Unique frequency of known mutations in Brazilian MPS I patients

The frequency of 10 known mutations in the IDUA gene-Q70X, A75T, H82P, R89Q, 678-7 g-->a, L218P, A327P, R383H, W402X, and P533R-was estimated in a group of 24 index cases with mucopolysaccharidosis type I. Three affected relatives were also analysed. Six of the 10 mutations screened were present in our patients (Q70X, R89Q, A327P, R383H, W402X, and P533R). These mutations account for 54% of the alleles; 37% of the genotypes were defined. Frequencies of these mutations are markedly different from those in the literature. A novel combination Q70X/A327P is described. This was the first time Brazilian MPS I patients were analysed with molecular techniques. The low frequency of common mutations indicates that a more comprehensive analysis of the IDUA gene should be done to delineate the mutation profile of MPS I better in our population.     

Analysis of five mutations in 20 mucopolysaccharidois type 1 patients: high prevalence of the W402X mutation. Mutations in brief no. 121. Online

Mucopolysaccharidosis type 1 is a lysosomal storage disease due to a L-Iduroniase deficiency. Three main phenotypes have been reported: Hurler (severe), Scheie (mild) and Hurler/Scheie (intermediate). High prevalence of mutations W402X and Q70X has been described. We studied these two mutations in 20 unrelated MPSI Spanish patients. In addition we have also analysed the P533R mutation because of its frequency in the close Mediterranean country Italy and mutations R89Q and 678-7g->a because of its prevalence in European Scheie syndrome. We found that 60% (24/40) mutated alleles carried the W402X mutation, 40% of them in homozygosity. Such a high prevalence of this mutation has not been described so far. Patients who carry this mutation in both alleles or in combination with Q70X and P533R have a severe phenotyoe. Mutation Q70X was found in 10% (4/40) of the alleles, two of them in heterozygosity with W402X. Patient with Q70X/Q70X genotype had a severe Hurler phenotype. The P533R mutation accounts for 10% (4/40) of the alleles. One Hurler phenotype patient was homozygous for this mutation. No patient presented the R89Q or 678-7g->a mutations. In conclusion, screening of Spanish patients for mutations W402X, Q70X and P533R allowed identification of 80% of the mutant alleles and genotyping of 70% of patients.     

Identification and characterization of 13 new mutations in mucopolysaccharidosis type I patients

In this study we have investigated a group of 29 Brazilian patients, who had been diagnosed with the lysosomal storage disorder, Mucopolysaccharidosis type I (MPS-I). MPS I is caused by a deficiency in the lysosomal hydrolase, alpha-L-iduronidase. Ninety percent of the MPS I patients in this study were genotyped and revealed 10 recurrent and thirteen novel IDUA gene mutations. Eight of these new mutations and three common mutations W402X, P533R, and R383H were individually expressed in CHO-K1 cells and analyzed for alpha-L-iduronidase protein and enzyme activity. A correlation was observed between the MPS I patient clinical phenotype and the associated mutant alpha-L-iduronidase protein/enzyme activity expressed in CHO-K1 cells. This was the first time that Brazilian MPS I patients had been thoroughly analyzed and highlighted the difficulties of mutation screening and clinical phenotype assessment in populations with high numbers of unique mutations.     

Mutation analysis of 19 North American mucopolysaccharidosis type I patients: Identification of two additional frequent mutations

Mucopolysaccharidosis type I (MPS I) is an autosomal recessive genetic disorder caused by deficiency of the lysosomal glycosidase α-L-iduronidase. Patients with this disorder present with varied clinical phenotypes ranging from early severe onset of disease and death in early childhood to mild manifestations compatible with adult life. An understanding of the molecular basis of iduronidase deficiency and its correlation to clinical phenotype will improve prognostic prediction at diagnosis, aid in genetic counselling of families, and provide a framework to more accurately assess experimental treatment protocols. We have used the approach of single-strand conformational polymorphism analysis and direct sequencing of the α-L-iduronidase gene in an attempt to define the molecular basis of iduronidase deficiency in affected individuals. An initial series of 19 patients representing 35 independently segregating mutant alleles were studied. In addition to five previously identified mutations (W402X, Q70X, E274X, H82P, and P533R) two novel mutations (A75T and 474-2a→g) were found. These seven mutations account for 71% of the mutant alleles and 53% of the genotypes in this group of patients. Analysis of a larger independently ascertained group of 103 MPS I patients, mainly of Northern European origin, revealed that together the two novel mutations account for 7% of mutant alleles and are associated with severe clinical phenotypes. These mutations are the most frequent MPS I mutations detected so far after W402X and Q70X. With the definition of these two mutations, a clear picture of the molecular heterogeneity of MPS I is emerging. © 1994 Wiley-Liss, Inc.     

