A novel complex allele and two new point mutations in type 2 (acute neuronopathic) Gaucher disease

Identification of GM1-Ganglioside Secondary Accumulation in Fibroblasts from Neuropathic Gaucher Patients and Effect of a Trivalent Trihydroxypiperidine Iminosugar Compound on Its Storage Reduction

Gaucher disease (GD) is a rare genetic metabolic disorder characterized by a dysfunction of the lysosomal glycoside hydrolase glucocerebrosidase (GCase) due to mutations in the gene GBA1, leading to the cellular accumulation of glucosylceramide (GlcCer). While most of the current research focuses on the primary accumulated material, lesser attention has been paid to secondary storage materials and their reciprocal intertwining. By using a novel approach based on flow cytometry and fluorescent labelling, we monitored changes in storage materials directly in fibroblasts derived from GD patients carrying N370S/RecNcil and homozygous L444P or R131C mutations with respect to wild type. In L444P and R131C fibroblasts, we detected not only the primary accumulation of GlcCer accumulation but also a considerable secondary increase in GM1 storage, comparable with the one observed in infantile patients affected by GM1 gangliosidosis. In addition, the ability of a trivalent trihydroxypiperidine iminosugar compound (CV82), which previously showed good pharmacological chaperone activity on GCase enzyme, to reduce the levels of storage materials in L444P and R131C fibroblasts was tested. Interestingly, treatment with different concentrations of CV82 led to a significant reduction in GM1 accumulation only in L444P fibroblasts, without significantly affecting GlcCer levels. The compound CV82 was selective against the GCase enzyme with respect to the β-Galactosidase enzyme, which was responsible for the catabolism of GM1 ganglioside. The reduction in GM1-ganglioside level cannot be therefore ascribed to a direct action of CV82 on β-Galactosidase enzyme, suggesting that GM1 decrease is rather related to other unknown mechanisms that follow the direct action of CV82 on GCase. In conclusion, this work indicates that the tracking of secondary storages can represent a key step for a better understanding of the pathways involved in the severity of GD, also underlying the importance of developing drugs able to reduce both primary and secondary storage-material accumulations in GD.

Hemophagocytic lymphohistiocytosis triggered by Gaucher disease in a preterm neonate

OBJECTIVE

To present the diagnostic workup in an extremely low birth weight infant patient with signs of both sepsis and hemophagocytosis.

PARTICIPANTS

A preterm infant presented with clinical and laboratory signs of early-onset sepsis including hepatosplenomegaly, thrombocytopenia, direct hyperbilirubinemia, and elevated liver enzymes.

METHODS

Despite extensive septic workup, no underlying infection was detected. Additional hyperferritinemia and other elevated inflammatory parameters raised the suspicion of a primary or secondary hemophagocytic lymphohistiocytosis (HLH).

RESULTS

However, further metabolic analysis yielded a positive result for Gaucher disease (GD) type 2, a rare, but possible trigger of HLH.

CONCLUSIONS

Our case shows that GD may lead to the picture of a secondary HLH and that a metabolic workup should always be performed in patients in whom primary HLH has been excluded.

A Novel Functional Missense Mutation p.T219A in Type 1 Gaucher's Disease

Background:

Gaucher's disease (GD) is an autosomal recessive disorder caused by a deficiency of acid β-glucosidase (glucocerebrosidase [GBA]) that results in the accumulation of glucocerebroside within macrophages. Many mutations have been reported to be associated with this disorder. This study aimed to discover more mutations and provide data for the genetic pattern of the gene, which will help the development of quick and accurate genetic diagnostic tools for this disease.

Methods:

Genomic DNA was obtained from peripheral blood leukocytes of the patient and Sanger sequencing is used to sequence GBA gene. Sequence alignments of mammalian β-GBA (GCase) and three-dimensional protein structure prediction of the mutation were made. A construct of this mutant and its compound heterozygous counterpart were used to measure GCase in vitro.

Results:

GCase is relatively conserved at p.T219A. This novel mutation differs from its wild-type in structure. Moreover, it also causes a reduction in GCase enzyme activity.

Conclusion:

This novel mutation (c.655A>G, p.T219A) is a pathogenic missense mutation, which contributes to GD.

The clinical management of Type 2 Gaucher disease

Gaucher disease, the inherited deficiency of the enzyme glucocerebrosidase, is the most common of the lysosomal storage disorders. Type 2 Gaucher disease, the most severe and progressive form, manifests either prenatally or in the first months of life, followed by death within the first years of life. The rarity of the many lysosomal storage disorders makes their diagnosis a challenge, especially in the newborn period when the focus is often on more prevalent illnesses. Thus, a heightened awareness of the presentation of these rare diseases is necessary to ensure their timely consideration. This review, designed to serve as a guide to physicians treating newborns and infants with Gaucher disease, discusses the presenting manifestations of Type 2 Gaucher disease, the diagnostic work-up, associated genotypes and suggestions for management. We also address the ethical concerns that may arise with this progressive and lethal disorder, since currently available treatments may prolong life, but do not impact the neurological manifestations of the disease.

