Tension seals axons fate

Young rat hippocampal neurons are a ball of undifferentiated processes, one of which will become the axon, whereas the rest become dendrites. On page 499, Lamoureux et al. show that any of the processes can become the axon when given the right stimulus. But this cue is not a hormone or growth factor. The stimulus that tells an axon to form is more physical than chemical.

What the neurite needs to become an axon is a good tug, which the authors applied by attaching a needle to the end of a process. In most cases, the processes that were pulled extended rapidly and expressed axonal markers. Thus, every process appears ready to form an axon, perhaps with stores of unassembled tubulin and vesicles ready to be secreted....