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PubMed1994

Recombinant alpha-L-iduronidase: characterization of the purified enzyme and correction of mucopolysaccharidosis type I fibroblasts.

Mucopolysaccharidosis type I (MPS I, Hurler and Scheie syndromes) is an autosomal recessive lysosomal storage disorder that results from a deficiency of the hydrolase alpha-L-iduronidase (IDUA) which is involved in the lysosomal degradation of both heparan sulphate (HS) and dermatan sulphate (DS). Patients with MPS I store and excrete large amounts of partially degraded HS and DS. In order to evaluate enzyme replacement therapy for MPS I patients we have expressed human IDUA cDNA in Chinese Hamster Ovary (CHO)-K1 cells utilizing a plasmid vector that places the cDNA under the transcriptional control of the human polypeptide-chain-elongation factor I alpha gene promoter. A clonal cell-line that secreted recombinant IDUA in a precursor form at approximately 2.2 micrograms/10(6) cells per day was identified. This enzyme was shown to be endocytosed into cultured MPS I fibroblasts via mannose-6-phosphate receptors and to correct the storage phenotype of these cells by enabling the lysosomal-digestion of accumulated sulphated glycosaminoglycans. The recombinant IDUA had on SDS/PAGE a molecular mass of 85 kDa and was processed to 74 kDa and smaller forms following its uptake by fibroblasts. Milligram quantities of the recombinant IDUA were immunopurified and the enzyme was shown to have pH optimum and kinetic parameters differing from those of the mature enzyme purified from human liver. The specific activity of the recombinant enzyme was shown to increase on dilution and on incubation with reducing agents. This was in contrast to the mature IDUA form (74 kDa) which did not have its activity stimulated by reducing agents or dilution.

Base Sequence↗
PubMed1991

Human alpha-L-iduronidase: cDNA isolation and expression.

alpha-L-Iduronidase (IDUA; EC 3.2.1.76) is a lysosomal hydrolase in the metabolic pathway responsible for the degradation of the glycosaminoglycans heparan sulfate and dermatan sulfate. A deficiency of IDUA in humans leads to the accumulation of these glycosaminoglycans and results in the lysosomal storage disorder mucopolysaccharidosis type I. We have isolated and sequenced cDNA clones containing part of the human IDUA coding region and used PCR from reverse-transcribed RNA to obtain the full IDUA sequence. Analysis of the predicted 653-amino acid precursor protein shows that IDUA has a 26-amino acid signal peptide that is cleaved immediately prior to the amino terminus of the 74-kDa polypeptide present in human liver IDUA. The protein sequence contains six potential N-glycosylation sites. Northern blot analysis with IDUA cDNA detected only a single 2.3-kilobase mRNA species in human placental RNA; however, PCR analysis of fibroblast, liver, kidney, and placental RNA showed the existence of alternatively spliced mRNA from the IDUA gene. Southern blot analysis failed to detect major deletions or gene rearrangements in any of the 40 mucopolysaccharidosis type I patients studied. Expression of a full-length IDUA cDNA construct in Chinese hamster ovary cells produced human IDUA protein at a level 13-fold higher than, and with a specific activity comparable to, IDUA present in normal human fibroblasts.

Base Sequence↗
PubMed1996

Long-term in vitro correction of alpha-L-iduronidase deficiency (Hurler syndrome) in human bone marrow.

Allogeneic bone marrow transplantation is the most effective treatment for Hurler syndrome but, since this therapy is not available to all patients, we have considered an alternative approach based on transfer and expression of the normal gene in autologous bone marrow. A retroviral vector carrying the full-length cDNA for alpha-L-iduronidase has been constructed and used to transduce bone marrow from patients with this disorder. Various gene-transfer protocols have been assessed including the effect of intensive schedules of exposure of bone marrow to viral supernatant and the influence of growth factors. With these protocols, we have demonstrated successful gene transfer into primitive CD34+ cells and subsequent enzyme expression in their maturing progeny. Also, by using long-term bone marrow cultures, we have demonstrated high levels of enzyme expression sustained for several months. The efficiency of gene transfer has been assessed by PCR analysis of hemopoietic colonies as 25-56%. No advantage has been demonstrated for the addition of growth factors or intensive viral exposure schedules. The enzyme is secreted into the medium and functional localization has been demonstrated by reversal of the phenotypic effects of lysosomal storage in macrophages. This work suggests that retroviral gene transfer into human bone marrow may offer the prospect for gene therapy of Hurler syndrome in young patients without a matched sibling donor.

