粘多糖贮积症Ⅱ型患者IDS基因的2个新突变

为了研究粘多糖贮积症II型(MPS Ⅱ)患者发病的分子遗传学机制, 采用PCR扩增艾杜糖-2-硫酸酯酶(IDS)基因突变热点区(外显子2、3、5、7、8和9)、DNA测序分析和限制性内切酶图谱分析的方法, 对2个粘多糖贮积症Ⅱ型家系进行了遗传突变分析。结果表明, 2个家系患者的IDS 基因分别出现IVS 6-1g→a和c.1587~1588 ins T 2个新突变。前者属于单碱基替换, 位于内含子6的3′端剪接位点, 导致跨外显子剪接; 后者属于插入突变, 插入点位于外显子9的cDNA 1,587和1,588碱基之间, 是迄今为止报道的人类IDS基因插入突变中最接近肽链末端的突变, 导致移码突变和转录提前终止。经限制性酶切分析, 证实2个家系中的患者母亲是突变基因的携带者, 符合该病X染色体隐性遗传的规律。另外,在对随机抽取的50名正常人及另外6名不相关的粘多糖病人的测序分析中, 未检测到这2个突变, 说明不是多态性。对于筛查所得的2个新突变是否是患者的致病原因, 尚需进一步证实。

Detection of two novel mutations of iduronate-2-sulfatase gene in patients with mucopolysaccharidosis type Ⅱ

In the present study, through PCR amplification and direct sequencing of mutation "hotspots", we were able to identify two novel mutations in the human iduronate-2-sulfatase (IDS) gene in two patients from unrelated families with mucopolysaccharidosis type II(MPS II). The novel mutation IVS 6 -1g-->a affected the 3' splice acceptor site of intron 6, and was predicted to result in exon skipping. The novel mutation c.1587-1588 ins T involved a single base insertion be-tween nucleotides 1,587 and 1,588 in exon 9, and was predicted to result in frame shift and premature termination. The two novel mutations did not occur in 6 other unrelated MPS patients or in 100 alleles from normal individuals, indicating that they were not polymorphisms. The PCR-restriction enzyme digestion showed that the two newly identified mutations were of maternal origin, which was consistent with the X-linked recessive disorder. These findings suggest that the IDS gene mutations could be detected by amplifying mutation "hotspots", direct sequencing and restriction digestion analysis, and the newly identified mutations may be disease-causing.