Detection of homozygous and heterozygous SMN deletions of spinal muscular atrophy in a single assay with multiplex ligation-dependent probe amplification.
OBJECTIVE
Spinal muscular atrophy(SMA), an autosomal recessive neuromuscular degeneration of the anterior horn cells of the spinal cord and brain stem, results in one of the most common diseases with muscle fatigue and atrophy. Most SMA cases including all the types are due to the homozygous deletion of at least exon 7 within the survival motor neuron 1 (SMN-1) gene. Although a "golden standard" assay (PCR with mismatch primer followed by enzyme digestion) is very reliable for the identification of homozygous SMN-1 deletion, the carrier detection of heterozygous SMN-1 deletion remains a challenge.


METHODS
Some PCR-based gene dosage assays or multiplex PCR allow for the determination of the copy number of SMN-1 gene to identify heterozygous deletion, but these procedures are often time consuming and available on a limited clinical basis. Recently developed MLPA (multiplex ligation-dependent probe amplification) is an efficient procedure that can accurately analyze relative quantification to establish the copy number of the SMN gene. We performed a validation for simultaneous detection of homozygous SMN-1 deletions of SMA patients and heterozygous SMN-1 deletions of SMA carriers in a simple assay using a MLPA-SMA assay specific reagent.


RESULTS
Six out of 20 patients with SMA were found to have homozygous SMN-1 deletion, confirmed by the PCR/digestion assay. All 4 parents of the children with SMA had heterozygous SMN-1 deletion, confirmed by an independent relative quantitative analysis.


CONCLUSIONS
MLPA provides a simple, rapid and accurate method of simultaneously detecting homozygous deletions and heterozygous deletions in a single assay for both SMN-1 and SMN-2 genes.
Tomaszewicz
Keith
K
Department of Laboratory Medicine, Children's Hospital and Harvard Medical School, Boston, MA 02115, USA.
Kang
Peter
P
Wu
Bai-lin
BL
D017362:Cyclic AMP Response Element-Binding Protein / Q000235:genetics*; D005091:Exons / Q000235:genetics; D017353:Gene Deletion; D006580:Genetic Carrier Screening; D005820:Genetic Testing; D006801:Humans; D009134:Muscular Atrophy, Spinal / Q000175:diagnosis / Q000235:genetics*; D009419:Nerve Tissue Proteins / Q000235:genetics*; D016133:Polymerase Chain Reaction / Q000379:methods; D016601:RNA-Binding Proteins / Q000235:genetics*; D055532:SMN Complex Proteins
D017362:Cyclic AMP Response Element-Binding Protein; D009419:Nerve Tissue Proteins; D016601:RNA-Binding Proteins; D055532:SMN Complex Proteins