The laboratory diagnosis of Sanfilippo disease

Coinheritance of novel mutations in NAGLU causing mucopolysaccharidosis type IIIB and in DDHD2 causing spastic paraplegia54 in a Turkish family

Mucopolysaccharidosis type IIIB (MPSIIIB) is one of the lysosomal storage diseases, clinically related to developmental delay in the early phase and loss of skills in the late phases of the disease. The disease is caused by homozygous mutations in the NAGLU gene. Spastic paraplegia54 (SPG54) is a neurodegenerative disorder caused by homozygous mutations in the DDHD2 gene. Clinical features are progressive spasticity and weakness in the lower limbs and corpus callosum agenesis. We report on two siblings in a consanguineous family, presenting both the clinical and molecular diagnoses of MPSIIIB and SPG54 with novel mutations by using whole exome sequencing (WES). This interesting finding shows that we should be aware of the importance of using WES for diagnosing rare diseases in consanguineous families.

Scoring evaluation of the natural course of mucopolysaccharidosis type IIIA (Sanfilippo syndrome type A)

OBJECTIVE

Mucopolysaccharidosis types IIIA through IIID (Sanfilippo syndrome) are caused by deficiencies of enzymes involved in the degradation of heparan sulfate. The onset and severity of the disease are highly variable. The purpose of this study was to describe the natural course of mucopolysaccharidosis type IIIA in a large cohort of patients.

PATIENTS AND METHODS

The natural course of mucopolysaccharidosis type IIIA was assessed in 71 patients by using a detailed questionnaire and a 4-point scoring system and compared with the course of the disease in 14 patients with mucopolysaccharidosis type IIIB and 4 patients with mucopolysaccharidosis type IIIC.

RESULTS

In the cohort of patients with mucopolysaccharidosis type IIIA, first symptoms of disease were observed, on average, at 7 months of age. Speech and motor development were delayed in 66.2% and 33.9% of patients, respectively. The median age at diagnosis was 4.5 years. The onset of regression in speech, motor, and cognitive function was observed at an average age of 3.3 years. The loss of all 3 of the assessed abilities was observed at an average age of 12.5 years. Speech was lost before motor and cognitive functions. In a small group of patients who were >12.5 years of age (9.9%), speech, motor, and cognitive skills were partially preserved up to a maximum age of 23.8 years.

CONCLUSIONS

To our knowledge, this is the first systematic and comprehensive study on the natural course of mucopolysaccharidosis type IIIA. The 4-point scoring system may be used to classify patients into groups with a rapid or slower course of the disease. This may have an important impact on parental counseling as well as therapeutic interventions.

Molecular defects in Sanfilippo syndrome type B (mucopolysaccharidosis IIIB)

Sanfilippo syndrome type B (mucopolysaccharidosis IIIB) is an autosomal recessive disease that is caused by the deficiency of the lysosomal enzyme alpha-N-acetylglucosaminidase (NAGLU). NAGLU is involved in the degradation of the glycosaminoglycan (GAG) heparan sulphate, and a deficiency results in the accumulation of partially degraded GAGs inside lysosomes. Early clinical symptoms include hyperactivity, aggressiveness and delayed development, followed by progressive mental deterioration, although there are a small number of late-onset attenuated cases. The gene for NAGLU has been fully characterized and we report the molecular analysis of 18 Sanfilippo B families. In total, 34 of the 36 mutant alleles were characterized in this study and 20 different mutations were identified including 8 novel changes (R38W, V77G, 407-410del4, 703delT, A246P, Y335C, 1487delT, E639X). The four novel missense mutations were transiently expressed in Chinese hamster ovary cells and all were shown to decrease the NAGLU activity markedly, although A246P did produce 12.7% residual enzyme activity.

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.

A novel missense mutation in lysosomal sulfamidase is the basis of MPS III A in a spontaneous mouse mutant

Sanfilippo syndrome type III A (Mucopolysaccharidosis (MPS) III A) is a rare, autosomal recessive, lysosomal storage disease, characterized by the accumulation of heparan sulfate and the loss of function of lysosomal heparan N-sulfatase activity. The disease leads to devastating mental and physical consequences and a mouse model that can be used to explore gene therapy and enzyme or cell replacement therapies is needed. We have previously identified a mouse with low sulfamidase activity and symptoms and pathologies typical of MPS III A (Bhaumik, M., Muller, V. J., Rozaklis, T., Johnson, L., Dobrenis, K., Bhattacharyya, R., Wurzelmann, S., Finamore, P., Hopwood, J. J., Walkley, S. U., and Stanley, P. [1999] A mouse model for mucopolysaccharidosis type III A (Sanfilippo syndrome). Glycobiology 9, 1389--1396). We now show that the sulfamidase gene of the MPS III A mouse carries a novel mutation (G91A) that gives an amino acid change (D31N) likely to interfere with the coordination of a divalent metal ion in the active site of this sulfatase. This spontaneous mouse mutant is an excellent model for MPS III A in humans as this disease often arises due to a missense mutation in lysosomal sulfamidase.

