Transcription factor involved in the production of cranial mesenchymal tissues. Favors nuclear targeting of ARID3A. Heterodimer with ARID3A. Interacts with unphosphorylated RB1 (By similarity). Expressed at high levels in testis. Also expressed in prostate, thyroid and thymus. First detected at 7 dpc. Strongly expressed in cranial mesenchyme and caudal mesoderm. Expression in cranial mesenchyme decreases starting from 10.5 dpc. Embryos die before 11.5 dpc and display various abnormalities, including wavy neural tube, small branchial arches and defects of cardiovascular system.