Rockefeller Scientists Show That Axon Degeneration Is Actively Controlled by Signaling from Nerve Cell Body; Expression of Puma Protein in Nerve Cell Body Appears to Be Key to Process

As tiny embryos in the womb, we start out with a lot more neuronal material than we actually need. During development, the body drastically prunes back the excess—cutting the branches from nerve cell bodies, known as axons, as well as entire neurons. Scientists have long assumed that the decision whether to cull or keep an axon was coordinated by the axon itself, rather than by the cell body from which it extends. In recent years, tantalizing clues from several research groups have challenged that assumption. Now, researchers at The Rockefeller University in New York City have proven that the cell body actively controls axon degeneration, and they have uncovered many of the molecular details that allow this long-range communication. In an article published online on February 18, 2016 in Cell, the Rockefeller scientists report that the instructions telling axons in developing embryos whether to live or die come from the cell body, not the axon. “This is a surprising finding,” notes senior author Marc Tessier-Lavigne, Ph.D., President of The Rockefeller University and the Carson Family Professor and Head of the University’s Laboratory of Brain Development and Repair. “When the axon senses a ‘distress signal’—a lack of a growth factor called NGF—it doesn’t make the decision to degenerate by itself. It actually sends the information to the cell body, which is quite far away, and the cell body sends its decision back down the axon.” The Cell article is titled “Axon Degradation Gated by Retrograde Activation of Somatic Pro-Apoptotic Signaling.” The survival of some axons depends on the presence of NGF in their local environment, a sign that there are plenty of nutrients around.
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