目的：研究儿童型脊肌萎缩症(SMA)患者中运动神经元生存基因缺失与微突变情况。方法：收集经临床和肌肉活检确诊的SMA I~III型25例,其中I型5例,II型3例,III 17例及直系亲属24例。采用PCR-RFLP检测SMNt缺失情况,对无SMNt缺失的患者及SMA直系亲属,应用PCR-SSCP结合DNA序列分析的方法,进行SMN基因微突变分析。结果：5例I型和3例II型SMA患者均见SMNt缺失,缺失率100%,6例III型见缺失,缺失率35%(6/17)。11例无缺失的SMA III型患者的gDNA编码区域未发现微突变;24例SMA的直系亲属中未发现SMN基因缺失及突变。结论：①检测到SMNt外显子7缺失可作为SMA的确诊手段,有望替代肌电图和肌活检等有创检查;②对无SMNt外显子7缺失的III型SMA患者,要结合临床进行诊断;③该组无SMNt缺失的III型患者未发现微突变,提示存在遗传异质性。[中国当代儿科杂志,2005,7(6):489-492]

OBJECTIVE: This study examined the prevalence of deletion and subtle mutations of survival motor neuron (SMN) gene in children with spinal muscular atrophy(SMA). METHODS: Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) was used to detect the deletion of SMNt exon 7 in 25 children with SMA (type I 5 cases, type II 3 cases, and type III 17 cases) and in 24 healthy relatives of these patients. SMA was diagnosed clinically and pathologically. The subtle mutations of SMN in encode regions were screened by polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) combined with DNA direct sequencing in the patients without SMNt deletion and their relatives. RESULTS: Deletion of exon 7 of the SMNt gene was found in 5 cases of SMA type I(100%), 3 cases of type II (100%) and 6, type III(35%). No subtle mutation of SMN was found in encoded regions in 11 cases of type III SMA without SMNt deletion. The 24 relatives of SMA patients did not show the deletion and subtle mutation of SMN. CONCLUSIONS:  ①Detection of SMNt gene exon 7 deletion can be recommend as a definitive diagnostic method for SMA, and showed promise to replace invasive examinations, such as electromyogram and muscular biopsy. ②In patients with type III SMA without SMNt deletion, diagnosis is still made clinically. ③No subtle mutation of SMN was found in SMA type III patients without SMNt deletion, suggesting genetic heterogenicity might exist.