Analysis of Cas gene requirement in the DRG. (a–b) Wholemount neurofilament immunostaining of control (a) and HtPACre; TcKO embryos (b). Sideview of e12.5 spinal cords stained with 2H3. The defasciculation of DRG central projections observed in HtPACre; TcKO embryos (b) resembles that of Wnt1Cre; TcKO embryos (Fig. 5). (c–d) Transverse vibratome sections through e11.5 Control (c) and HtPACre; TcKO (d) spinal cords at thoracic level stained using an antibody against neurofilament (2H3, red). Nuclei were counterstained with ToproIII (blue). Sensory axons prematurely invade the spinal cord gray matter of HtPACre; TcKO animals (d, white arrows). Gray arrowheads: DREZ. (e) Quantification of free axon terminals (ATs) per spinal hemisegment, visualized from the side. Two-tailed t-student test ***p = 1.26e-19, 4–5 thoracic segments per animal, 5 animals for each genotype. (f) Quantification of number of axons invading the spinal cord per section. Two-tailed t-student test ***p = 1.76e-25. 5 thoracic sections per animal, 5 animals for each genotype. Error bars represent SEM. (g–h) Dorsal whole-mount view of e14.5 limbs stained with NF200. Select axonal branches that innervate the digits appear hyperfasciculated in HtPACre; TcKO (h) hindlimbs (black arrows). Fluorescent images were inverted to facilitate visualization. n = 6 limbs per genotype. Scale bars: 200 μm for (a,b); 100 μm for (c,d), and 250 μm for (g,h).