Biologists at the University of Bayreuth have discovered an exceptionally rapid form of regeneration in injured neurons and their role in the central nervous system of zebrafish . The scientists have published their findings in the journal Communications Biology .
In the central nervous systems of other animal species, such a complete regeneration of neurons has not yet been definitively demonstrated.
Mauthner cells are the largest cells found in the brains of animals. They are part of the central nervous system of most species of fish and amphibians and trigger life-saving escape responses when predators approach.
The transmission of signals in Mauthner cells to their motor neurons is only guaranteed if a certain part of these cells, the axon, is intact. The axon is an elongated structure that limits the cell body with its cell nucleus at one of its two ends. If the axon injury occurs near the cell body, the Mauthner cell dies . If the axon is damaged at its opposite end, the lost functions are not restored at all or only in a slow and limited way.
However, the Mauthner cell reacts to injury in the middle of the axon with rapid and complete regeneration. In fact, within a week after injury, the axon and its function are fully restored, and the fish can again escape from approaching predators .
It could be possible that other neurons in the zebrafish could induce this life-saving escape behavior and thus take on the lost function of Mauthner cells. However, precisely this possibility was ruled out by previously published findings. According to one of the lead researchers, Hecker :
Mauthner cells now offer us the possibility to investigate very different responses to individual cell injury within the same nervous system: an absence or insufficient regeneration processes on the one hand, and a robust and complete regeneration on the other. Surprisingly, the injuries to the axon, which led to such conflicting responses, were not far off. Elucidating the causes is an exciting field of research, which also includes the identification of genes that are active in the regeneration of neurons. And if we discover why regeneration processes in Mauthner cells do not occur, we could also better understand the mechanisms that prevent the regeneration of neurons in humans.