Somite positioning in the Mesp quadruple mutant. (A-F) Immunostaining of Tbx6 in wild-type, Mesp quadruple mutant and ripply1; ripply2 double mutant embryos fixed at the 1-somite stage (A-C) and 9-somite stage (D-F). In wild-type and Mesp quadruple mutant embryos, a clear anterior border of the Tbx6 protein domain is seen. In contrast, in the ripply1; ripply2 double mutant embryo, this domain has expanded anteriorly. (G-N) Expression of ripply1 (G,H,K,L) and ripply2 (I,J,M,N) in wild-type (G,K,I,M) and Mesp quadruple mutant (H,L,J,N) embryos. In the Mesp quadruple mutant, the expression of ripply1 in the anterior PSM is not affected, although expression in the somite region is severely reduced at the 1-somite stage (G,H; 100%; n=15) and 11-somite stage (K,L; 100%; n=14). Expression of ripply2 is not affected at the 1-somite stage (I,J; 100%; n=17) or 11-somite stage (M,N; 100%; n=15). (O-T) The effect of overexpression of mespba on the expression of ripply1 and ripply2 in embryos fixed at the 11-somite stage. In tbx6:ggff; uas:mespba double transgenic fish, the ectopic expression of mespba is detected in the mature somite region and anterior PSM (S,T; n=10; 100%). The expression of ripply1 at the anterior PSM is not affected by the overexpression of mespba, although the expression of somite region is strongly enhanced (O,P; 100%; n=11). The expression of ripply2 is not altered by the overexpression of mespba (Q,R,G,H; 100%; n=7). Scale bars: 50µm.
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