Combined adenine phosphoribosyltransferase and N-acetylgalactosamine-6-sulfate sulfatase deficiency.

We describe a Czech patient with combined adenine phosphoribosyltransferase (APRT) deficiency (2,8-dihydroxyadenine urolithiasis) and N-acetylgalactosamine-6-sulfate sulfatase (GALNS) deficiency (mucopolysaccharidosis Type IVA, Morquio disease A). Adenine and its extremely insoluble derivative, 2,8-dihydroxyadenine, were identified in the urine, and APRT deficiency was confirmed in erythrocytes. There was excessive excretion of keratan sulfate in the urine, and GALNS deficiency was confirmed in leukocytes. GALNS and APRT are both located on chromosome 16q24.3, suggesting that the patient had a deletion involving both genes. PCR amplification of genomic DNA indicated that a novel junction was created by the fusion of sequences distal to GALNS exon 2 and proximal to APRT exon 3, and that the size of the deleted region was approximately 100 kb. The deletion breakpoints were localized within GALNS intron 2 and APRT intron 2. Several other genes, including the alpha subunit of cytochrome B (CYBA), which is deleted or mutated in the autosomal form of chronic granulomatous disease, are located in the 16q24.3 region, but PCR amplification showed that this gene was present in the proband. A patient with hemizygosity for GALNS deficiency and APRT deficiency has been reported from Japan recently. These findings indicate that: (i) APRT is located telomeric to GALNS; (ii) GALNS and APRT are transcribed in the same orientation (centromeric to telomeric); and (iii) combined APRT/GALNS deficiency may be more common than hitherto realized.     

Mucopolysaccharidosis IVA: screening and identification of mutations of the N-acetylgalactosamine-6-sulfate sulfatase gene

Mutations causing mucopolysaccharidosis IVA in 15 Japanese andone Caucasian patient were characterized. To screen these mutations,we used a combination of single strand conformation polymorphismanalysis and heteroduplex analysis for PCR products of targetedcDNA or genomic DNA. Various small mutations were identifiedin 23 of 26 alleles, while the other six alleles had large rearrangements.Cycle sequencing of PCR products revealed 15 different mutations,including 12 missense, one nonsense, one frame shift (2 bp deletion)and one splice site mutation, in accord with the broad rangeof clinical phenotypes. Two alleles have different mutationsin the same nucleotide position of exon 3 (R94C, CGC     

Biochemical and structural analysis of missense mutations in N-acetylgalactosamine-6-sulfate sulfatase causing mucopolysaccharidosis IVA phenotypes

Mucopolysaccharidosis IVA (MPS IVA; OMIM#253000), a lysosomal storage disorder caused by a deficiency of N -acetylgalactosamine-6-sulfate sulfatase (GALNS), has variable clinical phenotypes. To date we have identified 65 missense mutations in the GALNS gene from MPS IVA patients, but the correlation between genotype and phenotype has remained unclear. We studied 17 missense mutations using biochemical approaches and 32 missense mutations, using structural analyses. Fifteen missense mutations and two newly engineered active site mutations (C79S, C79T) were characterized by transient expression analysis. Mutant proteins, except for C79S and C79T, were destabilized and detected as insoluble precursor forms while the C79S and C79T mutants were of a soluble mature size. Mutants found in the severe phenotype had no activity. Mutants found in the mild phenotype had a considerable residual activity (1.3-13.3% of wild-type GALNS activity). Sulfatases, including GALNS, are members of a highly conserved gene family sharing an extensive sequence homology. Thus, a tertiary structural model of human GALNS was constructed from the X-ray crystal structure of N -acetylgalacto-samine-4-sulfatase and arylsulfatase A, using homology modeling, and 32 missense mutations were investigated. Consequently, we propose that there are at least three different reasons for the severe phenotype: (i) destruction of the hydrophobic core or modification of the packing; (ii) removal of a salt bridge to destabilize the entire conformation; (iii) modification of the active site. In contrast, mild mutations were mostly located on the surface of the GALNS protein. These studies shed further light on the genotype-phenotype correlation of MPS IVA and structure-function relationship in the sulfatase family.     

