A widely used model organism to study cell cycle regulation is the frog Xenopus laevis. It is particularly satisfying that its eggs can be used to make a cell-free extract to study various cellular processes in vitro. Female frogs can lay thousands of eggs every time, which can be induced by a hormone injection. Frog egg extract is then obtained after a series of centrifugation steps, essentially containing the cytoplasm of all the eggs (see figure). The extract lends itself for in vitro study since it is easy to manipulate: it can be put into tubes, droplets can be formed, or put in a container with another geometry and visualized under a microscope. In the extract, all biochemical components underlying the cell cycle progression are still present. Organelles can spontaneously form in the extract, and by adding nuclear material in the form of sperm chromatin, nuclei can also form. As such, these experiments are a powerful way of studying various types of cellular dynamics under controlled conditions.
Nuclei determine the spatial origin of mitotic waves
In: eLife, vol. 9, pp. e52868, 2020, ISSN: 2050-084X.
Delay models for the early embryonic cell cycle oscillator
In: PLoS One, vol. 13, no. 3, pp. 1-21, 2018.