In the mouse intestine, loss of Cdx2 leads to the formation of a squamous epithelium that resembles the esophagus (Beck et al., 1999), whereas, in Barrett's esophagus, Cdx2 is ectopically expressed in metaplastic cells (Eda et al., 2003). The gene discussed is CDX2; the disease is esophageal adenocarcinoma.