The mouse inner cell mass (ICM) segregates into the epiblast and primitive endoderm (PrE) lineages coincident with implantation of the embryo. The epiblast subsequently undergoes considerable expansion of cell numbers prior to gastrulation. To investigate underlying regulatory principles, we performed systematic single-cell RNA sequencing (seq) of conceptuses from E3.5 to E6.5. The epiblast sho...

Oct4 and Sox2 regulate the expression of target genes such as Nanog, Fgf4, and Utf1, by binding to their respective regulatory motifs. Their functional cooperation is reflected in their ability to heterodimerize on adjacent cis regulatory motifs, the composite Sox/Oct motif. Given that Oct4 and Sox2 regulate many developmental genes, a quantitative analysis of their synergistic action on differ...

In vitro differentiation of human pluripotent stem cells (hPSCs) recapitulates early aspects of human embryogenesis, but the underlying processes are poorly understood and controlled. Here we show that modulating the bulk cell density (BCD: cell number per culture volume) deterministically alters anteroposterior patterning of primitive streak (PS)-like priming. The BCD in conjunction with the c...

The focal adhesion (FA) protein PINCH-1 is required for the survival of primitive endoderm (PrE) cells. How PINCH-1 regulates this fundamental process is not known. Here, we use embryoid bodies (EBs) and isolated EB-derived PrE cells to investigate the mechanisms by which PINCH-1 promotes PrE survival. We report that loss of PINCH-1 in PrE cells leads to a sustained activity of JNK and the pro-...

In the mouse blastocyst, some cells of the inner cell mass (ICM) develop into primitive endoderm (PE) at the surface, while deeper cells form the epiblast. It remained unclear whether the position of cells determines their fate, such that gene expression is adjusted to cell position, or if cells are pre-specified at random positions and then sort. We have tracked and characterised dynamics of a...

The intestine and colon carries out vital functions, and their lifelong maintenance is of the upmost importance. Research over the past decades has carefully addressed bowel function, how it is maintained and begun to unravel how disorders such as cancer and inflammatory bowel disease form. In contrast, very little is known about the molecular mechanisms that trigger tissue maturation during de...

The inner cell mass (ICM) of the mammalian blastocyst contains pluripotent epiblast (EPI) and differentiating primitive endoderm (PE) cells, intermingled like salt and pepper. In mouse, the earliest known driver of EPI and PE cell fates is FGF4, but it was unclear whether cellular or molecular heterogeneity existed upstream of Fgf4. In a new study, published in the journal Nature Cell Biology, ...

Although important progress has been made recently in the elucidation of the molecular mechanisms that regulate differentiation and morphogenesis of endoderm-derived tissues such as pancreas and liver, less is known about the preliminary steps of early regional specification. Recent evidence supports the proposal that the early endoderm contains a bipotential precursor cell type for pancreas an...

The directed differentiation of iPS and ES cells into definitive endoderm (DE) would allow the derivation of otherwise inaccessible progenitors for endodermal tissues. However, a global comparison of the relative equivalency of DE derived from iPS and ES populations has not been performed. Recent reports of molecular differences between iPS and ES cells have raised uncertainty as to whether iPS...

In order to study the deployment of cells during gastrulation and early organogenesis, it is necessary to have an in situ cell marker which can be used to follow cell fate. To create such a marker a transgenic mouse strain, designated Tg(Act-lac Z)-1, which carries 6 copies of the Escherichia coli lac Z gene under the control of the rat beta-actin promoter, was made by pronuclear injection of D...