The Forkhead-box (FOX) genes comprise a superfamily of at least 43 members that encode proteins which are involved in transcriptional regulation and may be associated with the pathogenesis of various cancers. FOXB1 (forkhead box B1), also known as FKH5 or HFKH-5, and FOXB2 (forkhead box B2) are members of the FOX family and each contain one forkhead DNA-binding domain. Both FOXB1 and FOXB2 localize to the nucleus where they are thought to function as transcription factors that can bind to DNA via their forkhead domains. In mice, defects in the gene encoding FOXB1 are associated with retarded development of the central nervous system (CNS), suggesting that FOXB1 may play a role in CNS organization and functio