Embryonic Cells Differentiate Earlier Than Previously Thought, Researchers Say

The latest research conducted by Harvard Medical School researchers may revolutionize our current understanding of embryonic development. Specifically, a new study published last week in the journal Cell offers a new model to describe the way in which cells gain specific functions within the embryo.

The prevailing model of embryonic differentiation—a process in which infant cells develop specialized structures and functions—suggests that the identities assigned to cells are entirely determined by their location within the embryo.

“The textbook model is that the cells sit still, they listen for a signal, and then once they get the signal they adopt a fate,” said Sean G. Megason, assistant professor of systems biology at HMS and one of the study’s authors.

Megason’s team, however, found that this classic model was not completely consistent with their research, which suggests that the identity and function of an embryonic cell may be decided before the cell’s location is determined.

By studying the motion of embryonic zebrafish cells, the researchers observed cells undergoing differentiation before they moved into their proper positions.

“One thing that is quite intriguing is...they make the decision much earlier, before they get into their positions. That’s when it struck me that there is something unknown here,” said Fengzhu Xiong, lead author of the study and a graduate student in systems biology.

To make their observations, the team developed and utilized a new imaging and data analysis technique that allowed them to track the movement and changes of individual cells over time. As a result, the researchers were able to directly and closely observe how organs and tissues develop in the embryo.

“We’re using a type of microscopy that captures 3-D volumes, and then we do that over time, every couple minutes.” Megason said.

The team’s research sheds light into the processes by which all embryos develop the same set of complex structures, despite facing a wide variety of different genetic and environmental factors. The research may have important implications for the future of regenerative biology in the long run.

“If we’re to understand how we can ever make an organ, in vitro or in the laboratory, it’s important to understand how embryos actually do it, since embryos are so good at it,” Megason said.

Megason’s team will build on its findings to delve deeper into the mechanisms that govern the sorting of cells and the assignment of their functions.