Naïve human pluripotency stem cells respond to Wnt, Nodal and LIF signalling to produce expandable naïve extra-embryonic endoderm

Embryonic stem cells (ESCs) can exist in at least two states that transcriptionally resemble different stages of embryonic development. Naïve ESCs resemble peri-implantation stages and primed ESCs the pre-gastrulation epiblast. In mouse, primed ESCs give rise to definitive endoderm in response to pathways downstream of Nodal and Wnt signalling. However, when these cytokines are applied to naïve ESCs, they differentiate to a cell type that approximates early primitive endoderm (PrE), the blastocyst stage progenitor layer that gives rise to the extra-embryonic endoderm. Here, we apply this context dependency to human ESCs, showing that these cytokines drive the differentiation of naïve pluripotent cells to generate extra-embryonic PrE, or hypoblast, and, as in mouse, expanded as an in vitro model for naïve extra-embryonic endoderm (nEnd) in defined conditions. Consistent with observations made in mouse, human PrE differentiation is dependent on FGF signalling in vitro, and we show, that by inhibiting FGF receptor signalling, we could simplify naïve pluripotent culture such that inhibitor requirements closer resembled those used in mouse. These nEnd cultures represent stable extra-embryonic endoderm, or human hypoblast, cell lines. Overall design: Embryonic stem cell and endoderm types were cultured in their respective standard culture systems for 5 days, after which total RNA was isolated. After this, labelled RNA was purified by standard chemistry, libraries prepared and sequenced.