GATA4 MOs cause defects in heart and liver development. A: Translation of injected GATA4-GR.HA mRNA, detected by Western blotting with anti-HA antibody, is blocked by G4 but not by other MOs indicated. 1 ng of mRNA was injected into 1- or 2-cell embryos and 10–15 minutes later the embryos were injected with 50 ng of indicated MOs. E-Uninjected embryos. B: Injection of 50 ng/embryo of G4 MO leads to a reduction in heart and liver precursors and to cardiac morphogenesis defects such as cardia bifida, highlighted by arrows in B3 (B1-5). The same dose (50 ng/embryo) of the C2 MO has no effect on heart and liver development (B6,7). B1-3,5,7: ventral view. B4,6: lateral view. Heart and liver precursors were revealed by MLC2 and Hex probes (BM purple and BCIP, respectively). C: 10 ng/embryo of C2 MO has no effect on heart in X. tropicalis embryos, but the same dose of G4 MO causes heart defects. D: G4SP MO causes dose-dependent splicing out of exon 4 in both Xenopus laevis and Xenopus tropicalis. The injected dose is indicated (in ng). 3–4–5, cDNA that contains exon 4 and regions of exons 3 and 5 determined by target sites of the primers; 3–5, cDNA without exon 4. Below are shown the sequences of the wt 3–4–5 and 3–5 cDNAs showing in-frame splicing in both species. E (top): Injection of 80 or 100 ng/embryo of G4SP MO, but not of 80 ng of C1 MO, causes splicing out of exon 4 with ~90% efficiency, as detected by RT-PCR analyses of mRNA from st. 15 embryos. +/- RT-indicates presence or absence of Reverse Transcriptase in samples that were analysed by PCR.E (bottom): 80 ng of C1 MO has no effect on heart and liver development (E1), whereas the same amount of the G4SP MO causes cardia bifida and liver defects (E2-4). In E2 remnants of cardiac tissue detected by weak expression of cardiac marker in severely affected embryo with cardia bifida are shown by arrows. Ventral views are shown. Heart was labelled by cTnI (purple) and liver with Hex (light blue/turquoise) probes.