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. Author manuscript; available in PMC: 2008 Nov 25.
Published in final edited form as: Dev Dyn. 2008 May;237(5):1359–1372. doi: 10.1002/dvdy.21536

Figure 6. The MHB is initially established but can not be sustained without SHH.

Figure 6

A, B E9 Embryos shown in sagittal view with rostral to the right. The non-overlapping expression of Otx2 (blue) and Gbx2 (brown) demonstrates that a spatially coherent MHB is initially established in the Shh-/- mouse (B) and its wild-type littermate (A). C-J. Wholemounts with rostral to the top, ventricular surface facing the reader. C, D. Wnt1 (blue) and Fgf8 (brown) domains are correctly established and segregated in the Shh-/- mouse (D) and its wild-type littermate (C) at E9. Note that the continuous expression of Wnt1 and Fgf8 across the ventral midline reflects a loss of ventral midline structures by this age. E, F. Wnt1 expression at the MHB is broadened in the E10.5 Shh-/- mouse (F) compared to the wild-type (E). Inset shows Wnt1+ cells scattered several cell diameters (arrow) away from the MHB. G-J. Wnt1 (G, H) and Fgf8 (I, J) expression in control (G, I) and Shh-/- brains (H, J) demonstrating that the MHB in the Shh-/- mouse is severely disrupted and displays a near complete loss of Wnt1 (H) and a complete loss of Fgf8 by E12.5 (J). A morphological constriction can be seen between the midbrain and hindbrain in the Shh-/- mutant in J (arrowhead). K-N. E12.5 embryos shown in sagittal view with rostral to the right. Otx2 (K, L) and Gbx2 (M, N) expression in the midbrain showing that the sharp boundary formed by Otx2 at the wildtype MHB (K) is maintained in the Shh-/- mouse (L) and that Gbx2+ hindbrain cells are never seen in the midbrain of wildtype (M) or the Shh-/- (N) mouse. Arrowheads in J, L and N mark the boundary between the midbrain and hindbrain. Abbreviations: HB: hindbrain; MB: midbrain; MHB: midbrain-hindbrain boundary; rFP: rostral floor plate.