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. 2017 Oct 30;10:346. doi: 10.3389/fnmol.2017.00346

Figure 6.

Figure 6

On laminin-111 BDNF is dispensable for axon growth and F-actin assembly in growth cones. (A) Representative images of trkBTK+/+ and trkBTK−/− motoneurons cultured on laminin-111 for 7 days in vitro and stained against tau (scale bar: 150 μm). TrkB mutant motoneurons (357.2 ± 29.33 μm, Q2 363 μm, n = 8, N = 579) grew shorter axons (p = 0.0417) in comparison to wild type controls (468.8 ± 39.31 μm, Q2 454.9 μm, n = 9, N = 615). (B) Representative images of axonal growth cones of trkBTK+/+ and trkBTK−/− motoneurons cultured for 5 days in vitro on laminin-111 and stained against β-actin (green), F-actin (yellow), and tau (magenta) (scale bar: 5 μm). (C) TrkBTK−/− motoneurons (16.55 ± 1.26 μm2, Q2 17.12 μm2, n = 11, N = 178) developed significantly smaller growth cones (p = 0.0132) than the corresponding controls (27.51 ± 4.58 μm2, Q2 25.06 μm2, n = 7, N = 113). There were no significant alterations between both genotypes with respect to β-actin, F-actin and tau levels. (D) Representative images of wild type motoneurons cultured on laminin-111 for 7 days in vitro with BDNF, CNTF or GDNF and stained against tau (scale bar: 150 μm). There was no difference in axonal elongation between each neurotrophic factor (BDNF 425.3 ± 14.93 μm, Q2 423.3 μm, n = 5, N = 256; CNTF 439.0 ± 18.37 μm, Q2 439.9 μm, n = 6, N = 258; GDNF 388.6 ± 24.47 μm, Q2 412.1 μm, n = 5, N = 273; p(B-C) = 0.8710, p(B-G) = 0.4295). (E) Representative images of axonal growth cones of motoneurons cultured on laminin-111 for 5 days in vitro in the presence of BDNF, CNTF or GDNF and stained against F-actin (magenta) and tau (green) (scale bar: 5 μm). (F) There was no significant difference in growth cone size between each condition (BDNF 32.83 ± 4.93 μm2, Q2 29.04 μm2, n = 6, N = 165; CNTF 33.01 ± 4.41 μm2, Q2 30.96 μm2, n = 6, N = 175; GDNF 37.85 ± 4.72 μm2, Q2 38.52 μm2, n = 6, N = 172; p(B-C) = 0.9996, p(B-G) = 0.7352). Furthermore, F-actin (BDNF 1.00 ± 0.02, Q2 1.00, IQR 0.04, n = 6, N = 165; CNTF 1.14 ± 0.22, Q2 0.95, IQR 0.97, n = 6, N = 175; GDNF 0.99 ± 0.28, Q2 0.79, IQR 1.02, n = 6, N = 172; p(B-C) > 0.9999, p(B-G) > 0.9999) and tau levels appeared not altered.