The primitive streak—a structure that emerges in mammalian and avian embryos to help assign spatial information to cells during early development—has long been regarded as essential for the genesis of an organism’s body plan and individuality, and was thus used as a landmark in ethical guidelines for stem cell research. But a new literature review pulls together evidence from stem cell research, evolutionary history papers, and developmental biology studies to make the argument that the primitive streak may not be so necessary after all. In doing so, the review—which was published today (December 2) in Science—challenges century-old assumptions that scientists have been making regarding how an embryo changes from a collection of identical cells into an organism with a distinct, asymmetric form.
The new review suggests that the streak is “unnecessary” and “dispensable,” University of Michigan developmental biologist and biomedical engineer Jianping Fu, who didn’t work on the review but ...
