Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA 15260, USA. lad43@pitt.edu
A recent paper by Ninomiya and Winklbauer explores the role of the epithelium in restricting the natural capacity of mesenchymal cells to form amorphous aggregates. They propose the epithelium controls mesoderm adhesion, thereby ensuring that embryos and, by extension, adults are not multilayered balls of cells, but are instead elongate with a linearly segmented architecture.