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. 2011 Sep 28;5:62. doi: 10.3389/fnana.2011.00062

Figure 4.

Figure 4

Wnt5a gradients simultaneously increase axon outgrowth and induce repulsive axon turning. (A,B) Time lapse images of a cortical axon and its growth cone at the beginning and end of a 1-h exposure to a point source of BSA (control) (A) or 10 μg/ml Wnt5a (B) emitted by the pipette at right. The axon extends straight in the BSA gradient but is repelled by the Wnt5a gradient. Right, tracings of trajectories of individual axons extending during 1 h exposure to BSA (n = 20 axons) or Wnt5a gradients (n = 25 axons) showing random turning in the presence of BSA and repulsive turning in response to Wnt5a. Note that axons repelled by Wnt5a are also significantly longer. (C) Cumulative distribution of turning angles of axons showing random turning in BSA and repulsive turning in Wnt5a gradients. (D) Bar graphs comparing average turning angles and average axon outgrowth rates in BSA and Wnt5a. In all experiments, neurons were obtained from P2 pups and cultured for 2–3 day before the turning assays. Scale bar, 5 μm. In all histograms, **p < 0.01. (Reprinted from Li et al., 2009; with permission from the Society for Neuroscience).