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Fig. 3. VEGF expression is a marker for prehypochord cells. All embryos are assayed by in situ hybridization for VEGF transcripts. (A,B) Cross sections through stage-24 embryos at the level of the trunk, posterior to the pronephric tubules. Expression of VEGF can be seen in the nucleus of a hypochord precursor cell in the dorsalmost endoderm. n, notochord; s, somites; e, endoderm.
(C) Frontal section through the ventral notochord (arrows) of a stage- 24 embryo. No VEGF expression is visible in the notochord cells. Anterior to the right. (D) Same embryo as C, showing VEGF expression in the cells of the endoderm immediately ventral to the notochord (marked by arrows). Anterior is to the right. (E) Whole- mount in situ hybridization for VEGF in the mature hypochord (arrowheads). Notice declining expression in the anterior portion of the hypochord (large arrow), while expression in the posterior portion of the hypochord remains abundant (small arrow). Prominent staining is also visible in the somite nuclei and the pronephros. |