Gaucher disease with prenatal onset and perinatal death due to compound heterozygosity for the missense R131C and null Rec Nci I GBA mutations

Gaucher disease is an autosomal recessive disorder resulting from deficient activity of the lysosomal enzyme glucocerebrosidase (GBA, E.C.3.2.1.45). Three clinical forms of Gaucher disease have been described: type 1, nonneuronopathic; type 2, acute neuronopathic; and type 3, subacute neuronopathic (OMIM 230800, 230900, 231000). Over the past decade, recognition of a distinct, perinatal lethal form of Gaucher disease (PLGD) has led researchers and clinicians to evaluate Gaucher disease in the differential diagnosis of congenital ichthyosis and nonimmune hydrops fetalis. To date, more than 30 cases of PLGD have been genotyped and reported. It has been observed that homozygosity for recombinant GBA alleles, which are fundamentally null alleles, leads to early lethality, usually in utero or during the 1st few days of life, whereas genotypes involving a recombinant allele and a missense mutation may be less detrimental. Here, we report a case of Gaucher disease with prenatal onset and death within hours of birth, likely due to compound heterozygosity for the GBA Rec Nci I null allele and a R131C missense mutation. In view of the patient's severe clinical course, and based on reviews of other PLGD cases, we postulate that a missense mutation that abruptly disrupts the structure/function of GBA, in combination with a null allele, may result in early lethality in patients with PLGD. We also speculate that R131C is an extremely severe mutation that has occurred more than once in different populations and, in either the homozygous form or heterozygous with another severe mutation, will result in a poor prognosis.

Type 2 Gaucher disease: phenotypic variation and genotypic heterogeneity

Gaucher disease (GD), the most common lysosomal storage disease, results from a deficiency of the lysosomal enzyme glucocerebrosidase. GD has been classified into 3 types, of which type 2 (the acute neuronopathic form) is the most severe, presenting pre- or perinatally, or in the first few months of life. Traditionally, type 2 GD was considered to have the most uniform clinical phenotype when compared to other GD subtypes. However, case studies over time have demonstrated that type 2 GD, like types 1 and 3, manifests with a spectrum of phenotypes. This review includes case reports that illustrate the broad range of clinical presentations encountered in type 2 GD, as well as a discussion of associated manifestations, pathological findings, diagnostic techniques, and a review of current therapies. While type 2 GD is generally associated with severe mutations in the glucocerebrosidase gene, there is also significant genotypic heterogeneity.

Myoclonic epilepsy in Gaucher disease: genotype-phenotype insights from a rare patient subgroup

Gaucher disease, the inherited deficiency of lysosomal glucocerebrosidase, presents with a wide spectrum of manifestations. Although Gaucher disease has been divided into three clinical types, patients with atypical presentations continue to be recognized. A careful phenotypic and genotypic assessment of patients with unusual symptoms may help define factors that modify phenotype in this disorder. One such example is a rare subgroup of patients with type 3 Gaucher disease who develop progressive myoclonic epilepsy. We evaluated 16 patients with myoclonic epilepsy, nine of whom were diagnosed by age 4 y with severe visceral involvement and myoclonus, and seven with a more chronic course, who were studied between ages 22 and 40. All of the patients had abnormal horizontal saccadic eye movements. Fourteen different genotypes were encountered, yet there were several shared alleles, including V394L (seen on two alleles), G377S (seen on three alleles), and L444P, N188S, and recombinant alleles (each found on four alleles). V394L, G377S, and N188S are mutations that have previously been associated with non-neuronopathic Gaucher disease. The spectrum of genotypes differed significantly from other patients with type 3 Gaucher disease, where genotypes L444P/L444P and R463C/null allele predominated. Northern blot studies revealed a normal glucocerebrosidase transcript, whereas Western studies showed that the patients studied lacked the processed 56 kD isoform of the enzyme, consistent with neuronopathic Gaucher disease. Brain autopsy samples from two patients demonstrated elevated levels of glucosylsphingosine, a toxic glycolipid, which could contribute to the development of myoclonus. Thus, although there were certain shared mutant alleles found in these patients, both the lack of a shared genotype and the variability in clinical presentations suggest that other modifiers must contribute to this rare phenotype.

