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Fig. 9. Irx1 and Irx3 are positively regulated by retinoic
acid signalling. Embryos are shown in lateral views and red arrowheads
indicate the kidney territory. Embryos were injected in a single blastomere
(V2.2) at the 8- to 16-cell stage and lacZ mRNA was used as linear
tracer. All panels show Xenopus tadpole embryos.
(A,B,E,F) Embryos injected with a dominant
negative RA receptor mRNA (RAR-DN) showed impaired Irx1 (A,B) and
Irx3 (E,F) expression. (C,D,G,H). Embryos
injected with a constitutive RA receptor mRNA (RAR-VP16) showed a strong
expansion of Irx1 (C,D) and Irx3 (G,H) expression.
(I-Y) Embryos treated at different developmental stages (as indicated)
with DMSO (I,M,Q,U), with the inhibitor of RA signalling pathway DEAB
(J-L,R-T) or with RA (N-P,V-Y), and analyzed for Irx1 (I-P) or
Irx3 (Q-Y) expression. Both genes negatively or positively responded
to DEAB (J,R) or RA (N,V), respectively, only when the drugs were added at
stage 12.5.