Deletion analysis of spinal muscular atrophy in southern Indian population.
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.


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.


CONCLUSIONS
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.
Swaminathan
Bhairavi
B
Molecular Genetics Laboratory, Department of Psychiatry, National Institute of Mental Health and Neurosciences, Bangalore, India.
Shylashree
S
S
Purushottam
Meera
M
Taly
A B
AB
Nalini
A
A
D000328:Adult; D017668:Age of Onset; D002648:Child; D004252:DNA Mutational Analysis; D005091:Exons / Q000235:genetics; D020022:Genetic Predisposition to Disease; D005838:Genotype; D006801:Humans; D007194:India; D009134:Muscular Atrophy, Spinal / Q000145:classification / Q000235:genetics*; D051616:Neuronal Apoptosis-Inhibitory Protein / Q000235:genetics*; D012150:Polymorphism, Restriction Fragment Length / Q000235:genetics; D017384:Sequence Deletion / Q000235:genetics*; D055533:Survival of Motor Neuron 1 Protein / Q000235:genetics*
C496800:NAIP protein, human; D051616:Neuronal Apoptosis-Inhibitory Protein; C526471:SMN1 protein, human; D055533:Survival of Motor Neuron 1 Protein