Spatiotemporal expression pattern of zebrafish atf7a. Distribution of endogenous mRNA was detected by whole-mount in situ hybridization. A,B: The 80% epiboly stage. C-E: The bud stage. F: The 10-somite stage. G,H: At 1 day. A,C: Dorsal views with animal pole to the top. B,D,E,F: Lateral views with animal pole or anterior to the top. E,H: Double staining with atf7a (blue) and ntl (red). Arrows indicate the notochord precursors or the notochord. E,H: Arrowheads indicate the germ ring (E) or tail bud (H) where only ntl is expressed.

The spatiotemporal expression pattern of zebrafish atf7b. In contrast to atf7a, atf7b is ubiquitously expressed at all stages examined. A: At the one-cell stage, with the animal pole to the top. B: The shield stage, lateral view with dorsal to the right. C: The shield stage, animal-pole view with dorsal to the right. D: The bud stage, lateral view with the dorsal to the right. E: At 24 hours postfertilization, lateral view with anterior to the left.

Regulation of atf7a expression by transcription factors Ntl, Spr2, and Flh. A,E: Control embryos injected with green fluorescent protein (GFP) mRNA. B,D,F: Injection with 150 pg of ntl mRNA (B), 100 pg of spr2 mRNA (D), or 100 pg of flh mRNA (F) enhanced atf7a expression. C: Injection with 10 ng of ntl-morpholino inhibited atf7a expression. G,H: The expression of atf7a was not detected in the flh^nl mutant embryo (H), whereas it was expressed in the wild-type embryo from the same cross (G). A-D,G,H: The bud stage. E,F: The 90% epiboly stage. All embryos were dorsal views, with the animal pole to the top.