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目的探讨中国人儿童型脊髓性肌萎缩症(SMA)的基因序列、基因缺失情况及错配聚合酶链反应限制性片段长度多态性分析(PCRRFLP)技术在儿童型SMA基因诊断中的价值。方法应用错配PCRRFLP分析对34例拟诊为儿童型SMA(Ⅰ型18例,Ⅱ型11例,Ⅲ型5例)的患者、20名SMA患者的健康家系成员及20名健康人进行运动神经元存活基因(SMN)7号外显子缺失检测,并选择1例SMA患者的SMNc和1例健康人的SMNt基因7号外显子进行基因测序。结果34例拟诊SMA患者31例(91.2%)有SMNt7号外显子缺失,其中Ⅰ型18例,Ⅱ型10例,Ⅲ型3例,所有健康人均无SMN7号外显子缺失。SMNc和SMNt基因7号外显子测序长度均为187bp,两者的序列只有1个碱基的差异(T→C),与国外报道一致。结论中国人儿童型SMA基因序列与国外报道一致,Ⅰ～Ⅱ型基因缺失频率高,Ⅲ型缺失频率较低,错配PCRRFLP可作为诊断Ⅰ、Ⅱ型SMA的有效手段。
Objective To investigate the gene sequence and gene deletion of Chinese children with spinal muscular atrophy (SMA) and the value of PCR-RFLP in the diagnosis of childhood SMA gene. Methods 34 patients with SMA diagnosed as pediatric SMA (18 cases of type Ⅰ, 11 cases of type Ⅱ and 5 cases of type Ⅲ), 20 healthy SMA patients and 20 healthy volunteers were analyzed by mismatched PCR-RFLP. Metastasis gene (SMN) exon 7 was detected by deletion, and SMNc in 1 patient and SMNt gene exon 7 in 1 healthy person were selected for gene sequencing. Results There were 31 (91.2%) SMNt7 exon deletions in 34 patients with suspected SMA, including 18 cases of type Ⅰ, 10 cases of type Ⅱ and 3 cases of type Ⅲ. All healthy individuals had no deletion of SMN7 exon. The sequencing of exon 7 of SMNc and SMNt genes was 187bp in length, with only one base difference (T → C) between the two sequences, which was consistent with that reported in foreign countries. Conclusion The sequence of childhood SMA gene in Chinese is consistent with that reported in other countries. The frequency of type Ⅰ-Ⅱ deletion and type Ⅲ deletion are lower. Mismatch PCRRFLP can be used as an effective method to diagnose type Ⅰ and type Ⅱ SMA.