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Fig. 5-S3
Ubiquitous Activin expression can partially rescue maternal-zygotic one-eyed pinhead embryos.
Maternal-zygotic one-eyed pinhead (oep) embryos are insensitive to Nodal signaling, but receptive to the related TGFβ ligand Activin (Gritsman et al., 1999; Donovan et al., 2017). At 1 day post-fertilization (dpf), MZoep embryos (B) lack mesendoderm-derived head and trunk structures in contrast to wild type embryos (A). (D) MZoep embryos were injected with the indicated amounts of myc-tagged human activin mRNA (Donovan et al., 2017) at the one- to two-cell stage and scored at 1 dpf, similar to Gritsman et al., 1999. 0.2–0.4 pg hActivin mRNA can rescue some loss of trunk tissue and somites; amounts higher than 0.4 pg result in severe deformities and embryo rupture. One MZoep embryo injected with 0.3 pg hActivin mRNA exhibited two separated, non-cyclopic eyes and moderate rescue of head and trunk mesensoderm (C). (E–L) Representative images of 1 dpf MZoep embryos injected with hActivin mRNA at the one-cell stage. Injected amount indicated in the lower right corner, number of embryos with the displayed phenotype out of total shown in the left corner. The inability to fully rescue loss of Nodal signaling with ubiquitous Activin expression suggests an important role for the localization of Nodal expression at the margin, in contrast to Lefty (e.g. Figures 5 and 6).