title: A 3' splice site mutation of IDS gene in a Chinese family with mucopolysaccharidosis type II.
abstract: The purpose of this study was to identify the underlying genetic cause in a four generation Chinese family diagnosed with mucopolysaccharidosis type II. Peripheral blood samples were collected from family members and the iduronate-2-sulfatase (IDS) gene was analyzed by DNA sequencing. The impact of IDS mutations on mRNA transcription was determined by quantitative real-time RT-PCR (qRT-PCR) in both patients as well as in healthy control samples. In addition, RT-PCR was performed to confirm the characteristics of a found mutation located in non-canonical splicing site. A 3' splice site mutation c.880-8A>G (IVS 6-8A>G) was identified in two members of the analyzed MPS II family and sequencing of RT-PCR products showed that this mutation activates an upstream cryptic splice-site in intron 6, leads to the 7 nucleotide insertion in exon 7, which in turn results in an exon 7 frameshift introducing a premature stop codon and shorter peptide chain. In addition, qRT-PCR products from the two patients showed a reduced IDS mRNA expression (43.9% and 71.2%, respectively), when compared with the average IDS mRNA expression in healthy control samples, possibly as a result of nonsense-mediated mRNA decay. In conclusion, in this study, we have identified an IDS gene splice mutation which is associated with clinically attenuated MPS II phenotype. In addition, our study accentuates the importance of cDNA analysis in the detection of intronic mutations, since in the studies examining only gDNA, the link between genotype and phenotype may have been misinterpreted.
authors.affiliation: Division of Endocrinology, 3nd Xiangya Hospital, Central South University, 410007 Changsha, Hunan, China.
authors.forename: Ping
authors.initials: P
authors.lastname: Jin
authors.forename: Jing-Wen
authors.initials: JW
authors.lastname: Hao
authors.forename: Ke
authors.initials: K
authors.lastname: Chen
authors.forename: Chang-Sheng
authors.initials: CS
authors.lastname: Dong
authors.forename: You-Bo
authors.initials: YB
authors.lastname: Yang
authors.forename: Zhao-Hui
authors.initials: ZH
authors.lastname: Mo
mesh_terms: D000328:Adult; D044466:Asian People; D001483:Base Sequence; D016022:Case-Control Studies; D002675:Child, Preschool; D018389:Codon, Nonsense; D003241:Consanguinity; D004252:DNA Mutational Analysis; D005260:Female; D015870:Gene Expression; D056726:Genetic Association Studies; D006023:Glycoproteins / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D007438:Introns; D008297:Male; D016532:Mucopolysaccharidosis II / Q000000981:diagnostic imaging / Q000201:enzymology / Q000235:genetics*; D010375:Pedigree; D017354:Point Mutation; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D022821:RNA Splice Sites; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011859:Radiography; D060888:Real-Time Polymerase Chain Reaction
chemical_list: D018389:Codon, Nonsense; D006023:Glycoproteins; C018322:IDS protein, human; D020033:Protein Isoforms; D022821:RNA Splice Sites; D012333:RNA, Messenger
keywords: HGMD; Human Gene Mutation Database; IDS; Iduronate-2-sulfatase; MPS II; Mucopolysaccharidosis type II; NMD; Nonsense-mediated Decay; PCR; PTCs; Polymerase Chain Reaction; Premature Translation Stop Codons; Quantitative Real-time Polymerase Chain Reaction; Splicing mutations; qRT-PCR