Two novel mutations of the arylsulfatase B gene in two Italian patients with severe form of mucopolysaccharidosis. Mutations in brief no. 127. Online

ARSB gene variants causing Mucopolysaccharidosis VI in Miniature Pinscher and Miniature Schnauzer dogs

Mucopolysaccharidosis (MPS) VI is a lysosomal storage disease caused by a deficiency of N-acetylgalactosamine-4-sulfatase, also called arylsulfatase B (ARSB, EC 3.1.6.12). Dogs with MPS VI show progressive predominantly oculoskeletal signs homologous to those in human and feline patients. We report herein two pathogenic ARSB gene variants in Miniature Pinscher and Miniature Schnauzer dogs with MPS VI and a genotyping survey in these breeds. All exons and adjacent regions of the ARSB gene were sequenced from three affected Miniature Pinschers and three affected Miniature Schnauzers. Allelic discrimination assays were used for genotyping. A missense variant (NM_001048133.1:c.910G>A) was found in exon 5 of MPS VI-affected Miniature Pinschers that is predicted to result in a deleterious amino acid substitution of a highly conserved glycine to arginine (NP_001041598.1:p.Gly304Arg). In MPS VI-affected Miniature Schnauzers, a 56 bp deletion (NM_001048133.1:c.-24_32del) was found at the junction of exon 1 and its upstream region, predicting no enzyme synthesis. All clinically affected Miniature Pinschers and Miniature Schnauzers were homozygous for the respective variants, and screened healthy dogs in each breed were either heterozygous or homozygous for the wt allele. Whereas the Miniature Pinscher variant seemed to occur commonly (0.133 allele frequency), the Miniature Schnauzer variant was presumed to be rare. In conclusion, two breed-specific pathogenic ARSB gene variants were identified in Miniature Pinscher and Miniature Schnauzer dogs with MPS VI, allowing for genotyping and informed breeding to prevent the production of affected offspring.

Identification of arylsulfatase B gene mutations and clinical presentations of Iranian patients with Mucopolysaccharidosis VI

BACKGROUND

Mucopolysaccharidosis (MPS) type VI, also known as Maroteaux-Lamy syndrome, is an autosomal recessive lysosomal storage disorder caused by a deficiency in arylsulfatase B (ARSB) enzyme. Our objectives were to investigate clinical phenotypes and performed molecular studies in Iranian patients with MPS VI, for the first time, in the southwestern Iran.

METHODS

We studied 14 cases from 10 unrelated kindreds with MPS VI that were enrolled during 8 years. The mutational analysis of coding and flanking regions of ARSB gene was performed for the patients and their families using genomic DNA from whole blood by direct sequencing.

RESULTS

All cases had parental consanguinity. Except one who had Fars ethnicity and presented with a very mild degree of coarse face, but normal otherwise, even near normal height, all were from Arab ethnicity with characteristic phenotypes including severe facial changes, cardiac involvement and dysostosis multiplex. Sequencing analysis of ARSB gene revealed four pathogenic homozygote mutations, including a novel nonsense mutation c.281C>A (p.Ser94X) in 9 patients, as well as, a known nonsense mutation c.753C>G (p.Try251X) in 3 cases, and two missense mutations c.904G>A (p.Gly302Arg) and c.454C>T (p.Arg152Trp) in two cases. The type of mutations affected the severity patient's phenotypes.

CONCLUSIONS

These findings increased the genetic databases of Iranian patients with MPS VI and would be so much helpful for the high-risk families to speed the detection of carriers with accuracy and perform the prenatal test of disorder with cost-effective in this population.

Molecular findings of Colombian patients with type VI mucopolysaccharidosis (Maroteaux-Lamy syndrome)

Introduction

Maroteaux–Lamy syndrome, or mucopolysaccharidosis (MPS) type VI, is an autosomal recessive lysosomal storage disease caused by a deficient activity of the enzyme arylsulfatase B (ARSB), required to degrade dermatan sulfate. The onset and progression of the disease vary, producing a spectrum of clinical presentation. So far, 133 mutations have been reported. The aim of this study is to determine the mutations in the ARSB gene that are responsible for this disease in Colombian patients.

