Figure 6: Summary of decisive factors in PS patterning revealed in this study.

The four cornerstone conditions investigated in this study result in distinct progression of the hPSCs during exit of pluripotency. Depending on the level of CHIR (WNT pathway) stimulation and the BCD, primitive streak-like patterning along the anteroposterior axis occurs that ultimately determine cell fate into prospective definitive endoderm, cardiac mesoderm and PSM. WNT (CHIR) and BMP signalling act as main driver of PS progression over time, while cell-borne factors (LEFTY1 and CER1) antagonize the progression of the streak formation depending on the BCDs.