can be found both in patients with and without neurologic manifestations. Moreover, although some generalizations can be made about mutations that are more frequently encountered in particular patient populations, Gaucher patients sharing identical genotypes can exhibit considerable clinical heterogeneity. Thus in considering rationale for population screening one cannot rely solely on PCR determined DNA mutation analysis to reliably predict prognosis in Gaucher disease. © 1994 WiIey-Liss, Inc. © 1994 Wiley-Liss, Inc.     

The role of saposin C in Gaucher disease

Saposin C is one of four homologous proteins derived from sequential cleavage of the saposin precursor protein, prosaposin. It is an essential activator for glucocerebrosidase, the enzyme deficient in Gaucher disease. Gaucher disease is a rare autosomal recessive lysosomal storage disorder caused by mutations in the GBA gene that exhibits vast phenotypic heterogeneity, despite its designation as a "simple" Mendelian disorder. The observed phenotypic variability has led to a search for disease modifiers that can alter the Gaucher phenotype. The PSAP gene encoding saposin C is a prime candidate modifier for Gaucher disease. In humans, saposin C deficiency due to mutations in PSAP results in a Gaucher-like phenotype, despite normal in vitro glucocerebrosidase activity. Saposin C deficiency has also been shown to modify phenotype in one mouse model of Gaucher disease. The role of saposin C as an activator required for normal glucocerebrosidase function, and the consequences of saposin C deficiency are described, and are being explored as potential modifying factors in patients with Gaucher disease.     

Type 2 Gaucher Disease with Hydrops Fetalis in an Ashkenazi Jewish Family Resulting from a Novel Recombinant Allele and a Rare Splice Junction Mutation in the Glucocerebrosidase Locus

Gaucher disease, the deficiency of the lysosomal enzyme glucocerebrosidase (EC 3.2.1.45), is frequently encountered in the Ashkenazi Jewish population. Carrier screening for Gaucher disease by enzyme analysis performed during a routine pregnancy indicated that both Ashkenazi parents were carriers. Screening for four common Gaucher mutations was subsequently performed on fetal and parental DNA. None of the common Ashkenazi mutations were identified. However, when exons 9–11 were amplified and digested withNciI to detect the L444P mutation, it appeared that the mother and the fetus had an unusual allele and that the expected paternal allele was not present. When the fetal amniocytes were found to have less than 2% of the normal glucocerebrosidase activity and a fetal sonogram revealed hydrops fetalis, the pregnancy was terminated. The diagnosis of severe type 2 Gaucher disease was confirmed at autopsy. Ultrastructural studies of epidermis from the fetus revealed the characteristic disruption of lamellar bilayers, diagnostic for type 2 Gaucher disease. In subsequent studies of the fetal DNA, long-template polymerase chain reaction amplification revealed one appropriately sized band (6.5 kb) and one smaller (5.2 kb) band. Sequencing of the 5.2-kb fragment identified a novel fusion allele resulting from recombination between the glucocerebrosidase gene and its pseudogene beginning in intron 3. This fusion allele was inherited from the father. The result was confirmed by Southern blot analysis using the enzymeSstII. Sequencing of the 6.5-kb fragment identified a previously described, although rare, T-to-G splice junction mutation in intron 10 of the maternal allele, which introduced anNciI site. The couple had a subsequent pregnancy which was also found to be affected. This case study identifies a novel recombinant allele and an unusual splice junction mutation, and demonstrates that even in the Ashkenazi population, screening for common mutations may not accurately identify the most severe forms of the disease.     

Gaucher disease and the synucleinopathies

Several recent observations suggest a connection between Gaucher disease, the inherited deficiency of glucocerebrosidase, and the synucleinopathies. Rare patients have been observed who develop both Gaucher disease and parkinsonism. Autopsy studies on these subjects reveal synuclein-positive Lewy bodies and inclusions. An increased incidence of synucleinopathies also has been noted in relatives of Gaucher probands. In complementary studies, screening of patients with parkinsonism has identified a greater than expected frequency of glucocerebrosidase mutations. These glucocerebrosidase mutation carriers have a wide spectrum of associated parkinsonian phenotypes, ranging from classic L-dopa-responsive Parkinson disease to a phenotype more characteristic of Lewy body dementia. Despite this association, the vast majority of Gaucher carriers and patients with Gaucher disease never develop parkinsonism. However, mutations in this gene are likely to be a contributing risk factor in subjects otherwise prone to developing synucleinopathies.     