Results

Fourteen patients with clinical manifestations and biochemical diagnosis of MPS VI were studied, including two siblings. The 8 exons of the gene were directly sequenced from patients' DNA, and 14 mutations were found. 57% of these mutations had not been previously reported (p.H111P, p.C121R, p.G446S, p.*534W, p.S334I, p.H147P, c.900T > G, and c.1531_1553del) and 43% had been previously reported (p.G144R, p.W322*, p.G302R, p.C447F, p.L128del, and c.1143-1G > C). Of the previously reported mutations, 80% have been associated with severe phenotypes and 20% with intermediate-severe phenotypes. Bioinformatic predictions indicate that the new mutations reported in this paper are also highly deleterious.

Conclusions

Most of the Colombian patients in this study had private mutations.

Molecular Analysis of Turkish Maroteaux-Lamy Patients and Identification of One Novel Mutation in the Arylsulfatase B (ARSB) Gene

Mucopolysaccharidosis type VI (MPS VI, Maroteaux-Lamy syndrome) is an autosomal recessive disorder caused by the deficit of the arylsulfatase B (ARSB) enzyme, which leads to dermatan sulfate pathological storage, resulting in a wide spectrum of clinical phenotypes. To date more than 130 different mutations were reported, most of them being restricted to individual families. We here report the first study on the ARSB gene mutations in MPS VI patients of Turkish ethnogeographic origin. On the whole we analyzed 13 unrelated families recruited from 3 different Turkish clinical centers, for a total of 52 subjects, including patients, parents, and siblings. The molecular characterization of ARSB gene in these subjects lead to the identification of eight different mutations (6 missense mutations and two single-nucleotide deletions) one of which novel: c.532C>G (p.H178D). We characterized seven different genotypes, all homozygous except one. The analysis highlighted c.962T>C (p.L321P) as the most frequently detected mutation in the group of patients examined and the c.1072G>A (p.V358M) as the most frequent polymorphism. All parents and 50% of the healthy siblings analyzed carried in a heterozygous condition the mutation identified in the affected relative. The high number of homozygotes reported in this study reflects the high degree of consanguinity of the Turkish population, being the parents of most of the patients here examined, first-degree cousins. As consanguineous marriages are an integral part of the Turkish society, carriers identification accompanied by genetic counseling in families at risk is the eligible approach to minimize the effects of consanguinity in this population.

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.

Evolution of the couple cytochrome c and cytochrome c oxidase in primates

Mitochondrial energy metabolism has been affected by a broad set of ancient and recent evolutionary events. The oldest example is the endosymbiosis theory that led to mitochondria and a recently proposed example is adaptation to cold climate by anatomically modern human lineages. Mitochondrial energy metabolism has also been associated with an important area in anthropology and evolutionary biology, brain enlargement in human evolution. Indeed, several studies have pointed to the need for a major metabolic rearrangement to supply a sufficient amount of energy for brain development in primates.The genes encoding for the coupled cytochrome c (Cyt c) and cytochrome c oxidase (COX, complex IV, EC 1.9.3.1) seem to have an exceptional pattern of evolution in the anthropoid lineage. It has been proposed that this evolution was linked to the rearrangement of energy metabolism needed for brain enlargement. This hypothesis is reinforced by the fact that the COX enzyme was proposed to have a large role in control of the respiratory chain and thereby global energy production.After summarizing major events that occurred during the evolution of COX and cytochrome c on the primate lineage, we review the different evolutionary forces that could have influenced primate COX evolution and discuss the probable causes and consequences of this evolution. Finally, we discuss and review the co-occurring primate phenotypic evolution.