alpha-L-iduronidase mutations (Q70X and P533R) associate with a severe Hurler phenotype.

Mucopolysaccharidosis type I (MPS-I) is an autosomal recessive genetic disease caused by a deficiency of the glycosidase alpha-L-iduronidase which is required for the lysosomal degradation of the glycosaminoglycans heparan sulfate and dermatan sulfate. Patients with MPS-I store forms of these partially degraded glycosaminoglycans in their lysosomes. MPS-I patients present with a wide range of clinical phenotypes, which makes prognostic predictions and genetic counselling difficult, therefore impeding the selection and evaluation of patients undergoing experimental therapy, such as bone marrow transplantation. We report the presence of two mutations, one that introduces a stop codon at position 70 (Q70X), and the other that alters the proline at position 533 to an arginine (P533R) in the 653 amino acid alpha-L-iduronidase protein. These mutations were originally detected by chemical cleavage and then by direct PCR sequencing. Allele specific oligonucleotides were used to detect the mutations in a group of 73 MPS-I patients and Q70X was found to account for 15% of all MPS-I alleles and P533R for 3% of MPS-I alleles. Both mutations are associated with an extremely severe clinical phenotype in homozygotes. MPS-I patients heterozygous for either mutation may have a wide range of clinical phenotypes. We have now described three mutations, W402X (Scott et al., 1992c), Q70X, and P533R totalling 53% of MPS-I alleles which together define 28% of MPS-I genotypes.     

Molecular analysis of 30 mucopolysaccharidosis type I patients: evaluation of the mutational spectrum in Italian population and identification of 13 novel mutations

Mucopolysaccharidosis type I (MPS-I orMPS1) is an autosomal recessive condition characterized by a broad range of clinical symptoms. Molecular diagnosis of MPS-I is important for analyzing genotype-phenotype correlation and for selecting patients for innovative therapies. In this study we analyzed 30 Italian MPS-I patients with different phenotypes (20 severe, 6 intermediate, 4 mild) in an attempt to recognize the mutational spectrum in our population and to identify major DNA alterations specific to our country. We identified 93% of mutated alleles (56 out of 60) with the reconstruction of the complete genotype in 26 patients out of 30. Twenty-three different mutations were found, 13 of which are novel while the remaining 10 have been already described. Among the novel mutations we found 5 non conservative missense mutations (A160D, E178K, P183R, G197D, D349Y), one nonsense mutation (C53X), 6 deletions (468-470del3, 486-491del6, 755-759del5, 1251delC, 1839-1867del29, 1902-1903del2), and one splice site mutation (IVS11+5G>A). No common mutation for MPS-I is present in our country. Frequently (40% of the alleles), mutations were found in just one or two patients. However, Q70X, P533R, G51D, and W402X mutations were present in several patients (15%, 13.3%, 13.3%, and 11.6% of the alleles respectively) suggesting a Mediterranean origin of the P533R and G51D mutations. In most cases the patients' genotypes were unique combinations of mutations. The great heterogeneity found in our MPS-I population hampers mutation detection and hinders the genotype-phenotype correlation.     

