Mahony D , Gurdon JB .

Wellcome Trust

	FIG. 1. Nucleotide sequence and the deduced amino acid sequence of the XTrR-I clone. The N-terminal hydrophobic signal sequence and transmembrane domain are overlined (thin lines; aa 1-18 and 123-144, respectively) and the putative N-glycosylation site is underlined (thick line; aa 39-41). The beginning and end of the kinase domain (aa; 204-495) are indicated by arrows. The cysteine residues in the extracellular domain are boxed and shaded, and a glycine/serine-rich sequence (aa 173-199) is boxed by a thick line. The PCR primers that were used are shown by half arrows (aa 226-231, 328-332, and 375-379), and the end of the open reading frame is marked with an asterisk (aa 500).
	FIG. 2. RNase protection analysis of XTrR-I expression in development. (a) RNase protection analysis of XTrR-I mRNA levels in whole embryos at early stages of development: stage 1, egg; stage 6, morula; stage 8, midblastula; stage 9½/2, late blastula; stage 11, early gastrula; stage 14, midneurula; and stage 26, tail bud. The stage numbers refer to developmental stages of Xenopus (38). The FGF-receptor (FGF-R) is used as a loading control. (b) RNase protection analysis of XTrR-I RNA in animal caps (An), marginal zones (MZ), and vegetal poles (Veg) at the early gastrula stage of development. An X-brachyury (Xbra) analysis of the same material shows that the animal cap and vegetal pole explants are largely free of contaminating mesodermal tissue. (c) RNase protection analysis of XTrR-I RNA in dorsal mesoderm (D), dorsolateral mesoderm (DL), and ventral mesoderm (V) at the early gastrula stage of development.
	FIG. 3. Injection of XTrR-I mRNA into the ventral side of 4-cell embryos causes ectopic muscle expression in the ventral region. (a) Embryo injected in the ventral side with 6 ng of ,3-galactosidase mRNA and stained with the muscle antibody 12/101. (b) Embryo injected in the ventral side with 6 ng of XTrR-I mRNA and stained with 12/101. (c) Section of an .t^ embryo injected with 6 ng of XTrR-I mRNA and stained with 12/101.
	FIG. 4. Injection of XTrR-I mRNA into the lateral region of a 2-cell embryo increases the size of the notochord. (a) Notochord antibody MZ 15 was used to stain an embryo injected in the lateral region with 6 ng of 13-galactosidase mRNA (Upper) and an embryo injected with 6 ng of XTrR-I mRNA (Lower). (b) Section of an embryo injected laterally with 6 ng of 13-galactosidase mRNA and stained with MZ 15. (c) Section of an embryo injected laterally with 6 ng of XTrR-I mRNA and stained with MZ 15.
	FIG. 5. Injection of XTrR-I mRNA into UV-treated embryos creates a partial dorsal axis. Ventralized embryos were produced by UV irradiation 25 min after fertilization. After irradiation, 6 ng of XTrR-I mRNAwas injected into one blastomere at the 2-cell stage. (a) Uninjected, UV-treated embryo. (b) UV-treated embryo injected with 6 ng of XTrR-I mRNA. (c) Control, uninjected, untreated, sibling embryo.

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