the GCL showed that majority of these grafted cells (>80%) stained positive for the neuronal marker, TUJ1, and ∼40% were also positive for the DG granule neuron marker, PROX1 (Figure 5B). These grafted neurons had cell bodies within the GCL and branching processes in the molecular layer, which is the region of their inputs from the perforant path. They also sent extensive processes, as labeled by human neurofilament (Steinbeck et al., 2012), to the CA3 regions along the mossy fiber path (Figure 5D). These grafted neurons demonstrated remarkable changes in morphological complexity between 2 and 6 weeks posttransplantation (Figures 5I and 5J). Quantitative analysis of the development of these neurons in vivo using Neurolucida morphometrics revealed significant increases in the soma size, total dendrite length, and branching at 6 weeks compared to 2 weeks posttransplantation, indicating that the transplanted hippocampal NPCs were able to engraft and develop in the DG in vivo (Figures 5K and 5L). Whole-cell patch-clamp recordings of transplanted neurons at 6 months postsurgery showed transient sodium inward current and sustained potassium outward currents induced by voltage step depolarization (Figure 5E) as well as action potential firing following somatic current injections (Figure 5F). Furthermore, these neurons demonstrated spontaneous
