Expression studies of mutations underlying Taiwanese Hunter syndrome (mucopolysaccharidosis type II)

Abstract

Nearly 300 different mutations underlying mucopolysaccharidosis type II (MPS II) have been identified worldwide. To investigate the molecular lesions underlying Taiwanese MPS II, probands and families were identified and screened for iduronate-2-sulfatase (IDS) mutation by single-strand conformation polymorphism and DNA sequencing. Five novel and five previously reported mutations were found. Together with those previously reported, a total of 17 identified missense, small deletion, and nonsense mutations were further characterized by transient expression studies. Transfection of COS-7 cells by the mutated cDNA did not yield active enzyme, demonstrating the deleterious nature of the mutations. A 57% decrease in IDS mRNA level was seen with the 231del6 mutation. Among the 11 missense mutations examined, K347E substitution showed apparent normal maturation and targeting on immunoblot and confocal fluorescence microscopy examination. The other 10 missense mutations showed apparent normal precursor with little or reduced mature forms, indicating normal maturation but incorrect targeting of the mutant enzymes. Among the six deletion and nonsense mutations examined, 1055del12 and E521X showed abnormal maturation. The staining pattern of the truncated W267X and 1184delG proteins suggested retention within early vacuolar compartments. The mutated 231del6 and 1421delAG proteins were unstable and largely degraded. Molecular analysis of the IDS gene will clearly identify the cause of the disease within patients and allow antenatal and family studies. The further characterization of gene mutations may delineate their functional consequences on IDS activity and processing and may enable future studies of genotype-phenotype correlation to estimate a prognosis and to lead to possible therapeutic interventions.

Effect of Hunter disease (mucopolysaccharidosis type II) mutations on molecular phenotypes of iduronate‐2‐sulfatase: Enzymatic activity, protein processing and structural analysis

“…IDS cDNA and its genomic DNA gene have been isolated and characterized (Flomen et al 1993;Robert et al 1989;Wilson et al 1990Wilson et al , 1993. Nearly 300 different mutations have been described in Hunter patients (http://www.hgmd.org/); some of the mutations have been examined in expression studies (Bonuccelli et al 2001;Chang et al 2005;Crotty et al 1992;Cudry et al 2000;Millat et al 1997Millat et al , 1998Ricci et al 2003;Sukegawa et al 1995;Villani et al 2000), but the correlation between genotype and phenotype has remained unclear. We previously identified the missense and nonsense mutations of the IDS gene in Hunter disease and characterized the mutant proteins with the transiently transfected cells (Sukegawa et al 1992(Sukegawa et al , 1995.…”

Molecular analysis of the iduronate‐2‐sulfatase gene in Thai patients with Hunter syndrome

“…In addition, transcript splicing errors have been reported to be involved in up to 50% of mutations in some populations (Alves et al 2006). Although many IDS gene mutations have been identified in Asia, including in China, Taiwan, Japan and Korea (Chang et al 2005;Dou et al 2007;Kato et al 2005;Kim et al 2003), none have previously been reported from South-East Asia. Here, we provide the first description of the molecular basis of Hunter syndrome in Thailand from analysis of 20 patients representing all regions of the country.…”

Detection of a new mutation (T1140C) in a patient with Hunter syndrome from Guangdong, China

“…The second is in exon-3, about 21% and the third is in exon-8, about 20% (Rathmann et al, 1996). The types of the mutation include missense mutation, nonsense mutation, shearing mutation, insertion mutation, deletion mutation, complicated rearrangement and so on (Chang et al, 2005;Chou et al, 2005;Guo et al, 2005;Guo et al, 2006;Li et al, 1999;Zhang et al, 2004). Molecular genetics research on Hunter syndrome was launched in foreign countries many years ago.…”