Speed of life: tuning the ticktock of the segmentation clock

Although vertebrates share a similar body plan, different vertebrate species can develop at very different rates. In recent years, there has been an increasing appreciation of the fact that protein stability regulates the pace of differentiation. For example, global differences in protein stability may help explain why humans develop more slowly than mice. Mechanisms controlling the stability of particular proteins are also likely to play a role. In keeping with this idea, in this issue of Genes & Development , Meijer and colleagues (doi:10.1101/gad.352909.125) report that cells must keep tight control over the stability of the Notch1 intracellular domain (NICD) to tune developmental timing in the context of human somitogenesis.