SMN1 (Survival of motor neuron 1, component of gems 1, GEMIN1) is a gene that is part of a 500 kb inverted duplication on chromosome 5q13. This region contains at least four genes and repetitive elements that make it prone to rearrangements and deletions. The telomeric (SMN1) and centromeric (SMN2) copies of SMN are nearly identical and encode the same protein. However, mutations in the telomeric copy of this gene are associated with spinal muscular atrophy, while those in the centromeric copy do not lead to disease. The protein encoded by SMN1 or SMN2 localizes to both the cytoplasm and the nucleus. Within the nucleus, the protein localizes to subnuclear bodies called gems which are found near coiled bodies containing high concentrations of small ribonucleoproteins (snRNPs). This protein forms heteromeric complexes with proteins such as SIP1 and GEMIN4, and also interacts with several proteins known to be involved in the biogenesis of snRNPs, such as hnRNP U protein and the small nucleolar RNA binding protein. In immunohistochemistry, SMN1 is positive in all tissues throughout the body. References: The UniProt Consortium. Nucleic Acids Res. 47: D506-515 (2019); Nucleic Acids Res. 2016 Jan 4;44(D1):D733-45, PMID:26553804; Cell. 80 (1): 155–65, PMID: 7813012;