Xenbase Image ID: 144602

Figure 5. The presumptive anterior endoderm confers anterior character to overlying ectoderm. (a) Schematic illustration of the experiment, showing the deep endoderm cells that were dissected and recombined with gastrula-stage ectoderm. At stage 9, a central region of vegetal tissue was isolated and recombined with ectoderm from early gastrulae. All recombinants were allowed to develop to late tadpole stages (stage 35) before analysis. (b) Dorsoanterior endoderm imparts an anterior character to recombined ectoderm. This was marked by cement gland formation (arrows). (c) Cement gland formation did not occur in combinations of ventral endoderm and ectoderm. (d) Central vegetal tissue from late blastulae (the XHex-expressing cells evident in Figure 1a,b) induced cement glands (arrows) when recombined with gastrula ectoderm. (e)XHex-expressing ventral endoderm behaved as dorsoanterior endoderm and induced cement gland formation (arrows). Ventral endodermal tissue was derived from Xenopus embryos injected at the one-cell stage with 0.5 ng XHex RNA. (f,g) Molecular analysis of endoderm–ectoderm recombinants by RT–PCR. Recombinants containing (f) stage 10 dorsoanterior endoderm, stage 9 central region endoderm and (g) XHex-expressing ventral endoderm (derived from embryos injected with 0.5 ng XHex RNA) expressed CG13, a cement-gland-specific marker. Note that gastrula endoderm recombinants do not express NCAM, Otx2 or MLC, demonstrating that they are not neural and that the endodermal tissue was not contaminated with dorsal mesoderm The absence of NCAM expression in lane 2 of (f) was confirmed in longer exposures of the gel (see Supplementary material). Isolated endoderm alone did not express CG13 (data not shown). In one experiment, the dorsal endoderm recombinants did express MLC, and in this case NCAM and Otx2 were also detected, presumably as a response to neural-inducing signals derived from contaminating dorsal mesoderm. Data are representative of results obtained when no dorsal mesoderm markers were detected. Stage 9 endoderm induced expression of MLC, but no neural markers were observed. Image published in: Jones CM et al. (1999) Copyright © 1999. Image reproduced with permission of the Publisher, Elsevier B. V. Larger Image Printer Friendly View

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