Gaucher disease and parkinsonism: a phenotypic and genotypic characterization

Among the many phenotypes associated with Gaucher disease, the inherited deficiency of glucocerebrosidase, are reports of patients with parkinsonian symptoms. The basis for this association is unknown, but could be due to alterations in the gene or gene region. The human glucocerebrosidase gene, located on chromosome 1q21, has a nearby pseudogene that shares 96% identity. Immediately adjacent to the glucocerebrosidase pseudogene is a convergently transcribed gene, metaxin, which has a pseudogene that is located just downstream to the glucocerebrosidase gene. We describe a patient with mild Gaucher disease but impaired horizontal saccadic eye movements who developed a tremor at age 42, followed by rapid deterioration of her gait. A pallidotomy at age 47 was unsuccessful. Her motor and cognitive deterioration progressed despite enzyme replacement therapy. Sequencing of the glucocerebrosidase gene identified mutations L444P and D409H. Southern blot analysis using the enzyme SspI showed that the maternal allele had an additional 17-kb band. PCR amplifications and sequencing of this fragment demonstrated a duplication which included the glucocerebrosidase pseudogene, metaxin gene, and a pseudometaxin/metaxin fusion. Gene alterations associated with this novel rearrangement, resulting from a crossover between the gene for metaxin and its pseudogene, could contribute to the atypical phenotype encountered in this patient.     

The identification of eight novel glucocerebrosidase (GBA) mutations in patients with Gaucher disease

Mutations in the gene encoding for the lysosomal enzyme glucocerebrosidase (GBA) result in Gaucher disease. In this study, seven novel missense mutations in the glucocerebrosidase gene (A136E, H162P, K198E, Y205C, F251L, Q350X and I402F) and a splice site mutation (IVS10+2T-->A) were identified by direct sequencing of three amplified segments of the glucocerebrosidase gene. Five of the novel mutations were found in patients with neuronopathic forms of Gaucher disease, two of which, K198E and F251L, appear to be associated with type 2 Gaucher disease.     

Gaucher disease: molecular screening of the glucocerebrosidase 1601G and 1601A alleles in Victoria, British Columbia, Canada.

Gaucher disease is the most prevalent lysosomal storage disease and it results from inherited deficient glucocerebrosidase activity. The glucocerebrosidase gene from normal people was sequenced by several laboratories and it was noted that a G or A nucleotide may be present at cDNA position 1601, resulting in 495arginine or 495histidine in the glucocerebrosidase polypeptide. In order to rule out the possibility of cloning error and to elucidate the genetic status of the two genotypes and their distribution in the population, we have developed a convenient and reliable method for the molecular screening of the 1601G and 1601A genotypes in the population. This method uses PCR amplification of glucocerebrosidase genomic DNA in blood samples, followed by BsaHI restriction fragment length polymorphism analysis. Out of the 256 subjects without Gaucher disease and 15 Gaucher patients surveyed, the 1601G genotype was present in the homozygous form in all of the asymptomatic subjects and 14 Gaucher patients. In one Gaucher patient who was diagnosed as having type 1 (non-neuropathic) Gaucher disease with the A1226G/T1366G mutations, the heterozygous 1601G/A genotype was detected. These findings indicate that the 1601G genotype which encodes 495arginine of the glucocerebrosidase polypeptide is not a cloning error. Instead, it constitutes the normal as well as predominant genotype in the population in the municipality of Greater Victoria, British Columbia. The 1601A genotype, on the other hand, appears to be quite infrequent in this population. The availability of our restriction enzyme based method has allowed the screening and frequency determination of these two alleles in other populations.     

Molecular analysis of Gaucher disease: screening of patients in the Montreal/Quebec region.

