This movie illustrates how cells form blurry stripes in response to a developmental signal and then, over time, move and differentiate. Towards the end, crisply defined structures emerge, including differentiating motor neurons (in green). Movie: Sean Megason
A team of researchers led by Sean Megason, Harvard Medical School assistant professor of systems biology, has shown through a novel imaging technique that our classic understanding of cell differentiation may be flawed. In a paper published in the April 25th issue of Cell, Megason and colleagues developed a data analysis technique that allows direct observation of the cells in an embryo as they move and change over time. They used it to see what happens in the embryo between the early and late snapshots. Based on the results of the technique, the researchers theorize that cell differentiation is in fact predetermined before being influenced by location-dependent factors. In other words, it is the cell itself that determines the differentiation, not the other way around as was previously thought.
The researchers used the imaging technology to film zebrafish embryos as they grew under a microscope. The embryos were individually identifiable through high-resolution imaging. Then, markers and software developed in the Megason lab allowed the movements of every cell in the ventral neural tube to be tracked over time. Following the cells in the videos backwards, the researchers were able to come to the source of their conclusion.
According to Megason in a Harvard press release, “Embryos may be evolutionarily designed to reach the same end in spite of the variation Mother Nature throws their way…In the textbook model, the cells should stay in the same place because that model says the cells adopt their fates based on position. But when we tracked the cells back in time, they all got mixed up.”
This is a novel development that may change our embryology textbooks.
Original article in Cell: Specified Neural Progenitors Sort to Form Sharp Domains after Noisy Shh Signaling…
Harvard Medicine press statement: New View of How Embryos Develop…