Résumé :
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Communication n° 113 Spinal muscular dystrophy (SMA) is a hereditary neurodegenerative disease often causing death in early childhood. This disease is caused by anterior -horn-cell death in the spinal cord leading to paralysis and skeletal muscular atrophy. The candidate gene for this disease is survival motor neuron gene (SMN) that exists in two nearly identical copies; telomeric SMN (SMNt) and centromeric SMN (SMNc). Because of gene deletion or conversion, exon 7 of SMNt gene is homozygously absent in approximately 94% of patients with clinically typical SMA. SMA affects approximately 1 in 10,000 live births, and with a carrier frequency of approximately 1 in 50. In this study we decided to determine the carrier frequency of this disease which is extremely common in Iran. Two hundred unrelated individuals were selected from different ethnic populations of Iran. In all individuals, exon 7 of SMN gene was amplified by polymerase chain reaction (PCR) and PCR products were digested by DraI restriction enzyme and then electrophoresed on 8% polyacrylamide gel. In all steps, control samples with normal SMN alleles, heterozygous and homozygous deletion of exon 7 were used. To differentiate carriers and normal individuals, the intensity of digested fragments was analyzed by LabWorks software to calculate the ratio of telomeric to centromeric portion of SMN gene. Surprisingly, the carrier frequency of this disease seems to be around 12%, and not evenly distributed among the ethnic subgroups that is much higher than the carrier frequency of 1/40 to 1/60 that has been reported before in the West.
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