Gaucher disease, the most prevalent lysosomal storage disease, is an autosomal recessive sphingolipidosis resulting from deficient glucocerebrosidase activity. Genomic DNA of the structural gene of glucocerebrosidase from normal individuals and fifteen unrelated patients with the three clinical forms of Gaucher disease from the Montreal/Quebec region were amplified by the polymerase chain reaction technique. Allele-specific oligonucleotide dot blot hybridization and restriction fragment length polymorphism were used to screen for five of the mutations [mutations 120, 370, 415, 444 (Nci), and 463] in exons 5, 9, and 10 of glucocerebrosidase gene. It was noted that all of the patients had at least one of the known mutant alleles. However, 9 patients (9/15 = 60%) had an unknown allele. Mutation 370 in exon 9 was present in the heteroallelic form in eight out of the nine patients with type 1 Gaucher disease, but was present in none of the six patients with type 2 or type 3 Gaucher disease. The Nci mutation in exon 10 was present in the heteroallelic form in three patients with type 1 Gaucher disease and in either the heteroallelic or homoallelic form in all of the six patients with type 2 or type 3 Gaucher disease. The 415/Nci mutations were found in a mildly affected 29-year-old patient with type 1 Gaucher disease, as well as in an infant with the type 2 form. These findings demonstrate the clinical and molecular genetic heterogeneities of Gaucher disease, the presence of unknown Gaucher allele(s) in most (60%) of the patients surveyed, and the occasional inexplicable lack of phenotype-genotype correlation among some patients.(ABSTRACT TRUNCATED AT 250 WORDS)     

Glucocerebrosidase gene mutations in patients with type 2 Gaucher disease

Gaucher disease, the most common lysosomal storage disorder, results from the inherited deficiency of the enzyme glucocerebrosidase. Three clinical types are recognized: type 1, non-neuronopathic; type 2, acute neuronopathic; and type 3, subacute neuronopathic. Type 2 Gaucher disease, the rarest type, is progressive and fatal. We have performed molecular analyses of a cohort of 31 patients with type 2 Gaucher disease. The cases studied included fetuses presenting prenatally with hydrops fetalis, infants with the collodion baby phenotype, and infants diagnosed after several months of life. All 62 mutant glucocerebrosidase (GBA) alleles were identified. Thirty-three different mutant alleles were found, including point mutations, splice junction mutations, deletions, fusion alleles and recombinant alleles. Eleven novel mutations were identified in these patients: R131L, H255Q, R285H, S196P, H311R, c.330delA, V398F, F259L, c.533delC, Y304C and A190E. Mutation L444P was found on 25 patient alleles. Southern blots and direct sequencing demonstrated that mutation L444P occurred alone on 9 alleles, with E326K on one allele and as part of a recombinant allele on 15 alleles. There were no homozygotes for point mutation L444P. The recombinant alleles that included L444P resulted from either reciprocal recombination or gene conversion with the nearby glucocerebrosidase pseudogene, and seven different sites of recombination were identified. Homozygosity for a recombinant allele was associated with early lethality. We have also summarized the literature describing mutations associated with type 2 disease, and list 50 different mutations. This report constitutes the most comprehensive molecular study to date of type 2 Gaucher disease, and it demonstrates that there is significant phenotypic and genotypic heterogeneity among patients with type 2 Gaucher disease. Hum Mutat 15:181-188, 2000. Published 2000 Wiley-Liss, Inc.     

Molecular analysis of Gaucher disease in a Vietnamese-Czechoslovak patient with high residual glucocerebrosidase activity

A Vietnamese-Czechoslovak type 1 Gaucher disease patient with mild hematological complications was found to have approximately 20% of the normal level of fibroblast glucocerebrosidase activity. Using primers that recognize exon 9 sequences of the glucocerebrosidase structural gene absent in the pseudogene, genomic DNA sequences flanking exons 9 and 10 of the glucocerebrosidase structural gene were amplified by the polymerase chain reaction. Allele-specific oligonucleotide hybridization to amplified genomic DNA sequence of exons 9 and 10 showed an A----G transition in exon 9 that resulted in the 370Ser----370Asp substitution in one of the alleles. In the other allele, a T----C transition in exon 10 resulted in the 444Leu----444Pro substitution, creating a NciI cleavage site. The heterozygote status of the patient's parents was confirmed biochemically by the detection of intermediate levels (42-55% of normal) of fibroblast glucocerebrosidase activity. Allele-specific oligonucleotide hybridization to amplified parental genomic DNA showed that the exon 9 mutation was present in the Czechoslovak father, whereas the exon 10 mutation was inherited from the patient's Vietnamese mother. This is the first report of the exon 10 mutation in a person of Vietnamese origin.