Nanog regulates Pou3f1 expression and represses anterior fate at the exit from pluripotency.

Pluripotency is regulated by a network of transcription factors (TF) that maintains early embryonic cells in an undifferentiated state while allowing them to proliferate. NANOG is a vital TF in maintaining pluripotency and its role in primordial germ cells (PGCs) differentiation has been well described. However, Nanog is expressed during gastrulation across all the posterior epiblast, and only later in development its expression is restricted to PGCs. In this work we unveiled a previously unknown mechanism by which Nanog specifically represses spatially the anterior epiblast lineage. Transcriptional data collection and analysis from both E6.5 embryos and embryonic stem (ES) cells revealed Pou3f1 to be negatively correlated with NANOG during gastrulation. We have functionally proved Pou3f1 to be a target of Nanog by using a dual transgene system for controlled expression of Nanog and Nanog null ES cells that further demonstrated a role for Nanog in repressing anterior neural genes. Deletion of a NANOG binding site (BS) 9kb downstream Pou3f1 transcription start site revealed to have a specific role in the regionalization of Pou3f1 expression. Our results indicate an active role of Nanog in inhibiting neural fate at the onset of gastrulation by repressing Pou3f1 .