Spinal Muscular Atrophy (SMA)

Spinal muscular atrophy (SMA) is an autosomal recessive disease caused by degeneration of spinal cord anterior horn motor neurons and brainstem motor nerve nuclei resulting in muscle weakness and atrophy, with progressive loss of motor functions including breathing and swallowing, and it is a serious genetic disease leading to the deaths of infants and children under the age of two. The population carrier rate is 1/72-1/47, and the incidence rate is 1/10,000-1/6,000. The disease is included in the First Catalog of Rare Diseases, which is jointly formulated by five departments, including the National Health Commission.
SMA is caused by a loss of function in the causative gene SMN1, which is located on chromosome 5q13, is approximately 28 Kb in length, and contains a total of eight exons. While normal individuals contain two normally functioning copies of SMN1 and one copy on each chromosome (1+1), approximately 95% of SMA patients are caused by a pure deletion mutation of Exon7 in the SMN1 gene (0+0), and the remaining 5% are accompanied by heterozygous point mutations in the SMN1 gene (0+1d). In addition, increased copy number of SMN2, a homozygous modifier gene of SMN1, can alleviate the symptoms of SMA, which is important for the typing diagnosis of SMA.
While about 91-94% of carriers have only one normal functioning copy of SMN1 (1+0), 2-5% contain two copies of SMN1 but one of them contains the causative point mutation (1+1d), and the other 4% are silent carriers, i.e., they have two copies of SMN1 but they are both located in the same chromosome or there is a curative point mutation (2+0/2+1d).
With the advantages of long read length, high precision, no GC preference, and ultra-low cost, AXBIO's four-generation sequencing platform can realize high-efficiency and high-precision sequencing of long fragments of SMN1 and SMN2 genes, and can detect SMN1 and SMN2 gene copy numbers, pathogenic SNVs and Indels, covering 0+0, 0+1d, 1+0, and 1+1d types.