FOXN1GFP/w Reporter hESCs Enable Identification of Integrin-β4, HLA-DR, and EpCAM as Markers of Human PSC-Derived FOXN1+ Thymic Epithelial Progenitors

• FOXN1-GFP reporter hESC lines were generated
• KGF promotes the proliferation of FOXN1-GFP+ cells
• FOXN1-GFP+ cells express TEC-associated genes
• ITGB4, HLA-DR, and EpCAM can be used to purify FOXN1+ TEC progenitors (219)

SummaryThymic epithelial cells (TECs) play a critical role in T cell maturation and tolerance induction. The generation of TECs from in vitro differentiation of human pluripotent stem cells (PSCs) provides a platform on which to study the mechanisms of this interaction and has implications for immune reconstitution. To facilitate analysis of PSC-derived TECs, we generated hESC reporter lines in which sequences encoding GFP were targeted to FOXN1, a gene required for TEC development. Using this FOXN1GFP/w line as a readout, we developed a reproducible protocol for generating FOXN1-GFP+ thymic endoderm cells. Transcriptional profiling and flow cytometry identified integrin-β4 (ITGB4, CD104) and HLA-DR as markers that could be used in combination with EpCAM to selectively purify FOXN1+ TEC progenitors from differentiating cultures of unmanipulated PSCs. Human FOXN1+ TEC progenitors generated from PSCs facilitate the study of thymus biology and are a valuable resource for future applications in regenerative medicine.