A 3' splice site mutation of IDS gene in a Chinese family with mucopolysaccharidosis type II.
A 3' splice site mutation of IDS gene in a Chinese family with mucopolysaccharidosis type II.
复制标题
中国II型粘多糖贮积症家系IDS基因3剪接位点突变。
作者：
P. Jin;Jing Hao;Ke Chen;C. Dong;You;Z. Mo
本研究的目的是确定潜在的遗传原因，在一个四代中国家庭诊断为粘多糖样沉积症II型。采集家系成员外周血样本，通过DNA测序分析艾杜糖醛酸-2-硫酸酯酶（IDS）基因。IDS突变对mRNA转录的影响通过定量实时RT-PCR（qRT-PCR）在两个患者以及健康对照样品中确定。此外，我们还对发现的一个位于非典型剪接位点的突变进行了RT-PCR验证，发现一个3′剪接位点突变c.880-8A>G在所分析的MPS II家族的两个成员中鉴定出IVS 6-8A>G突变，并且RT-PCR产物的测序显示该突变激活了内含子6中的上游隐蔽剪接位点，导致外显子7中的7个核苷酸插入，这又导致外显子7移码，从而引入提前终止密码子和较短的肽链。此外，与健康对照样品中的平均IDSmRNA表达相比，来自两名患者的qRT-PCR产物显示IDSmRNA表达降低（分别为43.9%和71.2%），这可能是无义介导的mRNA衰减的结果。总之，在本研究中，我们发现了一个IDS基因剪接突变，该突变与临床减毒MPS II表型相关。此外，我们的研究强调了cDNA分析在检测内含子突变中的重要性，因为在仅检查gDNA的研究中，基因型和表型之间的联系可能被误解。
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 reducedIDSmRNA expression (43.9% and 71.2%, respectively), when compared with the averageIDSmRNA expression in healthy control samples, possibly as a result of nonsense-mediated mRNA decay. In conclusion, in this study, we have identified anIDSgene 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.