Inhibitory synaptic events would be expected given the preponderance of inhibitory medium spiny neurons in the striatum.

Accordingly, inhibitory postsynaptic currents could also be elicited by extracellular stimulation, confirming that the transplanted neurons received abundant inhibitory synaptic inputs from the surrounding neurons in the striatum (Figure 6H). Previous studies demonstrated the principal feasibility of converting nonneuronal human cells into iN cells but also described a low conversion efficiency and a diminished capacity of the resulting iN cells for synapse formation (Pang Carfilzomib et al., 2011; Ambasudhan et al., 2011; Qiang et al., 2011; Pfisterer et al., 2011a, 2011b; Yoo et al., 2011; Caiazzo et al., 2011; Son et al., 2011). However, realization AZD2014 concentration of the potential of iN cells for studying the pathogenesis of neurological diseases, for developing drug screening systems, and for producing neurons for regenerative medicine requires the capability of producing human iN cells at a large scale and high yield and necessitates the generation of iN cells that readily form synapses. Moreover, such goals would be facilitated by a high degree of reproducibility of iN cell generation independent of the starting cell line and

by production of a relatively homogeneous population of GPX6 functional iN cells for experiments. In the present study, we describe a new, highly effective method that generates a homogeneous population of iN cells by forced expression of a single transcription factor in ESCs or iPSCs. We demonstrate that the new method results in the reproducible generation of the same type of neuron with quantitatively the same properties independent of the ESC or iPSC line used. The entire procedure generates iN cells in only a few weeks, allowing a rapid turnaround of experiments, and the resulting iN cells exhibit short-term plasticity, are modulated at the level

of their synapses, and integrate into neuronal networks when transplanted into the mouse brain. Moreover, the new iN cells can be used for studying synaptic properties including plasticity, for large-scale Ca2+imaging (e.g., for drug screening purposes), and for disease modeling as exemplified in our Munc18-1 KD experiments. Thus, we believe that the approach described here has the potential to enable mechanistic and translational studies on human neurons that exceed currently existing capabilities and hope that the simplicity of the approach will allow its wide dissemination. Table 1 shows a comparison of the properties of the method described here with selected other widely used methods to illustrate the advantages and disadvantages of the various approaches that have been described.