Study On The Gene Diagnosis And The Genotype-Phenotype Correlation Of Spinal Muscular Atrophy

Objectives 1.To make the gene diagnosis system perfect.2.To provide evidence for genetic counseling by screening the carriers of SMA.3.To study the correlation between the SMN2 copies and the phenotype,and further elucidate the pathogenesis of SMA by quantitative study on SMN2 gene.Methods:1PCR-restriction enzyme digestion and denaturing high-performance liquid chromatography(DHPLC) methods were applied to detect the deletion of the exon 7 and 8 of SMN1 gene.2.Real-time fluorescence quantitative PCR was applied to study the SMN1 and SMN2 gene copies.3.SPSS 10.0 package was applied to analyzed the difference of SMN1 copies among normal people,SMA family members and SMA carriers ,the difference of SMN2 copies between different types of SMA patients and the correlation between the survival time of patients and SMN2 copies.Results:1. 48 out of 51 patients were found to delete exon 7 of SMN1 gene and 47delete exon 8 of SMN1 gene.2.Different DNA segments were separated on the DHPLC chromatogram. Three peaks including SMN1/SMN2 heteroduplex peak, SMN2 homoduplex peak and SMN1 homoduplex peak were detected in normal individuals. Only the SMN2 homoduplex peak was detected in SMA patients, indicating deletion of SMN1,On the contrary,only SMN1 homoduplex peak was detected in normal individuals indicating deletion of SMN2 gene.3.The results of SMN1 and SMN2 copy number detected by real-time fluorescence quantitative PCR are stable and accurate.4. 7 confirmed SMA carriers were detected from 264 normal people and 32 SMA family members.5.The SMN2 copies were examined from 50 nomal people and 51 patients .There was significant correlation between SMN2 copies and phenotype ﹙R=0.682,P<0.01﹚.There was significant difference in the survival time among different SMN2 group(P=0.02).Conclusions:1.We have made the gene diagnosis more accurate and more sensitive by the combination of PCR-restriction enzyme digestion and DHPLC methods.2. We can provide important evidence for genetic counseling by screening the carriers of SMA from normal people and SMA family members.3.There is significant reverse correlation between SMN2 copies and the severity of phenotypes. The prognosis of patients can be estimated according to the SMN2 copies.The data of SMN2 copies also established the foundation for gene therapy in the future.