Fig. 2

Effects of overexpressed zebrafish smad1 and smad5 in wild-type and swirl (swr) mutant embryos. All embryos are photographed at 36 hr after fertilization. A–D: Injection of variable amounts of smad1 RNA in wild-type 1-cell stage embryos. A: Uninjected control. B: 50 pg/embryo, leading to a weak ventralization (V1), characterized by extra ventral tail fin tissue and slightly enlarged blood islands (indicated by arrows). C, D: 100 pg/embryo, leading to intermediate ventralization (V2), characterized by enlarged blood islands (indicated by arrow) and smaller eyes (indicated by arrowhead), or strong ventralization (V4), characterized by enlarged blood islands (indicated by arrow) and complete loss of head structures (indicated by arrowhead) and notochord (indicated by bar). E, F: Injection of smad5 RNA in wild-type embryos. E: 100 pg/embryo, leading to V1 ventralization. F: 100 pg/embryo, leading to V4 ventralization. G–I: Injection of smad1 and smad5 RNA in swr mutant embryos. G: Uninjected swr control with ruptured yolk sac (C5 dorsalization). H: Rescued swr mutant after injection of 25 pg/embryo smad1 RNA; the embryo was genotyped as swr homozygous after photography. I: swr mutant after injection of 200 pg/embryo smad5 RNA, displaying C5 dorsalization as uninjected control. Embryos in (G) and (I) had been sorted at the tailbud stage, displaying the typical elongated “football-like” shape. Compare Kishimoto et al. (1997) for the classification of ventralization (V1–V4) and dorsalization (C1–C5) strengths. J, K: Reverse transcriptase–polymerase chain reaction analysis for transcripts of smad1, the ventral marker eve1 (Joly et al., 1993), and the control gene ef1α (Nordness et al., 1994). J: animal cap explants of wild-type embryos after injection of smad1 or smad5 mRNA and cultivation until control embryos had reached the shield stage. (K) 80% epiboly stage swirl mutant embryos from a cross of two homozygous swr^ta72 parents after injection of smad5 mRNA. All injected control embryos (12 of 12) that had been allowed to develop further displayed unweakened C5 dorsalization. Abbreviations: ctr, control; emb, control embryo; WT, wild type.