For several decades it has been possible to culture embryos from a single cell, the fertilised egg, to the blastocyst, a ball of some 64 cells all derived from the first by repeated rounds of cell division. In practical terms this has allowed the development of the in vitro fertilisation techniques that are used world-wide to assist fertility.
It has also enabled scientists to learn much about these early stages of development during which cells take the very first decisions about their future. This is because in the first 4 days it is possible to observe developmental events as they happen and, in model systems such as the mouse, manipulate the expression of the genes involved in the process in order to better understand their roles.
Image: A mouse embryo in which the outer membranes of all cells are glowing red. A subset of cells are expressing a green glowing protein that identifies them as cells that will signal head development.
Credit: Lab of Professor Magdalena Zernicka-Goetz , Gurdon Institute
Reproduced courtesy of the University of Cambridge