Spinal muscular atrophy type III: Molecular genetic characterization of Turkish patients

Spinal Muscular Atrophy (SMA) is a neurodegenerative disease with autosomal recessive inheritance. Homozygous loss of exon 7 of the Survival of motor neuron 1 (SMN1) gene is the main cause of SMA. Although progressive muscle weakness and atrophy are common symptoms, disease severity varies from severe to mild. Type III is one of the milder and less frequent forms of SMA. In this study, we report molecular genetic characteristics of 24 Turkish type III SMA patients. Homozygous loss of SMN1 exon 7 and 8 was analysed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and multiplex ligation dependent probe amplification (MLPA). SMN2, homologue of SMN1, and Neuronal apoptosis inhibitory protein (NAIP) genes were also evaluated considering their influence on disease severity. We determined that male patients who were born in consanguineous families were predominant in our cohort and these patients mostly carry the homozygous loss of SMN1 exon 7 and 8 and four copies of SMN2 gene without NAIP deletions.