SMN_1基因实时荧光定量分析在脊髓性肌萎缩携带者检测中的应用

Application of real-time PCR analysis of the SMN_1 gene in the carrier testing of spinal muscular atrophy

目的脊髓性肌萎缩(spinal muscular atrophy,SMA)是以脊髓前角运动神经元退化变性为特征的一种常见的常染色体隐性遗传病。SMA的发病率为1/10000,携带者频率为1/50,因此,对于运动神经元存活基因(survival motor neuron,SMN1)缺失携带者的检测在遗传咨询中尤为重要。然而SMA位点的重复使得携带者的检测比较困难。该研究的目的是探讨SMN1基因定量分析在SMA携带者检测中的作用。方法应用TaqMan技术的实时荧光定量PCR方法对109例不同临床表型的SMA患者父母和40例正常对照者的SMN1基因拷贝数进行检测。结果①SMA肯定携带者的SMN1基因的平均拷贝数为0.777±0.035,变异系数(CV)值4.5%;正常人(1例,用于验证检测方法的重复性)SMN1基因的平均拷贝数为2.064±0.120,CV值5.8%;②SMA患者父母SMN1基因平均拷贝数为0.798±0.108,CV值13.5%;正常人(38/40,为人群SMN1拷贝数)SMN1基因平均拷贝数为2.106±0.18,CV值8.5%。结论SMA患者父母和正常对照者的SMN1拷贝数的分布不同,前者为1个拷贝的SMN1基因;后者以2个拷贝的SMN1基因为主。因此,SMN1基因定量检测可用于区分大部分正常人和SMA携带者。

Objective Spinal muscular atrophy （SMA） is one of common autosomal recessive diseases and is characterized by degeneration of the anterior horn cells of the spinal cord, The reported prevalence is 1/10 000 live births with a cartier rate of one in 50. It is important in genetic counseling to identify the carriers with one copy deletion for the survival motor neuron （SMN1 ） gene. However, the duplication of the SMA locus makes the detection of SMA carriers difficult. This study aimed to determine the potential of the quantitative PCR analysis in the identification of SMA carriers. Methods The SMN1 gene copy number was detected by real-time PCR with TaqMan technology in 109 SMA parents of affected children and 40 normal controls. Results The average copy numbers of SMN1 in the individuals with known one copy of the SMN1 gene and with the two copies were 0,777 ±0.035 （ CV = 4.5% ） and 2. 064 ±0. 120 （ CV = 5.8% ） respectively. The average copy number of SMN1 in all of the parents with affected individuals was 0. 798 ±0. 108 （ CV = 13.5% ）, and that of normal controls was 2. 106 ±0.18 （ CV= 8.5% ）. About 98% of SMA patients＇ parents carried 1 copy SMN1 , and 95% of normal controls carried 2 copies. Conclusions The gene copy numbers for SMN1 were one and two for SMA carriers and non-carriers, respectively. Our results suggested that the quantitative PCR analysis can distinguish the SMN1 deletion carriers from non-carriers.