Spinal muscular atrophy: why do low levels of survival motor neuron protein make motor neurons sick?

Nat Rev Neurosci. 2009 Aug;10(8):597-609. doi: 10.1038/nrn2670. Epub 2009 Jul 8.


Many neurogenetic disorders are caused by the mutation of ubiquitously expressed genes. One such disorder, spinal muscular atrophy, is caused by loss or mutation of the survival motor neuron1 gene (SMN1), leading to reduced SMN protein levels and a selective dysfunction of motor neurons. SMN, together with partner proteins, functions in the assembly of small nuclear ribonucleoproteins (snRNPs), which are important for pre-mRNA splicing. It has also been suggested that SMN might function in the assembly of other ribonucleoprotein complexes. Two hypotheses have been proposed to explain the molecular dysfunction that gives rise to spinal muscular atrophy (SMA) and its specificity to a particular group of neurons. The first hypothesis states that the loss of SMN's well-known function in snRNP assembly causes an alteration in the splicing of a specific gene (or genes). The second hypothesis proposes that SMN is crucial for the transport of mRNA in neurons and that disruption of this function results in SMA.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Humans
  • Models, Biological
  • Motor Neurons / metabolism*
  • Muscular Atrophy, Spinal* / genetics
  • Muscular Atrophy, Spinal* / metabolism
  • Muscular Atrophy, Spinal* / pathology
  • Muscular Atrophy, Spinal* / physiopathology
  • Ribonucleoproteins, Small Nuclear / metabolism
  • Survival of Motor Neuron 1 Protein / genetics
  • Survival of Motor Neuron 1 Protein / metabolism*


  • Ribonucleoproteins, Small Nuclear
  • SMN1 protein, human
  • Survival of Motor Neuron 1 Protein