Before a critical development point, the animals did not succeed in closing the wound that was made by the cut, making the two embryo helfper cells simply spit in the area. A little later, however, there was an excellent survival and the main part of the embryo could regenerate a star segment. This tells us that the normal signal routes that are present in the embryo are sufficient to help the process move forward.
But the tail of the embryo seems to be unable to rebuild his head at this stage. But the researchers discovered that they could inhibit WNT signaling in these rear fragments, and that was enough to have the head developed.
Lack of muscles
One possibility is that WNT signaling on this point is active on a large scale in the rear of the embryo, thereby blocking the formation of front structures. As an alternative, the researchers assume that the problem is with the muscle cells that normally help to organize the formation of a stem cell blastema that is needed to start the regeneration process. Since the front end of the embryo develops earlier, they suggest that there can simply not be enough muscle cells in the tail to start this process in early stages of development.
To test their hypothesis, they conducted a somewhat unusual experiment. They started by cutting off the tails of embryos and saving them for 24 hours. At that moment they cut off the front of tails, creating a new wound to cure. At this point the regeneration went normally and the tails grew a new head. This is not definitive evidence that muscle cells are missing at an early stage, but it does indicate that there is an important development step in the tail within the 24-hour window after the first cut.
The results reinforce the idea that the regeneration of important parts of the body the restoration of the signals that the organization of the embryo in development contains in development require that is to be complicated if those signals are currently acting to organize the embryo. And it clearly shows that the cells needed to do this reorganization not only not only put aside in development, but instead take some time to appear. All that information will help clarify the greater question of how these animals manage such a complex regeneration process.
Current biology, 2025. DOI: 10.1016/J.CUB.2025.03.065 (About Dois).
