脊髓性肌萎缩症SMN基因拷贝数定量分析  

Quantitative analysis of SMN gene copies in spinal muscular atrophy

作　　者：丁华新[1] 杨晓苏[1] 肖波[1] 吴志国[1] 张丽芳[1] 

机构地区：[1]中南大学湘雅医院神经内科

出　　处：《中华医学遗传学杂志》2004年第2期153-155,共3页Chinese Journal of Medical Genetics

基　　金：国家自然科学基金 (30 1 70 330 );湖南省自然科学基金 (0 2 JJY30 1 6)~~

摘　　要：目的　探讨临床诊断为脊髓性肌萎缩症 (spinal muscular atrophy,SMA)而 PCR定性无运动神经元生存 (survival motor neuron,SMN )基因 T拷贝 (SMN - T)缺失患者的遗传基础 ;并探索 SMA表型与SMN基因 C(SMN- C)拷贝数的关系及 SMA患者及其直系亲属和正常人 SMN基因拷贝数的分布。方法对临床和病理诊断为 SMA ～ 型及少见型 4 5例患者、2 5名表型正常的 SMA直系亲属进行 SMN- T和SMN- C基因拷贝数定量分析 ,并与 33名正常人进行对比 ;所有对象均已经 PCR Dra 酶切法定性检测SMN基因 ,其中 ～ 型的 7例和 型的 2例为 SMN- T纯合缺失 ,余者无缺失。建立 SMN- T和囊性纤维化跨膜调节因子 (cystic fibrosis transmembrane conductance regulator,CFTR)的内标 ,所有标本进行非放射性、非荧光标记的多重竞争性 PCR,根据产物 SMN- T/ CFTR和 SMN- C/ CFTR比值 ,计算 SMN- T和SMN - C拷贝数。结果　 7例 ～ 型 SMN - T拷贝数均为 0 ; 型 2例拷贝数为 0 ,2例为 1个拷贝数 ,系杂合缺失 ,4例为 2个拷贝 ; 型及其他型患者均为 2个拷贝 ;直系亲属中 9例为 1个拷贝 ,系杂合缺失 ,其余及正常对照组均为 2个拷贝。SMN - C拷贝数在 SMA 型为≤ 2 , ～ 型为≤ 3, 型及其它型 SMA、直系亲属和正常对照组均为 0～ 3。Objective To study the genetic basis in the patients with clinical diagnosis of spinal muscular atrophy(SMA) but without survival motor neuron telomeric copy (SMN-T) deletion; the relationship between the SMN-C (centromeric) copies and the phenotype; and the distribution of SMN-C and SMN-T copies in the SMA patients, the carriers and the controls. Methods Quantitative PCR analysis of SMN-T and SMN-C copies were carried out in 45 patients, 25 consanguineous and 33 control individuals. The patients were identified by clinical manifestation and muscular pathology. Two internal standards of SMN-T and cystic fibrosis transmembrane conductance regulator (CFTR) were constructed. Nonradioactive and nonfluorescence-labeling competitive PCR were used. The numbers of SMN-T and SMN-C copies were determined by calculating the ratios of SMN-T/CFTR and SMN-C/CFTR. Results Quantitation of SMN-T gene copies in SMA patients revealed that nine cases of type Ⅰ-Ⅲ were homozygously deleted. Two cases of type Ⅲ had only one copy and four cases of type Ⅲ had two copies. SMA Ⅳ and other type cases had two copies. Nine cases of consanguineous individuals had one copy, but other 16 had two copies. All of the normal individuals had two copies. Analysis of SMN-C copies showed that SMA Ⅰ had ≤2 copies, Ⅱ-Ⅲ had ≤3 copies, SMA Ⅳ and others had 0-3 copies, the consanguineous individuals and normal individuals had 0-3 copies. Conclusion The number of copies determined by PCR quantitative assay of SMN-T is accordant with the result of PCR qualitative assay of homozygous deletion. Quantitative assay of the number of copies can find out the cases and the carriers of heterozygous deletion. The SMA phenotype is related to the number of copies of SMN-C; the smaller the number of copies the patient has, the severer the patient's phenotype will be. The pathogenesis of SMA Ⅳ and other types of SMA may not relate to SMN gene.

关 键 词：脊髓性肌萎缩症 运动神经元生存基因 基因拷贝数 定量分析 

分 类 号：R744[医药卫生—神经病学与精神病学]