Fig. 3

TarMR interferes with the inducing activities of cyc and sqt. (A) Structures of Tar MR381 (MR). Wild-type Tar (TAR) is composed of an extracellular domain (EC), a transmembrane domain (black), aGS domain (GS), and a kinase domain (Kinase). TarMR (MR) carries a point mutation that substitutes an arginine for methionine 381 in the kinase domain (star). This methionine is highly conserved between zebrafish TAR, human ALK1, mouse ALK3, human ALK4, and Xenopus ALK4 (boxed). (B) Embryos were injected with sqt RNA (2 pg), combined with tarMR RNA (20 pg) alone or with tarRNA(100 pg), the animal caps were dissected, cultivated until the shield stage, and analysed by RT-PCR for different mesendodermal markers. tarMR blocks the effect of exogenous nodal-related molecules on meso- or endodermal markers as indicated. Ef1α is used as a loading control. In the -RT lane, the reverse transcription step has been omitted. In the WE lane, RT-PCR products from whole embryos were loaded. (C–P) Embryos were injected with sqt, cyc, activin (act), tarMR, tar*, RNA, or a combination as indicated, fixed at the shield stage, and analysed by in situ hybridisation with the marker indicated in the upper right corner. Animal pole views, dorsal to the right when it can be determined.