Pre- and postnatal diagnosis of patients with CLN1 and CLN2 by assay of palmitoyl-protein thioesterase and tripeptidyl-peptidase I activities

Palmitoyl-protein thioesterase (PPT) and tripeptidyl-peptidase I (TPP-I) activities were measured in leucocytes and fibroblasts. Fourteen patients were confirmed as having late infantile neuronal ceroid lipofuscinosis due to a deficiency of TPP-I activity. This included one patient with a milder and more protracted form of the disease. In addition this enzyme deficiency was found in a clinically normal younger sibling of a patient. Of particular importance was the finding of normal TPP-I activity in two patients who had been diagnosed as having classical late infantile neuronal ceroid lipofuscinosis. A deficiency of PPT was confirmed retrospectively in stored fibroblasts from two patients who had already died having been diagnosed with infantile neuronal ceroid lipofuscinosis. Palmitoyl-protein thioesterase or TPP-I activities were measured in chorionic villi and cultured chorionic villi cells in three pregnancies. The enzyme results were confirmed by mutational analysis if the mutations were known, or, in the case of the pregnancy at risk for infantile neuronal ceroid lipofuscinosis by electron microscopy of the chorionic villi. Our results show that assay of PPT and TPP-I is reliable in the diagnosis of patients with mutations in the CLN1 and CLN2 genes. It is imperative to assay these enzymes in all patients to confirm the diagnosis and ensure accurate genetic counselling of other family members. Once an enzyme deficiency has been confirmed reliable prenatal diagnosis is available even if both mutations have not been detected.

Identification of molecular defects in Italian Sanfilippo A patients including 13 novel mutations

Sanfilippo syndrome type A or mucopolysaccharidosis IIIA (MPS IIIA) is a lysosomal storage disorder caused by the deficiency of the enzyme heparin sulfamidase (EC 3.10.1.1), required for the degradation of the mucopolysaccharide heparan sulfate. Patients develop central nervous system degeneration resulting in progressive dementia, developmental delay, hyperactivity, and aggressive behaviour; subjects may present a wide spectrum of clinical severity. Here, we report the results from molecular analysis of 24 Italian MPS IIIA patients diagnosed over the last 15 years in our laboratory. Altogether, we were able to characterize 38 out of the 48 (79%) pathogenic alleles. We identified 16 molecular defects, 13 novel. The majority of alterations were missense mutations: on exon two (Y40N; A44T; S66W; R74C), on exon four (G122R; P128L; L146P; R150Q), on exon five (D179N; R182C), on exon six (P227R) and on exon eight (E369K; R377C). Single base pair deletions: on exon two (A52nt-1) and on exon eight (T360nt-1) and one base pair insertion on exon eight (V361nt+1) were also identified. Restriction enzyme or ARMS analyses were used to confirm each alteration. S66W represents the most common alteration in our patients population accounting for 33% of the total alleles. Interestingly, all six patients from Sardinia present this mutation, and five of them are homozygous for this change, suggesting that these subjects may have been derived from a common founder.

Long-term follow-up following bone marrow transplantation for Hunter disease

Bone marrow transplantation (BMT) was performed in 10 patients with Hunter disease (mucopolysaccharidosis type II, iduronate-2-sulphatase deficiency). The donor was an HLA-identical sibling in 2 cases, an HLA-nonidentical relative in 6 cases, a volunteer unrelated donor in 1 case, and details were not available in 1 case. Only three patients have survived for more than 7 years post BMT; however, this high mortality probably resulted from poor donor selection. In two, there has been a steady progression of physical disability and mental handicap. One patient has maintained normal intellectual development, with only mild physical disability. It is possible that BMT may be useful in selected patients with MPS II.

Bone marrow transplantation for Maroteaux-Lamy syndrome (MPS VI): long-term follow-up

We describe the results of bone marrow transplantation (BMT) in four patients with mucopolysaccharidosis type VI (MPS VI, McKusick 253200)--Maroteaux-Lamy disease. The indications for transplantation were cardiomyopathy in three patients and severe obstructive sleep apnoea in one. The follow-up period ranges between 1 and 9 years, and three of the patients are at mainstream schools. In all of the patients the facial features have become less coarse and the cardiac manifestations have improved or remained stable. However, skeletal changes have persisted or even progressed, although posture and joint mobility have improved and all the patients have remained ambulatory and active. BMT appears to prolong survival and improve the quality of life in MPS VI patients, but careful selection of patients is essential.

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.

Discontinuous electrophoresis of glycosaminoglycans: a screening method for mucopolysaccharidoses

A modified discontinuous electrophoretic method for the separation of standard and urinary glycosaminoglycans has been reported. The merits of the method are the simple and easy to handle apparatus, non-requirement of elaborate cooling system, sensitivity and high reproducibility of the results and applicability of the method for the preliminary grouping of the MPS patients to reduce the number of enzyme assays to be done.

