SMN1 is produced chiefly by the SMN1 gene, located on the telomeric portion of chromosome 5q. SMN1 protein is one of a group of proteins called the SMN complex, which is important for the maintenance of specialized nerve cells called motor neurons. In cells, the SMN complex plays an important role in processing mRNA. The SMN complex helps to assemble the cellular machinery needed to process pre-mRNA. The SMN complex is also important for the development of specialized outgrowths from nerve cells called dendrites and axons. Deletion or mutation of the SMN1 gene results in a reduced level of full-length SMN protein and manifests as a range of neuromuscular phenotypes in humans as the disease spinal muscular atrophy (SMA).