Movements in mouse egg after fertilization predicts developmental success of embryos

In vitro fertilization (or IVF for short) can be pretty hit-or-miss. That’s why many embryos have to be implanted in a woman to successfully have one baby. Wouldn’t it be nice if there was a way to easily predict which embryos are going to make it, and which ones are duds?

New research in mouse embryos may have found a way to do just this. A team of scientists led by Magdalena Zernicka-Goetz discovered that specific movements of inside an egg right after fertilization can predict how successful development will be for a given embryo. The research was published this month in Nature Communications.

Research with animals such as sea urchins, frogs, and even flies have led to many insights about what happens in an egg immediately following fertilization. In frogs and sea urchins, the concentration of calcium inside the egg increases rapidly, starting from the exact point where the sperm entered the egg.

But this kind of research has not been done in much detail yet in mammals. Even more, we still don’t know how calcium waves are related to other events in development. We know that the calcium wave is necessary for events later on in development, but exactly why is not clear.

In this paper, the authors describe in detail movements of the cytoskeleton (the internal “skeleton”, or structural support structure of the cell) that start right after sperm entry. They also, for the first time, show how these are connected to the calcium wave and to later developmental events. One surprising result was the connection between the movements in the cell and movements around the fertilization cone, a structure that forms to bring the sperm into the egg (you can see a neat animation of the fertilization cone here).