Tracing neuromesodermal progenitors in zebrafish Free

Neuromesodermal progenitors (NMps) contribute to both spinal cord and paraxial mesoderm in amniote embryos long after gastrulation. However, the spatiotemporal details of NMp self-renewal and differentiation during development has remained unclear, as have the mechanisms by which NMps act in distinct species, particularly where body axis elongation differs markedly. Now, Benjamin Steventon and colleagues utilise a suite of cutting edge lineage tracing and imaging technologies to address the self-renewal and lineage of NMps in zebrafish embryos. Using ScarTrace, a CRISPR/Cas9 genetic scarring technique for determining clonal history, they find that adult muscle and spinal cord cells group together and distinctly from more anterior ectodermal tissues. Photoconversion-based lineage tracing reveals that the segregation of spinal cord and mesoderm fates occurs by 50% epiboly. Analysis of a multi-view light-sheet imaging dataset identifies a mixed population of mono-fated (a cell gives rise only to neural or mesodermal cells) or bi-fated (a cell can give rise to both) cells near the marginal zone of the embryo. To follow NMp lineages in the tailbud, an online tracking light-sheet microscope was developed to keep the region of interest in view until the completion of somitogenesis. This revealed tailbud NMps to be a mixed population of mono-fated cells. This complete lineage analysis not only confirms the existence of a conserved NMp lineage in zebrafish, it also reveals species-specific aspects of the NMp lineage in embryos developing at distinct scales of time and space.