一个中国人Liddle综合征家系的SCNN1G基因新突变及其临床特征

Liddle＇s syndrome caused by a novel mutation of the γ-subunit of epithelial sodium channel gene SCNN1G in Chinese

目的分析2个Liddle综合征家系上皮细胞钠通道编码基因SCNN1B及scNN1G的基因突变。方法收集2个临床诊断为Liddle综合征的家系，抽取先证者及其家系成员外周血基因组DNA，PCR扩增上皮细胞钠通道8亚单位编码基因SCNN1B和γ亚单位编码基因SCNN1G第13外显子，产物直接DNA测序进行基因突变检测。结果 例1 SCNN1B基因第13外显子的扩增片段经双向测序显示第564密码子存在CGA-TGA（R-X）杂合无义突变，其家系成员均未发现这一基因突变；例2 SCNN1G基因第567密码子存在CAGTAG（Q-X）杂合无义突变，2个家系成员携带此突变基因，这一突变位点尚未在国内外报道过，50名无关正常人中未发现此突变基因。结论对临床诊断的Liddle综合征患者及其亲属，进行基因突变检测有助于确定诊断及早期筛查出家系中的其他患者。编码人类肾小管上皮细胞钠通道7亚单位基因SCNN1G第13外显子第567密码子CAG—TAG（Q-X）杂合无义突变可能会导致Liddle综合征。

Objective To screen the mutation of the 13 and 7 subunits of epithelial sodium channel gene SCNN1 in two families with Liddle＇s syndrome. Methods Two patients clinically diagnosed as Liddle＇s syndrome and their family members were enrolled. Peripheral blood samples were collected and total genomic DNA was prepared. Polymerase chain reaction （PCR） was used to amplify the exon 13 of the SCNNIB and SCNN1G gene. PCR products were purified and subjected to direct DNA sequencing. Results A heterozygous nonsense mutation at codon 564 of the SCNN1B gene from CGA（Arg） to stop codon（TGA） was detector in the proband of family 1. More importantly, a novel heterozygous nonsense mutation of CAG （Gln） to stop codon TAG at codon 567 of the SCNN1G gene was detected in the proband and another two members of family 2. Conclusion Screening for specific mutations of the SCNN1 gene in relatives of patients with Liddle＇s syndrome can be used to identify the previously unrecognized cases within the family. A new nonsense mutation（Q567X） of the SCNN1G gene is likely the cause of Liddle＇s syndrome in family 2.