Differential BMP signaling controls formation and differentiation of multipotent preplacodal ectoderm progenitors from human embryonic stem cells.

Sensory and endoneurocrine tissues as diverse as the lens, the olfactory epithelium, the inner ear, the cranial sensory ganglia, and the anterior pituitary arise from a common pool of progenitors in the preplacodal ectoderm (PPE). Around late gastrulation, the PPE forms at the border surrounding the anterior neural plate, and expresses a unique set of evolutionarily conserved transcription regulators including Six1, Eya 1 and Eya2. Here, we describe the first report to generate and characterize the SIX1(+) PPE cells from human embryonic stem (ES) cells by adherent differentiation. Before forming PPE cells, differentiating cultures first expressed the non-neural ectoderm specific transcriptional factors TFAP2A, GATA2, GATA3, DLX3, and DLX5, which are crucial in establishing the PPE competence. We demonstrated that bone morphogenetic protein (BMP) activity plays a transient but essential role in inducing expression of these PPE competence factors and eventually the PPE cells. Interestingly, we found that attenuating BMP signaling after establishing the competence state induces anterior placode precursors. By manipulating BMP and hedgehog signaling pathways, we further differentiate these precursors into restricted lineages including the lens placode and the oral ectoderm (pituitary precursor) cells. Finally, we also show that sensory neurons can be generated from human PPE cells, demonstrating the multipotency of the human ES-derived PPE cells.