Mucopolysaccharidosis type II (MPS II) is a rare X-linked disorder caused by alterations in the iduronate-2-sulfatase (IDS) gene. In this study, IDS activity in peripheral mononuclear blood monocytes (PMBCs) was...
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Mucopolysaccharidosis type II (MPS II) is a rare X-linked disorder caused by alterations in the iduronate-2-sulfatase (IDS) gene. In this study, IDS activity in peripheral mononuclear blood monocytes (PMBCs) was measured with a fluorimetric enzyme assay. Urinary glycosaminoglycans (GAGs) were quantified using a colorimetric assay. All IDS exons and intronic flanks were bidirectionally sequenced. A total of 15 mutations (all exonic region) were found in 17 MPS II patients. In this cohort of MPS II patients, all alterations in the IDS gene were caused by point nucleotide substitutions or small deletions. Mutations ***88His and ***172* occurred twice. All mu- tations were inherited except for ***489Alafs*7, a germline mutation. We found four new mutations (***142Phe, ***233Gly, ***430*, and ***360Tyrfs*31). In Epstein-Barr virus (EBV)-immortalized PMBCs derived from the MPS II patients, no IDS protein was detected in case of the ***142Phe and ***360Tyrfs*31 mutants. For ***233Gly and ***430*, we observed a residual expression of IDS. The ***233Gly and ***430* mutants had a residuary enzymatic activity that was lowered by 14.3 and 76-fold, respectively, compared with healthy controls. This observation may help explain the mild disease phenotype in MPS II patients who had these two mutations whereas the ***142Phe and ***360Tyrfs*31 mutations caused the severe disease manifestation.
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