Figure 5: Outgrowth-promoting effects of draxin on thalamic axons.

(a) Draxin-AP binding in coronal sections from E14.5 brains of wild-type mice. The draxin-AP signal was observed in the intermediate zone of the neocortex (arrowhead) and the internal capsule (arrow). Scale bar, 500 μm. (b) Draxin-AP bound to the majority of neurites extending from dissociated neurons of the neocortex (CTX), anterior dorsal thalamus (anterior DT) and posterior dorsal thalamus (posterior DT) of E14.5 wild-type mice. Arrows indicate draxin-AP binding to the growth cones of dissociated neurons. In contrast, control-AP did not bind to neurites from these neurons (arrowheads). Scale bar, 50 μm. (c) Dissociated cultures of thalamic neurons with different concentrations of draxin-AP proteins showed that neurite outgrowth was promoted by low draxin concentrations and inhibited by high draxin concentrations. Error bars are s.e.m. (n=5 independent experiments). *P<0.05 and **P<0.01 by Welch’s t-test. Scale bar, 100 μm. (d) Dissociated cultures of thalamic neurons on neocortical neurons prepared from wild-type, draxin^−/− and Ctx-draxin mice. Neurite outgrowth was reduced in thalamic neurons cultured on draxin^−/− neocortical neurons compared with that in thalamic neurons cultured on wild-type neocortical neurons. This decreased neurite outgrowth was significantly rescued when thalamic neurons were cultured on Ctx-draxin neocortical neurons. Error bars are s.e.m. (n=3 independent experiments). **P<0.01 by one-way analysis of variance followed by Tukey’s honest significance test. Scale bars, 100 μm.