The brain-expressed X-linked (Bex) family of proteins is expressed in the central nervous system, with highest levels detected in cerebellum, temporal lobe and pituitary tissues. Bex1 plays an important role in neuronal differentiation in response to nerve growth factor (NGF), as well as in cell cycle progression. Bex1 is a highly ubiquitinated protein and acts as a link between the cell cycle and neurotrophic factor signaling. Bex2 interacts with LMO2, thereby regulating the transcriptional activity of a DNA-binding complex. Bex1 and Bex 2 are widely expressed outside of the central nervous system with high expression in the liver. Bex1 and Bex2 shuttle between the cytoplasm and the nucleus. Though the role of Bex1 is largely unknown, it may function by coordinating internal cellular states with the ability of cells to respond to external signals.