Magic embryology: how do stem cells reach a destination (Introduction)

by David Turell , Monday, March 28, 2022, 20:28 (1102 days ago) @ David Turell

This is how they migrate by chemical and mechanical signals, but not how they know where they are intended to go:

https://www.quantamagazine.org/cells-blaze-their-own-trails-to-navigate-through-the-bod...

"It starts from the earliest stages of life. When we are embryos just a few weeks old, a special population of “neural crest” cells in our back suddenly spreads through the body to become a wide range of essential tissues — bones, cartilage and nerves in the face, tendons, pigment cells in the skin, parts of the heart and more.

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"Now researchers have discovered another crucial part of the answer, one that helps explain how cells are directed to their destinations in the neural crest migration and probably other movements as well. The new work shows that in addition to using chemical cues, neural crest cells “feel” their way through the body, creating patterns of physical tension in the surrounding tissue that point them the right way. In effect, the cells create the signals that they use to steer themselves.

"Finding this navigation mechanism doesn’t just clarify how neural crest cells make their vital migration. It also further validates an idea that has been gathering force in just the last few years: that “self-generated gradients” are essential to cell migrations, and that these gradients can be built from all kinds of factors — not just chemicals.

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"Self-generated gradients have now made sense of perplexing behavior in cancer cells, fish embryos, immune cells, bacteria, slime mold, and more — and findings are accumulating rapidly. “People are opening their eyes, and it’s now seen everywhere, suddenly,” said Jonna Alanko, a postdoc at the Institute of Science and Technology Austria. “I’m pretty sure that this is only the tip of the iceberg.”

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"Much of the research to date on self-generated gradients has looked at chemical signals, but cells can create gradients in other physical attributes, too, including mechanical properties. The recent paper analyzing migrating neural crest cells revealed a self-generated gradient of stiffness, to the authors’ surprise.

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"The researchers already knew that the “placode” cells in front of the migrating cells produces a chemical attractant to help draw the cells forward. These placode cells are repelled by the touch of the neural crest cells, so they run in the opposite direction. The newly discovered mechanical gradient works in tandem with the chemical cues to drive the migration of the neural crest cells forward by a “chase and run” mechanism.

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"The idea is catching on. Once the paper was published, Mayor’s inbox was flooded with messages from other researchers about the same kind of mechanism that seemed to be at work in embryos, immune cells and cancer. Self-generated stiffness gradients will turn out to be common, Mayor predicted. “There are many papers coming out very soon that will show this.'”

Comment: in the exact designed creation of a new embryo, each new cell daughter of the first stem cells must know exactly where it is supposed to go or the embryo would be a jumbled inexact copy of what is intended. This is how they use a system to migrate. Not how they know or decide where to go on their own in advance. I simply imagine each cell has a GPS system with the proper endpoint presented which they must follow. Just like we use in our cars to reach an intended destination. The designer at work.