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Fig. 8 Excess ntl mutant floor plate cells originate from a fate map position corresponding to the wild-type notochord domain. Caged fluorescein fate mapping (see Materials and Methods and text) was used to determine fates of dorsal marginal cells of ntl– embryos. (A) The fluorophore was uncaged in the early gastrula in a small population of approximately 20 dorsal marginal cells of wild-type embryos and embryos depleted of ntl function (using ntl-MO). (B-E) Uncaged fluorescein label was detected at 24 hpf by fluorescence (B,C) and/or using anti-fluorescein antibody (D,E). Representative examples of deep layer cell (DEL) fates are shown. (B,D) In control wild-type embryos, the fluorophore was always detected in large populations of notochord cells, occasionally in hatching gland, and only rarely in floor plate. (C,E) In ntl-depleted embryos, the fluorophore was detected in large numbers of floor plate cells. See text for details. Scale bars: 50 μm, in A for A-C and in D for D,E.