First glimpses of the human form

Mere weeks into human embryonic development, an indistinct ball of cells called a blastocyst rearranges itself into an orderly three-layered structure—a process called gastrulation that sets up the eventual emergence of the human form.

Understanding the molecular underpinnings of this pivotal event could help scientists prevent miscarriages and head off a host of serious disorders. But gastrulation has long been a black box. “It is the first moment that separates our heads from our behinds, and yet we had never seen ourselves at that stage,” says Ali H. Brivanlou, the Robert and Harriet Heilbrunn Professor.

That changed this year when Brivanlou and his Laboratory of Synthetic Embryology created a new platform for studying human gastrulation through the use of blastoids—models of blastocysts developed from stem cells that can be cloned, manipulated, and programmed in the lab. Crucially, the platform allows blastoids to attach to plastic surfaces, much as real blastocysts attach to the uterus.

Data

Year the first human stem cell line was created.

Thanks to this innovation, the team was able to directly observe key moments in process, including the emergence of molecular markers for two crucial structures in embryonic development: the so-called primitive streak, which marks the beginning of gastrulation; and the mesoderm, which gives rise to muscles, bones, and the circulatory system.

The future applications are many, says first author Riccardo De Santis, a research associate in Brivanlou’s lab: “A better understanding of gastrulation impacts everything from survival of the fetus to autism to neurodegeneration.”