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Fig. 2 Dominant-negative Sox3 constructs induce ectopic expression of bozozok and axis duplication. (A) Effect of Sox3 mutants as compared with WT Sox3 (a) on boz expression by RNA injection at the 1- to 2-cell stage and analysed at 4.5 hpf. Animal pole view, dorsal to the right, except Ab for which orientation cannot be certain. Injection of WT Sox3 caused loss of boz expression (b). Neither Sox3N40I (c) nor Sox3dNLS (d) repressed endogenous boz expression, but caused ectopic expression of boz in the majority of embryos. (B) Analysis 24 hours after injection showed that Sox3dNLS caused various extents of axis duplication, as shown by analyzing the expression of ncad (cdh2) (a-a′), hoxb1b (b-b′), shh (c-c′) and krox20 (egr2) (d-d′). (C) The percentage of embryos of each duplication phenotype following injection of Sox3dNLS RNA (n=279). Scale bars: ∼200 μm.