Transcriptional regulator of the circadian clock components: CLOCK, ARNTL/BMAL1, ARNTL2/BMAL2, PER1/3, CRY1/2, NR1D1/2 and RORA/C. Positively regulates the transcriptional activity of CLOCK a core component of the circadian clock. Regulates transcription through chromatin remodeling by interacting with other proteins in chromatin as well as proteins in the basic transcriptional machinery. May be important for embryonic and postnatal development. May be involved in neuronal differentiation. In neurons, localized to neurites. Detected in all tissues examined with strong expression in the thymus and brain. Expressed in epithelial cells involved in organogenesis. No expression was seen in the corpus callosum of the brain. Haploinsufficiency cause obesity and craniofacial abnormalities. Homozygous mice die during gastrulation and organogenesis. The few surviving mice experienced postnatal growth retardation and most of them died before weaning.