Figure 1.
Figure 1. Syb2 is not necessary for Sema3C-mediated attraction, but is essential for Sema3A-mediated repulsion in cortical explants. (A) Scheme of areas quantified for each explant. P, proximal area; D, distal area; T, areas perpendicular to the gradient where turning angles were measured; Exp, cortical explant. (B) E15 cortical explants were grown in front of mock-, Sema3C-, or Sema3A-secreting cell aggregates with or without BoNT/D in the culture medium. Bar, 200 µm. (C) Axons in the areas perpendicular to the gradient were analyzed and their angles to the explants measured in different guidance conditions with or without toxin. (D) Ratio of maximal axonal lengths between proximal (P) and distal (D) areas in different guidance conditions with or without toxin (error bars indicate SEM; control, n = 44; control + BoNT/D, n = 45; Sema3C, n = 43; Sema3C + BoNT/D, n = 54; Sema3A, n = 33; Sema3A + BoNT/D, n = 50 explants). (E) Mean ± SEM values (error bars) of turning angles in the different guidance conditions with or without toxin (control, n = 716; control + BoNT/D, n = 744; Sema3C, n = 191; Sema3C + BoNT/D, n = 172; Sema3A, n = 412; Sema3A + BoNT/D, n = 486 axons). (F) E15 cortical explants from Syb2+/+, Syb2+/−, and Syb2−/− embryos were grown in front of mock-, Sema3C-, or Sema3A-secreting cell aggregates. Bar, 200 µm. (G) Axons in the areas perpendicular to the gradient were analyzed and their angles to the explants measured in the different conditions and genotypes. (H) Mean ± SEM (error bars) of the ratio of proximal over distal axonal length in different conditions and genotypes (control: Syb2+/+, n = 69; Syb2+/−, n = 125; Syb2−/−, n = 117; Sema3C: Syb2+/+, n = 43; Syb2+/−, n = 56; Syb2−/−, n = 54; Sema3A: Syb2+/+, n = 40; Syb2+/−, n = 88; Syb2−/−, n = 78 explants). (I) Mean values ± SEM (error bars) of turning angles in different conditions and genotypes (control: Syb2+/+, n = 641; Syb2+/−, n = 1,164; Syb2−/−, n = 945; Sema3C: Syb2+/+, n = 347; Syb2+/−, n = 542; Syb2−/−, n = 641; Sema3A: Syb2+/+, n = 344; Syb2+/−, n = 416; Syb2−/−, n = 715 axons). ***, P < 0.0005 by Student’s t test.

Syb2 is not necessary for Sema3C-mediated attraction, but is essential for Sema3A-mediated repulsion in cortical explants. (A) Scheme of areas quantified for each explant. P, proximal area; D, distal area; T, areas perpendicular to the gradient where turning angles were measured; Exp, cortical explant. (B) E15 cortical explants were grown in front of mock-, Sema3C-, or Sema3A-secreting cell aggregates with or without BoNT/D in the culture medium. Bar, 200 µm. (C) Axons in the areas perpendicular to the gradient were analyzed and their angles to the explants measured in different guidance conditions with or without toxin. (D) Ratio of maximal axonal lengths between proximal (P) and distal (D) areas in different guidance conditions with or without toxin (error bars indicate SEM; control, n = 44; control + BoNT/D, n = 45; Sema3C, n = 43; Sema3C + BoNT/D, n = 54; Sema3A, n = 33; Sema3A + BoNT/D, n = 50 explants). (E) Mean ± SEM values (error bars) of turning angles in the different guidance conditions with or without toxin (control, n = 716; control + BoNT/D, n = 744; Sema3C, n = 191; Sema3C + BoNT/D, n = 172; Sema3A, n = 412; Sema3A + BoNT/D, n = 486 axons). (F) E15 cortical explants from Syb2+/+, Syb2+/−, and Syb2−/− embryos were grown in front of mock-, Sema3C-, or Sema3A-secreting cell aggregates. Bar, 200 µm. (G) Axons in the areas perpendicular to the gradient were analyzed and their angles to the explants measured in the different conditions and genotypes. (H) Mean ± SEM (error bars) of the ratio of proximal over distal axonal length in different conditions and genotypes (control: Syb2+/+, n = 69; Syb2+/−, n = 125; Syb2−/−, n = 117; Sema3C: Syb2+/+, n = 43; Syb2+/−, n = 56; Syb2−/−, n = 54; Sema3A: Syb2+/+, n = 40; Syb2+/−, n = 88; Syb2−/−, n = 78 explants). (I) Mean values ± SEM (error bars) of turning angles in different conditions and genotypes (control: Syb2+/+, n = 641; Syb2+/−, n = 1,164; Syb2−/−, n = 945; Sema3C: Syb2+/+, n = 347; Syb2+/−, n = 542; Syb2−/−, n = 641; Sema3A: Syb2+/+, n = 344; Syb2+/−, n = 416; Syb2−/−, n = 715 axons). ***, P < 0.0005 by Student’s t test.

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