Lineage tracing of axial progenitors using Nkx1-2CreER mice defines their trunk and tail contributions.

The vertebrate body forms by continuous generation of new tissue from progenitors at the posterior end of the embryo. The study of these axial progenitors has proved to be challenging largely because of the lack of unique molecular markers to identify them. Here, we elucidate the expression pattern of the transcription factor in the mouse embryo and show that it identifies axial progenitors throughout body axis elongation, including neuromesodermal progenitors and early neural and mesodermal progenitors. We create a tamoxifen-inducible Nkx1-2CreER transgenic mouse and exploit the conditional nature of this line to uncover the lineage contributions of -expressing cells at specific stages. We show that early -expressing epiblast cells contribute to all three germ layers, mostly neuroectoderm and mesoderm, excluding notochord. Our data are consistent with the presence of some self-renewing axial progenitors that continue to generate neural and mesoderm tissues from the tail bud. This study identifies -expressing cells as the source of most trunk and tail tissues in the mouse and provides a useful tool to genetically label and manipulate axial progenitors .