Mutation prevalence among 51 unrelated Spanish patients with Gaucher disease: identification of 11 novel mutations

Gaucher disease is an autosomal recessive disorder caused by mutations in the lysosomal beta-glucocerebrosidase (GBA) gene. Gaucher disease is a very heterogeneous entity due to the large number of different mutations existing in the GBA gene, resulting in a defective protein whose impaired activity is the cause of the disease. We present a mutation analysis of the GBA gene in 51 unrelated Spanish Gaucher disease patients together with clinical findings. Two common mutations, c.1226A>G (N370S) and c.1448T>C (L444P), were determined by restriction enzyme digestion after PCR amplification of genomic DNA. The remaining alleles were screened by amplifying the entire GBA gene followed by nested PCR and SSCP analysis under four different conditions. The c.1226A>G (N370S) and c.1448T>C (L444P) mutations were common, accounting for 56 alleles (55%) and 16 alleles (15%), respectively. In addition, 25 different mutations were found, 11 of which are described here for the first time: c.(-203)A>G, c.160G>A (V15M), c.256C>T (R47X), c.445-2a>g (IVS4-2a>g), c.485T>C (M123T), c.914C>T (P266L), c.953delT, c.1124T>C (L336P), c.1207A>C (S364R), c.1214delG,C, and c.1510delT,C,T (465delSer). Two mutations, S364R and P266L, were associated with neuronopathic forms of Gaucher disease: S364R mutation in heterozygosity with the L444P mutation and the P266L mutation in a homozygous state. Two type 1 patients were found to be carriers of two mutations in the same allele (genotypes [N370S] + [E326K + N188S] and [N370S] + [IVS4-2a>g+c.(-203)A>G]). This study allowed us to identify 100% of mutant alleles, and therefore we conclude that the method used to screen for mutations in the GBA gene is very reliable and there is a broad spectrum of mutations in the GBA gene in the Spanish population.

Glucocerebrosidase pseudogene variation and Gaucher disease: Recognizing pseudogene tracts in GBA alleles

We surveyed the genetic variability of the glucocerebrosidase pseudogene (psGBA) in a worldwide sample of 100 human chromosomes. psGBA is the non-functional duplicate of the gene responsible for Gaucher disease (GBA), the most common lipid storage disorder. The existence of only one psGBA allele described until now, together with the high homology between GBA and psGBA, often prevented recognition of the complex alleles formed by the combination of GBA and psGBA, because psGBA variants could be confused with GBA mutations. In order to determine the variability existent in psGBA, the whole psGBA DNA segment was PCR-amplified and sequenced, and the genotype for all samples was obtained. The ascertainment of the phase among the heterozygous sites was possible through cloning and sequencing a single allele. Eighteen variable sites were detected along psGBA. Two of the variants already have been reported as Gaucher-causing mutations when present in GBA alleles. The other variants were unknown. The knowledge of the psGBA variants described in this report will allow identification of psGBA-GBA complex alleles that may aid in understanding the intricate phenotype-genotype relationship in Gaucher disease.

Glucocerebrosidase mutations among African-American patients with type 1 Gaucher disease

While the inherited deficiency of the enzyme glucocerebrosidase (Gaucher disease) is panethnic in its distribution, there have not been studies of the mutations encountered in specific ethnic groups in the United States, other than those on Ashkenazi Jews. We present the clinical descriptions and genotypes of seven patients of African-American ancestry with type 1 Gaucher disease, and summarize the published literature regarding the genotypes encountered in this population. All seven of the patients had moderate-to-severe manifestations of the disease, and all developed symptoms by adolescence. Genotypic analyses revealed that no two probands shared the same genotype. The common mutations N370S, c.84-85insG, IVS2+1 G-->A, and R463C were not seen. Mutation L444P was present on one allele in each of the patients; but the same mutation was encountered as a single point mutation in three of the patients, and as part of a recombinant allele in four of the patients. Southern blot analyses revealed a glucocerebrosidase fusion allele in one patient, and a duplication resulting from recombination in the region downstream from the glucocerebrosidase gene in three of the patients. Five different point mutations (A90T, R48W, N117D, R170C, and V352L), one deletion mutation (c.222-224 delTAC), and one insertion mutation (c.153-154 insTACAGC) were encountered. Our results demonstrate that there is significant genotypic heterogeneity among African-American patients with type 1 Gaucher disease, and that recombinations in the glucocerebrosidase gene locus are particularly common in this patient group. Published 2001 Wiley-Liss, Inc.

