Genotype-phenotype correlation of survival motor neuron and neuronal apoptosis inhibitory protein genes in spinal muscular atrophy patients from Iran

Molecular analysis of SMN2, NAIP, and GTF2H2 gene deletions and relationships with clinical subtypes of spinal muscular atrophy

SMA (spinal muscular atrophy) is an autosomal recessive neuromuscular disease that causes muscle atrophy and weakness. SMA is diagnosed by a homozygous deletion in exon 7 of the SMN1 gene. However, mutations in genes located in the SMA region, such as SMN2, NAIP, SERF1, and GTF2H2, may also contribute to the severity of the disease. Within our study's scope, 58 SMA patients who applied in 2018-2021 and 40 healthy controls were analyzed. The study retrospectively included the SMN1 and SMN2 copy numbers previously determined by the MLPA method. Then, NAIP gene analyses with the multiplex PCR method and GTF2H2 gene analyses with the RFLP method were performed. There was a significant correlation (p = 0.00001) between SMN2 copy numbers and SMA subtypes. Also, the NAIP gene (p = 0.01) and the GTF2H2 gene (p = 0.0049) revealed a significant difference between healthy and SMA subjects, whereas the SMA subtypes indicated no significant differences. We detected a significant correlation between clinical subtypes and HFMSE scores in 32 pediatric SMA patients compared (p = 0.01). While pediatric patients with GTF2H2 deletions demonstrated higher motor functions, and those with NAIP deletions demonstrated lower motor functions. In this study, we examined the relationship between NAIP and GTF2H2, called SMN region modifier genes, and the clinical severity of the disease in Turkish SMA patients. Despite its small scale, this research will benefit future investigations into the pathogenesis of SMA disease.

Molecular characterization of exonic rearrangements and frame shifts in the dystrophin gene in Duchenne muscular dystrophy patients in a Saudi community

BACKGROUND

In individuals with Duchenne muscular dystrophy (DMD), exon skipping treatment to restore a wild-type phenotype or correct the frame shift of the mRNA transcript of the dystrophin (DMD) gene are mutation-specific. To explore the molecular characterization of DMD rearrangements and predict the reading frame, we simultaneously screened all 79 DMD gene exons of 45 unrelated male DMD patients using a multiplex ligation-dependent probe amplification (MLPA) assay for deletion/duplication patterns. Multiplex PCR was used to confirm single deletions detected by the MLPA.

RESULTS

There was an obvious diagnostic delay, with an extremely statistically significant difference between the age at initial symptoms and the age of clinical evaluation of DMD cases (t value, 10.3; 95% confidence interval 5.95-8.80, P < 0.0001); the mean difference between the two groups was 7.4 years. Overall, we identified 147 intragenic rearrangements: 46.3% deletions and 53.7% duplications. Most of the deletions (92.5%) were between exons 44 and 56, with exon 50 being the most frequently involved (19.1%). Eight new rearrangements, including a mixed deletion/duplication and double duplications, were linked to seven cases with DMD. Of all the cases, 17.8% had duplications with no hot spots. In addition, confirmation of the reading frame hypothesis helped account for new DMD rearrangements in this study. We found that 81% of our Saudi patients would potentially benefit from exon skipping, of which 42.9% had a mutation amenable to skipping of exon 51.

CONCLUSIONS

Our study could generate considerable data on mutational rearrangements that may promote future experimental therapies in Saudi Arabia.

Spinal Muscular Atrophy and Ependymoma

Spinal muscular atrophy (SMA) is an autosomal recessive disorder, characterized by a progressive degeneration of anterior horn cells of the spinal cord resulting in hypotonia, skeletal muscle atrophy and weakness. We report the case of a 33-year-old female with SMA type IV (SMA4) who presented with symptoms of spinal cord lesion that was initially missed. Further evaluation resulted in the diagnosis of ependymoma. To the best of our knowledge, this is the first time that the coexistence of SMA4 and ependymoma has been reported.

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.