Sulfamidase deficiency in a family of Dachshunds: a canine model of mucopolysaccharidosis IIIA (Sanfilippo A)

Mucopolysaccharidosis IIIA (MPS IIIA or Sanfilippo A, McKusick 25290) was diagnosed in two adult wire-haired Dachshund littermates. Clinical and pathologic features paralleled the human disorder; both dogs exhibited progressive neurologic disease without apparent somatic involvement. Pelvic limb ataxia was observed when the dogs were 3 y old and progressed gradually within 1-2 y to severe generalized spinocerebellar ataxia. Mentation remained normal throughout the course of the disease. A mucopolysaccharide storage disorder was indicated in both dogs by positive toluidine blue spot tests of urine. The diagnosis of MPS IIIA was confirmed by documentation of urinary excretion and tissue accumulation of heparan sulfate and decreased sulfamidase activity in fibroblasts and hepatic tissue. Mild cerebral cortical atrophy and dilation of the lateral ventricles were grossly evident in both dogs. Light microscopically, fibroblasts, hepatocytes, and renal tubular epithelial cells were vacuolated. Within the nervous system, cerebellar Purkinje cells, neurons of brainstem nuclei, ventral and dorsal horns, and dorsal ganglia were distended with brightly autofluorescent, periodic acid-Schiff-positive, sudanophilic material. Ultrastructurally, visceral storage presented as membrane-bound vacuoles with finely granular, variably electron-lucent contents. Neuronal storage appeared as membranous concentric whorls, lamellated parallel membrane stacks, or electron-dense lipid-like globules. This represents the first reported animal disease homolog of the human Sanfilippo A syndrome.

Identification of a common mutation (R245H) in Sanfilippo A patients from The Netherlands

We have identified a common mutation (R245H) in the sulphamidase gene of Sanfilippo syndrome type A (mucopolysaccharidosis type IIIA, MPS IIIA) patients from The Netherlands. Allele-specific oligonucleotide hybridization was used to determine the incidence of this mutation in 45 unrelated MPS IIIA patients from different regions of The Netherlands. R245H was present in 51 alleles, representing 56.7% of the total allelic population. Of 39 patients, for whom we have uniform clinical details, 13 MPS IIIA patients who were homozygous for this common mutation had a more uniform but severe clinical phenotype than the remaining 21 or 5 patients, containing respectively one or no R245H alleles. The R245H allele had a higher prevalence in western rather than eastern regions of The Netherlands.

Recombinant human sulphamidase: expression, amplification, purification and characterization

Mucopolysaccharidosis type IIIA (MPS IIIA, Sanfilippo A syndrome) is a lysosomal storage disease that causes a profound neurological deterioration. The disorder is caused by a deficiency of the lysosomal enzyme sulphamidase which is a requisite for the degradation of heparan sulphate. To facilitate the development of enzyme-replacement strategies for MPS IIIA patients, we have constructed a high-level expression system for recombinant human sulphamidase in Chinese hamster ovary (CHO) cells. An expression construct containing a methotrexate-resistant dihydrofolate reductase (DHFR) gene allowed amplification of expression levels from less than 1 mg of sulphamidase per litre of culture medium to approx. 15 mg/l. Unlike many cell lines made by gene amplification in DHFR-deficient CHO cells, and utilizing the normal DHFR gene, these cell lines appeared to be stable in the absence of selective pressure. Recombinant human sulphamidase was purified from unamplified and amplified cell lines. The native enzyme was found to be a dimer of 115 kDa. Denaturing and reducing SDS/PAGE revealed a subunit size of 62 kDa. Kinetic analysis demonstrated that the recombinant enzyme had broadly similar kinetic characteristics to sulphamidase purified from liver. Recombinant human sulphamidase was able to correct the storage phenotype of MPS IIIA fibroblasts after endocytosis via the mannose-6-phosphate receptor.

Bone marrow transplantation for mucopolysaccharidosis type I: experience of two British centres

Bone marrow transplantation was carried out on 38 patients with mucopolysaccharidosis type I over a period of 15 years. The donor was an HLA identical relative in 10 cases, an HLA non-identical relative in 16 cases, and an HLA identical unrelated volunteer donor in 12 cases. Ten patients received a second transplant. One patient received three transplants. Thirteen engrafted patients have survived five years or more. Most patients have shown an arrest or slowing down of psychomotor regression. However, dysostosis multiplex has progressed. Careful selection of patients may be necessary to ensure optimum results.

