Cas genes are required for normal fasciculation in vitro. (a–d) e13.5 DRG explants from WT animals cultured on 100 μg/ml poly-D-lysine plus different concentrations of laminin. Cells were visualized using Calcein-AM. (e) Quantification of in vitro DRG phenotypes presented as percentage of explants that display webbing (black bars) vs. percentage of explants with normal morphology (gray bars). There is a significant difference in the webbing percentages under different culture conditions (Freeman-Halton extension of the Fisher exact probability test, p = 4.94e-8; 9–16 explants for each condition). (f–g) DRG explants from control (f) and HtPACre; TcKO (g) embryos cultured on 100 μg/ml poly-D-lysine and 5 μg/ml laminin. Cells were visualized using Calcein-AM. The proportion of explants from each genotype displaying webbing is shown at the lower left corner of each panel. HtPACre; TcKO explants display an abnormal “cobweb” morphology (g), similar to WT explants cultured on poly-D-lysine alone (d). (h) Percentage of explants that display webbing (black bars) vs. percentage of explants with normal morphology (gray bars). The difference in the proportion of WT and HtPACre; TcKO explants that display the cob-web phenotype is highly significant (two-tailed Fisher exact test, p = 7.47e-7; 12–15 explants for each genotype). Scale bars 200 μm.