Sanfilippo syndrome type A or mucopolysaccharidosis IIIA (MPS IIIA) results from the deficiency of the enzyme heparan N-sulfatase (NS, EC 3.10.1.1), required for the degradation of heparan sulfate. Molecular defects of 24 Italian MPS IIIA patients were recently reported by our group. We report here two novel mutations: 1040insT and Q365X and the expression studies on 15 of the identified defects. Transient expression of COS cells by cDNA mutagenized to correspond to heparan N-sulfatase mutations Y40N, A44T, 166delG, G122R, P128L, L146P, R150Q, D179N, R182C, R206P, P227R, 1040insT, 1093insG, E369K, R377C did not yield active enzyme, demonstrating the deleterious nature of the mutations. Western blot analysis and metabolic labeling experiments revealed, for cells transfected with wild-type enzyme, a precursor 62-kDa form and a mature 56-kDa form. Western blot resulted, for 11 mutations, in the presence of both forms, indicating a normal maturation of the mutant enzyme. Western blot, metabolic labeling and immunofluorescence experiments suggested, for mutations 166delG, L146P, 1040insT and 1093insG, an increased degradation of the mutant enzymes.

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. Hum Mutat 11:313–320, 1998. © 1998 Wiley‐Liss, Inc.

Maroteaux-Lamy syndrome (mucopolysaccharidosis type VI, MPS VI) is an autosomal recessive disorder due to the deficiency of the lysosomal enzyme N-acetylgalactosamine-4-sulfatase (arylsulfatase B, ASB). Mutation analysis in Maroteaux-Lamy syndrome resulted in the identification of approximately 40 molecular defects underlying a great genetic heterogeneity. Here we report five novel mutations in Italian subjects: S65F, P116H, R315Q, Q503X, P531R; each defect was confirmed by restriction enzyme or amplification refractory mutation system (ARMS) analysis. We also performed a three-dimensional (3-D) structure analysis of the alterations identified by us, and of an additional 22 point mutations reported by other groups, in an attempt to draw helpful information about their possible effects on protein conformation.

Hunter disease (mucopolysaccharidosis type II or MPS II) is an X-linked recessive disorder caused by the deficiency of the lysosomal enzyme iduronate-2-sulfatase (IDS) (E.C.3.1.6.13.) involved in the catabolism of mucopolysaccharides dermatan sulfate and heparan sulfate. A large variety of alterations have been detected at the IDS locus. We report here the identification, in 7 unrelated Italian patients, of IDS gene mutations, four of which are novel and have been confirmed by amplification refractory system (ARMS) or restriction analysis. Our findings include: the missense mutation P86L found in a severe phenotype, the splicing mutation G374G and the nonsense mutation W475X, both associated with mild phenotypes. The four novel mutations were: the missense mutations R88P and R88H, associated with severe phenotypes, concerning a position found to be a mutational "hot-spot" for the IDS gene due to a mutation-prone CpG dinucleotide; mutations T1181 and P266H, both in mild patients. Interestingly, four of our mutations are located on exon III of IDS gene, confirming the high mutation frequency of this exon. After this manuscript was submitted, Rathman et al (Am. J.Hum.Genet.59,1202,1996) reported a total of 101 mutations including one R88H which is one of the novel mutations in this report.

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