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Available structures
PDBOrtholog search: PDBe RCSB
AliasesSMN2, BCD541, C-BCD541, GEMIN1, SMNC, TDRD16B, survival of motor neuron 2, centromeric, survival motor neuron 2, centromeric
External IDsMGI: 109257 HomoloGene: 292 GeneCards: SMN2
Gene location (Human)
Chromosome 5 (human)
Chr.Chromosome 5 (human)[1]
Chromosome 5 (human)
Genomic location for SMN2
Genomic location for SMN2
Band5q13.2Start70,049,612 bp[1]
End70,078,522 bp[1]
RefSeq (mRNA)



RefSeq (protein)


Location (UCSC)Chr 5: 70.05 – 70.08 MbChr 13: 100.12 – 100.14 Mb
PubMed search[3][4]
View/Edit HumanView/Edit Mouse

Survival of motor neuron 2 (SMN2) is a gene that encodes the SMN protein (full and truncated) in humans.[5][6]


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).

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[edit]

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.


  1. ^ a b c ENSG00000205571, ENSG00000273772 GRCh38: Ensembl release 89: ENSG00000277773, ENSG00000205571, ENSG00000273772 - Ensembl, May 2017
  2. ^ a b c GRCm38: Ensembl release 89: ENSMUSG00000021645 - Ensembl, May 2017
  3. ^ "Human PubMed Reference:".
  4. ^ "Mouse PubMed Reference:".
  5. ^ Lefebvre S, Bürglen L, Reboullet S, Clermont O, Burlet P, Viollet L, Benichou B, Cruaud C, Millasseau P, Zeviani M (January 1995). "Identification and characterization of a spinal muscular atrophy-determining gene". Cell. 80 (1): 155–65. doi:10.1016/0092-8674(95)90460-3. PMID 7813012.
  6. ^ a b "Entrez Gene: SMN2 survival of motor neuron 2, centromeric".

Further reading[edit]

This article incorporates text from the United States National Library of Medicine, which is in the public domain.