Fucosidosis: genetic and biochemical analysis of eight cases

The molecular basis of the deficiency of alpha-L-fucosidase has been investigated in eight patients who had been diagnosed clinically and enzymatically as suffering from the autosomal recessive lysosomal storage disease fucosidosis. None of the patients had a deletion or gross alteration of the alpha-L-fucosidase gene (FUCA1). Single strand conformation polymorphism (SSCP) analysis followed by direct sequencing of amplified exons and flanking regions identified putative disease causing mutations in six of the patients, who had severe forms of the disease and very low residual alpha-L-fucosidase activity and protein. They were a 10 bp deletion in exon 1 (E113fs), a 1 bp deletion at position -2 of intron 2 (S216fs), a g-->a transition at IVS5+1, point mutations W183X and N329Y in exons 3 and 6, respectively, and a compound allele consisting of a point mutation in the signal peptide in exon 1, P5R, and a 1 bp insertion in exon 6 (Y330fs). One patient in whom an SSCP change was not detected had residual alpha-L-fucosidase activity and cross reacting protein in the heterozygous range and normal metabolism of metabolites containing fucose in his fibroblasts, consistent with the low activity polymorphism. The eighth patient, who had a partial deficiency of alpha-L-fucosidase in her fibroblasts and leucocytes at a young age but normal alpha-L-fucosidase activity and protein at a later age, was homozygous for the common Q281R polymorphism in exon 5. She had no other sequence changes and Kivlin (Peters plus) syndrome has subsequently been diagnosed. The basis of her transient deficiency of alpha-L-fucosidase is not known. The detection of five novel mutations in six severely affected patients confirms the genetic heterogeneity in fucosidosis.

Correction of Sanfilippo A skin fibroblasts by retroviral vector-mediated gene transfer

The recent cloning of the sulfamidase gene has made possible the consideration of gene-based therapies for Sanfilippo A syndrome (mucopolysaccharidosis type IIIA), one of the most common of the mucopolysaccharidoses. In this paper, we present the construction of a retroviral vector in which a sulfamidase cDNA is under the transcriptional control of the Moloney murine leukemia virus long terminal repeat. This construct was used to make a high-titer (4 x 10(5) colony-forming units/ml) producer cell line, PA317/LNSSN#19, in the amphotropic packaging cell line PA317. This producer cell line was shown to be helper virus free using an assay for horizontal spread of virus. Virus supernatant from PA317/LNSSN#19 was used to transduce Sanfilippo A fibroblasts, resulting in complete correction of both the enzymatic defect and the storage phenotype as assessed by intracellular accumulation of 35SO4(-)-labeled material. Phenotypic correction was seen even when the levels of viral transduction were low. These results show that gene therapy of the Sanfilippo A syndrome is practicable, although the nature of the disorder suggests that careful consideration needs to be given to the choice of the cellular target for gene transfer.

A fluorimetric enzyme assay for the diagnosis of Sanfilippo disease type A (MPS IIIA)

4-Methylumbelliferyl-alpha-D-N-sulphoglucosaminide (MU-alpha-GlcNS) was synthesized and shown to be a substrate for the lysosomal heparin sulphamidase. Sanfilippo A patients' fibroblasts (n = 42) and lymphocytes (n = 1) showed 0-3% of mean normal heparin sulphamidase activity; in total leukocytes from patients (n = 8) sulphamidase activity was clearly deficient. In fibroblasts from obligate heterozygotes for Sanfilippo A, the sulphamidase activity was reduced in 9 out of 10 cases. Heparin sulphamidase desulphates MU-alpha GlcNS to MU-alpha GlcNH2 and further hydrolysis during a second incubation is required to liberate 4-methylumbelliferone, which can be measured. Yeast alpha-glucosidase, which has low but sufficient alpha-glucosaminidase activity, was used to hydrolyse the reaction intermediate MU-alpha GlcNH2 to release 4-methylumbelliferone and free glucosamine.

Cloning of the sulphamidase gene and identification of mutations in Sanfilippo A syndrome

Sanfilippo A syndrome is one of four recognised Sanfilippo sub-types (A, B, C and D) that result from deficiencies of different enzymes involved in the lysosomal degradation of heparan sulphate; patients suffer from severe neurological disorders. The Sanfilippo syndrome sub-types are also known as mucopolysaccharidosis (MPS) type III (MPS-IIIA, B, C and D), and are part of the large group of lysosomal storage disorders. Each of the MPS-III types is inherited as an autosomal recessive disorder with considerable variation in severity of clinical phenotype. The incidence of Sanfilippo syndrome has been estimated at 1:24,000 in The Netherlands with MPS IIIA (MIM #252900) the most common. MPS-IIIA is the predominant MPS-III in the United Kingdom, and has a similar high incidence to that found in The Netherlands (E. Wraith, personal communication). There is a particularly high incidence of a clinically severe form of MPS-IIIA in the Cayman Islands with a carrier frequency of 0.1 (ref. 4). Due to the mild somatic disease compared to other MPS disorders there is difficulty in diagnosing mild cases of MPS-III, hence Sanfilippo syndrome may be underdiagnosed, especially in patients with mild mental retardation. Here, we report the isolation, sequence and expression of cDNA clones encoding the enzyme sulphamidase (EC 3.10.1.1). In addition, we report the chromosomal localisation of the sulphamidase gene as being 17q25.3. An 11-bp deletion, present in sulphamidase cDNA from two unrelated Sanfilippo A patients, is described.

