Fig. 1.

Spinal cord clones are closely associated to mesodermal, but not anterior, neural derivatives. (A) Experimental workflow for Scartrace lineage tracing of the zebrafish larvae. (B) Clustering of weighted distances (see Materials and Methods) of scars in dissected body structures of fish R1. The smaller the distance the closer the association between body structures. (C) Bootstrapped tree of weighted distances of scars in dissected body structures of fish R1. The tree was bootstrapped 100 times and the final proportion of clades (clade support values) are shown at each node of a clade. Coloured boxes highlight three groups: the ectodermal group (green), the mesodermal/endodermal group (orange), and the mixed ectodermal and mesodermal group (blue) containing muscle and spinal cord. There is close association of spinal cord and mesodermal cells across the anterior to posterior axis, that is distinct from brain regions. spc, spinal cord; antIntes, anterior intestine; postIntes, posterior intestine; l, left; r, right. (D) Model 1. The continuous allocation model is based on lineage analysis in mouse embryos and proposes that a group of self-renewing neuromesodermal stem cells continually generates spinal cord and paraxial mesoderm throughout axial elongation. (E) Model 2. The direct allocation model proposes that an early segregation of neural and mesodermal lineages occurs during gastrulation, the derivatives of which then expand rapidly by convergence and extension.