Stem cells are thought to hold great potential for improving our understanding and thus for developing treatment for many diseases1. Takahashi and Yamanaka (2006) made a remarkable breakthrough in stem cell research when they generated ES-like cells from adult somatic cells using a cocktail of transcription factors2–5. More recently, new methods have been developed to reprogram adult somatic cells (such as fibroblasts) into pluripotent cells (iPSCs). This development has made it possible to generate patient-specific cells for the treatment of various diseases and disorders6,7. The advantage of patient-specific cells is that the cells could have the patient’s genetic background without any modification and are therefore not likely to be rejected by the immune system of the patients when transplanted. As iPSCs are derived from adult somatic cells, the ethical concerns of human embryo use do not apply. The possibility of creating neuronal cultures from human stem cells, particularly from human-induced pluripotent stem cells (hiPSC), originating from a patient, has received wide attention for the potential to create translatable disease-in-a-dish models. Following the discovery of iPSCs, several studies have fueled enthusiasm