Antigens, CD34↗
PubMed2004

Lipoprotein receptor binding, cellular uptake, and lysosomal delivery of fusions between the receptor-associated protein (RAP) and alpha-L-iduronidase or acid alpha-glucosidase.

Enzyme replacement therapy for lysosomal storage disorders depends on efficient uptake of recombinant enzyme into the tissues of patients. This uptake is mediated by oligosaccharide receptors including the cation-independent mannose 6-phosphate receptor and the mannose receptor. We have sought to exploit alternative receptor systems that are independent of glycosylation but allow for efficient delivery to the lysosome. Fusions of the human lysosomal enzymes alpha-l-iduronidase or acid alpha-glucosidase with the receptor-associated protein were efficiently endocytosed by lysosomal storage disorder patient fibroblasts, rat C6 glioma cells, mouse C2C12 myoblasts, and recombinant Chinese hamster ovary cells expressing individual members of the low-density lipoprotein receptor family. Uptake of the fusions exceeded that of phosphorylated enzyme in all cases, often by an order of magnitude or greater. Uptake was specifically mediated by members of the low-density lipoprotein receptor protein family and was followed by delivery of the fusions to the lysosome. The advantages of the lipoprotein receptor system over oligosaccharide receptor systems include more efficient cellular delivery and the potential for transcytosis of ligands across tight endothelia, including the blood-brain barrier.

Animals↗
PubMed2002

In utero injection of alpha-L-iduronidase-carrying retrovirus in canine mucopolysaccharidosis type I: infection of multiple tissues and neonatal gene expression.

Canine alpha-L-iduronidase (alpha-ID) deficiency is caused by a single base pair mutation in the alpha-ID gene, resulting in no enzyme activity in homozygous affected pups. The disease clinically resembles human mucopolysaccharidosis type I (MPSI). We used the canine MPSI model system to address the efficacy of a new retroviral vector, MND-MFG, containing the human alpha-ID cDNA (MND-MFG-alpha-ID) for direct in utero gene delivery to MPSI cells. In vitro, the MND-MFG-alpha-ID vector showed high-level, long-term expression of the transgene in both canine and human alpha-ID-deficient fibroblasts. The effectiveness of this vector for in utero gene transfer and expression in multiple tissues was assessed by injecting viral supernatants into MPSI fetuses and evaluating transduction efficiency and enzyme expression at various times after birth. Transduction of a spectrum of cell types and tissues was observed in all seven live-born pups and in one stillborn pup. Although enzyme activity was not detected in adult tissues from the seven surviving pups, significant alpha-ID enzyme activity was detected in both the liver and kidney of the deceased pup. Our combined gene delivery vector and in utero transfer approach, while encouraging in terms of overall gene transfer efficiency to multiple tissues and successful short-term gene expression, was unable to meet the important requirement of sustained in vivo gene expression.

Animals↗
PubMed1999

Enzymatic correction and cross-correction of mucopolysaccharidosis type I fibroblasts by adeno-associated virus-mediated transduction of the alpha-L-iduronidase gene.

Mucopolysaccharidosis type I (MPS I), a deficiency in the lysosomal enzyme alpha-L-iduronidase (IDUA), is characterized by skeletal abnormalities, hepatosplenomegaly and neurological dysfunction. To evaluate the potential for treatment of the disease using a gene delivery approach, recombinant adeno-associated virus (rAAV) vectors were constructed and evaluated for expression of the human IDUA cDNA in transduced cells. 293 cells transduced with these AAV vectors contained IDUA activity at 0.5 to 1.4 micromol/mg x hr, 50- to 140-fold above background (control-transduced) levels. In time course studies of transduced 293 cells, IDUA activity levels peaked 1 week after transduction and persisted at 50% of the peak level for at least 6 weeks. Transduced MPS I fibroblasts also expressed high levels of IDUA activity (114-290 nmol/mg x hr), which persisted for at least 3 weeks in the absence of selection. In addition, transduced MPS I fibroblasts were capable of clearing intracellular radiolabeled glycosaminoglycan (GAG). As a test of the ability of these vectors to mediate metabolic cross-correction, transduced HuH7 human hepatoma cells were demonstrated to release enzyme that was subsequently taken up by nontransduced MPS I fibroblasts. These results illustrate the effectiveness of AAV vectors for delivery and expression of human IDUA gene sequences and for potential treatment of MPS I.

