Cells' precise pattern readout

Running from head to tail in a fly embryo, the Bicoid (Bcd) gradient is the blueprint for anterior–posterior development. How cells read the blueprint to give a precise pattern was thought to require multiple mechanisms to smooth out sloppy Bcd input signals. Now, two papers from Thomas Gregor and colleagues (Princeton University, Princeton, NJ) put numbers on the cells' Bcd readout abilities and show the system to be highly precise—approaching the limits set by the inherent noise in any physical system.

Using live embryos to image the dynamics of the Bcd gradient, the team determined that the gradient was established within ∼1 hour after fertilization and that Bcd diffused through the cytoplasm of the syncytial embryo with a diffusion constant of 0.3...