Canonical endoderm (sox17) expression profile. Z-stack through a Tg(cryaa:Venus; 5xC120:sox32); Tg(sox17:GFP) embryo at approximately 70% epiboly. The embryo was injected with H2B-mCherry mRNA to label all nuclei (red). Images were acquired every 0.9 μm on a Nikon Ti-E microscope equipped with a Yokogawa CSU-22 spinning disk confocal unit. The z-stack starts at the embryo surface and goes through towards the yolk. Tg(sox17:GFP) expression (green) appears in only at the innermost layer closest to at the yolk, consistent with endogenous endoderm localization.