Fig. 6: Posterior node cells can induce caudal mesoderm.

a Schematic depicting the transplantation assay, where wild-type (WT) stage HH6 nodes were transplanted into GFP-positive HH4 hosts, followed by dissociation for single-cell RNA-seq (n = 5). b UMAP plot displaying GFP-positive host cells across different clusters, showing the formation of ectodermal and mesodermal cells. Gray dots represent unconverted cells. c, d Schematic of node transplantation experiments into transgenic embryos. WT stage HH4 embryos were electroporated with CHRD-E (notochord enhancer) or TCF15-E (somite enhancer), followed by node grafting from GFP-positive HH6 embryos. e After ~ 16 h, CHRD-E activity is detected in the notochord, confirming the induction of trunk-specific structures in the host (n = 10/17 biological replicates with similar results). f High magnification image of the marked region within the transplanted cells shown in panel (e), showing activation of CHRD-E within the induced secondary axis. g TCF15-E activity is observed in the somite region (arrows), confirming the induction of paraxial mesoderm in host embryos (n = 6/10 biological replicates with similar results). h HCR-FISH showing CHRD (notochord – magenta, arrowhead) and LMO2 (blood islands - blue) expression in embryos after 16 h post-transplantation of stage HH6 GFP-positive node (n = 5/5 biological replicates with similar results). i, j High magnification image of the marked region shown in panel (h). GFP-positive cells from the donor form posterior structures (somites, notochord) and are shown in green (i). HCR-FISH for CHRD (magenta) showing that some notochord cells are GFP-negative (j). Scale bar = 100 μm. NC = Notochord, S = Somite.