Expression of Foxb1 reveals two strategies for the formation of nuclei in the developing ventral diencephalon

Fork head b1 (Foxb1; also called Fkh5, HFH-e5. 1, Mf3) is a winged helix tr anscription factor gene whose widespread early expression in the developing neural tube is soon restricted to the ventral and caudal diencephalon. Dur ing diencephalic neurogenesis, Foxb1 is expressed in one patch of neuroepit helium comprising a large mammillary portion and a smaller tuberal portion. The labeled cells coming from this patch contribute to nuclear formation b y means of two different strategies: (1) caudally, the young neurons aggreg ate and settle immediately, giving rise to the nuclei of the mammillary bod y; (2) rostrally, the young neurons separate from the neuroepithelium formi ng a trail of cells which spans the mantle layer mediolaterally and which w ill give rise to two separate cell groups (the dorsal premammillary and par t of the lateral hypothalamic area). Our results show the elaborate, region alized histogenetic mechanisms necessary for the differentiation of the cau dal diencephalon; moreover, they suggest that specifically labeled populati ons, arising from specifically labeled neuroepithelial patches and giving p lace to specific brain nuclei could be a common mechanism to build complex, nonlaminar regions of the forebrain, Copyright (C) 2000 S. Karger AG. Base l.