May 4, 2018

See a Single Stem Cell Grow Into a Complete Creature

“Your life is a result of many, many choices. School, career, relationships; each decision is made in sequence, building upon the past to create a traceable map of what led you to your current state of being.

Cells, in an act of meta metamorphosis, determine their fate in much the same way.

“The creation of different types of cells during development is akin to a child growing up. A 5-year-old has the potential to do anything,” explains Sean Megason, associate professor of systems biology at Harvard Medical School. Similarly, almost all life on Earth starts as embryonic stem cells, which then divide and develop into the various specialized parts of a complex being. (See “First There Were Microbes. Then Life on Earth Got Big.” in National Geographic magazine.)

“Cells that end up as neurons make one set of choices, while muscle cells make a different set of choices,” says Megason. But exactly how these embryonic stem cells make their choices is still shrouded in mystery.

UNITED AND DIVIDED

Multicellular life forms are the new kids on the block, evolutionarily speaking. They first appeared on Earth roughly 600 million years ago, at least two billion years after their single-celled ancestors evolved. For reasons we still don’t fully understand, single cells began to replicate, eventually forming more complex organisms.

“On the first day, they mostly just divide, so at the end of the day they are a round ball of cells,” Megason says. “But when you come back the next morning, that ball of cells has turned into a little fish. It has eyes, a beating heart; it has muscles and can wag its tail.””