UBA5 Mutations Cause a New Form of Autosomal Recessive Cerebellar Ataxia

PLoS One. 2016 Feb 12;11(2):e0149039. doi: 10.1371/journal.pone.0149039. eCollection 2016.

Abstract

Autosomal recessive cerebellar ataxia (ARCA) comprises a large and heterogeneous group of neurodegenerative disorders. For many affected patients, the genetic cause remains undetermined. Through whole-exome sequencing, we identified compound heterozygous mutations in ubiquitin-like modifier activating enzyme 5 gene (UBA5) in two Chinese siblings presenting with ARCA. Moreover, copy number variations in UBA5 or ubiquitin-fold modifier 1 gene (UFM1) were documented with the phenotypes of global developmental delays and gait disturbances in the ClinVar database. UBA5 encodes UBA5, the ubiquitin-activating enzyme of UFM1. However, a crucial role for UBA5 in human neurological disease remains to be reported. Our molecular study of UBA5-R246X revealed a dramatically decreased half-life and loss of UFM1 activation due to the absence of the catalytic cysteine Cys250. UBA5-K310E maintained its interaction with UFM1, although with less stability, which may affect the ability of this UBA5 mutant to activate UFM1. Drosophila modeling revealed that UBA5 knockdown induced locomotive defects and a shortened lifespan accompanied by aberrant neuromuscular junctions (NMJs). Strikingly, we found that UFM1 and E2 cofactor knockdown induced markedly similar phenotypes. Wild-type UBA5, but not mutant UBA5, significantly restored neural lesions caused by the absence of UBA5. The finding of a UBA5 mutation in cerebellar ataxia suggests that impairment of the UFM1 pathway may contribute to the neurological phenotypes of ARCA.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Amino Acid Sequence
  • Animals
  • Cerebellar Ataxia / enzymology
  • Cerebellar Ataxia / genetics*
  • DNA Mutational Analysis
  • Drosophila melanogaster
  • Enzyme Stability
  • Female
  • Gene Expression
  • Genes, Recessive
  • Genetic Association Studies
  • HEK293 Cells
  • Half-Life
  • Humans
  • Male
  • Molecular Sequence Data
  • Mutation, Missense
  • Protein Transport
  • Proteins / metabolism
  • Ubiquitin-Activating Enzymes / genetics*
  • Ubiquitin-Activating Enzymes / metabolism

Substances

  • Proteins
  • UBA5 protein, human
  • UFM1 protein, human
  • Ubiquitin-Activating Enzymes

Grant support

The State Key Program of the National Natural Science Foundation of China (grant number: 81130021), National Natural Science Foundation of China (grant number: 81571253, 81172513, 81071028).