Molecular analysis of mucopolysaccharidosis type IIIB in Portugal: evidence of a single origin for a common mutation (R234C) in the Iberian Peninsula

Mucopolysaccharidosis type IIIB (Sanfilippo B disease) is a rare autosomal recessive disorder caused by defective α-N-acetylglucosaminidase (NAGLU). We examined the NAGLU gene in 11 MPS IIIB Portuguese patients, having identified five novel (M1K, W147X, G304V, S522P, and R533X) and four previously reported mutations (W168X, R234C, R565W and R643C). R234C attained the high prevalence of 32% of the mutated alleles. Because R234C had already been reported to be common in Spanish patients, a haplotypic analysis was conducted to address the question of its origin in the Iberian Peninsula. Three neutral markers were studied that allowed for the identification of the probable founder haplotype (174-234-G) on which R234C arose. The sharing of the ancestral haplotype by Portuguese and Spanish patients clearly implied a common origin of the mutation in Iberia, through an event that was inferred to have been rather recent. Therefore, the reconstructed history of R234C explains the high incidence of the mutation in Iberian patients with Sanfilippo B disease.     

Phenotype and genotype heterogeneity in Mediterranean citrullinemia.

We summarize the diagnosis, outcome, and molecular studies of five Mediterranean patients with citrullinemia: four neonatal classical forms and one subacute form, who also suffers from Down syndrome and presented with severe hepatic encephalopathy at age 7. Mutational analysis revealed three alleles with a common mutation and five new mutations: two Moroccan siblings are homozygous for G390R, the subacute form is compound heterozygous for G390R/G117D (new mutation), and the two other neonatal forms are compound heterozygous for four new mutations: V69A/E270Q and T119I(R108L)/?.     

Mucopolysaccharidosis I mutations in Chinese patients: identification of 27 novel mutations and 6 cases involving prenatal diagnosis

Mucopolysaccharidosis I (MPS I) is a lysosomal storage disease that results from the deficiency of α-l-iduronidase and is transmitted in an autosomally recessive manner. This report describes the first systematic screening for mutations in Chinese MPS I patients from mainland China, wherein we have summarized the phenotype/genotype correlation of the individuals in Chinese MPS I patients. Mutational analyses were performed in 57 unrelated Chinese MPS I patients. Overall, 105 mutant alleles were identified from a set of 41 different mutations. Notably, of these 41 mutations, 27 were novel mutations that consisted of 8 splicing mutations (c.1-2C>G, c.296+4G>A, c.300-1G>C, c.792+1G>C, c.973-4G>A, c.1189+5G>T, c.1402+1G>T and c.1402+2T>G), 1 nonsense mutation (p.W41X), 1 insertion (c.668-670ins GCG), 5 duplications (c.531dupT, c.657dupG, c.883dupC, c.1147dupG and c.1225dupG), 3 deletions (c.349delT, c.1593delG and c.1244-1271del27),1 nucleotide substitution c.2T>C and 8 missense mutations (p.H33P,p.F52L, p.G168V,p.T179R,p. E182D, p.L237R, p.L238R and p.L421P). The missense mutations p.A79V and p.L346R, which accounted for 16.7% (19/114) and 12.3% (14/114) respectively, were the common mutations in Chinese patients but were rare in the mutational profiles reported for other populations. These results indicate that Chinese MPS I patients may have a different mutational spectrum compared to those of other populations. Moreover, for the first time in China, molecular genetic methods were used for prenatal diagnosis of six cases in five families.     

Sanfilippo B syndrome: molecular defects in Greek patients

Sanfilippo syndrome type B [mucopolysaccharidosis IIIB (MPS IIIB] is the most prevalent type of MPS III in Greece, accounting for 81% of all MPS III cases diagnosed at the Institute of Child Health (Athens) over the last 20 years. The majority of the patients originated from East Central/Central Greece, Thessaly, and Macedonia. We present the results of mutation analysis in 21 Greek patients from 18 different families, all of whom had the severe form of the disorder. Patients were initially screened for five previously known mutations by restriction enzyme digestion of polymerase chain reaction products. Unknown mutations were identified by single-strand conformation polymorphism analysis and DNA sequencing and were confirmed by restriction enzyme analysis. Seven previously described mutations (Y140C, R626X, 503-512del, H414R, G292R, 334del25, and E452K) and four novel mutations (P516L, L242P, E446K, and R482Q) were identified. Expression of the latter and H414R showed that they were all null activity mutations. Considerable genetic heterogeneity has been described in MPS IIIB patients of different origins. In our population, Y140C, H414R, and R626X account for approximately 70% of the studied alleles. Our findings, especially in combination with the origin of individual patients, can improve carrier detection and genetic counseling in affected families.     

