Centre for Biomedical Genetics, Hubrecht Laboratorium, Koninklijke Nederlandse Akademie van Wetenschappen, Utrecht, The Netherlands.
The intestinal epithelium is a relatively simple developmental system and a prime example of tissue renewal from a source of multipotent stem cells. Throughout adulthood, intestinal epithelial proliferation, cell-fate specification and differentiation are coupled to migration in discrete units known as crypts of Lieberkühn. Physically guided by Eph receptors and their ligands, the ephrins, stem cell progeny transit through the proliferation/differentiation switch, and Notch diversifies their subsequent fates. Wnt signalling appears to control most of these events.