摘要
目的 对3例脊髓性肌萎缩患儿及其家系成员进行运动神经元存活（survival motor neumn,SMN）基因的突变分析,探讨突变对SMN蛋白功能的影响及与临床表型的关系.方法 采用多重连接依赖性探针扩增技术分析SMN拷贝数,采用RT-PCR及克隆测序技术进行SMN1基因点突变研究,通过对患儿父母的基因分析来明确SMN1基因缺失和点突变在家系中的传递.结果 2例来自不同家系的患儿SMN1均为单拷贝,且发生了相同的p.Glu134Lys突变;另1例患儿及其哥哥的SMN1基因也为单拷贝,均发生了p.Ser230Leu突变.这些患儿的SMN1基因点突变均来自父亲,SMN1单拷贝缺失均来自母亲.结论 共确定2种SMN1基因的点突变,其中p.Glu134Lys突变首次在中国脊髓性肌萎缩症患者中被发现.p.Glu134Lys和p.Ser230Leu均为致病性突变.
Objective Spinal muscular atrophy （SMA） is an autosomal recessive neuromuscular disorder. About 80% -90% of SMA patients are missing both copies of SMN1, and 5% -10% of patients are compound heterozygotes. In the present study, we aimed to analyze survival motor neuron 1 （SMN1） gene mutation in three patients with spinal muscular atrophy and their families to explore the effect of mutation on SMN protein function and the relationship between mutation and clinical phenotype. Method According to the international criterion, all patients were diagnosed by a neurologist. Patient 1 is a 5 years old boy with SMA type lI. Patient 2, female, 2. 5 years old, was SMA type lI. Patient 3, female, 9 years old, was SMA type m. The brother of patient 3 was SMA type 1I , too. The age at last examination was 14 years. Genomic DNA was extracted from peripheral blood leukocytes by using standard phenol/chloroform method and total RNA was extracted from whole blood with QIAamp RNA Blood Mini Kit. PCR/RFLP was used to detect the homozygosis deletion of the SMN1 exon 7, and multiplex ligation-dependent probe amplification （MLPA） were performed to analyze the gene dosage of SMN1 and SMN2 for each patient and his/her family members ; reverse transcriptase （RT）- PCR and clone sequencing were conducted for identifying the point mutation of SMN1 in three patients . The sequencing of genomic DNA and MLPA were carried out in the 3 families members to confirm the transition of mutation. Result No homozygous deletion of the SMN1 exon 7 was observed in any member of the 3 families. Case 1 and case 2 had one SMN! copy compound with c. 400G 〉 A （p. Glu134Lys） mutation on it and SMN2 was two copies, respectively. Case 3 and her brother also had one copy of SMN1 and two copies of SMN2, and a mutation c. 689C 〉 T （p. Ser230Leu） occurred on the retained SMN1. All point mutations were from their fathers and deletion come from their mothers for SMN1 gene. Conclusion In this work, p. Glu134Lys and p. Ser230Leu mutations were identified in three unrelated families and p. Glu134Lys from two patients was first discovered in Chinese SMA. The p. Glu134Lys mutation within the SMN Tudor domain prevents the binding of SMN and Sm. The fact that p. Ser230Leu results in a polar amino acid substituted for non-polar amino acid possibly affects the structure of SMN and then damages its function. SMN1 point mutation analysis is not only advantageous to the diagnosis of those patients with heterozygous deletion of SMN1, but will be beneficial to the prenatal diagnosis and genetic counseling for their families.
出处
《中华儿科杂志》
CAS
CSCD
北大核心
2011年第6期411-415,共5页
Chinese Journal of Pediatrics
基金
国家自然科学基金（81050034）
北京市自然科学基金SMA复合杂合突变机制和新突变对蛋白功能影响的研究（7112020）
首都儿科研究所基金（10-B09）
关键词
脊髓性肌萎缩
儿童
突变
逆转录聚合酶链反应
序列分析
拷贝数
Spinal muscular atrophy of childhood
Mutation
Reverse transcription-polymerase chain reaction
Sequence analysis
Copy number
