Molecular Analysis of Exon 7 and 8 of SMN Gene in Spinal Muscular Atrophy Patients

Abstract

Scientific background: The spinal muscular atrophy (SMA) causing degeneration of the anterior ham cells of the spinal cord is the most common autosomal recessive disease, affecting approximately 1 in 6.000- 10.000 live births and having a carrier frequency of approximately 1 in 40-60. SMA is diagnosed with detection of homozygous deletions of SMN7 (exon 7-8 or exon 7) gene in molecular level. Objectives: It is aimed to conduct molecular analysis of exon 7 and 8 of SMN gene in a hundred and eight subjects of SMA (53 patients and 55 suspected subjects).Materials and methods: PCR-RFLP method is used far detection of homozygous exon 7-8 deletions. PCR-SSCP method was used either to identify for intragenic mutations and especially compound heterozygotes or to confirm some SMA patients homozygous deletions detected by RFLP.Conclusion: In this study, 92.4% (49/53) of SMA patients including all types were found homozygous far exon 7 and 8 deletions with RFLP method. The rate of homozygous deletions determined was 94.7% (18/19) in type I patients, 91.6% (11/12) in type II and 89.4% (17/19) in type III. SSCP method was used only for 4 subjects who are clinically diagnosed as SMA patients but not confirmed with RFLP analysis. The results of SSCP analyses led to decision that patients may be of compound heterozygous or intragenic mutations.