Genetic analysis of 17 children with Hunter syndrome: identification and functional characterization of four novel mutations in the iduronate-2-sulfatase gene.
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 p.Arg88His and p.Arg172* occurred twice. All mutations were inherited except for p.Gly489Alafs*7, a germline mutation. We found four new mutations (p.Ser142Phe, p.Arg233Gly, p.Glu430*, and p.Ile360Tyrfs*31). In Epstein-Barr virus (EBV)-immortalized PMBCs derived from the MPS II patients, no IDS protein was detected in case of the p.Ser142Phe and p.Ile360Tyrfs*31 mutants. For p.Arg233Gly and p.Glu430*, we observed a residual expression of IDS. The p.Arg233Gly and p.Glu430* 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 p.Ser142Phe and p.Ile360Tyrfs*31 mutations caused the severe disease manifestation.
Department of Medical Nanobiotechnology, Pirogov Russian State Medical University, Moscow 117997, Russia; Department of Molecular and Genetic Diagnostics, Division of Laboratory Medicine, Institute of Pediatrics, Research Center for Children's Health, Moscow 119991, Russia. Electronic address: dimitry.chistiakov@gmail.com.
Dimitry A
DA
Chistiakov
Department of Psychoneurology and Psychosomatic Pathology, Institute of Pediatrics, Research Center for Children's Health, Moscow 119991, Russia.
Lyudmila M
LM
Kuzenkova
Department of Molecular and Genetic Diagnostics, Division of Laboratory Medicine, Institute of Pediatrics, Research Center for Children's Health, Moscow 119991, Russia.
Kirill V
KV
Savost'anov
Institute of Preventive Pediatrics and Rehabilitation, Research Center for Children's Health, Moscow 119991, Russia.
Anait K
AK
Gevorkyan
Department of Molecular and Genetic Diagnostics, Division of Laboratory Medicine, Institute of Pediatrics, Research Center for Children's Health, Moscow 119991, Russia.
Alexander A
AA
Pushkov
Department of Molecular and Genetic Diagnostics, Division of Laboratory Medicine, Institute of Pediatrics, Research Center for Children's Health, Moscow 119991, Russia.
Alexey G
AG
Nikitin
Department of Psychoneurology and Psychosomatic Pathology, Institute of Pediatrics, Research Center for Children's Health, Moscow 119991, Russia.
Nato D
ND
Vashakmadze
Department of Molecular and Genetic Diagnostics, Division of Laboratory Medicine, Institute of Pediatrics, Research Center for Children's Health, Moscow 119991, Russia.
Natalia V
NV
Zhurkova
Department of Psychoneurology and Psychosomatic Pathology, Institute of Pediatrics, Research Center for Children's Health, Moscow 119991, Russia.
Tatiana V
TV
Podkletnova
Institute of Preventive Pediatrics and Rehabilitation, Research Center for Children's Health, Moscow 119991, Russia.
Leila S
LS
Namazova-Baranova
Research Center for Children's Health, Moscow 119991, Russia.
Alexander A
AA
Baranov
D000595:Amino Acid Sequence; D002478:Cells, Cultured; D002675:Child, Preschool; D005091:Exons; D006801:Humans; D007066:Iduronate Sulfatase / Q000097:blood / Q000235:genetics*; D007223:Infant; D007963:Leukocytes, Mononuclear / Q000201:enzymology; D008297:Male; D008969:Molecular Sequence Data; D016532:Mucopolysaccharidosis II / Q000235:genetics*; D009154:Mutation; D020641:Polymorphism, Single Nucleotide; D017422:Sequence Analysis, DNA
D007066:Iduronate Sulfatase
Glycosaminoglycans; Hunter syndrome; Iduronate-2-sulfatase; Mucopolysaccharidosis type II; Mutations