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. Author manuscript; available in PMC: 2016 Jul 1.
Published in final edited form as: Wiley Interdiscip Rev Dev Biol. 2015 Mar 16;4(4):377–389. doi: 10.1002/wdev.185

Figure 2. Commissural axons switch the polarity of their response to Shh.

Figure 2

Pre-crossing spinal commissural neurons signal attraction to midline-derived Shh through the receptor Boc. These neurons turn anteriorly after they have crossed the midline, in response to a posterior high to anterior low gradient of Shh, but the relevant Shh receptor is not known. 14-3-3 is specifically expressed in post-crossing commissural neurons and is required for Shh-dependent repulsion, but not attraction. Both attractive and repulsive Shh signaling depend on Smo, but it is not clear whether the Shh co-receptor Patched, which relieves repression of Smo to permit Shh signaling in other contexts, is required for Shh-dependent attraction or repulsion.