Stick hard, signal fast

Cell type specification by Notch (N) in one cell and Delta (Dl) in another must happen quickly, before morphogenesis further changes the cellular landscape. On page 1217 Ahimou et al. find that the adhesion force between N and Dl peaks and drops in just 10 min, symptomatic of a peak and drop in intercellular signaling. Pulling on Dl can accelerate this process.

To measure the in vivo adhesion force between N and Dl, Ahimou et al. attached a Drosophila cell expressing one or the other protein to a cantilever tip of an atomic force microscope (AFM) and placed cells expressing the other protein in a culture dish. When they brought the AFM tip with the cell near those in the culture dish, they found that, unlike many biologically active molecular pairs, there was no attractive force detected between...