Transcription factor that plays a role in the development of the hypothalamo-pituitary axis, postnatal brain growth, and visual and renal function. Specifically recognizes the xenobiotic response element (XRE). Efficient DNA binding requires dimerization with another bHLH protein (By similarity). Heterodimer with NPAS4 or SIM1 (PubMed:27782878). Heterodimer with the aryl hydrocarbon receptor (AHR) or the SIM1 protein (By similarity). Interacts with TACC3 (PubMed:11025203). Restricted to adult brain and kidney.