Axonal guidance receptors are active in the human embryo prior to development of the CNS in the trophectoderm.

We measured total transcription in the inner cell mass (ICM) and the trophectoderm (TE) of the human embryo to understand the mechanisms underlying TE commitment. We describe here discovery of axonal guidance receptors as lineage commitment cooperating factors in embryonic stem cells of the human embryo. Slitrk3 and Ephb3 were essential and basic components of the TE commitment signature. The data indicate a broader function for axonal guidance receptors and the repulsive or attractive cues associated with their combinatorial functions and interaction, in orchestration of complex differentiation processes.