Fig. 5. Xsix3 and Bmp4 repress each other. (A-Q) Control and injected embryos, and animal caps, were analysed at stage 13 for the expression of the genes indicated. (A-C) Xsix3 overexpression represses Bmp4 expression in embryos (A) and animal caps (C), whereas uninjected caps (B) strongly express Bmp4. (D) Xsix3 is repressed in embryos injected with Bmp4. (E) tBR injection expands the Xsix3 expression domain. (G-I) Animal caps injected with tBR (H) or Chordin (I) strongly express Xsix3, whereas uninjected caps (G) do not express Xsix3. (J,K) MoXsix3- and VP16-Xsix3-injected embryos display anterior expansion of Bmp4 (the white dots indicate the anterior neural plate border). (L,M) VP16-Xsix3 and Bmp4 injection induces apoptosis (TUNEL staining) in the anterior neural plate. (N,O) MoXsix3 reduces (N) and tBR expands (O) the domain of Zic2 expression. (P,Q) Zic2 repression is rescued in embryos co-injected either with MoXsix3 and tBR (P, compare with N), or with MoXix3 and Xsix3 (Q, compare with N).