A 5' splice site mutation in fucosidosis

Fucosidosis is a rare, autosomal recessive, lysosomal storage disease, resulting from a deficiency of the enzyme alpha-fucosidase (EC 3.2.1.51). It is characterised clinically by progressive mental and motor deterioration, growth retardation, coarse facies, and often recurrent infections, but the course of the disease is variable. The gene encoding lysosomal alpha-fucosidase has been mapped to the short arm of chromosome 1 at position 1p34.1-36.1 and has been called FUCA1. Two mutations causing disease have been described previously, a C-->T change in exon 8 giving rise to a premature, in frame TAA stop codon, and a deletion of at least two exons from the 3' end of the gene. In this paper we present evidence that a homozygous G-->A transition in the first position of the 5' splice site of intron 5 of FUCA1 is the disease causing mutation in a 9 year old child of distantly related parents. A new banding pattern was detected in the patient by Southern blotting of genomic DNA using TaqI restriction and a cDNA FUCA1 probe. The patient was homozygous for this pattern. Three sibs with alpha-fucosidase activity below the normal reference range and both parents were heterozygous. This pattern was not detected in 26 other fucosidosis patients and has not been found in any controls. The mutation was localised by a combination of restriction mapping using different cDNA probes, single stranded conformational polymorphism analysis of exons and flanking regions amplified by the polymerase chain reaction, and by direct sequencing of the amplified sequence. A view of the nature of the mutation, its cosegregation with the disease mutation and its absence in controls, it is probable that the 5' splice site mutation causes fucosidosis in this child.

Bone marrow transplantation for Sanfilippo disease type B

Allogeneic bone marrow transplantation was performed on twins with Sanfilippo B disease. They were the first two patients with this disorder to undergo the procedure. There was definite evidence of engraftment as shown by conversion to donor blood group antigen and tissue type, and increased leukocyte alpha-glucosaminidase activity. Nine years post transplant, neither twin is as handicapped as her untreated brothers were at the same age, although in one twin hyperactivity and behavioural problems, characteristic of the disorder, are present. Details of the twins' intellectual development and growth, their alpha-glucosaminidase activity and urinary glycosaminoglycan excretion are reported.

Carrier detection for Sanfilippo A syndrome

Leukocytes from 21 obligate carriers in 12 Sanfilippo A families and 49 normal controls were assayed for heparan sulphamidase (EC 3.10.1.1) at 55 degrees C. At this assay temperature the results show an absolute distinction between heterozygous carriers and the normal controls.

Carrier detection in Sanfilippo A syndrome

Leucocytes or fibroblasts from 10 obligate heterozygotes for Sanfilippo A syndrome gave decreased heparan N-sulphatase levels, using a modification of the method of Hall et al. (1978), which did not overlap normal control values. Five family members gave decreased values and are presumed heterozygotes.

Multiple sulphatase deficiency: prenatal diagnosis using chorionic villi

Multiple sulphatase deficiency was diagnosed in the first trimester of pregnancy by demonstrating markedly reduced activities of arylsulphatases and heparin sulphamidase by direct assays on chorionic villi (CV). The diagnosis was confirmed by assays on cell cultures of villi and fetal skin fibroblasts. Two further pregnancies of this mother were monitored similarly and predicted to be unaffected; one produced a normal healthy infant, the other miscarried shortly after CV sampling.

Carrier detection for Sanfilippo A syndrome

In Sanfillipo A families, sulphamidase activities in leukocytes and cultured fibroblasts determined at 55 degrees C distinguish between heterozygote-carriers, normal individuals and the homozygotes.

Collagen and non-collagenous protein content (osteocalcin, sialoprotein, proteoglycan) in the iliac crest bone and serum osteocalcin in women with and without hand osteoarthritis

Quantitative and qualitative variations in bone composition were studied in postmortem iliac crest bone specimens from 32 women aged 60 to 75, grouped according to the presence of osteoarthritis at the hand joints. The EDTA extraction yield of macromolecules was significantly greater in the osteoarthritis group. Collagen and osteocalcin content were significantly increased and proteoglycan content decreased in the osteoarthritis group. No difference in sialoprotein content was found. In a clinical study of 20 patients with generalised osteoarthritis, we found compared to 15 controls also significantly increased serum levels of osteocalcin. These results indicate in an unselected group of cases that differences in bone matrix constituents exist between elderly women with and without an osteoarthritic constitution. The finding that these alterations are present even far away from the articular lesion, and the fact that the serum osteocalcin levels are elevated, indicate that osteoarthritis is part of a more generalised bone disease and not a purely cartilage disease.