Genetic studies in a cluster of mucopolysaccharidosis type VI patients in Northeast Brazil

Mucopolysaccharidosis type VI (MPS VI, Maroteaux-Lamy syndrome) is a lysosomal storage disease caused by deficiency of arylsulphatase B. The incidence of MPS VI is very low, usually less than 1 case for every 1,000,000 newborns. In Northeast Brazil we identified in the county of Monte Santo (52,360 inhabitants) thirteen patients with MPS VI. The aim of this work was to identify the mutation(s) present in these patients and analyze intragenic SNPs to define possible haplotypes. The 13 MPS VI patients were found to be homozygous for the p.H178L mutation. All patients have the same haplotype for the intragenic SNPs. Based on current data, the prevalence of MPS VI in this region is estimated as 1:5,000 newborns. These results, together with pedigree analysis, strongly suggest a founder effect accounting for the high frequency of p.H178L mutation in this area. This reinforces the need of a comprehensive community genetics program for this area.

Large deletion involving exon 5 of the arylsulfatase B gene caused apparent homozygosity in a mucopolysaccharidosis type VI patient

Apparent homozygosity for the mutation p.R315X present on exon 5 of the arylsulfatase B (ARSB) gene in a mucopolysaccharidosis type VI patient was solved in this study by further testing for a second mutation. Patient cDNA analysis revealed that the entire exon 5 of the ARSB gene was lacking; this new mutation was identified as c.899-1142del. As the genomic DNA sequencing excluded the presence of splicing mutations, polymerase chain reaction analysis was performed for polymorphisms listed in the NCBI SNP database for the ARSB gene. This allowed the mutation at the genomic DNA level to be identified as g.99367-102002del; this gross deletion, involving the entire exon 5 of the gene and parts of introns 4 and 5 led to a frameshift starting at amino acid 300 and resulting in a protein with 39% amino acids different from the normal enzyme. We stress that extensive DNA analysis needs to be performed in case of apparent homozygosity to avoid potential errors in genetic counseling.

Maroteaux-Lamy syndrome: functional characterization of pathogenic mutations and polymorphisms in the arylsulfatase B gene

Mucopolysaccharidosis VI (MPS VI; Maroteaux-Lamy syndrome) is an autosomal recessive lysosomal disorder caused by deficiency of N-acetylgalactosamine-4-sulfatase (ARSB), which is required for the degradation of dermatan sulfate. We recently reported mutational screening of 12 Spanish and 4 Argentinian MPS VI patients. In the present study, seven missense mutations (c.245T>G [p.L82R], c.413A>G [p.Y138C], c.719C>T [p.S240F], c.922G>A [p.G308R], c.937C>G [p.P313A], c.1340G>T [p.C447F] and c.1415T>C [p.L472P]) were transiently expressed in COS-7 cells and 4-sulfatase activity was measured in cell extracts. All mutations resulted in less than 6% of wild-type enzyme activity, in most cases undetectable. Mutations were expressed in their original haplotype context with respect to two non-synonymous polymorphisms present in the ARSB protein, p.V358M and p.S384N. The three less frequent haplotype combinations yielded an ARSB activity of 16%, 57% and 70%, when compared to the most frequent haplotype (p.358V and p.384S). Western blot analyses showed that the expressed mutations significantly reduced the amount of mature protein. Sub-cellular localization studies of mutant ARSB proteins in fibroblasts of MPS VI patients were performed. RNA analysis confirmed that nonsense-mediated RNA decay had taken place for all mutant alleles (c.1143-1G>C, c.1143-8T>G, p.W322X, c.427delG and c.1142+2T>A) which were candidates for causing RNA degradation by this mechanism. In summary, all the ARSB mutations studied had a significant effect on enzyme activity, protein processing and/or mRNA stability.

Identification of the molecular defects in Spanish and Argentinian mucopolysaccharidosis VI (Maroteaux-Lamy syndrome) patients, including 9 novel mutations

