Figure 5

Ventral shift of gene expression along the D-V axis of the optic cup after BMP4 treatment. Beads are indicated with asterisks and domains of gene expression are demarcated with arrows. (A) Post-culture embryo showing normal dorsal Tbx5 expression in the control optic cup. (B) Contralateral BMP4-treated eye, showing extension of the Tbx5 expression domain. (C) Post-culture embryo showing normal dorsal Tbx2 expression in the control BSA-treated optic cup. (D) Contralateral BMP4-treated eye, showing extension of the Tbx2 expression domain into the ventral optic cup and induction of expression in the lens. (E) Post-culture embryo showing normal dorsal Tbx3 expression in the control BSA-treated optic cup. (F) Contralateral BMP4-treated eye, showing induction of Tbx3 expression throughout the ventral optic cup. (G) Post-culture embryo showing normal ventral expression of Vax2 in the control BSA-treated optic cup. (H) Contralateral BMP4-treated eye, showing complete absence of Vax2 expression. (I, J) Double in situ hybridisation of Tbx2 expression (red) and Vax2 expression (blue) in control BSA-treated (I) and contralateral BMP4-treated eyes (J). (K-N) Transverse sections through the planes indicated in I and J, showing induction of ectopic Tbx2 expression (K, L) and repression of Vax2 expression (M, N) upon BMP4 treatment. (O) Schematic representation of gene expression domains 1–4 along the D-V axis of the whole mount optic cup and the ventral shift of domains upon BMP4 treatment. Domain 3* is Tbx2-negative, Tbx3-positive, Vax2-negative. Scale bars: A-J, 0.5 mm; K-N, 0.1 mm. Abbreviations: L, lens vesicle; MN, mandibular process of the first branchial arch; MX, maxillary process of the first branchial arch; NR, neural retina.