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Molecular analysis and electromyoneurographic abnormalities in Croatian children with proximal spinal muscular
Insights
This study found that deletions in survival motor neuron and neuronal apoptosis inhibitor protein genes correlate with spinal muscular atrophy severity in children. Larger deletions indicate more severe disease and poorer nerve function.
Area of Science:
- Genetics
- Neurology
- Pediatrics
Background:
- Childhood onset proximal spinal muscular atrophy (SMA) exhibits significant clinical variability.
- SMA is a genetic disorder affecting motor neurons, leading to progressive muscle weakness.
Purpose of the Study:
- To investigate the correlation between genetic deletions and clinical severity in childhood onset SMA.
- To analyze the impact of specific gene deletions on nerve conduction and muscle potentials.
Main Methods:
- Included 14 Croatian children (11 days to 8 years) with SMA types I-III.
- Screened DNA for deletions in survival motor neuron (SMN) gene exons 7/8 and neuronal apoptosis inhibitor protein (NAIP) gene exon 5.
- Performed electromyoneurography to assess motor nerve conduction velocity and compound muscle action potential amplitude.
Main Results:
- Decreased motor nerve conduction velocity and compound muscle action potential amplitude observed in SMA types I and II.
- Children with SMA types I-II showed deletions in SMN exons 7/8 and NAIP exon 5, suggesting more genetic abnormalities than type III.
- Reduced nerve function correlated with disease severity, likely due to axonal degeneration.
Conclusions:
- Phenotypic severity in childhood onset SMA is directly correlated with the extent of SMN and NAIP exon deletions.
- Genetic deletions are key determinants of SMA severity and neurological deficits.
Abstract:
Childhood onset proximal spinal muscular atrophy presents with considerable clinical variability. This study included 14 Croatian children aged 11 days to 8 years with spinal muscular atrophy types I-III verified clinically and electromyoneurographically. DNA of affected children was screened for deletions of exons 7 and 8 of the survival motor neuron gene and for deletion of exon 5 of the neuronal apoptosis inhibitor protein gene. Motor nerve conduction velocity and compound muscle action potential amplitude were decreased in children with spinal muscular atrophy type I and II. Deletions of exons 7 and 8 of the survival motor neuron gene and of exon 5 of the neuronal apoptosis inhibitor protein gene in children with spinal muscular atrophy type I-II suggested existence of more genetic abnormalities as compared to type III. A decrease in compound muscle action potential amplitude and motor nerve conduction velocity in children with spinal muscular atrophy correlated with the disease severity, probably as a result of axonal degeneration. Phenotypic severity in children onset spinal muscular atrophy is directly correlated with the extent of survival motor neuron and neuronal apoptosis inhibitor protein exon deletions.