CAJ | 학술논문

目的通过运动神经元存活基因1(survival motor neuron gene 1,SMN1)点突变研究,对SMN1单拷贝缺失的疑似脊髓性肌萎缩症(spinal muscular atroph,SMA)患儿给予基因诊断.探讨SMN1复合杂合突变患儿的临床表型.方法按照国际SMA诊断标准对3例患者进行临床拟诊和随访分型.应用多重连接探针扩增技术(multiplex ligation-dependent probe amplification,MLPA)技术进行SMN1和SMN2基因的拷贝数定量分析.应用逆转录PCR和克隆测序技术进行SMN1点突变研究.通过核心家系成员拷贝数和点突变分析,明确突变在家系中的传递.结果确定了2种SMN1基因点突变:p.Leu228X(1例)和p.Arg288Met(2例).其中错义突变p.Arg288Met为中国SMA中首次报道,无义突变p.Leu228X为中国大陆地区首次报道.携带p.Leu228X突变的患儿具有2个SMN2拷贝,为Ⅰ型SMA;而携带p.Arg288Met突变的2例患儿SMN2的拷贝数均为3,表型分别为Ⅰ型和Ⅱ型.结论 p.Leu228X和p.Arg288Met突变均遗传自父母,而非新发突变.两种突变导致了严重的Ⅰ型和较为严重的Ⅱ型SMA.3例SMA患儿发生SMN1基因杂合缺失同时伴有SMN1基因点突变,提示我国SMA存在复合杂合突变机制.对SMN1基因单拷贝缺失的疑似SMA患儿,进行点突变分析十分必要,能够为患儿的临床诊断、家庭的遗传咨询和产前诊断提供依据.
목적 통과운동신경원존활기인1(survival motor neuron gene 1,SMN1)점돌변연구,대SMN1단고패결실적의사척수성기위축증(spinal muscular atroph,SMA)환인급여기인진단.탐토SMN1복합잡합돌변환인적림상표형.방법 안조국제SMA진단표준대3례환자진행림상의진화수방분형.응용다중련접탐침확증기술(multiplex ligation-dependent probe amplification,MLPA)기술진행SMN1화SMN2기인적고패수정량분석.응용역전록PCR화극륭측서기술진행SMN1점돌변연구.통과핵심가계성원고패수화점돌변분석,명학돌변재가계중적전체.결과 학정료2충SMN1기인점돌변:p.Leu228X(1례)화p.Arg288Met(2례).기중착의돌변p.Arg288Met위중국SMA중수차보도,무의돌변p.Leu228X위중국대륙지구수차보도.휴대p.Leu228X돌변적환인구유2개SMN2고패,위Ⅰ형SMA;이휴대p.Arg288Met돌변적2례환인SMN2적고패수균위3,표형분별위Ⅰ형화Ⅱ형.결론 p.Leu228X화p.Arg288Met돌변균유전자부모,이비신발돌변.량충돌변도치료엄중적Ⅰ형화교위엄중적Ⅱ형SMA.3례SMA환인발생SMN1기인잡합결실동시반유SMN1기인점돌변,제시아국SMA존재복합잡합돌변궤제.대SMN1기인단고패결실적의사SMA환인,진행점돌변분석십분필요,능구위환인적림상진단、가정적유전자순화산전진단제공의거.
Objective To identify the point mutations in survival motor neuron gene 1 (SMN1) gene and confirm the existence of compound heterozygous mutations in Chinese patients with spinal muscular atrophy (SMA). Methods Three unrelated patients were diagnosed and clinically typed according to the criteria of proximal SMA established by the International SMA Consortium. Multiplex ligation-dependent probe amplification (MLPA) analysis was carried out to measure the copy numbers of SMN1, SMN2 and neuronal apoptosis inhibitory protein gene (NAIP) in the patients. The point mutation analysis of SMN1 gene was performed by reversed transcript-polymerase chain reaction (RT-PCR) and cloning sequencing. The MLPA assay and point mutation analysis were also performed in the family members to confirm the transmission of the mutations. Results Two point mutations were identified in the present study, i.e., the p. Leu228X in one patient and p. Arg288Met in two patients. The mutation p. Arg288Met was first reported in Chinese and p. Leu228X was first reported in Mainland Chinese. The case carrying p. Leu228X mutation was diagnosed as SMA Ⅰ with 2 copies of SMN2, and the cases with p. Arg288Met were diagnosed as SMA Ⅰ and SMA Ⅱ, respectively, with 3 copies of SMN2 gene. Conclusion The mutations p. Leu228X and p.Arg288Met caused severe clinical phenotypes, SMA Ⅰ or SMA Ⅱ. This study suggested that the compound heterozygous mutations of SMN1 existed in Chinese SMA patients, which was rarely reported previously in Chinese. It was necessary to detect the point mutation in SMN1 for genetic diagnosis of those patients with heterozygous deletion of SMN1, which would be beneficial to prenatal diagnosis and genetic counseling in these families.