Medknow Publications on behalf of the Neurological Society of India
Abstract
Background: Proximal spinal muscular atrophy (SMA) is a genetically
heterogeneous disease with paresis and muscle atrophy due to loss of
anterior horn cell function. The survival of motor neuron gene (SMN)
and neuronal apoptosis inhibitory protein (NAIP) play a primary role.
Both the gene homologues exist as inverted duplications on Chromosome
5q. The telomeric/functional (SMN1) and the centromeric (SMN2) copies
differ from each other in eight nucleotides. The C→T transition
(at Codon 280) within Exon 7 of SMN2 causes disruption of an exonic
splicing enhancer (ESE) and/or creates an exonic splicing silencer
(ESS) leading to abnormal splicing and a truncated protein. Objective:
To determine the molecular genetics of SMN1 and NAIP genes in SMA from
southern India. Materials and Methods: In the present study, 37
patients from the neuromuscular disorders clinic of National Institute
of Mental Health and Neurosciences were assayed for the deletions in
the SMN1 and NAIP genes using PCR-RFLP methods. Results: Among the SMA
Type I patients, 43% showed deletions of SMN1 and NAIP. In patients
Type II SMA, 57% showed deletions of the SMN1 exons. Conclusion: Thus,
deletions were found to occur in 47.8% of the Type I and II patients.
Lower sensitivity of gene deletion study in clinically suspected SMA
needs further study as clinical diagnosis of SMA is not gold standard.
However, the results do correlate with other studies conducted in
India