Fig. 6-S3
Artificial, uniform Nodal inhibition rescues mesendodermal gene expression in lefty1-/-;lefty2-/- mutants.
Wild type and lft1-/-;lft2-/- mutant embryos were exposed to 2.5 μM SB-505124 (Nodal inhibitor drug) starting at the 8 cell stage (A,B), 3 μM starting at sphere stage (C,D), or 5 μM starting at shield stage (E,F), slightly after gastrulation commences. Endodermal (sox32/casanova) (A,C,E) and mesodermal (noto/floating head) (B,D,F) gene expression was assessed using in situ hybridization. Embryos were fixed at the indicated times post drug-exposure. Mesodermal gene expression in lft1-/-;lft2-/- mutants exposed at the 8 cell stage or sphere (B,D) appears normal, while endodermal gene expression in drug-exposed embryos is reduced (A,C). In contrast, mesendodermal gene expression is upregulated in embryos exposed at shield stage until ~5 hr post-exposure (E,F). Some images from A, B, E, and F are also used in Figure 6.