Fibronectin for branching

Branched organs are shaped when epithelia make their own paths, according to a study by Takayoshi Sakai, Melinda Larsen, and Kenneth Yamada (National Institutes of Health, Bethesda, MD). The pathmaker in this process is fibronectin (FN), which tells cells to let go of their neighbors and instead grab hold of the underlying matrix.

Organs such as the lung and kidney gain surface area by forming numerous branches, which are generated by cycles of budding and cleft formation in epithelial cells. Branching is known to involve growth factor–regulated interactions between the epithelium and mesenchyme, but the authors wanted to know how individual cells respond during branching. Using the developing mouse salivary gland as a model, the group now reports that epithelia change their architecture by secreting FN fibrils in newly forming clefts.

Although cleft-initiating...