Neuromesodermal Progenitors are a Conserved Source of Spinal Cord with Divergent Growth Dynamics

During gastrulation, embryonic cells become specified into distinct germ layers. In mouse, this continues throughout somitogenesis from a population of bipotent stem cells called neuromesodermal progenitors (NMps). However, the degree self-renewal is associated with NMps in the fast-developing zebrafish embryo is unclear. With a genetic clone tracing method, we labelled early embryonic progenitors and find a strong clonal similarity between spinal cord and mesoderm tissues. We then followed individual cell lineages by light-sheet imaging and reveal a common neuromesodermal lineage contribution to a subset of spinal cord tissue across the anterior-posterior body axis. An initial population subdivides at mid gastrula stages and is directly allocated to neural and mesodermal compartments during gastrulation. A second population in the tailbud undergoes delayed allocation to contribute to the neural and mesodermal compartment only at late somitogenesis. We suggest that NMps undergo vastly different rates of differentiation and growth in a species-specific manner.