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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??M ( n?=?17/23) and 30??M ( n?=?15/16), e, f) decreases ventral drl expression, while chemical Nodal inhibition with SB-505124 (20??M ( n?=?18/18) and 60??M ( 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??m