Abstract
Defining which key factors control commitment of an embryonic lineage among a myriad of candidates is a longstanding challenge in developmental biology and an essential prerequisite for developing stem cell-based therapies. Commitment implies that the induced cells not only express early lineage markers but further undergo an autonomous differentiation into the lineage. The embryonic neural crest generates a highly diverse array of derivatives, including melanocytes, neurons, glia, cartilage, mesenchyme, and bone. A complex gene regulatory network has recently classified genes involved in the many steps of neural crest induction, specification, migration, and differentiation. However, which factor or combination of factors is sufficient to trigger full commitment of this multipotent lineage remains unknown. Here, we show that, in contrast to other potential combinations of candidate factors, coactivating transcription factors Pax3 and Zic1 not only initiate neural crest specification from various early embryonic lineages in Xenopus and chicken embryos but also trigger full neural crest determination. These two factors are sufficient to drive migration and differentiation of several neural crest derivatives in minimal culture conditions in vitro or ectopic locations in vivo. After transplantation, the induced cells migrate to and integrate into normal neural crest craniofacial target territories, indicating an efficient spatial recognition in vivo. Thus, Pax3 and Zic1 cooperate and execute a transcriptional switch sufficient to activate full multipotent neural crest development and differentiation.