Human variants in the neuronal basic helix-loop-helix/Per-Arnt-Sim (bHLH/PAS) transcription factor complex NPAS4/ARNT2 disrupt function

PLoS One. 2014 Jan 17;9(1):e85768. doi: 10.1371/journal.pone.0085768. eCollection 2014.

Abstract

Neuronal Per-Arnt-Sim homology (PAS) Factor 4 (NPAS4) is a neuronal activity-dependent transcription factor which heterodimerises with ARNT2 to regulate genes involved in inhibitory synapse formation. NPAS4 functions to maintain excitatory/inhibitory balance in neurons, while mouse models have shown it to play roles in memory formation, social interaction and neurodegeneration. NPAS4 has therefore been implicated in a number of neuropsychiatric or neurodegenerative diseases which are underpinned by defects in excitatory/inhibitory balance. Here we have explored a broad set of non-synonymous human variants in NPAS4 and ARNT2 for disruption of NPAS4 function. We found two variants in NPAS4 (F147S and E257K) and two variants in ARNT2 (R46W and R107H) which significantly reduced transcriptional activity of the heterodimer on a luciferase reporter gene. Furthermore, we found that NPAS4.F147S was unable to activate expression of the NPAS4 target gene BDNF due to reduced dimerisation with ARNT2. Homology modelling predicts F147 in NPAS4 to lie at the dimer interface, where it appears to directly contribute to protein/protein interaction. We also found that reduced transcriptional activation by ARNT2 R46W was due to disruption of nuclear localisation. These results provide insight into the mechanisms of NPAS4/ARNT dimerisation and transcriptional activation and have potential implications for cognitive phenotypic variation and diseases such as autism, schizophrenia and dementia.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Aryl Hydrocarbon Receptor Nuclear Translocator / chemistry
  • Aryl Hydrocarbon Receptor Nuclear Translocator / genetics*
  • Aryl Hydrocarbon Receptor Nuclear Translocator / metabolism*
  • Basic Helix-Loop-Helix Transcription Factors / chemistry
  • Basic Helix-Loop-Helix Transcription Factors / genetics*
  • Basic Helix-Loop-Helix Transcription Factors / metabolism*
  • Brain-Derived Neurotrophic Factor / metabolism
  • Cell Nucleus / metabolism
  • Genes, Reporter
  • HEK293 Cells
  • Humans
  • Mice
  • Models, Molecular
  • Molecular Sequence Data
  • Mutant Proteins / metabolism
  • Mutation / genetics*
  • Phenylalanine / metabolism
  • Protein Multimerization
  • Protein Transport
  • Repressor Proteins / metabolism
  • Structural Homology, Protein

Substances

  • ARNT2 protein, human
  • Basic Helix-Loop-Helix Transcription Factors
  • Brain-Derived Neurotrophic Factor
  • Mutant Proteins
  • NPAS4 protein, human
  • Repressor Proteins
  • SIM1 protein, human
  • SIM2 protein, human
  • Aryl Hydrocarbon Receptor Nuclear Translocator
  • Phenylalanine

Grant support

This research was supported by the Australian Research Council. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.