SMN1

SMN1 (Survival Motor Neuron 1) is a gene that encodes the survival motor neuron protein, which is critical for the maintenance of motor neurons. Mutations in this gene are associated with spinal muscular atrophy (SMA), a genetic disorder characterized by progressive muscle weakness and atrophy.

Function[edit | edit source]

The SMN1 gene is located on chromosome 5q13.2 and is approximately 20 kilobases in length. It contains nine exons and encodes the 38-kDa SMN protein. The SMN protein is part of a complex that is necessary for the biogenesis of U snRNPs, which are essential components of the spliceosome, the molecular machinery that processes pre-mRNAs to produce mature mRNAs.

Clinical significance[edit | edit source]

Mutations in the SMN1 gene are the primary cause of spinal muscular atrophy (SMA), a leading genetic cause of infant mortality. SMA is characterized by the degeneration of motor neurons in the anterior horn cells of the spinal cord, leading to muscle weakness and atrophy. The severity of SMA is inversely correlated with the number of copies of a nearly identical gene, SMN2, which can partially compensate for the loss of SMN1 function.

Diagnosis[edit | edit source]

Diagnosis of SMA is confirmed by genetic testing, which involves the detection of homozygous deletions or mutations in the SMN1 gene. Prenatal testing is also available for families with a known history of SMA.

Treatment[edit | edit source]

There is currently no cure for SMA. Treatment is supportive and aims to manage symptoms and improve quality of life. In recent years, therapies that target the underlying genetic defect, such as Nusinersen and Onasemnogene abeparvovec, have shown promise in clinical trials.

File:SMN1 gene location on chromosome.png

Location of the SMN1 gene on chromosome 5