A new gene-pseudogene fusion allele due to a recombination in intron 2 of the glucocerebrosidase gene causes Gaucher disease

Gaucher disease is the most prevalent sphingolipid storage disorder in humans caused by a recessively inherited deficiency of the enzyme glucocerebrosidase. More than 100 mutations have been described in the glucocerebrosidase gene causing Gaucher disease. Some of them are complex alleles with several mutations due to recombination events between the gene and its highly homologous pseudogene. The generation of these recombinant alleles involves, in most cases, a crossover in the 3' end of the gene, beyond exon 8. However, in a few cases recombination took place in a more upstream location. Here we describe the analysis of a patient with type I Gaucher disease who bears a new complex allele. This allele was originated by a crossover between the gene and the pseudogene at intron 2, the most upstream recombination site described so far, which gave rise to a fusion gene. The patient was first diagnosed as homozygous for the c.1226 A --> G (N370S) mutation but the early onset of the disease prompted us to perform parental DNA analysis which showed that the mother was not a N370S carrier, suggesting deletion of at least part of the gene. Molecular analysis of the complex allele was carried out by Southern blot, PCR, and sequencing. We were able to close down the region of the recombination event to an interval of 18 nucleotides, corresponding to the last 15 nucleotides of intron 2 and the first 3 nucleotides of exon 3 of the gene. These 18 nucleotides are identical between the gene and pseudogene making any further refinement impossible. An exhaustive list of published glucocerebrosidase complex alleles, describing their recombination points, is included for comparison.

Identification of a novel recombinant allele in three unrelated Italian Gaucher patients: implications for prognosis and genetic counseling

Gaucher disease (GD) results from deleterious mutations in the glucocerebrosidase gene. The relatively high frequency of some of these, especially at cDNA nucleotide 1226G (N370S) and at cDNA nucleotide 1448C (L444P), has led to the development of rapid screening techniques that can sometimes be misleading. In this report, we describe a novel rearrangement between the glucocerebrosidase gene and its pseudogene, identified as a consequence of a discrepancy between the genotype, homozygous for the common 1226G mutation, of an Italian patient with type 1 Gaucher disease, and the absence of the 1226G allele in her daughter. Additional investigations went on to reveal a novel recombinant allele beginning in intron 6 and extending through the rest of the coding sequence. Italian GD patients found homozygous for a specific mutation or with one or both alleles still unknown were further investigated and the novel recombinant allele was identified in an adult type 1 patient previously genotyped 1226G/1226G and in a young patient with an unknown genotype. The detection of this allele in three unrelated GD patients originating from the same geographic area in central Italy suggested a founder effect. This study emphasizes the implications of an accurate genotyping for the prognostic value of glucocerebrosidase genotype and reliable genetic counseling.

Functional characterization of the novel mutation IVS 8 (-11delC) (-14T>A) in the intron 8 of the glucocerebrosidase gene of two Italian siblings with Gaucher disease type I

Gaucher disease, the most common glycolipid storage disease, can be caused by a large variety of mutations. We report here the identification and characterization of a novel mutation in the human glucocerebrosidase gene, IVS 8 (-11delC) (-14T>A), in two siblings with Gaucher disease type I which occurs within the 3' end of intron 8. Both siblings were compound heterozygotes for the IVS 8 (-11delC) (-14T>A) mutation and for the c.626 G>C (R170P) substitution within exon 6. No mRNA species carrying the IVS 8 (-11delC) (-14T>A) mutation were detected by RT-PCR analysis of the RNA extracted from the patients' fibroblasts. To study the possible effects of the IVS 8 (-11delC) (-14T>A) sequence alteration on the splicing of the proximal exon 9, we have established an in vitro system generating a minigene carrying the genomic region of human glucocerebrosidase spanning from exon 8 to exon 10. Transfections into the human Hep3B cell line of the wild-type construct resulted in the expression of mRNA with the glucocerebrosidase exons correctly spliced. On the contrary, transfections of the construct carrying the IVS 8 (-11delC) (-14T>A) mutation resulted in the expression of mRNA with an 11-bp insertion located between the end of exon 8 and the beginning of exon 9. These results indicated that the 5243T>A substitution created a new 3' splice site 11 bp upstream of the wild-type one, leading to the incorporation into the mRNA of these extra 11 bases. Moreover, the new 3' splice site created by this 5243T>A transversion was preferred over the wild-type one in 100% of cases. The in vitro studies suggest that, in the patients, the 11-bp inclusion causes a shift in the reading frame with the generation of a stop codon after codon 388 which undergoes early degradation.

Type 2 Gaucher disease: the collodion baby phenotype revisited

The association of Gaucher disease, the inherited deficiency of lysosomal glucocerebrosidase (EC 3.2.1.45), and congenital ichthyosis was first noted a decade ago. Subsequently, a null allele type 2 Gaucher mouse was generated that also exhibited ichthyotic skin, confirming that the skin disorder and enzyme deficiency were directly related. This paper details the clinical and molecular characterisation of 6 cases of type 2 Gaucher disease presenting with the collodion baby phenotype. The identified mutant glucocerebrosidase alleles include two novel mutations (S196P and R131L) and two rare point mutations (R120W and R257Q), as well as alleles resulting from recombination with the nearby glucocerebrosidase pseudogene. There is significant genotypic heterogeneity in this rare subset of patients with type 2 Gaucher disease. Gaucher disease should be considered in the differential diagnosis of congenital ichthyosis in the newborn period.

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.