Members of the Ngn family are basic-helix–loop–helix transcription factors that regulate many aspects of neural development [22]. Ngn2 regulates the commitment of neural progenitors to neuronal fate during development [23–25] and is sufficient to induce early postnatal astroglia into neurons [26]. Although overexpression of Ngn2 in human [19–21] and mouse [27] pluripotent stem cells is sufficient to induce excitatory neurons, Ngn2 also has a critical role in specifying motor neuron identity during spinal cord development [28,29]; in fact, overexpression of Ngn2 together with Islet-1 and Lhx3 can induce motor neurons from human pluripotent stem cells [30]. Moreover, overexpression of Ngn2 and Sox11 induces fibroblasts into cholinergic neurons [31], while γ-aminobutyric acid (GABA)-ergic neuronal differentiation is inhibited by Ngn2 overexpression [32].