Maroteaux-Lamy syndrome, or mucopolysaccharidosis VI (MPS VI), is an autosomal recessive lysosomal storage disorder caused by a deficiency of N-acetylgalactosamine-4-sulfatase or arylsulfatase B (ARSB). We aimed to analyze the spectrum of mutations responsible for the disorder in Spanish and Argentinian patients, not previously studied. We identified all the ARSB mutant alleles, nine of them novel, in 12 Spanish and 4 Argentinian patients. The new changes were as follows: six missense mutations: c.245T>G [p.L82R], c.413A>G [p.Y138C], c.719C>T [p.S240F], c.922G>A [p.G308R], c.1340G>T [p.C447F] and c.1415T>C [p.L472P]; one nonsense mutation: c.966G>A [p.W322X]; and two intronic changes involving splice sites: c.1142+2T>A, in the donor splice site of intron 5, which promotes skipping of exon 5, and c.1143-1G>C, which disrupts the acceptor site of intron 5, resulting in skipping of exon 6. We also report 10 previously described mutations as well as several non-pathogenic polymorphisms. Haplotype analysis indicated a common origin for most of the mutations found more than once. Most of the patients were compound heterozygotes, whereas only four of them were homozygous. These observations confirm the broad allelic heterogeneity of the disease, with 19 different mutations in 16 patients. However, the two most frequent mutations, c.1143-1G>C and c.1143-8T>G, present in both populations, accounted for one-third of the mutant alleles in this group of patients.

Mutational analysis of mucopolysaccharidosis type VI patients undergoing a phase II trial of enzyme replacement therapy

Mucopolysaccharidosis type VI (MPS VI; Maroteaux-Lamy syndrome) is a lysosomal storage disorder caused by mutations in the N-acetylgalactosamine-4-sulfatase (ARSB) gene. These mutations result in a deficiency of ARSB activity. Ten MPS VI patients were involved in a phase II clinical study of enzyme replacement therapy. Direct sequencing of genomic DNA from these patients was used to identify ARSB mutations. Each individual exon of the ARSB gene was amplified by PCR and subsequently sequenced. Thirteen substitutions (c.215T>G [p.L72R] c.284G>A [p.R95Q], c.305G>A [p.R102H], c.323G>T [p.G108V], c.389C>T [p.P130L], c.511G>A [p.G171S], c.904G>A [p.G302R], c.944G>A [p.R315Q], c.1057T>C [p.W353R], c.1151G>A [p.S384N], c.1178A>C [p.H393P], c.1289A>G [p.H430R] and c.1336G>C [p.G446R]), one deletion (c.238delG), and two intronic mutations (c.1213+5G>A and c.1214-2A>G) were identified. Nine of the 16 mutations identified were novel (R102H, G108V, P130L, G171S, W353R, H430R, G446R, c.1213+5G>A and c.1214-2A>G). The two common polymorphisms c.1072G>A [p.V358M] and c.1126G>A [p.V376M] were identified in some of the patients, along with the silent mutations c.972A>G and c.1191A>G. Cultured fibroblast ARSB mutant protein and residual activity were determined for each patient and, together with genotype information, used to predict the expected clinical severity of each patient.

Mucopolysaccharidosis type VI: Structural and clinical implications of mutations in N-acetylgalactosamine-4-sulfatase

Mucopolysaccharidosis type VI (MPS-VI) is an autosomal recessive lysosomal storage disorder caused by the deficiency of N-acetylgalactosamine-4-sulfatase (4S; or ARSB). Mutations in the 4S gene are responsible for 4S deficiency, which leads to the intralysosomal storage of partially degraded glycosaminoglycans, dermatan sulfate, and chondroitin 4-sulfate. To date, a total of 45 clinically relevant mutations have been identified in the human 4S gene. Missense mutations are the largest group, with 31 identified mutations. Nonsense mutations and small insertions or deletions comprise the remainder, with seven mutations each. Six polymorphisms have also been reported: two amino acid substitutions and four silent transitions. Mapping of the missense mutations onto the 4S structure shows that they are distributed throughout the three subunits of the mature 4S polypeptide. Mutations have been identified in active site residues, in residues adjacent to the active site, in potential substrate binding residues, in residues exposed on the surface, and in residues buried within the protein core. Missense mutations have also been identified in disulfide crosslinks. Molecular modeling of MPS-VI mutations onto the 4S structure suggests that the majority cause 4S deficiency via destabilization and the consequent reduction of 4S protein concentration. The vast majority of MPS-VI mutant alleles are either unique to a patient or are present in a small number of patients. So far, no common mutations have been described. Therefore, screening of the general population for MPS-VI alleles will be difficult.