Cell Line↗
PubMed1992

Correction of mucopolysaccharidosis type I fibroblasts by retroviral-mediated transfer of the human alpha-L-iduronidase gene.

Three retroviral constructs containing a full-length human alpha-L-iduronidase (IDUA) cDNA were made. The first, pLIdSN, is designed so that expression of the IDUA cDNA is from the 5' viral long terminal repeat (LTR). The second, pLNCId, is designed to express the IDUA cDNA from the cytomegalovirus (CMV) immediate early promoter, while in the third, pLNTId, the CMV promoter is replaced by a promoter fragment of the mouse CD45 (T200) gene. All vectors transduce resistance to G418 (neomycin). High-titer virus-producing cell lines for these constructs were made by infection of the amphotropic packaging cell line PA317 after transient expression in, and virus rescue from, the ecotropic packaging cell line psi CRE. The high-titer virus-producing cell lines were assayed for absence of helper virus, synthesis of human IDUA, and for integrity of proviral structure. Suitable lines were used as a source of virus to infect two different mucopolysaccharidosis type I (MPS I) skin fibroblast cultures. All three of the recombinant viruses corrected the enzymatic defect in MPS I fibroblasts. Surprisingly, increasing over-expression of IDUA resulted in reduced phenotypic correction of these cells as assayed by intracellular accumulation of 35S-labeled glycosaminoglycan. This was shown to be due to the induction of a phenotype analogous to mild I-cell disease in cells expressing large amounts of IDUA.

3T3 Cells↗
PubMed1995

In vivo delivery of human alpha-L-iduronidase in mice implanted with neo-organs.

Mucopolysaccharidose type I is a lysosomal storage disease caused by a deficiency in the enzyme alpha-L-iduronidase (IDUA). The existence of a secretory pathway for lysosomal enzymes and the capture of secreted molecules by distant cells through binding to mannose-6-phosphate receptors have provided a rationale for enzyme replacement therapy in lysosomal storage diseases. We have used genetically modified fibroblasts implanted into neo-organs as an in vivo delivery system for IDUA. The human IDUA cDNA was isolated and inserted into a retroviral vector where it was expressed from the phosphoglycerate kinase 1 gene promoter. MPS I fibroblasts transduced with this vector showed high levels of IDUA activity and secreted phosphorylated molecules that could be internalized by naive deficient cells. Neo-organs containing 2 x 10(7) IDUA-secreting cells were implanted into nude mice. Human and murine IDUA activities were measured in the liver and spleen of animals sacrificed 35-77 days after implantation. Human IDUA activity corresponded to 0.6-2.3% of the murine enzyme activity in the liver and to 0.1-0.3% in the spleen. These data indicated that human IDUA was secreted from neo-organs and internalized in distant tissues.

Animals↗
PubMed2006

Limited transgene immune response and long-term expression of human alpha-L-iduronidase in young adult mice with mucopolysaccharidosis type I by liver-directed gene therapy.

Mucopolysaccharidosis type I (MPS I) due to deficient alpha-L-iduronidase (IDUA) activity results in the accumulation of glycosaminoglycans (GAGs) in many of the cells of affected patients. Stable gene replacement by in vivo administration of lentiviral vectors (LVs) has therapeutic potential for metabolic disorders and other systemic diseases. We have previously shown in a murine model the therapeutic potential of lentiviral IDUA vector-mediated gene therapy, in which human IDUA cDNA was driven by the cytomegalovirus promoter. However, the major limitation of this approach was the induction of an immune response against the therapeutic protein, which limited the efficacy and long-term duration of treatment. In this study, we evaluate the potential of liver-directed gene therapy, that is, programming of murine hepatocytes to secrete the enzyme with mannose 6-phosphate (M6P), which can be taken up by distant cells. Eight- to 10-week-old mice were injected via the tail vein with a lentiviral vector expressing human IDUA cDNA driven by the albumin gene promoter selectively expressed in hepatocytes. One month after treatment, IDUA activity was present in the liver and spleen of treated mice; an expression level of 1% normal IDUA activity was sufficient to reduce the GAG level in liver, spleen, kidney, heart, and lung. Interestingly, 6 months after a single injection of this vector, IDUA activity was detectable in several murine tissues; the level of enzyme activity was low but sufficient to maintain the decrease in GAG levels in liver, spleen, kidney, heart, and lung. Also, the level of enzyme-specific antibodies reached at 6 months postinjection was nearly null, and real-time polymerase chain reaction analysis showed high levels of vector DNA content in liver and spleen. Thus, these results show that the use of LV with the albumin gene promoter selectively expressed in hepatocytes limited the immune response to the transgene and allowed stable and prolonged expression of the IDUA enzyme and a partial correction of the pathology.