Development of MPS IVA mouse (Galnstm(hC79S.mC76S)slu) tolerant to human N-acetylgalactosamine-6-sulfate sulfatase

Mucopolysaccharidosis IVA (MPS IVA) is an autosomal recessive disease caused by N-acetylgalactosamine-6-sulfate sulfatase (GALNS) deficiency. In recent studies of enzyme replacement therapy for animal models with lysosomal storage diseases, cellular and humoral immune responses to the injected enzymes have been recognized as major impediments to effective treatment. To study the long-term effectiveness and side effects of therapies in the absence of immune responses, we have developed an MPS IVA mouse model, which has many similarities to human MPS IVA and is tolerant to human GALNS protein. We used a construct containing both a transgene (cDNA) expressing inactive human GALNS in intron 1 and an active site mutation (C76S) in adjacent exon 2 and thereby introduced both the inactive cDNA and the C76S mutation into the murine Galns by targeted mutagenesis. Affected homozygous mice have no detectable GALNS enzyme activity and accumulate glycosaminoglycans in multiple tissues including visceral organs, brain, cornea, bone, ligament and bone marrow. At 3 months, lysosomal storage is marked within hepatocytes, reticuloendothelial Kupffer cells, and cells of the sinusoidal lining of the spleen, neurons and meningeal cells. The bone storage is also obvious, with lysosomal distention in osteoblasts and osteocytes lining the cortical bone, in chondrocytes and in the sinus lining cells in bone marrow. Ubiquitous expression of the inactive human GALNS was also confirmed by western blot using the anti-GALNS monoclonal antibodies newly produced, which resulted in tolerance to immune challenge with human enzyme. The newly generated MPS IVA mouse model should provide a good model to evaluate long-term administration of enzyme replacement.     

Mucopolysaccharidosis IVA (Morquio A): identification of novel common mutations in the N-acetylgalactosamine-6-sulfate sulfatase (GALNS) gene in Italian patients

Mucopolysaccharidosis IVA (MPS IVA) is a lysosomal storage disorder caused by the deficiency of N-acetylgalactosamine-6-sulfate sulfatase (GALNS). Mutation screening of the GALNS gene was performed by RT-PCR with one amplicon and direct sequence analyses using cDNA samples from 15 Italian MPS IVA patients. Each mutation was confirmed at the genomic level. In this study, 13 different gene mutations with four common mutations (over 10% of mutant alleles) were identified in 12 severe and three milder (attenuated) MPS IVA patients. The gene alterations in 12 out of 13 were found to be point mutations and only one mutation was deletion. Ten of 13 mutations were novel. The c.1070C>T (p.Pro357Leu) mutation coexisted with c.1156C>T (p.Arg386Cys) mutation on the same allele. Together they accounted for 100% of the 30 disease alleles of the patients investigated. Four common mutations accounted for 70% of mutant alleles investigated. Urine keratan sulfate (KS) concentrations were elevated in all patients investigated. These data provide further evidence for extensive allelic heterogeneity and importance of relation among genotype, phenotype, and urine KS excretion as a biomarker in MPS IVA.     

Mouse model of N-acetylgalactosamine-6-sulfate sulfatase deficiency (Galns-/-) produced by targeted disruption of the gene defective in Morquio A disease

