VENTX gene expression marks a subset of human primordial germ cells

The Ventx genes are a family of non-clustered homeobox transcription factors that confer a ventral phenotype on mesodermal cells in the Xenopus laevis embryo. Ventx genes are conserved in vertebrates, although they have been lost in rodents. We evaluated the expression of VENTX during differentiation of a human pluripotent stem cell (hPSC) line in which a GFP reporter marked the expression of VENTX (VENTXGFP/w), discovering that VENTX was expressed in a subset of early primordial germ cell-like cells (PGCLCs). We generated a dual reporter hPSC line in which mCHERRY marked the pluripotency gene OCT4 (VENTXGFP/wOCT42AmCHERRY/w), and further modified this to also create a VENTX knock out line by deleting the VENTX homeodomain (VENTXGFP/-OCT42AmCHERRY/w).Transcriptional profiling experiments revealed two populations of PGCLCs, those that co expressed VENTX and OCT4 (GFP+mCHERRY+) and those that were VENTX-OCT4+ (GFP-mCHERRY+). Our analyses showed that VENTX+ and VENTX- PGCLCs clustered together, and also failed to reveal transcriptional consequences of VENTX deletion on commitment to PGCLCs. Evaluation of public databases confirmed expression of VENTX in populations of PGCLCs derived by others and in primary human embryonic germ cell samples. These results identify VENTX as a new PGC-associated gene in humans, however it does not seem to be required for initial human PGC commitment.