Fig. 7

The Chemokine Receptor cxcr4a Demarcates the Border of the Eye Field and Telencephalon Downstream of BMP and Rx3(A–D) Cxcr4a expression in rx3^/ or sib at 80% epiboly (A and B) and at bud stage in sib (C) and rx3^/ (D) embryos. Sdf1b/rx3 double in situ at 80% epiboly/midgastrula stage (E) and four-somite stage (4s) (F). Inset in (E) shows a sagittal section of the boxed area, anterior to the left.(G–J) Cxcr4a transcript expression (red) in dnBMPr transgenic mosaics (green in G and H) and caBMPr transgenic mosaics (green in I and J) at bud stage. (G and H) Close-up of the boxed area marked in the inset. (I and J) Repression of cxcr4a expression in caBMPr-overexpressing cells.(K–N) Cross-section at medial A-P level of the eye field (dashed line in the insets in K and L). Segregation of rx3 (blue) and emx3 (red) expression domains in WT (K and M) and cxcr4a^um20+/ x cxcr4a^um20+/ crosses (L and N; n = 14/61) at four-somite stage. Dotted lines mark the border of emx3-expressing cells as defined by fluorescent images (M and N).(O) A model of the genetic network leading to formation of the eye and telencephalon. Blue arrows demonstrate the present work. Dotted-arrow line indicates that Rx3 is not essential for induction but for maintenance of cxcr4a expression.