Mucopolysaccharidosis IVA is an autosomal recessive disorder caused by a deficiency of N-acetylgalactosamine-6-sulfate sulfatase (GALNS), a lysosomal enzyme required for the stepwise degradation of keratan sulfate (KS) and chondroitin-6-sulfate (C6S). To generate a model for studies of the pathophysiology and of potential therapies, we disrupted exon 2 of Galns, the homologous murine gene. Homozygous Galns-/- mice have no detectable GALNS enzyme activity and show increased urinary glycosaminoglycan (GAGs) levels. These mice accumulate GAGs in multiple tissues including liver, kidney, spleen, heart, brain and bone marrow. At 2 months old, lysosomal storage is present primarily within reticuloendothelial cells such as Kupffer cells and cells of the sinusoidal lining of the spleen. Additionally, by 12 months old, vacuolar change is observed in the visceral epithelial cells of glomeruli and cells at the base of heart valves but it is not present in parenchymal cells such as hepatocytes and renal tubular epithelial cells. In the brain, hippocampal and neocortical neurons and meningeal cells had lysosomal storage. KS and C6S were more abundant in the cytoplasm of corneal epithelial cells of Galns-/- mice compared with wild-type mice by immunohistochemistry. Radiographs revealed no change in the skeletal bones of mice up to 12 months old. Thus, targeted disruption of the murine Galns gene has produced a murine model, which shows visceral storage of GAGs but lacks the skeletal features. The complete absence of GALNS in mutant mice makes them useful for studies of pharmacokinetics and tissue targeting of recombinant GALNS designed for enzyme replacement.     

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.     

Long-term intra-articular administration of recombinant human N-acetylgalactosamine-4-sulfatase in feline mucopolysaccharidosis VI

Degenerative joint disease (DJD) is one aspect of mucopolysaccharidosis VI (MPS VI) pathology that has proven resistant to systemic enzyme replacement therapy (ERT). In this study the effect of repeated intra-articular injections (IA INJ) of recombinant human acetylgalactosamine-4-sulfatase (rh4S) on DJD was examined. Four MPS VI cats received i.v. ERT weekly from birth plus IA INJ (0 or 500 microg of rh4S per joint; monthly or every three months) while three MPS VI cats received IA INJ only. After 10 months, shoulders, elbows and knees were compared. Taken individually, an improvement in joint appearance was observed between the joints that received rh4S monthly or every three months compared with the contralateral joints treated with buffer or at lower frequency. Within articular cartilage of joints treated more frequently, the depth of clearance of lysosomal storage tended to be greater and uronic acid content was reduced reflecting the removal of glycosaminoglycans. Synovium in treated joints also showed less storage. No abnormal clinical signs were observed after the IA INJ and negligible antibody titres were measured throughout the study. No clear benefit was observed by combining IA INJ with weekly ERT and the most significant improvement in joint appearance resulted from increased IA INJ frequency. These data support the view that intra-articular therapy may be a good option for preventing the development of the severe articular pathology in MPS VI.     

Chondroitin 4- and 6-sulfate mucopolysaccharidosis--a morphological study.

A 17-year-old patient clinically manifesting gargoyle face, dwarfism, skeletal bone deformity, mild mental retardation and benign course was presented. Biochemically, increased urinary excretion of acidic glycosaminoglycans was confirmed and chondroitin 4-sulfate and chondroitin 6-sulfate were substantiated to be the major components of the acid mucopolysacchariduria. Light microscopically, variable numbers of foam cells were observed in the biopsy materials of the lymph nodes, liver and skin, as well as in the smears of bone marrow aspirates. In the liver, the parenchymal cells appeared vacuolated. Histochemically, accumulation of sulfated acid glycosaminoglycans was demonstrated in the cytoplasm of the foam cells proliferating in these tissues, as well as in the liver cells. Electron microscopically, all of these storage cells were found to contain numerous, membrane-bound, vacuolar inclusions filled with flocculent, finely reticulogranular materials of low electron density similar to those seen in the storage cells of Hurler, Hunter or Sanfilippo's syndrome. Empty vacuoles were often coexistent. Accordingly, this case should be termed "chondroitin 4- and 6-sulfate mucopolysaccharidosis", with emphasis on the possibility of a new type of genetic mucopolysaccharidosis.     

Characterization and biological effects of recombinant human erythropoietin

Human recombinant erythropoietin (rHuEPO) has been purified to apparent homogeneity and compared to purified human urinary erythropoietin (EPO). Both the purified natural and recombinant EPO preparations were characterized in a competition radioimmunoassay (RIA), the exhypoxic polycythemic mouse bioassay, in vitro tissue culture bioassays using bone marrow cells, and by Western analysis. In the immunological and biological activity assays, the rHuEPO shows a dose response which parallels that of the natural hormone. By Western analysis, the recombinant and human urinary EPO migrate identically. Administration of rHuEPO increases the hematocrit of normal mice in a dose-dependent manner. Additionally, the rHuEPO is able to increase the hematocrit of rats made uremic as a result of subtotal nephrectomy. In summary, by all criteria examined, the rHuEPO is biologically active and equivalent to the natural hormone.     

