This video shows mouse cells self-organising to form something like the early stages of an embryo. The process has been reconstructed for the first time in the lab.
As we know from biology class, cells start dividing after fertilisation to eventually form an embryo. But there's an important process that makes the cells arrange themselves into the right structure—with a head, a rear, a back, a belly. The process that implements the coordinates needed for this choreography is called gastrulation.
Alfonso Martinez Arias, a geneticist at the University of Cambridge who co-authored the study published in the journal Development, told me in an email he thinks of gastrulation as like "cellular origami in which what is basically a ball of cells is folded precisely to get an animal."
But we don't know where the origamist gets the instructions to fold just so. In their work, the researchers found that a key factor is the number of cells. A critical mass of around 300 is needed to start the self-organisation process.
"What we have achieved is to take embryonic stem cells from [a] mouse, which are similar to the cells of a very early dividing embryo, and coax them to start the origami process by controlling the medium in which they grow and, more importantly, their number," explained Martinez Arias. "Much to our surprise, after three days in culture they begin a series or movements that resemble those that organise the embryo and acquire coordinates and, as in the embryo, the seeds of the different tissues."
In the video, a marker makes any cell that turns into an endoderm cell—one of three major cells types in the early embryo—glow green. At first these cells appear scattered randomly, but then they clearly get organised, gathering at one end.
He said the process was not exactly the same as regular gastrulation and the result "only resembles a mouse embryo in its general features." But the method offers a system for researchers to study how cells organise themselves at this and other stages of development.
On a practical note, it could help researchers to obtain cells they currently find difficult to make, such as adult stem cells, as they now have more information on how an embryo makes them.