P19 Cells Overexpressing Lhx1 Differentiate into the Definitive Endoderm by Recapitulating an Embryonic Developmental Pathway.

Epiblasts occur at the last pluripotent stage of embryonic development and are important in elucidating how the three germ layers are formed. However, little is known of the molecular mechanisms of their development. We have shown that LIM homeobox 1 (Lhx1) was involved in epiblast development in embryonic stem cells, especially meso- and endodermal differentiation. However, since epiblasts in embryoid bodies spontaneously develop into a further stage, it is difficult to study their development in this system. Mouse embryonal carcinoma P19 cells which have properties similar to those of epiblasts provided new avenues of investigation into the regulatory mechanism of epiblasts. Overexpression of Lhx1 in P19 cells induced expression of organizer marker genes (Cer1, Gsc) and endoderm marker genes (Gata6, Foxa2, Sox17) but not extra-embryonic endoderm marker genes (Sox7 or Hnf4alpha). This study suggested that Lhx1 overexpression caused P19 cells to differentiate into an endodermal lineage. Thus, P19 cells and their derivatives can be a useful model system to study how the three germ layers are formed.