area compared to those of the wild type littermates, particularly in the ventral horn (LVI-VIII) and in the deep dorsal horn (LIV-V). Superficial dorsal horn (LI-III) and motor pools (LIX), however, appear relatively normal (Figures 2B–B” and S2B). Consistently, the most severe neuronal loss was detected in the ventral horn and to a lesser extent in the deep dorsal horn (~70% and ~50%, respectively). We also observed ~30% interneuron cell loss in the superficial dorsal horn, which was not reported previously. By contrast, motor neuron (LIX) counts in both mutants are the same as those in wild type controls (Figures 2H and S2B). As expected, Pcdhgtako/tako spinal cords are indistinguishable from the wild type controls, and neuronal cell counts in each of the 4 specified regions are normal (Figure S2B).
