Survival of motor neuron 2 (SMN2) is a gene that encodes the SMN protein (full and truncated) in humans.[5][6]
Gene
The SMN2 gene is part of a 500 kb inverted duplication on chromosome 5q13. This duplicated region contains at least four genes and repetitive elements which make it prone to rearrangements and deletions. The repetitiveness and complexity of the sequence have also caused difficulty in determining the organization of this genomic region. The telomeric (SMN1) and centromeric (SMN2) copies of this gene are nearly identical and encode the same protein. The critical sequence difference between the two genes is a single nucleotide in exon 7, which is thought to be an exon splice enhancer. The nucleotide substitution in SMN2 results in around 80-90% of its transcripts to be a truncated, unstable protein of no biological function (Δ7SMN) and only 10-20% of its transcripts being full-length protein (fl-SMN).[citation needed]
Note that the nine exons of both the telomeric and centromeric copies are designated historically as exon 1, 2a, 2b, and 3–8. It is thought that gene conversion events may involve the two genes, leading to varying copy numbers of each gene.[6]
Clinical significance
While mutations in the telomeric copy are associated with spinal muscular atrophy, mutations in this gene, the centromeric copy, do not lead to disease. This gene may be a modifier of disease caused by mutation in the telomeric copy.[citation needed]
Corcia P, Camu W, Praline J, Gordon PH, Vourch P, Andres C (2009). "The importance of the SMN genes in the genetics of sporadic ALS". Amyotrophic Lateral Sclerosis. 10 (5–6): 436–40. doi:10.3109/17482960902759162. PMID19922137. S2CID2326464.
Arkblad E, Tulinius M, Kroksmark AK, Henricsson M, Darin N (May 2009). "A population-based study of genotypic and phenotypic variability in children with spinal muscular atrophy". Acta Paediatrica. 98 (5): 865–72. doi:10.1111/j.1651-2227.2008.01201.x. PMID19154529. S2CID3134264.
Paushkin S, Gubitz AK, Massenet S, Dreyfuss G (June 2002). "The SMN complex, an assemblyosome of ribonucleoproteins". Current Opinion in Cell Biology. 14 (3): 305–12. doi:10.1016/S0955-0674(02)00332-0. PMID12067652.
Hasanzad M, Golkar Z, Kariminejad R, Hadavi V, Almadani N, Afroozan F, Salahshurifar I, Shafeghati Y, Kahrizi K, Najmabadi H (February 2009). "Deletions in the survival motor neuron gene in Iranian patients with spinal muscular atrophy". Annals of the Academy of Medicine, Singapore. 38 (2): 139–41. doi:10.47102/annals-acadmedsg.V38N2p139. PMID19271042.
Song F, Qu YJ, Zou LP, Wang LW, Long MJ, Wang X, Yang YL, Chen Q, Wang H, Jin YW (December 2008). "[Molecular analysis of survival motor neuron gene in 338 suspicious children patients with spinal muscular atrophy]". Zhonghua Er Ke Za Zhi = Chinese Journal of Pediatrics. 46 (12): 919–23. PMID19134255.
Irimura S, Kitamura K, Kato N, Saiki K, Takeuchi A, Matsuo M, Nishio H, Lee MJ (2009). "HnRNP C1/C2 may regulate exon 7 splicing in the spinal muscular atrophy gene SMN1". The Kobe Journal of Medical Sciences. 54 (5): E227-36. PMID19628962.
Yong J, Wan L, Dreyfuss G (May 2004). "Why do cells need an assembly machine for RNA-protein complexes?". Trends in Cell Biology. 14 (5): 226–32. doi:10.1016/j.tcb.2004.03.010. PMID15130578.
Cogulu O, Durmaz B, Pehlivan S, Alpman A, Ozkinay F (June 2009). "Evaluation of the SMN and NAIP genes in a family: homozygous deletion of the SMN2 gene in the fetus and outcome of the pregnancy". Genetic Testing and Molecular Biomarkers. 13 (3): 287–8. doi:10.1089/gtmb.2008.0139. PMID19397406.
