SMN has an important function in mRNA metabolism. The impaired assembly and function of the spliceosome formed by SMN and associated protein could cause motor neuron degeneration [126],[127] Homozygous deletion mutations in SMN genes are not found in ALS but an abnormal copy numbers in SMN1 could increase the risk for ALS [128]. The gene discussed is SMN1; the disease is amyotrophic lateral sclerosis.