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Fig. 3. HI-Xmsx-1 induces head organizer marker genes in the ventral endomesoderm. Two ventral blastomeres of 4-cell-stage embryos were coinjected marginally with 100 pg of HI- or TI-Xmsx-1 mRNA and 50 pg of β-galactosidase mRNA as a lineage tracer, then processed for RT-PCR (A) and whole-mount in situ hybridization (B) at stage 10.25. (A) The ventro-vegetal quarter of the embryos injected with the indicated mRNA (top, lanes 1, 2, 3) was dissected at stage 10.25 and RNA was extracted immediately, for early stage, or after being cultured until sibling embryos reached stage 18, for late stage. RNA extracted from each explant was analyzed by RT-PCR. Lane 4 shows the expression of each marker in whole embryos and lane 5 shows the control reactions with no RT step. (B) The injected embryos were stained by red Gal for lineage tracing and then analyzed by whole-mount in situ hybridization for Xotx-2, Xhex and cerberus gene expression. Anterior organizer genes were induced in the ventral endomesoderm. The dorsal blastopore lip is indicated by black arrowheads. Arrows indicate the RNA-injected ventral marginal zone, in which the nuclei of cells are stained red. AS, antisense probe; S, sense probe. |
