Opposing forces combine

The first step in epithelial stem cell differentiation is the alteration of the adhesive properties of an individual cell. This is achieved by systematically changing the complement of surface adhesion molecules used to attach to its neighbors, but little has been understood about the control of the expression of these molecules over time. In the March 20 Nature, Colin Jamora and colleagues at the Rockefeller University, New York, US, provide some answers to this question (Nature, 422: 317-322, March 20, 2003).

Epithelial buds are small bulges in undifferentiated embryonic epithelial layers that develop into a variety of complex structures, including teeth, limbs, and hair follicles. The formation of the epithelial bud is caused by a decrease in E-cadherin and an increase in P-cadherin levels. Cadherins are calcium-dependent proteins that mediate cell-cell adhesion and are clustered in structures called adherens junctions, which connect and orient cells...