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

Area of Science:

• Neuroscience
• Molecular Biology
• Genetics

Background:

• Neuronal Per-Arnt-Sim homology (PAS) Factor 4 (NPAS4) is a transcription factor crucial for regulating inhibitory synapse formation and maintaining neuronal excitatory/inhibitory balance.
• Dysregulation of NPAS4 is implicated in neuropsychiatric and neurodegenerative diseases, including autism, schizophrenia, and dementia.
• Understanding NPAS4 function and the impact of genetic variants is vital for comprehending cognitive function and disease mechanisms.

Purpose of the Study:

• To investigate the functional impact of human non-synonymous variants in NPAS4 and ARNT2 on NPAS4 transcriptional activity.
• To elucidate the molecular mechanisms by which identified variants disrupt NPAS4/ARNT2 heterodimer function.

Main Methods:

• Analysis of non-synonymous variants in NPAS4 and ARNT2 using a luciferase reporter gene assay to measure transcriptional activity.
• Assessment of NPAS4 target gene (BDNF) expression and NPAS4/ARNT2 dimerisation.
• Homology modelling to predict the structural impact of variants.

Main Results:

• Two NPAS4 variants (F147S, E257K) and two ARNT2 variants (R46W, R107H) significantly reduced NPAS4 heterodimer transcriptional activity.
• The NPAS4.F147S variant impaired BDNF gene activation due to reduced dimerisation with ARNT2, with F147 predicted to be at the dimer interface.
• The ARNT2 R46W variant's reduced transcriptional activation was linked to disrupted nuclear localisation.

Conclusions:

• Identified NPAS4 and ARNT2 variants disrupt NPAS4-mediated transcription through impaired dimerisation or nuclear localisation.
• These findings offer insights into NPAS4/ARNT2 dimerisation and transcriptional regulation mechanisms.
• The study highlights the potential role of NPAS4 and ARNT2 variants in cognitive variation and neurological disorders.