Regional variation of bone matrix components in osteoarthrotic and normal femoral heads

Three regios of cancellous bone, two subchondral and one central, from the femoral heads of five normal and ten osteoarthrotic individuals were analysed for their content of collagen, sialoprotein, proteoglycan and carbohydrate. Confirming previous findings in osteoarthrotic bone this study shows that there are significant quantitative changes in matrix composition consisting of a decrease in collagen content and increase in noncollagenous proteins in osteoarthrosis. Since these matrix alterations were present in all areas of the femoral head, also at areas distal from the subchondral area, it is unlikely that these changes are secondary to bone remodeling near the joint destruction. Difference in matrix composition according to the area of the femoral head was also found in the controls, indicating that bone matrix proteins are related to mechanic properties of the bone. The more stress the bone has to withstand, the lower the collagen/noncollagenous protein ratio in its matrix. These observations suggest that in osteoarthrosis, the bone is stiffer and can therefore absorb less well impact loading and by transmitting it back to the cartilage provokes cartilage dysfunction.

Sanfilippo disease in Greece

In a series of cases collected in most parts of the world, Sanfilippo disease type A is more frequent than type B. Skin biopsies were obtained from Greek patients suspected for Sanfilippo disease and cultured fibroblasts were assayed for both N-acetyl-a-glucosaminidase and sulfamidase activity. Eleven patients with Sanfilippo disease were identified. Ten of them were type B and one type A. The 10 patients with type B came from East-Central Greece and the neighboring areas of Thessaly and Macedonia. Both parents of the type A patient were from the Greek ethnic community of Turkey. It remains unknown whether or not the higher frequency of type B than type A appears only in Greece or if it occurs in other Mediterranean countries as well.

Ultrastructural and biochemical aspects of the Sanfilippo syndrome,--type III genetic mucopolysaccharidosis

The Sanfilippo Syndrome (SS) is a recessively inherited connective tissue disorder expressed in early life. It is classified as a genetic mucopolysaccharidosis (MPS) because the underlying defect involves the catabolism of heparan sulfate (HS), one of the glycosaminoglycans (GAG). Four variant forms, i.e., type A, B, C, and D, each associated with a different enzymatic defect, have been recognized in affected children. Biochemical studies show that characteristically HS accounts for most of the increased amounts of GAG excreted in the urine and those stored in viscera and brain. Gangliosides GM2, GM3 and GD2 are elevated considerably in the brain. Morphologically, the very water-soluble substances accumulating in the viscera are metachromatic, and consist ultrastructurally of finely granulo-floccular (or filamentous) material which is bound in cytoplasmic vacuoles. These substances are considered to represent the GAG. In the central nervous system (CNS) the stored substances are not soluble in water or alcohol and xylol, give a PAS-positive reaction, and stain for lipids and with luxol fast blue. Ultrastructurally, they consist of membranous arrays which often are of the "zebra body" variety. The CNS-inclusions are considered to represent the stored gangliosides; they were found also in small numbers in viscera of older children with SS. The search for a common denominator in the pathogenetic mechanism(s) culminating in both types of inclusions, continues.

Screening test for urinary glycosaminoglycans and differentiation of various mucopolysaccharidoses

The Ames MPS paper spot test and the cetylpyridinium chloride (CPC)-citrate turbidity test were used to detect urinary glycosaminoglycans (GAGs) as screening tests for the diagnosis of mucopolysaccharidoses (MPSs). The simplicity and reliability of these two methods were evaluated. The MPS paper spot test correlated more closely with the carbazole test than did the CPC-citrate turbidity test. The monodimensional electrophoresis of Cappelletti et al was also used to screen the subtypes of MPSs using differences in electrophoretic patterns. MPS VII cannot be distinguished from normal by its electrophoretic pattern, but can be detected by the MPS paper spot test. Therefore, the MPS paper spot test combined with monodimensional electrophoresis can detect these subtypes of MPSs (MPS I-II, III, IV, VI, VII). Since only 20 ml of random urine is needed and the result can be obtained with complete reliability in only 7 hours, this screening test appears to be useful for the early diagnosis of MPSs.

4-Methylumbelliferyl alpha-N-acetylglucosaminidase activity for diagnosis of Sanfilippo B disease

Conditions for assay of alpha-N-acetylglucosaminidase activity in human cultured fibroblasts, cultured amniotic fluid cells, leucocytes, serum, plasma and chorionic villi were studied using the fluorogenic substrate 4-methylumbelliferyl-2-acetamido-2-deoxy-alpha-D-glucopyranoside. The substrate was found to have advantage both in terms of sensitivity and ease of use over previously-used colorimetric substrates for assay of the enzyme in these tissues, and for diagnosis of Sanfilippo B disease and identification of carriers. It should have particular application in first trimester prenatal diagnosis using chorionic villus biopsies.

