Cas adaptor proteins are required for the fasciculation of DRG central projections. (a–d’) Whole embryo immunostaining for neurofilament (2H3, green) at e12.5, from a side view (a,c) or a dorsal view (b,d,d’). d’ shows a higher magnification view of the dotted area in d. The centrally projecting DRG axons are severely defasciculated as they enter the spinal cord (yellow arrows). n = 6 per gentoype; presented phenotypes displayed 100% penetrance. (e) Quantification of free axon terminals (ATs) per spinal hemisegment, visualized from the side. Two-tailed t-student test ***p = 9.05e-24, 3–5 thoracic segments per animal, 6 animals for each genotype. (f–g) Transverse vibratome sections through e11.5 Control (f) and Wnt1Cre; TcKO (g) spinal cords at forelimb level stained using an antibody against neurofilament (2H3). Sensory axons invade the spinal cord gray matter prematurely in Wnt1Cre; TcKO animals (g, white arrows). Gray arrowheads: DREZ. (h) Quantification of number of axons invading the spinal cord per section. Two-tailed t-student test ***p = 3.82e-26. 5 sections per animal, 5 animals for each genotype. Error bars represent SEM. Scale bars: 100 μm for (a,c); 200 μm (b,d); 66.7 μm for (d’); and 50 μm for (f,g).