Animals↗
PubMed1994

Mucopolysaccharidosis type I: identification of 8 novel mutations and determination of the frequency of the two common alpha-L-iduronidase mutations (W402X and Q70X) among European patients.

A group of 46 European patients with mucopolysaccharidosis type I (MPS I) was screened for mutations of the alpha-L-iduronidase gene. The 2 common nonsense mutations, W402X and Q70X, were identified in, respectively, 37% and 35% of mutant alleles. Considerable differences were seen in the frequency of these 2 mutations in patients from North Europe (Norway and Finland) and other European countries (mainly The Netherlands and Germany). In Scandinavia, W402X and Q70X account for 17% and 62% of the MPS I alleles, respectively, while in other European countries W402X is about 2.5 times more frequent (48%) than Q70X (19%). Eight novel mutations are described including 4 missense mutations, 1 nonsense mutation, 1 insertion of 2 base pairs, and 2 deletions of 1 and 12 base pairs.

Alleles↗
PubMed1997

Murine mucopolysaccharidosis type I: targeted disruption of the murine alpha-L-iduronidase gene.

Mucopolysaccharidosis type I (MPS I) is considered to represent the prototypical mucopolysaccharide storage disorder. Although a spectrum of severity is seen within the MPS I subgroup, Hurler syndrome represents the most severe and frequent manifestation of MPS I. We describe here the generation of a murine model for Hurler syndrome by targeted disruption of the murine Idua gene. Homozygous Idua -/- mice have no detectable alpha-L-iduronidase enzyme activity and show increased urinary glycosaminoglycan levels. Although normal appearing at birth, Idua -/- mice develop a flattened facial profile and thickening of the digits discernible by 3 weeks of age. No obvious growth deficiency nor mortality is seen within the first 20 weeks of life. Radiographs reveal anterior flaring of the ribs and thickening of the facial bones as early as 4 weeks of age with more extensive dysostosis detectable by 15 weeks of age. At 4 weeks of age, lysosomal storage is noted primarily within reticuloendothelial cells with abundant lysosomes noted in Kupffer cells, splenic sinusoidal lining cells, and glial cells. More widespread lysosomal storage is noted by 8 weeks of age in hepatocytes, chondrocytes, neurons, as well as renal tubular cells. Thus, targeted disruption of the murine Idua locus has produced a murine strain representative of the severe form of MPS I. This model should permit detailed evaluation of the pathophysiology of lysosomal storage disorders and provide a small animal model for the testing and development of enzyme replacement and gene therapy regimes.

Abnormalities, Multiple↗
PubMedDate not supplied

Diversity of mutations and distribution of single nucleotide polymorphic alleles in the human alpha-L-iduronidase (IDUA) gene.

PURPOSE: Mucopolysaccharidosis type I (MPS I) is an autosomal recessive disorder resulting from a deficiency of the lysosomal glycosidase, alpha-L-iduronidase (IDUA). Patients with MPS I present with variable clinical manifestations ranging from severe to mild. To facilitate studies of phenotype-genotype correlation, the authors performed molecular studies to detect mutations in MPS I patients and characterize single nucleotide polymorphism (SNP) in the gene. METHODS: Twenty-two unrelated MPS I patients were subjects for mutation detection using reverse transcriptional polymerase chain reaction (RT-PCR) and genomic PCR sequencing. Polymorphism analyses were performed on controls by restriction enzyme assays of PCR amplicons flanking nine intragenic single nucleotide polymorphic alleles. RESULTS: Eleven different mutations including two common mutations (Q70X, W402X), five recurrent mutations (D315Y, P533R, R621X, R628X, S633L), and four novel mutations (R162I, G208D, 1352delG, 1952del25bp) were identified from MPS I patients. Multiple SNP alleles coexisting with the disease-causing mutations were detected. Allelic frequencies for nine SNP alleles including A8, A20, Q33H, L118, N181, A314, A361T, T388, and T410 were determined. CONCLUSIONS: The results provide further evidence for the mutational heterogeneity among MPS I patients and point out possible common haplotype structures in the gene.

