Congenital lethal motor neuron disease with a novel defect in ribosome biogenesis

Neurology. 2014 Apr 15;82(15):1322-30. doi: 10.1212/WNL.0000000000000305. Epub 2014 Mar 19.


Objective: We describe a novel congenital motor neuron disease with early demise due to respiratory insufficiency with clinical overlap with spinal muscular atrophy with respiratory distress (SMARD) type 1 but lacking a mutation in the IGHMBP2 gene.

Methods: Exome sequencing was used to identify a de novo mutation in the LAS1L gene in the proband. Pathogenicity of the mutation was validated using a zebrafish model by morpholino-mediated knockdown of las1l.

Results: We identified a de novo mutation in the X-linked LAS1L gene in the proband (p.S477N). The mutation is in a highly conserved region of the LAS1L gene predicted to be deleterious by bioinformatic analysis. Morpholino-based knockdown of las1l, the orthologous gene in zebrafish, results in early lethality and disruption of muscle and peripheral nerve architecture. Coinjection of wild-type but not mutant human RNA results in partial rescue of the phenotype.

Conclusion: We report a patient with a SMARD phenotype due to a mutation in LAS1L, a gene important in coordinating processing of the 45S pre-rRNA and maturation of the large 60S ribosomal subunit. Similarly, the IGHMB2 gene associated with SMARD type 1 has been suggested to have an important role in ribosomal biogenesis from its role in processing the 45S pre-rRNA. We propose that disruption of ribosomal maturation may be a common pathogenic mechanism linking SMARD phenotypes caused by both IGHMBP2 and LAS1L.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Genotype
  • Humans
  • Infant
  • Infant, Newborn
  • Muscular Atrophy, Spinal / congenital
  • Muscular Atrophy, Spinal / genetics*
  • Muscular Atrophy, Spinal / metabolism
  • Mutation
  • Nuclear Proteins / genetics*
  • Nuclear Proteins / metabolism
  • Ribosomes / metabolism*
  • Zebrafish


  • Las1L protein, human
  • Nuclear Proteins