Prenatal tests for Sanfilippo disease type B in four pregnancies

We report the prenatal diagnosis of two fetuses with Sanfilippo disease type B. In both pregnancies there were excessive amounts of heparan sulphate in amniotic fluid and the activity of N-acetyl-alpha-D-glucosaminidase was undetectable in cultured amniotic fluid cells. The predictions were confirmed by enzyme assay of cultured skin fibroblasts from the aborted fetus or the affected infant. The disorder was excluded for two other pregnancies at risk and the predictions are considered to be correct because of the normal progress of the healthy children.

Urinary screening for abnormalities of amino acid or mucopolysaccharide metabolism in patients in a hospital for the mentally handicapped in Wessex

Urine from 348 patients of a hospital for the mentally handicapped in Wessex was screened for abnormalities of aminoacid and mucopolysaccharide excretion. Persistent aminoacid abnormalities were found in 16 patients: two had phenylketonuria and one a severe variant form of hyperphenylalaninaemia (dihydropteridine reductase deficiency). In at least nine of the other patients, the observed abnormality was probably a secondary phenomenon. Two patients excreted excessive amounts of a glycosaminoglycan identified tentatively as hyaluronic acid. The study also uncovered one undiagnosed diabetic and three patients with urinary tract infection.

Detection of the Sanfilippo type B syndrome using radiolabelled oligosaccharides as substrates for the estimation of alpha-N-acetylglucosaminidase

1. The following radiolabelled disaccharides were prepared from heparin and evaluated as substrates for alpha-N-acetylglucosaminidase present in cultured skin fibroblasts: O-(alpha-3-acetamido-2-deoxy-D-glucopyranosyl)-(1 leads to 4)-L-[6,3H]idose (GlcNAc-Ido), O-(alpha-2-acetamido-2-deoxy-D-glucopyranosyl)-(1 leads to 4)-1,6 anhydro-L-[6,3H]idose (GlcNAc-anIdo), O-(alpha-2-acetamido-2-deoxy-D-glucopyranosyl)-(1 leads to 4)-L-[6,3H]idose 2-sulfate (GlcNAc-Ido(OS)), O-(alpha 2-acetamido-2-deoxy-D-glucopyranosyl)-(1 leads to 3)-L-[6,3H]idonic acid (GlcNAc-IdOA). 2. Alpha-N-Acetylglucosaminidase activity assessed with GlcNAc-IdOA was 12 times higher than the values obtained using GlcNAc-Ido, GlcNAc-anIdo and GlcNAc-Ido(OS). Less than 5% of normal activity resulted when these substrates were incubated with fibroblasts from Sanfilippo B patients. These results demonstrate that a C6 carboxyl group on the adjacent residue to the N-acetylglucosaminide moiety is an important structural requirement in the mechanism of action or binding of alpha-N-acetylglucosaminidase toward alpha-linked N-acetylglucosaminide residues. The presence of a C2 sulfate group on the adjacent residue had no effect on enzyme activity. 3. Alpha-N-Acetylglucosaminidase activity in leucocyte and fibroblast homogenates assayed using GlcNAc-IdOA as substrate clearly distinguished Sanfilippo B patients from normal controls, and Sanfilippo A, C and D patients.

Selective depolymerisation of heparin to produce radio-labelled substrates for sulfamidase, 2-acetamido-2-deoxy-alpha-D-glucosidase, acetyl-CoA:2-amino-2-deoxy-alpha-D-glucoside N-acetyltransferase, and 2-acetamido-2-deoxy-D-glucose 6-sulfate sulfatase

