All life starts small. In the first few weeks of their development, human embryos are little more than a tiny ball of cells. Only gradually does the typical human shape emerge. One of the first major steps in this direction is the so-called gastrulation, in which the ball of cells – also called a blastocyst – transforms into an ordered three-layer structure that forms the basis for everything else.
“Gastrulation is the origin of our own individualization, the emergence of our axis,” says Ali Brivanlou of Rockefeller University in New York. “It is the first moment that separates our head from our butt.” But even though gastrulation is such a milestone on the way to becoming humans, it has so far resembled an invisible black box. Because technical and ethical hurdles have ensured that we have never been able to observe ourselves at this early stage – until now.
To witness the human beginning, Brivanlou and other scientists have now developed so-called blastoids – stem cell-based blastocyst models. Such a blastoid can also be seen in the picture above and somewhat resembles a blue and red disco ball. Blastoids can be cloned, experimentally manipulated and programmed, allowing a range of controlled studies on them.
So far, the team has been able to use the blastoids to observe the exact process of gastrulation and gain new insights into the details of this important process. In the future, blastoid research could lead to advances in the diagnosis and treatment of developmental disorders, but also provide insights into possible causes of early miscarriages during gastrulation.
“Many couples cannot have children because the embryo does not implant properly,” explains lead author Ricardo De Santis, also from Rockefeller University. “We now have a model system that can help us understand the molecular mechanism that determines whether a pregnancy is successful or not.”