Fig. 4: Reduced N-cadherin expression increases free edge, promoting cell-independent behavior at the expense of collective directionality.

a–f Wild-type testis stained for N-cadherin, F-Actin and DAPI. a Overview of the testis base. Areas marked with dashed lines are magnified in b, c, e, and f, respectively. Scale bar: 50 µm. b On the genital disc myotubes appear epithelial. c, c’ At the front edge of the migrating sheet, N-cadherin localized in foci along filopodia (white arrowhead). d, e, e’ The same is true for cells within the sheet. f, f’ In rare cases, completely isolated cells without N-cadherin staining could be observed. b, c, e, f Scale bar: 10 µm. g Still images of myotubes expressing N-cad-EGFP. Arrowheads mark positions of N-cad-EGFP enriched cell–cell junctions. Scale bar, 10 µm. h Wild-type (WT) testis 33 h APF in ex vivo culture. Overview at t = 0 min at the left side. Scale bar: 50 µm. Time steps from 0 to 45 min in ex vivo culture. Scale bar: 20 µm. h’ Tracks of wild-type and i N-cadherin knockdown myotubes. Isolated myotubes are marked by yellow asterisk (t = 0 min, 45–60 min). Different colors represent individual cell tracks. i’ Tracks upon knock down of N-cadherin. Different colors represent individual cell tracks. j Wild-type and k N-cad RNAi myotubes. Scale bar: 20 µm. l–o Data are presented as mean values ± SD. *P ≤ 0.05, **P  ≤ 0.01, ***P  ≤ 0.001, ****P  ≤ 0.0001. l, m Graphical representation of the values is depicted. l The number of gaps between cells is significantly increased. N = 8 testes. Unpaired t test (two tailed). m As proxy for free edge, we used the perimeter of the white-to-black edge. Cell-free edge is significantly increased in N-cad RNAi animals. N = 8 testes. Kruskal–Wallis test. n Neighbor permanency is significantly reduced in N-cadherin knock down. o Quantification of the migration distance. N = 5 testes. One-way ANOVA. p, q Boxplot center: median. Bounds: 25th and 75th percentiles. Whiskers: minimum/maximum values. n, p, q N = 5 testes with 289 cells (WT), 304 cells (RNAi #1), and 291 cells (RNAi #2). Statistical testing: Kruskal–Wallis test. p Biased angle in regard to the testis axis was measured. q Quantification of track speed mean in µm/s.