Heparin was carboxyl-reduced with NaBT4, and degraded under conditions of acid hydrolysis that selectively cleaved the 2-0-sulfo-L-idopyranosidic linkages. The resulting, radiolabelled-disaccharides and -tetrasaccharides were isolated by gel chromatography, and then fractionated by ion-exchange chromatography, paper chromatography, and paper electrophoresis. Of the nine disaccharides isolated and identified, eight were probably derived from the major repeating-disaccharide unit in heparin (2-deoxy-2-sulfoamino-D-glucosyl 6-sulfate leads to L-idosyluronic acid 2-sulfate). Sodium borotritide reduction and/or HNO2 deamination of these eight disaccharide fractions indicated four to contain L-idopyranose residues and the other four to contain 1,6-anhydro-L-idopyranose residues as terminal units. The latter, terminal unit probably represents a minor component formed during the acid hydrolysis. On the basis of N-acetylation, N-sulfation, and HNO2-deamination studies, and the known positions and configurations of the glycosidic and sulfate linkages in heparin, four disaccharides were identified as 0-(2-amino-2-deoxy-alpha-D-glucopyranosyl)-(1 leads to 4)-L-[6-3H]idopyranose, 0-(2-amino-2-deoxy-alpha-D-glycopyranosyl)-(1 leads to 4)-L-[6-3H]idopyranose 2-sulfate, and 0-(2-amino-2-deoxy-alpha-D-glucopyranosyl 6-sulfate]-(1 leads to 4)-L-[6-3H]idopyranose 2-sulfate. A similar set of four disaccharides contained 1,6-anhydro-L-[6-3H]idopyranose residues in place of the L-[6-3H]idopyranose residues. The other disaccharide was tentatively identified as 0-(2-acetamido-2-deoxy-alpha-D-glucopyranosyl)-(1 leads to 4)-L-[6-3H]idopyranose, the isolation of which suggests the presence of an IdA(OSO-3)-GlcNAc-IdA(OSO-3) sequence in the heparin preparation, which accounts for at least 1% of its total sequence. The tetrasaccharides were fractionated, on the basis of their sulfate content, into at least five species by ion-exchange chromatography or by paper electrophoresis. These were fractionated further into species with and without carboxyl groups, and with L-idopyranose or 1,6-anhydro-L-idopyranose residues as terminal units. Tentative structures for some of these tetrasaccharides are proposed. Disaccharide and tetrasaccharide species were evaluated before and after N-acetylation or N-sulfation, as substrates for sulfamidase, acetyl-CoA: 2-amino-2-deoxy-alpha-D-glucoside N-acetyl-transferase, 2-acetamido-2-deoxy-alpha-D-glucosidase, or 2-acetamido-2-deoxy-D-glucose 6-sulfate sulfatase in human-skin fibroblasts.

Radiolabelled oligosaccharides as substrates for the estimation of sulfamidase and the detection of the Sanfilippo type A syndrome

(1) A series of tritiated oligosaccharides, 2-sulfamino-2-deoxy-D-[1-14C]glucose (GlcNS) and [sulfamino-34S]heparin were evaluated as substrates for sulfamidase present in cultured human skin fibroblasts. (2) The following radiolabelled disaccharides were prepared from heparin: O-(alpha-2-sulfamino-2-deoxy-D-glucopyranosyl)-(1 leads to 3)-L-[6,3H]idonic acid (GlcNS-IdOA) and O-(alpha-2-sulfamino-2-deoxy-D-glucopyranosyl)-(1 leads to 3)-2,5 anhydro-L-[6,3H]idonic acid (HlcNS-anIdOA). Other radiolabelled oligosaccharides evaluated as sulfamidase substrates were the disaccharides O-(alpha-2-sulfamino-2-deoxy-D-glucopyranosyl)-(1 leads to 4)-L-[6,3H]idose (GlcNS-Ido) and O-(alpha-2-sulfamino-2-deoxy-D-glucopyranosyl)-)1 leads to 4)-L-[6,3H]idose 2-sulfate (GlcNS-Ido(OS)) and a preparation containing the tetrasaccharide GlcNS-UA-GlcNS-l-idonic acid, GlcNS-UA-GlcNS-anhydro-L-idonic acid and GlcNS-UA-GlcNS-L-gulonic acid. (3) Sulfamidase activity assessed with GlcNS-IdOA and GlcNS-anIdOA were approximately equal and up to 4, 8 and 800 times higher than the value obtained using [sulfamino-35S]heparin, GlcNS-Ido(OS) and GlcNS-Ido respectively. Under the assay conditions used GlcNS was not de-N-sulfated. These results demonstrate that C6 carboxyl and C2 sulfate ester groups on the adjacent residue to the sulfaminoglucosamine moiety are important structural requirements in the mechanism of action or binding of sulfamidase toward N-sulfated disaccharides. The results obtained for a partially characterized mixture of tetrasaccharides suggest that they are degraded four times faster than their disaccharide structural counterparts. (4) No detectable sulfamidase activity toward [sulfamino-35S]heparin, monosaccharide, disaccharide or tetrasaccharide substrates could be detected using homogenates of fibroblast cultures from Sanfilippo A patients (sulfamidase deficient). (5)sulfamidase activity measured with GlcNS-IdOA exhibited a pH optimum at 4.5 to 5.5, an apparent Km of approximately 220 mumol/l and potent inhibition by sulfate ions.

Lumbar kyphosis in Hunter's disease (MPS ii)

Although radiological involvement of the lower dorsal and upper lumbar vertebrae is common in the severe form of Hunter's disease (MPS II), there are reports in the literature that clinical kyphosis does not occur. We report a boy with marked clinical kyphosis in whom the diagnosis of MPS II was proved by demonstrating a severe deficiency of serum and leucocyte iduronate-sulphate sulphatase and an accelerated incorporation of radiosulphate into his cultured fibroblast glycosaminoglycans, which could not be corrected by the product of other typed reference MPS II cells. The existence of several other genetic diseases, sometimes complicated by kyphosis, was excluded by assay of fibroblast lysosomal enzymes.