Mucopolysaccharidosis type I: Identification of common mutations that cause Hurler and Scheie syndromes in Japanese populations

α-L -Iduronidase (IDUA) deficiency (mucopolysaccharidosis type I; MPS-I) is an inborn error of lysosomal degradation of glycosaminoglycans that results in storage of undegraded glycosaminoglycans in lysosomes. Previous studies in Caucasian populations showed that (1) homozygosity or compound heterozygosity for the W402X and Q70X mutations are the common causes of MPS-I with a severe form (Hurler syndrome), and (2) the presence of R89Q may lead to a milder phenotype. We studied mutations in the IDUA gene from 19 MPS-I patients, including two pairs of siblings, with various clinical phenotypes (Hurler, 6 cases; Hurler/Scheie, 7 cases; Scheie, 6 cases). We report the presence of two common mutations that account for 42% of the 38 alleles in these patients. One is a novel 5-bp insertion between the thymidine at nt 704 and a cytosine at nt 705 (704ins5), which is seen only in the Japanese population. The other is a missense mutation, R89Q, which is also seen in Caucasians, although uncommonly. In the 19 Japanese MPS-I patients, the 704ins5 mutation accounted for 7 of 38 alleles (18%), while the R89Q accounted for 9 of 38 (24%). No Japanese patient was found to carry the W402X or Q70X alleles, the two most common MPS-I mutations in Caucasians. Homozygosity for the 704ins5 mutation is associated with a severe phenotype, and for the R89Q mutation with a mild phenotype. Compound heterozygosity for these two mutations produced an intermediate phenotype. Haplotype analysis using polymorphisms linked to the IDUA locus demonstrated that each mutation occurs on a different specific haplotype, suggesting that individuals with each of these common mutations derive from common founders. These data continue to document the molecular heterogeneity and racial differences in mutations in MPS-I. © 1996 Wiley-Liss, Inc.     

Molecular analysis of mucopolysaccharidosis type VI in Poland, Belarus, Lithuania and Estonia

Mucopolysaccharidosis VI (MPS VI) is a rare autosomal recessive disorder caused by a deficiency of N-acetylgalactosamine-4-sulfatase (ARSB). Over 130 ARSB gene mutations have been identified thus far and most mutations are unique to individual families. We aimed to analyze the spectrum of mutations in the ARSB gene responsible for the disorder in Poland, Belarus and Baltic States. Twenty one families with MPS VI patients, in whom diagnosis was confirmed biochemically and enzymatically, were studied. Direct sequencing of patient genomic DNA was used to identify ARSB mutations. In total, fourteen different disease-causing mutations were found. Three novel mutations included insertion c.375_376insT, a missense mutation c.499G>A (p.G167R) and deletion/insertion c.750_754delinsCCTGAAGTCAAG. We also report 11 previously described mutations (p.A33V, p.W57C, p.Q88X, p.T92K, p.Q97X, p.R152W, p.R160Q, p.R160X, p.Y210C, p.Y266S, p.G302R). The mutation p.R152W was present at a high prevalence of 50% (21/42) the mutated alleles in this group of patients. High prevalence of p.R152W mutation in Poland, Belarus and Baltic States indicates a possible founder effect and suggests that screening for this mutation may be appropriate in MPS VI patients from this region. Our study has also provided evidence to support genotype-phenotype correlation.     

