Fig. 6

tarMR overexpression disrupts the formation of endoderm-derived structures and heart organogenesis. Wild-type embryos were either left uninjected or injected during the first cell cycle with lacZ RNA (200 pg), tarMR RNA (MR) (200 pg) alone, or combined with tar RNA (100 pg) as indicated in the lower left corner, analysed at 4 days as live samples (A, B), then fixed and sectioned (C, D) or at 30 hpf by in situ hybridisation (E–J). (A–D) At 4 days, large segments of the gut (arrowheads) are missing in em>tarMR-injected embryos (B, D) as compared to controls (A, C). (E) At 30 hpf, fkd7 labels the digestive structures from the pharynx to the digestive tube (arrowheads), as well as the ventral CNS. (G) Fkd7 expression is missing in digestive structures of tarMR expressing embryos but is restored upon coexpression of tar (I). (F, H, J) The same embryos were also labelled with the heart-specific probe nkx2.5 (arrow). A lateral view (F, J) or frontal view (H) is presented. Expression of tarMR leads to cardia bifida (H), which is rescued by coexpression of tar (J). Abbreviations: s, somite; nt, neural tube; nc, notochord; g, gut; y, yolk.