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. 2010 Aug;2(8):a002055. doi: 10.1101/cshperspect.a002055

Figure 4.

Figure 4.

Wnts organize axon connections along the A-P axis at both the Drosophila and vertebrate midline. (A–C) Wnt5 and Drl regulate the choice of anterior or posterior commissure. AC axons (orange) express Drl, PC axons (blue) do not. Wnt5 accumulates on the PC and repels axons expressing Drl. These phenotypes are only partially penetrant. (D) Trajectory of the dorsal spinal cord commissural axons along the dorsal–ventral (D–V) and anterior–posterior (A–P) axes in a transverse view; (E) Spinal cord is splayed open along the dorsal midline, showing the 90o anterior turning right after midline (floor plate) crossing. Several Wnts are expressed at differential levels along the A–P axis in the floor plate (FP) and broadly in the spinal cord with an anterior-high posterior-low gradient. Frizzled3 is expressed in commissural neurons; (F) Randomized turning along the A–P axis when Wnt gradient is disrupted in the open-book explants by Wnt inhibitors (sFRPs), Wnt4-secreting cell clumps positioned caudal to the explants or in Frizzled3 knockout mice (Lyuksyutova et al. 2003).