Multipotent tail bud cells originated with the chordate common ancestor

In vertebrate embryos, the tail bud region generates the neural tube, the notochord, and somites in the posterior part of the body, including the post-anal tail. Here, we traced the fate of tail bud cells during embryogenesis in the cephalochordate, amphioxus, the earliest diverging lineage of extant chordates, and showed that in amphioxus as well, these cells contribute to the neural tube, the notochord, and somites. Our work provides direct evidence to support the hypothesis that ancestral chordates possessed tail bud cells capable of producing both neural and mesodermal derivatives, illuminating the evolutionary origin of posterior body development in chordates.