Ⅱ型粘多糖贮积症致病基因IDS内含子中一个新的RNA剪切变异

Identification of a novel splicing variant of IDS gene in a pedigree affected with typeⅡglycosaminoglycan product storage disease

目的对1个粘多糖贮积症Ⅱ型(mucopolysaccharidosisⅡ,MPSⅡ)家系的艾杜糖-2-硫酸酯酶(iduronate-2-sulfatase,IDS)基因进行变异分析,探讨其分子遗传学发病机制。方法应用高通量测序和Sanger测序技术对先证者进行基因变异分析,基因变异确定后,对其母亲、父亲进行致病基因位点确认,确定变异基因的遗传关系;应用逆转录-聚合酶链反应检测变异对mRNA的影响。结果先证者IDS基因存在IVS1-3T>G半合子变异,导致变异等位基因产生了两种转录本,一种转录本保留了第1内含子的3′端c.104-216到c.104-1的216个核苷酸,并提前出现终止密码,导致肽链从550个氨基酸截短至38个;另一种转录本缺失了第2外显子5′端c.104-c.212的109个碱基,产生移码变异,IDS肽链由550个氨基酸缩短至92个。先证者为IVS1-3T>G变异的半合子,而其母亲为IVS1-3T>G变异的杂合子;其他家系成员及100名正常对照则未见该变异。结论IDS基因的IVS1-3T>G变异导致IDS基因表达异常,进而引起IDS蛋白异常,从而成为该粘多糖贮积症Ⅱ型患者的致病原因。

Objective To analyze variant of IDS gene in a pedigree affected with mucopolysaccharidosis typeⅡ(MPSⅡ).Methods The proband was subjected to next generation sequencing and Sanger sequencing to identify potential variants.Suspected variant was analyzed by its co-segregation with the disease in the pedigree.Its impact on mRNA splicing was analyzed by using reverse transcription PCR(RT-PCR).Results A hemizygous IVS1-3T>G variant was found in the IDS gene in the proband.RT-PCR results revealed two abnormal cDNA fragments of 600 bp and 300 bp.The 600 bp fragment had inserted 216 nucleotides at the 3′end of intron 1,while the 300 bp fragment had lost 109 nucleotides at the 5′end of exon 2,which resulted in two truncated proteins comprising 38 and 92 amino acids,respectively,instead of the normal product(550 amino acids).The proband and his mother were respectively hemizygous and heterozygous for the variant.The same variant was not found among 100 normal controls.Conclusion The IVS1-3T>G variant of the IDS gene probably underlies the MPSⅡin this pedigree by causing reduction or elimination of the IDS protein.