Proximal spinal muscular atrophy types I-IV: Specific features of molecular genetic diagnosis

Abstract

Proximal spinal muscular atrophy (SMA) types I-IV is the most common autosomal recessive neuromuscular disease caused by mutations in the SMN1 gene encoding the survival motor neuron protein. It is characterized by progressive muscle weakness due to injury of the motor neurons of the anterior horns of the spinal cord. The classification of the disease is based on the time of its onset, severity, and survival. The detection of the major mutation of exon 7 and/or 8 deletion in the SMN1 gene is a qualitative reliable and sensitive diagnostic test. The SMN1 gene has the almost complete homolog SMN2 gene, which hampers the analysis of heterozygous carriage of the disease. So the determination of the carriage status is based on the quantitative analysis of the number of SMN1 gene copies. The paper covers problems and new possibilities in themolecular genetic diagnosis of proximal SMA.

Keywords

• spinal muscular atrophy
• smn genes
• genetic analysis
• smn gene copy numbers
• spinal muscular atrophy locus
• genotype 2+0
• gene point mutations
• diagnostic algorithm
• pheno/genotypic correlation
• latent carriage