Direct conversion of fibroblasts traces the way back to our first organ—the placenta

Cell fate determination has always fascinated scientists predominantly embryologists and challenged them to decipher master genes or networks of transcriptional factors which together with cell signaling cascades act as key regulators for the cell lineage allocation. With the rediscovery of the pluripotent precursor cells in an adult body and the possibility to induce pluripotency in somatic cells (iPSCs), as sources for alternative therapeutic options in translational medicine, this field has attracted high interest in medical research and application (1). iPSC have several advantages over embryonic stem cells such as avoiding tumor formation and to circumvent ethical concerns. Meanwhile the understanding of pluripotency has broadened thanks to abundant studies on converting ESC and somatic cells into another cell fate using predominantly transfection of a bunch of lineage specific transcription factors. While many studies focused on the regulation of ESC conversion less is known about the hierarchically organized network of transcriptional factors which determine the trophoblast lineage for placenta development.