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Life Itself: These Videos Show Thousands Of Cells Growing And Dividing Inside An Embryo

For the first time, scientists can map embryogenesis in fruit flies, zebra fish, and mice.

If scientists could watch an embryo’s cells develop in real time, they might be able to understand, track, and ultimately prevent, the formation of mutations and diseases in human infants. Recently, researchers at the Howard Hughes Medical Institute’s Janelia Research Campus, have taken the first step toward doing just that.

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They’re using a brand-new high-powered microscope, to show how the nervous systems of fruit flies, zebra fish, and mice develop, from the organisms’ single-cell beginnings, to early adulthood. “We’re recording live image data of developing embryos over the whole period of embryogenesis says Dr. Philipp Keller, the project’s lead researcher. “It’s the entire building plan of what the animal looks like.”


As you might imagine, this is a daunting task. In a developing fruit fly, tens of thousands of cells form after only a few hours, so images are taken every 30 seconds. And to truly understand how the nervous system develops, it’s necessary to track not just the number of cells, but their spacial location and points of origin.

To do this complicated tracking, Keller’s team shines a razor-thin beam of light into each embryo, illuminating it section by section. As each segment lights up, the inner workings are recorded. This process happens thousands of times over hours and days until the nervous system is fully developed. The final data set allows the scientists to watch the development of specific cells within the developing organism from start to finish or at any point along the way.

To the untrained eye, the videos may resemble trippy, digitized Lite-Brites. But they hold the secret to how we are made. “The adult zebra fish shares the majority of brain regions that you’d find in a human brain,” says Keller.

Video 20

Video 20 (see above) depicts 13 hours of the early development of a zebra fish, played at hyper-speed. Every colored circle represents one cell and by the end, there are roughly 20,000 cells. At first, the colors don’t mean much, but as time progresses, the red and purple colors morph into the head region. “Some of the cells in the long red streak form the spinal cord. It’s the midline of the animal,” says Keller. “The right side of the movie shows the region in the embryo where the tail is forming. On the left side you can see the developing head.”

Video 25 shows the development of a fruit fly’s nervous system. The cells, shown in green, start on the surface of the embryo and then wend their way deeper into the organism. The small sperm-like tails demonstrate the history of the cell movement. In other words, they show where the cells came from and what direction they’re moving. If you look very closely, you can even see the cells split and multiply.

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About the author

Jennifer Miller is the author of The Year of the Gadfly (Harcourt, 2012) and Inheriting The Holy Land (Ballantine, 2005). She's a regular contributor to Co.Create.

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