Analysis of the glucocerebrosidase gene and mutation profile in 144 Italian gaucher patients

Gaucher disease (GD), the most prevalent lysosomal storage disease characterized by a remarkable degree of clinical variability, results from deleterious mutations in the glucocerebrosidase gene (GBA). In this paper we report the molecular characterization of 144 unrelated Italian GD patients with the three types of the disease. The allelic frequencies of Italians are reported and the mutation profile is analyzed. Besides the common N370S, L444P, RecNciI, G202R, IVS2+1G>A, D409H, F213I mutations, the different molecular strategies, used for the mutation detection, identified the rare N107L, R131C, R170C, R170P, N188S, S196P, R285C, R285H, W312C, D399N, A446P, IVS10-1G>A, RecDelta55, total gene deletion, as well as 12 mutant alleles that were exclusively present in the Italian population until now: the previously reported R353G, N370S+S488P mosaicism, IVS8(-11delC)-14T>A), Rec I, Y418C, and the seven novel alleles D127X, P159T, V214X, T231R, L354X, H451R, and G202R+M361I. The wide phenotypic differences observed within the genotypic groups as well as between siblings implicate a significant contribution of other modifying genetic and/or non-genetic factors and claim a comprehensive valuation of the patient including clinical., biochemical and molecular investigations for prognosis, appropriate interventive therapy and reliable genetic counseling.     

PKU in Minas Gerais State,Brazil: Mutation Analysis

This work was undertaken in order to ascertain the PKU mutational spectrum in Minas Gerais, Brazil, the relative frequency of the mutations in the State and the origin of these mutations by haplotype determination. Minas Gerais is a trihybrid population formed by miscegenation from Europeans, Africans and Amerindians. All 13 exons of the PAH gene from 78 PKU patients were analyzed, including splicing sites and the promoter region. We identified 30 different mutations and 98% of the PAH alleles were established. A new mutation (Q267X) was identified as well. The most common mutations found were V388M (21.2), R261Q (16.0%), IVS10‐11G>A (15.3%), I65T (5.8%), IVS2+5G>C (5.8%), R252W (5.1%), IVS2+5G>A (4.5%), P281L (3.8%) and L348V (3.2%). These nine mutations correspond to 80% of the PKU alleles in the state. Haplotypes were determined to characterize the origin of the PAH alleles. The majority of the mutations found, with respective haplotypes, are frequent in the Iberian Peninsula. However, there were some mutations that are rare in Europe and four previously unreported mutation‐haplotype associations. I65T and Q267X were found in association with haplotype 38 and may be African in origin or the result of miscegenation in the Brazilian population.     

Four novel mutations underlying mild or intermediate forms of α-L-iduronidase deficiency (MPS IS and MPS IH/S)

The α-L-iduronidase deficiency diseases (Mucopolysaccharidosis I) cover a spectrum of clinical severity ranging from the very severe (Hurler syndrome, MPS IH) through an intermediate (Hurler/Scheie syndrome, MPS IH/S) to a relatively mild form (Scheie syndrome, MPS IS). Numerous mutations of the gene encoding α-L-iduronidase (IDUA) are known in Hurler syndrome, but only three in the other disorders. We report on novel mutations of the IDUA gene in one patient with the Scheie syndrome and in three patients with the Hurler/Scheie syndrome. The novel mutations, all single base changes, encoded the substitutions R492P (Scheie), and X654G, P496L, and L490P (Hurler/Scheie). The L490P mutation was apparently homozygous, whereas each of the others was found in compound hettrozygosity with a Hurler mutation. The deleterious nature of the mutations was confirmed by absence of enzyme activity upon transfection of the corresponding mutagenized cDNAs into Cos-1 cells. These results provide additional information for genotype—phenotype correlations. © 1995 Wiley-Liss, Inc.     

Identification of 12 novel mutations in the alpha-N-acetylglucosaminidase gene in 14 patients with Sanfilippo syndrome type B (mucopolysaccharidosis type IIIB).

Sanfilippo syndrome type B or mucopolysaccharidosis type IIIB (MPS IIIB) is one of a group of lysosomal storage disorders that are characterised by the inability to breakdown heparan sulphate. In MPS IIIB, there is a deficiency in the enzyme alpha-N-acetylglucosaminidase (NAGLU) and early clinical symptoms include aggressive behaviour and hyperactivity followed by progressive mental retardation. The disease is autosomal recessive and the gene for NAGLU, which is situated on chromosome 17q21, is approximately 8.5 kb in length and contains six exons. Primers were designed to amplify the entire coding region and intron/exon boundaries of the NAGLU gene in 10 fragments. The PCR products were analysed for sequence changes using SSCP analysis and fluorescent DNA sequencing technology. Sixteen different putative mutations were detected in DNA from 14 MPS IIIB patients, 12 of which have not been found previously. The mutations include four deletions (219-237del19, 334-358del25, 1335delC, 2099delA), two insertions (1447-1448insT, 1932-1933insGCTAC), two nonsense mutations (R297X, R626X), and eight missense mutations (F48C, Y140C, R234C, W268R, P521L, R565W, L591P, E705K). In this study, the Y140C, R297X, and R626X mutations were all found in more than one patient and together accounted for 25% of mutant alleles.     