Black People↗
PubMed2006

Synthesis of enzymatically active human alpha-L-iduronidase in Arabidopsis cgl (complex glycan-deficient) seeds.

As an initial step to develop plants as systems to produce enzymes for the treatment of lysosomal storage disorders, Arabidopsis thaliana wild-type (Col-0) plants were transformed with a construct to express human alpha-l-iduronidase (IDUA; EC 3.2.1.76) in seeds using the promoter and other regulatory sequences of the Phaseolus vulgaris arcelin 5-I gene. IDUA protein was easily detected on Western blots of extracts from the T(2) seeds, and extracts contained IDUA activity as high as 2.9 nmol 4-methylumbelliferone (4 MU)/min/mg total soluble protein (TSP), corresponding to approximately 0.06 microg IDUA/mg TSP. The purified protein reacted with an antibody specific for xylose-containing plant complex glycans, indicating its transit through the Golgi complex. In an attempt to avoid maturation of the N-linked glycans of IDUA, the same IDUA transgene was introduced into the Arabidopsis cgl background, which is deficient in the activity of N-acetylglucosaminyl transferase I (EC 2.4.1.101), the first enzyme in the pathway of complex glycan biosynthesis. IDUA activity and protein levels were significantly higher in transgenic cgl vs. wild-type seeds (e.g. maximum levels were 820 nmol 4 MU/min/mg TSP, or 18 microg IDUA/mg TSP). Affinity-purified IDUA derived from cgl mutant seeds showed a markedly reduced reaction with the antibody specific for plant complex glycans, despite transit of the protein to the apoplast. Furthermore, gel mobility changes indicated that a greater proportion of its N-linked glycans were susceptible to digestion by Streptomyces endoglycosidase H, as compared to IDUA derived from seeds of wild-type Arabidopsis plants. The combined results indicate that IDUA produced in cgl mutant seeds contains glycans primarily in the high-mannose form. This work clearly supports the viability of using plants for the production of human therapeutics with high-mannose glycans.

Arabidopsis↗
PubMed1985

Neurochemical characterization of canine alpha-L-iduronidase deficiency disease (model of human mucopolysaccharidosis I).

This report presents the neurochemical findings on the first dog to die with deficiency of alpha-L-iduronidase (mucopolysaccharide alpha-L-iduronohydrolase; EC 3.2.1.76). The principal findings were (a) markedly increased glycosaminoglycan content in all neural tissues examined (from threefold in sciatic nerve to 15-fold in brainstem), (b) a modest increase in levels of gangliosides GM2, GM3, and GD3, particularly in gray matter, (c) excessive accumulation of glycosaminoglycans in the CSF, (d) the increased glycosaminoglycans were dermatan sulfate and heparan sulfate, and (e) the molecular weights of the liver glycosaminoglycans were shifted toward smaller sizes, indicating partial degradation. The canine disorder thus resembles mucopolysaccharidosis I in all aspects.

Animals↗
PubMed1976

Leucocyte values of alpha-L-iduronidase activity in mucopolysaccharidosis I.

Assay of alpha-L-iduronidase in peripheral leucocytes is a rapid and simple diagnostic aid in mucopolysaccharidosis I. The mean value for heterozygotes is one-half the value of normal controls, but overlap between the two groups occurs. Use of this assay may be helpful in genetic counselling of selected couples.

Glycoside Hydrolases↗
PubMed2005

[Outcome of two patients with Hurler's syndrome under enzyme replacement therapy with human recombinant alpha-L-iduronidase].

We performed a prospective study of two patients with Hurler's syndrome (aged 4.8 years and 17 months at the beginning of the intervention) under enzyme replacement therapy with human recombinant alpha-L-iduronidase for 452 and 28 weeks respectively. The aim of this study was to analyze the safety and efficacy of the intervention during the treatment periods. Several diagnostic imaging tests, clinical examinations, and serial laboratory determinations were performed to demonstrate the effectiveness of the therapy in both patients. In patient 1 (a boy aged 4.8 years, homozygote W402X), the treatment was always intended to be palliative because of the advanced stage of the disease. In patient 2 (a 17-month-old girl, heterozygote W402X) the treatment was initiated early with subsequent clinical stabilization without acquisition of regressive factors. Bone marrow transplantation from an unrelated donor was successful. Currently, because of the lack of histocompatible bone marrow donors, transplantation of hematopoietic stem cells from umbilical cord blood or peripheral blood are being performed with satisfactory results. In the future, gene therapy may be able to prevent the diseases associated with Hurler's syndrome and halt the neurocognitive deterioration characteristic of these patients.

