Homeosis and polyposis: a tale from the mouse

Homeobox genes play essential roles in specifying the fates of different cell types during embryogenesis. In Drosophila, the homeotic gene caudal is important for the generation of posterior structures. In the mouse, the caudal homologue Cdx2 has been implicated in directing early processes in intestinal morphogenesis and in the maintenance of the differentiated phenotype. A recent study showed that Cdx2 null mutation was embryonically lethal, whereas Cdx2+/- mice developed multiple intestinal polyps in the proximal colon in addition to developmental defects. There are striking phenotypic similarities and differences between Cdx2+/- and other mice predisposed to intestinal neoplasia. The possible role of Cdx2 in human colorectal tumorigenesis is discussed.