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Figure S6. Control embryos. Lineage tracing of dye injected cells (A-D). A mixture of LY in LiCl (A and B), or in Na (C and D) with dextran-rhodamine was injected into one dorsal blastomere of 32-cell stage embryos. Some of the injected embryos were fixed 10 min later and analyzed on frozen sections for LY transfer (not shown). Dye injected cells of sibling embryos cleaved normally. At the tadpole stage, some embryos were fixed and analyzed by fluorescence microscopy. Descendants of the injected cells are seen in the head and notochord of each embryo labeled with LY (A and C) and dextran-rhodamine (B and D). Controls for dorsal and ventral injections (E and F). LY and dextran-rhodamine was injected at the 32-cell stage into one dorsal (E) and one ventral (F) animal cell. Some of the injected embryos were fixed 10 min later and analyzed on frozen sections for LY transfer (not shown). Embryos developed normally and swimming tadpoles show either notochord and head fluorescence (E) or gut fluorescence (F). Controls for the detection of neurobiotin (G and H). Embryos at the 64-cell stage were coinjected with dextran-biotin and dextran fluorescein. Colocalization of the fluorescence indicates that neither free fluorescein nor free biotin were released from dextran complexes during the analysis of dye transfer. Bar, 200 µm. Alterations in the dorso-ventral axis of embryos whose siblings were analyzed in dye transfer assays (I-M). Normal embryos (I). Ventralized embryos by exposure of fertilized eggs to UV irradiation (J). Dorsalized embryos were generated by injection of Xwnt-8 RNA into two vegetal blastomeres at the 4-cell stage embryo (K). Normal embryos (L), their dorsalized siblings were generated by vegetal injection of Xwnt-8 RNA before the first cell cleavage (M).