Deletions in the survival motor neuron gene in Turkish spinal muscular atrophy patients

Deletions in the Survival Motor Neuron Gene in Iranian Patients with Spinal Muscular Atrophy

Introduction: Spinal muscular atrophy (SMA) is a common neuromuscular disorder with progressive paralysis caused by the loss of -motor neurons in the spinal cord. The survival motor neuron (SMN) protein is encoded by 2 genes, SMN1 and SMN2. The most frequent mutation is the biallelic deletion of exon 7 of the SMN1 gene. In SMA, SMN2 cannot compensate for the loss of SMN1, due to the exclusion of exon 7. The aim of our study was to estimate the frequency of the common SMN1 exon 7 deletion in patients referred to our centre for carrier detection and prenatal diagnosis. Materials and Methods: We performed the detection of exon 7 deletion of the SMN1 gene for the affected patients and fetuses suspected to have SMA. Results: Of 243 families, 195 were classified as SMA type I, 30 as type II, and 18 as type III according to their family histories. The analysis of exon 7 deletion among living affected children showed that 94% of the patients with SMA type I, 95% with type II families and 100% with type III had homozygous deletions. Of the prenatal diagnoses, 21 (22.8%) of the 92 fetuses were found to be affected and these pregnancies were terminated. Conclusions: The homozygosity frequency for the deletion of SMN1 exon 7 for all 3 types was (94%), similar to those of Western Europe, China, Japan and Kuwait. Key words: Iranian patients, SMN1

Molecular Analysis of Survival Motor Neuron and Neuronal Apoptosis Inhibitory Protein Genes in Macedonian Spinal Muscular Atrophy Patients

Spinal muscular atrophy (SMA) is classified according to the age of onset and severity of the clinical manifestations into: acute (Werding-Hoffman disease or type I), intermediate (type II) and juvenile (Kugelberg-Wilander disease or type III) forms. All three SMAs have been linked to markers at 5q11.2-q13.3. Two candidate genes deleted in SMA patients are the survival motor neuron (SMN) gene and the neuronal apoptosis inhibitory protein (NAIP) gene. We have performed molecular analyses of these genes in 30 unrelated Macedonian families (17 with type I, eight with type II and five with type III forms of the disease). Deletions of exons 7 and 8 of the SMN gene were found in 76.6% (23/30) of patients (94.1% in type I, 87.5% in type II). Among these 23 families, 19 had both exons deleted, while four had deletions only of exon 7. Deletions of exon 5 of the NAIP gene were found in 41.2% (7/17) patients with type I SMA and in 12.5% (1/8) of patients with type II SMA. No deletions of the SMN gene were found in 30 parents and 30 normal controls. We found 2/30 (6.7%) parents to be homozygous for the deletion of exon 5. Our data support the hypothesis that the telomeric SMN gene plays a major role in determining the clinical course of the disease, while the defects in the NAIP gene have only a modifying effect on the phenotype.

Deletion analysis in Turkish patients with spinal muscular atrophy

Childhood proximal spinal muscular atrophy (SMA) is an autosomal recessive disorder which presents as a severe, intermediate or mild condition. Here we present the molecular analysis of SMA candidate genes, the survival motor neuron gene (SMN), the neuronal apoptosis inhibitory protein gene (NAIP) and the p44 gene. Deletion frequency rate of these candidate genes is 93% in 106 Turkish SMA patients. Various deletion haplotypes by using genotypes of SMN, NAIP and p44 genes are constructed. Haplotype A, which is the deletion of all three involved genes, was found only in the most severe group with an early onset of usually less than 2 months of age.