title: Spinal Muscular Atrophy: Overview of Molecular Diagnostic Approaches.
abstract: Spinal muscular atrophy (SMA) is an autosomal recessive neurodegenerative disease and the most common genetic cause of infant mortality, affecting ∼1 in 10,000 live births. The disease is characterized by progressive symmetrical muscle weakness resulting from the degeneration and loss of anterior horn cells in the spinal cord and brain stem nuclei. The disease is classified on the basis of age of onset and clinical course. SMA is caused by mutations in the telomeric copy of the survival motor neuron 1 (SMN1) gene, but all patients retain a centromeric copy of the gene, SMN2. The homozygous absence of the SMN1 exon 7 has been observed in the majority of patients and is being utilized as a reliable and sensitive SMA diagnostic test. In the majority of cases, the disease severity correlates inversely with an increased SMN2 gene copy number. Carrier detection, in the deletion cases, relies on the accurate determination of the SMN1 gene copies. Since SMA is one of the most common lethal genetic disorders, with a carrier frequency of 1 in 40 to 1 in 60, direct carrier dosage testing has been beneficial to many families. This unit attempts to highlight the molecular genetics of SMA with a focus on the advantages and limitations of the current molecular technologies.
authors.affiliation: Department of Pathology, The Ohio State University, Columbus, Ohio.
authors.forename: Thomas W
authors.initials: TW
authors.lastname: Prior
authors.affiliation: Integrated Genetics, Laboratory Corporation of America Holdings, Westborough, Massachusetts.
authors.forename: Narasimhan
authors.initials: N
authors.lastname: Nagan
mesh_terms: D056915:DNA Copy Number Variations; D004252:DNA Mutational Analysis / Q000379:methods; D056726:Genetic Association Studies / Q000379:methods; D020022:Genetic Predisposition to Disease / Q000235:genetics*; D006801:Humans; D025202:Molecular Diagnostic Techniques / Q000379:methods; D009134:Muscular Atrophy, Spinal / Q000175:diagnosis / Q000235:genetics*; D009154:Mutation; D016133:Polymerase Chain Reaction; D012150:Polymorphism, Restriction Fragment Length; D055533:Survival of Motor Neuron 1 Protein / Q000235:genetics*; D055540:Survival of Motor Neuron 2 Protein / Q000235:genetics
chemical_list: C526471:SMN1 protein, human; C526477:SMN2 protein, human; D055533:Survival of Motor Neuron 1 Protein; D055540:Survival of Motor Neuron 2 Protein
keywords: SMN1; SMN2; carrier testing; genetic testing; spinal muscular atrophy; survival motor neuron