Breaking the first lineage barrier - many roads to trophoblast stem cell fate.

Recently, direct cell fate conversion attempts between the embryonic and extra-embryonic lineage gained new momentum. Two concomitant publications were published, describing the successful generation of transgene-independent, self-renewing trophoblast stem cells (TSCs) from murine fibroblasts. Cells were faithfully converted, displaying high similarity to blastocyst or extraembryonic ectoderm derived TSCs. Here, we summarize and compare published attempts aiming at the direct induction of trophoblast-fate from either mouse embryonic stem cells or fibroblasts.