Heteroallelic missense mutations of the galactosamine-6-sulfate sulfatase (GALNS) gene in a mild form of Morquio disease (MPS IVA)

Morquio disease (MPS IVA) is an autosomal recessive disorder caused by a deficiency of N-acetylgalactosamine-6-sulfate sulfatase (GALNS) activity. Patients commonly present in early infancy with growth failure, spondyloepiphyseal dysplasia, corneal opacification, and keratan sulfaturia, but milder forms have been described. We report on a patient who grew normally until age 5 years. Her keratan sulfaturia was not detected until adolescence, and she now has changes restricted largely to the axial skeleton. She has experienced only mildly impaired vision. At age 22, thin-layer chromatography of purified glycosaminoglycans showed some keratan sulfaturia. GALNS activity in fibroblast homogenate supernatants was 20 ± 5% of controls (as compared to 5 ± 3% of controls in severe MPS IVA, P <.003). Kinetic analysis of residual fibroblast GALNS activity in patient and parents revealed decreased K_m and increased V_max in the mother and daughter, but not in the father, compatible with compound heterozygosity. GALNS exons were amplified from patient genomic DNA and screened by SSCP. Two missense mutations, a C to T transition at position 335 (predicting R94C) and a T to G transversion at position 344 (predicting F97V), were found on sequencing an abnormally migrating exon 3 amplicon. Digestion of the amplicon with FokI and AccI restriction enzymes (specific for the R94C and F97V mutations, respectively) confirmed heterozygosity. In fibroblast transfection experiments, heterozygous R94C and F97V mutants independently expressed as severe and mild GALNS deficiency, respectively. We interpret these findings to indicate that our patient bears heteroallelic GALNS missense mutations, leading to GALNS deficiency and mild MPS IVA. Our findings expand the clinical and biochemical phenotype of MPS IVA, but full delineation of the genotype-phenotype relationship requires further study of native and transfected mutant cell lines. © 1996 Wiley-Liss, Inc.     

Keratan and herparan sulfaturia: glucosamine-6-sulfate deficiency

The pattern of excretion of urinary acid mucopolysaccharides (AMPS) has been helpful to establish the diagnosis of mucopolysaccharidoses. The importance of urine analysis for AMPS and the specific enzyme assays is exemplified in a 3 1/2 year old Caucasian male with severe mental retardation, small stature, thoracolumbar kyphosis, and dysostosis multiplex. Urine analysis for AMPS revealed excessive quantities of keratan and heparan sulfate. This mucopolysacchariduria was not associated with hepatosplenomegaly or corneal clouding. Enzymic studies on cultured skin fibroblasts indicated deficiency of N-acetylglucosamine-6-sulfate sulfatase. This enzyme deficiency is different from that responsible for Morquio's syndrome, and early recognition is essential for proper counseling.     

Mucopolysaccharidosis IVA: Submicroscopic deletion of 16q24.3 and a novel R386C mutation of n-acetylgalactosamine-6-sulfate sulfatase gene in a classical Morquio disease