Sanfilippo type B syndrome (mucopolysaccharidosis III B): allelic heterogeneity corresponds to the wide spectrum of clinical phenotypes

Sanfilippo B syndrome (mucopolysaccharidosis IIIB, MPS IIIB) is caused by a deficiency of alpha-N-acetylglucosaminidase, a lysosomal enzyme involved in the degradation of heparan sulphate. Accumulation of the substrate in lysosomes leads to degeneration of the central nervous system with progressive dementia often combined with hyperactivity and aggressive behaviour. Age of onset and rate of progression vary considerably, whilst diagnosis is often delayed due to the absence of the pronounced skeletal changes observed in other mucopolysaccharidoses. Cloning of the gene and cDNA encoding alpha-N-acetylglucosaminidase enabled a study of the molecular basis of this syndrome. We were able to identify 31 mutations, 25 of them novel, and two polymorphisms in the 40 patients mostly of Australasian and Dutch origin included in this study. The observed allellic heterogeneity reflects the wide spectrum of clinical phenotypes reported for MPS IIIB patients. The majority of changes are missense mutations; also four nonsense and nine frameshift mutations caused by insertions or deletions were identified. Only five mutations were found in more than one patient and the observed frequencies are well below those observed for the common mutations in MPS IIIA. R643C and R297X each account for around 20% of MPS IIIB alleles in the Dutch patient group, whilst R297X, P521L, R565W and R626X each have a frequency of about 6% in Australasian patients. R643C seems to be a Dutch MPS IIIB allele and clearly confers the attenuated phenotype. One region of the gene shows a higher concentration of mutations, probably reflecting the instability of this area which contains a direct repeat. Several arginine residues seem to be 'hot-spots' for mutations, being affected by two or three individual base pair exchanges.     

Mutation analysis of the GCDH gene in Italian and Portuguese patients with glutaric aciduria type I

Two novel (G390V and X439W) and five already known mutations were identified in a total of 14 GA I alleles from Italy and Portugal. The substitution X439W is a rare type of mutation, which breaks the stop codon of the GCDH gene. As described in other populations, R402W was the most common mutation. Genotype R227P/R402W was found in a patient with low glutarate excretion. Haplotype studies have also been performed.     

Molecular analysis of Turkish mucopolysaccharidosis IVA (Morquio A) patients: identification of novel mutations in the N-acetylgalactosamine-6-sulfate sulfatase (GALNS) gene

Mucopolysaccharidosis IVA (MPS IVA) is a lysosomal storage disorder caused by the deficiency of N-acetylgalactosamine-6-sulfate sulfatase (GALNS; EC 3.1.6.4). The deficiency of N-acetylgalactosamine-6-sulfate sulfatase leads to lysosomal accumulation of undegraded glycosaminoglycans, keratan sulfate and chondroitin-6-sulfate. Mutation screening of the GALNS gene was performed by SSCP and direct sequence analyses using genomic DNA samples from 10 Morquio A patients. By nonradioactive SSCP screening, 6 different gene mutations and 2 polymorphisms were identified in 10 severely affected MPS IVA patients. Five of the mutations and one of the polymorphisms are novel. The vast majority of the gene alterations were found to be single nucleotide deletions (389delG, 929delG, and 763delT) or insertions (1232-1233insT). The other two mutations were one previously identified missense mutation (Q473X) and one novel nonsense (P179S) mutation. Together they account for 95% of the disease alleles of the patients investigated. Beside mutations, one previously identified E477 polymorphism and one novel W520 polymorphism were found among Turkish MPS IVA patients.