Spatial waves control the mitotic divisions in the early Xenopus frog embryo

The early Xenopus laevis embryo rapidly divides twelve times to reduce its size from a single large cell of about 1mm to somatic cell size. The embryo completes these initial cleavages without any gap phases, checkpoints, and in the absence of transcription. In the last decade, cell cycle research has been very successful in understanding how local oscillations arise from a protein circuit centered on the cyclin – Cdk1 complex. Various feedback loops underlying cell cycle oscillations have been experimentally dissected and detailed theoretical models have been built. Here, we focus on understanding the collective dynamics of many spatially coupled cell cycle oscillators. By combining experiments and numerical modeling we show how the early frog embryo organizes its mitotic divisions in space and time through various spatial waves sweeping through the embryo.