• Journal of Genetic Medicine
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• v.1 no.1
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• pp.33-37
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• 1997

Spinal muscular atrophy (SMA) is the second most common fatal disease of childhood with autosomal dominant mode of inheritance, and in its less severe form the third most common neuromuscular disease of childhood after Duchenne muscular dystrophy. The genetic defect was found to be on the long arm of chromosome 5 (5q11.2-q13.3) where many genes and microsatellite markers were missing. One of the most important genes is the Survival Motor Neuron (SMN) gene which is homozygously missing in 90% of SMA patients. Another important gene, the Neuronal Apoptosis Inhibitory Protein (NAIP) gene was found to be defective in 67% of SMA type I patients. Studies so far suggest SMA occurs when the genes on the long arm of chromosome 5 are mutated or deleted. Recently our hospital encountered 2 SMA patients of type I and II respectively. These patients both had homozygously defective SMN genes but intact NAIP genes. We are reporting these cases with bibliographic review and discussion. Korean SMA patients presumably have defects in SMN genes similar to those found in European patients, although the significance of NAIP genes remains to be established. SMN gene defects can be easily diagnosed using PCR and restriction enzymes, and this method could be applied towards convenient prenatal diagnosis and towards screening for family members at risk.

• Journal of Genetic Medicine
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• v.2 no.2
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• pp.53-57
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• 1998

Spinal muscular atrophy (SMA) type I is a common severe autosomal recessive inherited neuromuscular disorder that has been mapped to chromosome 5q11.2-13.3. The survival motor neuron (SMN) gene, a candidate gene, is known to be deleted in 96% of patients with SMA type I. Presently, PCR and single strand conformation polymorphism (PCR-SSCP) analyses have been made possible for application to both archival slides and paraffin-embedded tissues. Archival materials represent valuable DNA resources for genetic diagnosis. We applied these methods for the identification of SMN gene of SMA type I in archival specimens for the prenatal diagnosis. In this study, we performed the prenatal diagnosis with chorionic villus sampling (CVS) cells on two women who had experienced neonatal death of SMA type I. DNA extraction was done from archival slide and tissue materials and PEP-PCR was performed using CVS cells. In order to identify common deletion region of SMN and neuronal apoptosis-inhibitory protein (NAIP) genes, cold PCR-SSCP and PCR-restriction site assay were carried out. Case 1 had deletions of the exons 7 and 8, and case 2 had exon 7 only on the telomeric SMN gene. Both cases were found to be normal on NAIP gene. These results were the same for both CVS and archival biopsied specimens. In both cases, the fetuses were, therefore, predicted to be at very high risk of being affected and the pregnancy were terminated. These data clearly demonstrate that archival slide and paraffin-embedded tissues can be a valuable source of DNA when the prenatal genetic diagnosis is needed in case any source for genetic analysis is not readily available due to previous death of the fetus or neonate.