Highly efficient neural conversion of human ES and iPS cells by dual inhibition of SMAD signaling

Current neural induction protocols in human ES cells (hESCs) rely on embryoid body formation, stromal feeder co-culture, or selective survival conditions; each strategy displaying significant drawbacks such as poorly defined culture conditions, protracted differentiation and low yield. Here we report that the synergistic action of two inhibitors of SMAD signaling, Noggin and SB431542, is sufficient for inducing rapid and complete neural conversion of hESCs under adherent culture conditions. Temporal fate analysis reveals a transient FGF5(+) epiblast-like stage followed by PAX6(+) neural cells competent of rosette formation. Initial cell density determines the ratio of CNS versus neural crest progeny. Directed differentiation of human iPSCs into midbrain dopamine and spinal motoneurons confirm robustness and general applicability of the novel induction protocol. Noggin/SB431542 based neural induction should greatly facilitate the use of hESC and hiPSCs in regenerative medicine and disease modeling and obviate the need for stromal feeder or embryoid body based protocols.