Genome complexity in embryology: nerve routes (Introduction)

by David Turell , Monday, April 24, 2017, 15:09 (2771 days ago) @ David Turell

Guiding axons to the proper spots requires chemical guidance:

https://www.sciencedaily.com/releases/2017/04/170420162153.htm

"As an embryo grows, neurons -- the cells in the nervous system -- extend axons into the developing spinal cord. Axons are then guided to reach other areas of the body, such as the brain, to establish a functioning nervous system. It has been generally understood that various guidance cues, which are cellular molecules such as proteins, either attract or repel axon growth as the axons reach out from neurons to find their destination in the nervous system.

"Previous research suggested that a particular guidance cue, called netrin1, functions over a long distance to attract and organize axon growth, similar to how a lighthouse sends out a signal to orient a ship from afar. However, previous research also shows that netrin1 is produced in many places in the embryonic spinal cord, raising questions about whether it really acts over a long distance. Most notably, netrin1 is produced by tissue-specific stem cells, called neural progenitors, which can create any cell type in the nervous system.

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"They found that neural progenitors organize axon growth by producing a pathway of netrin1 that directs axons only in their local environment and not over long distances. This pathway of netrin1 acts as a sticky surface that encourages axon growth in the directions that form a normal, functioning nervous system."

Comment: neurons in the lumbar spine must reach the feet of the newborn, perhaps eight to ten inches of travel accurately reaching the proper spots. The same is true for blood vessels. We have no idea how the genome directs all of this, but the chemical guides are becoming discovered as this study shows.