Mutations in the ER-shaping protein reticulon 2 cause the axon-degenerative disorder hereditary spastic paraplegia type 12

J Clin Invest. 2012 Feb;122(2):538-44. doi: 10.1172/JCI60560. Epub 2012 Jan 9.

Abstract

Hereditary spastic paraplegias (HSPs) are a group of genetically heterogeneous neurodegenerative conditions. They are characterized by progressive spastic paralysis of the legs as a result of selective, length-dependent degeneration of the axons of the corticospinal tract. Mutations in 3 genes encoding proteins that work together to shape the ER into sheets and tubules - receptor accessory protein 1 (REEP1), atlastin-1 (ATL1), and spastin (SPAST) - have been found to underlie many cases of HSP in Northern Europe and North America. Applying Sanger and exome sequencing, we have now identified 3 mutations in reticulon 2 (RTN2), which encodes a member of the reticulon family of prototypic ER-shaping proteins, in families with spastic paraplegia 12 (SPG12). These autosomal dominant mutations included a complete deletion of RTN2 and a frameshift mutation predicted to produce a highly truncated protein. Wild-type reticulon 2, but not the truncated protein potentially encoded by the frameshift allele, localized to the ER. RTN2 interacted with spastin, and this interaction required a hydrophobic region in spastin that is involved in ER localization and that is predicted to form a curvature-inducing/sensing hairpin loop domain. Our results directly implicate a reticulon protein in axonopathy, show that this protein participates in a network of interactions among HSP proteins involved in ER shaping, and further support the hypothesis that abnormal ER morphogenesis is a pathogenic mechanism in HSP.

Publication types

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

MeSH terms

  • Adenosine Triphosphatases / genetics
  • Adenosine Triphosphatases / metabolism
  • DNA Mutational Analysis
  • Endoplasmic Reticulum / metabolism
  • Endoplasmic Reticulum / ultrastructure*
  • HEK293 Cells
  • HeLa Cells
  • Humans
  • Membrane Proteins / genetics*
  • Membrane Proteins / metabolism
  • Muscle Proteins / genetics*
  • Muscle Proteins / metabolism
  • Mutation*
  • Nerve Tissue Proteins / genetics*
  • Nerve Tissue Proteins / metabolism
  • Spastic Paraplegia, Hereditary / genetics*
  • Spastic Paraplegia, Hereditary / pathology*
  • Spastic Paraplegia, Hereditary / physiopathology
  • Spastin

Substances

  • Membrane Proteins
  • Muscle Proteins
  • Nerve Tissue Proteins
  • RTN2 protein, human
  • Adenosine Triphosphatases
  • Spastin
  • SPAST protein, human