The organizer factors Chordin and Noggin are required for mouse forebrain development

In mice, there is evidence suggesting that the development of head and trun k structures is organized by distinctly separated cell populations(1,2). Th e head organizer is located in the anterior visceral endoderm (AVE) and the trunk organizer in the node and anterior primitive streak. In amphibians, Spemann's organizer, which is homologous to the node, partially overlaps wi th anterior endoderm cells expressing homologues of the AVE markers cerberu s, Hex and Hesx1 (refs 3-6). For mice, this raises the question of whether the AVE and node are independent of each other, as suggested by their anato mical separation, or functionally interdependent as is the case in amphibia ns(3-5). Chordin and Noggin are secreted bone morphogenetic protein (BMP) a ntagonists(7,8) expressed in the mouse node, but not in the AVE. Here we sh ow that mice double-homozygous mutants that are for chordin and noggin disp lay severe defects in the development of the prosencephalon, The results sh ow that BMP antagonists in the node and its derivatives are required for he ad development.