After fertilization, the eggs of many vertebrates demonstrate cortical wave activity. Notably, the embryo of Xenopus laevis have three contractile wave periods that cover the entire cortex of the egg pre-division and additional cortical waves with each round of mitosis before the midblastula transition. These waves are driven by Cdk-1 activation post-fertilization and actin-myosin contractility and are mechanically opposed by microtubule structures. The propagation of the wave requires simultaneous positive and negative feedback loops at the leading and lagging edge of the wave, respectively. How these feedback loops are established from non-excitable material, the relationship between cortical excitability and the cell cycle, and why cortical excitability is conserved across multiple species are still unclear. Using a cell-free extract platform, we seek to understand these mechanical properties by perturbing cytoskeletal and cell-cycle dynamics. The extract platform allows for direct manipulation of both the chemical and mechanical environment of the system and also makes high-resolution imaging more accessible. We have established the simultaneous imaging of Cdk-1 waves with contractility in 1D and 2D environments. Preliminary results show Cdk-1 trigger waves preceding contractile wave events, suggesting a relationship between biochemical and mechanical waves.
Maki-Fern et al. (Sun,) studied this question.