The N-acetylgalactosamine-6-sulfate sulfatase (GALNS) gene, which is responsible for autosomal recessive mucopolysaccharidosis IVA (MPSIVA), has been assigned to the long arm of chromosome 16, subregion 24.3, an area where the adenine phosophoribosyltransferase (APRT) gene and renal dipeptidase (DPEP I) gene are also localized. Molecular genetic studies on a severely affected patient with MPSIVA (Morquio disease), without karyotypic abnormality, revealed a partial submicroscopic deletion of 16q24.3 and a single point mutation on the other allele, with no functional GALNS activity. The patient, his mother, and siblings were hemizygous for GALNS and APRT loci, evidenced by informative RFLP and gene dosage analyses combined with a fluorescence in situ hybridization, utilizing a partial genomic clone of GALNS, but heterozygosity was retained at the DPEP I locus and proximal D16S7. Haplotyping of the family members revealed recombinational events between DPEP I locus and three other polymorphic loci on the paternal chromosome, localizing GALNS gene on the proximal side to DPEP I gene. As estimated from the genetic distance between two flanking markers of proximal D16S7 and distal DPEP I locus, size of the deletion was less than 3Mb. Mother of the boy and two older siblings were asymptomatic, despite this interstitial deletion of the Giemsa-light G band. The remaining paternal allele had no gene rearrangement but GALNS activity was not encoded as Arginine at 386 was replaced with Cysteine (R386C), suggesting this alteration accounts for the severe phenotype. Allelic loss of APRT is frequently observed in cancer tissues, thereby suggesting that the tumor suppressor gene locates near the APRT locus. No family member has evidence of any malignant disease. This study is apparently the first documentation of interstitial deletion of 16q24.3, involving GALNS and APRT genes. © 1996 Wiley-Liss, Inc.     

聚乙二醇化重组人白细胞介素-6药效研究

目的探讨体内外不同修饰度的聚乙二醇(PEG)化重组人白细胞介素-6(rhIL-6)的药效。方法以相对分子质量20000的PEG2-NHS修饰剂化学耦合修饰rhIL-6,利用毛细管电泳仪分离得单修饰PEG-rhIL-6(mono-PEG-rhIL-6)和双修饰PEG-rhIL-6(di-PEG-rhIL-6),采用标准方法(即7TD1细胞/MTT比色法)测定体外IL-6的生物学活性,参考品为已标定的rhIL-6。体内实验:小鼠腹腔注射环磷酰胺构建BALB/c小鼠模型,分为模型组、阳性对照组、mono-PEG-rhIL-6高剂量组、mono-PEG-rhIL-6低剂量组、di-PEG-rhIL-6高剂量组和di-PEG-rhIL-6低剂量组。各组按上述剂量1次/d皮下注射给药,连续5d,于给药的第3天各组小鼠同时腹腔注射环磷酰胺,每日1次,连续3d。于给药的第8、11、14、17天切尾采血测定各小鼠血小板数并进行统计学处理。结果体外生物活性检测表明,mono-PEG-rhIL-6与di-PEG-rhIL-6相差不大,均比rhIL-6低10倍;体内活性测定表明,阳性对照组、mono-PEG-rhIL-6和di-PEG-rhIL-6的高、低剂量组小鼠血小板数回升速度较同时期模型组快,它们之间的差异具有统计学意义(P0.05)。结论 PEG单修饰和多修饰(≥2)的rhIL-6在体外均具有促7TD1细胞增殖的活性;在体内均具有抗环磷酰胺致小鼠血小板减少的作用。mono-PEG-rhIL-6和di-PEG-rhIL-6均是药物的主要成分。     

Characterization of recombinant Streptococcus mitis-derived human platelet aggregation factor

We previously purified Streptococcus mitis-derived human platelet aggregation factor (Sm-hPAF) from the culture supernatant of S. mitis strain Nm-65, isolated from the tooth surface of a patient with Kawasaki disease. Here we produced recombinant Sm-hPAF protein (rSm-hPAF) in Escherichia coli, to determine whether rSm-hPAF conserves its platelet aggregation activity. rSm-hPAF precursor (665 amino acids) shows up to 36-56% identity with the family of cholesterol-dependent cytolysins (CDCs), and rSm-hPAF displayed potent hemolytic activity toward mammalian erythrocytes, including human erythrocytes with platelet aggregation activity. The 162-amino acid amino-terminal domain of rSm-hPAF was found in no other CDCs except lectinolysin; this domain is homologous to a portion of pneumococcal fucolectin-related protein. Interestingly, suilysin (SLY) and pneumolysin (PLY) of CDCs also exhibit substantial human platelet aggregation activity, similar to rSm-hPAF, and the platelet aggregation by rSm-hPAF, SLY, and PLY was morphologically confirmed using light and electron microscopy.