Child, Preschool↗
PubMed1999

Genetically corrected autologous stem cells engraft, but host immune responses limit their utility in canine alpha-L-iduronidase deficiency.

Canine alpha-L-iduronidase (alpha-ID) deficiency, a model of the human storage disorder mucopolysaccharidosis type I (MPS I), is an ideal system in which to evaluate the clinical benefit of genetically corrected hematopoietic stem cells. We performed adoptive transfer of genetically corrected autologous hematopoietic cells in dogs with alpha-ID deficiency. Large volume marrow collections were performed on five alpha-ID-deficient dogs. Marrow mononuclear cells in long-term marrow cultures (LTMCs) were exposed on three occasions during 3 weeks of culture to retroviral vectors bearing the normal canine alpha-ID cDNA. Transduced LTMC cells from deficient dogs expressed enzymatically active alpha-ID at 10 to 200 times the levels seen in normal dogs. An average of 32% of LTMC-derived clonogenic hematopoietic cells were provirus positive by polymerase chain reaction and about half of these expressed alpha-ID. Approximately 10(7) autologous gene-modified LTMC cells/kg were infused into nonmyeloablated recipients. Proviral DNA was detected in up to 10% of individual marrow-derived hematopoietic colonies and in 0.01% to 1% of blood and marrow leukocytes at up to 2 to 3 years postinfusion. Despite good evidence for engraftment of provirally marked cells, neither alpha-ID enzyme nor alpha-ID transcripts were detected in any dog. We evaluated immune responses against alpha-ID and transduced cells. Humoral responses to alpha-ID and serum components of the culture media (fetal bovine and horse sera and bovine serum albumin) were identified by enzyme-linked immunosorbent assay. Cellular immune responses to autologous alpha-ID but not neo(r) transduced cells were demonstrated by lymphocyte proliferation assays. To abrogate potential immune phenomena, four affected dogs received posttransplant cyclosporine A. Whereas immune responses were dampened in these dogs, alpha-ID activity remained undetectable. In none of the dogs engrafted with genetically corrected cells was there evidence for clinical improvement. Our data suggest that, whereas the alpha-ID cDNA may be transferred and maintained in approximately 5% of hematopoietic progenitors, the potential of this approach appears limited by the levels of provirally derived enzyme that are expressed in vivo and by the host's response to cultured and transduced hematopoietic cells expressing foreign proteins.

Animals↗
PubMed2002

Mucopolysaccharidosis type I: Identification and characterization of mutations affecting alpha-L-iduronidase activity.

Mucopolysaccharidosis type I (MPS I) is caused by a deficiency of the lysosomal enzyme alpha-L-iduronidase (IDUA). MPS I covers a broad spectrum of clinical severity ranging from severe Hurler syndrome through intermediate Hurler/Scheie syndrome to mild Scheie syndrome. Mutation screening was performed in two unrelated Taiwanese MPS I patients. A Hurler/Scheie patient had A79V (C to T transition in codon 79) in exon 2 and R619G (C to G transversion in codon 619) in exon 14. R619G has been shown to cause disease. Expression of A79V in COS-7 cells showed trace amounts of IDUA activity, demonstrating the deleterious nature of the mutation. A79V mutation did not cause a reduction in IDUA mRNA levels. The reduced level of IDUA protein suggests increased degradation of the mutant enzyme. A Hurler patient had 134del12 (in-frame deletion of codons 16-19 in signal peptide) in exon 1 and Q584X (C to T transition in codon 584) in exon 13. Transfection of COS-7 cells with Q584X did not yield active enzyme. Q584X mutation caused an apparent reduction in the IDUA mRNA level and no IDUA protein was detected. Conversely, 134del12 showed 124.6% of normal activity in transfected cells and a 77-kDa precursor protein was observed on Western blot, suggesting biologic activity of precursor IDUA without posttranslational cleavage. These findings provide further evidence of the molecular heterogeneity in mutations in MPS I.

Adolescent↗