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Fig. 4
Early drl-expressing LPM progenitors respond to ventral BMP. a Schematic of the BMP and Nodal signaling pathways and the corresponding signaling territories in the gastrulation-stage zebrafish embryo, compared to endogenous drl expression marked by mRNA ISH. Pathway schematic generated with BioRender. b– i mRNA ISH for endogenous drl expression during early gastrulation (shield stage to 75% epiboly), lateral view on the left and animal view on the right. b– d Wildtype (wt) controls ( n = 70/70), BMP-perturbed ( MZsbn, a dominant-negative Smad5 allele, n = 60/60) and Nodal-perturbed ( MZoep, mutant for the required Nodal co-receptor Oep, n = 15/16) showing that BMP perturbation abolishes endogenous drl expression. e– h Chemical inhibition of BMP via Dorsomorphin (15 μM ( n = 17/23) and 30 μM ( n = 15/16), e, f) decreases ventral drl expression, while chemical Nodal inhibition with SB-505124 (20 μM ( n = 18/18) and 60 μM ( n = 15/16), g, h) decreases dorsal drl expression, as indicated with the asterisks in the lateral views and the arrowheads in the animal views. i sox32 morphants that fail to form endoderm also lose dorsal drl expression, as indicated with asterisk in the lateral view and with arrowheads in the animal view ( n = 21/23). Scale bar ( b) 250 μm