CDX are homeodomain transcription factors related to the Drosophila caudal gene. The vertebrate CDX have been implicated in the development of the posterior embryo. Several signaling molecules, notably retinoic acid (RA) and members of the Wnt (wingless) and fibroblast growth factor (FGF) families, are also implicated in patterning of the posterior vertebrate embryo. CDX family is the target of Wnt, RA and FGF signaling, suggesting that CDX factors act to convey the activity of these signaling molecules to Hox genes.