May play a broad role in neurogenesis. May control regulatory pathways relevant to schizophrenia and to psychotic illness (By similarity). Efficient DNA binding requires dimerization with another bHLH protein. Interacts with ARNT; forms a heterodimer that binds core DNA sequence 5'-[AG]CGTG-3' within the hypoxia response element (HRE) of target gene promoters (By similarity). Ubiquitously expressed in the adult brain. A chromosomal aberration involving NPAS3 is found in a family with schizophrenia. Translocation t(9;14)(q34;q13).