Oct4 Cell-Autonomously Promotes Primitive Endoderm Development in the Mouse Blastocyst

Abstract

Summary In embryonic stem (ES) cells and in early mouse embryos, the transcription factor Oct4 is an essential regulator of pluripotency. Oct4 transcriptional targets have been described in ES cell lines; however, the molecular mechanisms by which Oct4 regulates establishment of pluripotency in the epiblast (EPI) have not been fully elucidated. Here we show that neither maternal nor zygotic Oct4 are required for formation of EPI cells in the blastocyst. Rather, Oct4 is first required for development of the primitive endoderm (PE), an extraembryonic lineage. EPI cells promote PE fate in neighboring cells by secreting Fgf4, and Oct4 is required for expression of Fgf4, but we show that Oct4 promotes PE development cell-autonomously, downstream of Fgf4 and Mapk. Finally, we show that Oct4 is required for expression of multiple EPI and PE genes, as well as multiple metabolic pathways essential for the continued growth of the preimplantation embryo.

Commonly used fertility drugs, a diet supplement, and stress force AMPK-dependent block of stemness and development in cultured mammalian embryos

“…Oct4 and Cdx2 are necessary at the blastocyst stage to allocate ESC and TSC lineages, respectively [109], and knockouts for either of these are lethal at the blastocyst stage [51,110]. But, Oct4 also regulates stem cell metabolism [50] and is necessary for stress preparation and response [48,49]. But, in mouse and human ESCs, Oct4 actively silences hundreds of promoters [111,112] that would mediate differentiation.…”

“…But, AMPK activation occurring in normal preimplantation blastocysts and cultured embryonic stem cells (ESCs) and trophoblast stem cells (TSCs), isolated from the blastocyst [41], leads to loss of potency factors and inhibitor of differentiation (Id)2, caudal domain homeobox (Cdx)2 in blastocysts, octamer-binding transcription factor (Oct)4 and nanog in pluripotent ESCs and inducible pluripotent stem cells (iPSCs) [42,43], and Cdx2 and Id2 in TSCs [41,[44][45][46] and in two-cell-stage embryos [41,45]. Oct4 is necessary for the ESC stress response and survival [47][48][49] and is necessary for metabolic control in the blastocyst [50], and null Oct4 mutants are lethal at the blastocyst stage due to insufficient function of cells of the inner cell mass (ICM)/ESC lineage cells [51]. Of significance is that small variations in Oct4 level, including loss in the levels caused by stress, change the fate of the ESC [52].…”

The molecular underpinnings of totipotency

“…Thus mouse mutants of many of the genes that are coexpressed at early stages, such as Oct4, Nanog and Gata6, can develop past these early time points and can undergo some aspects of lineage specification [49][50][51][52][53]. Hence, individually, these factors may not be explicitly required for sustaining a totipotent state.…”

From blastocyst to gastrula: gene regulatory networks of embryonic stem cells and early mouse embryogenesis

“…However, unlike Sox2, Oct4 expression does not become restricted to the Epi after implantation [20,111]. Recent studies have demonstrated that Oct4 is required for the maintenance of PrE-specific gene expression, which is disrupted in the absence of zygotic OCT4 protein [59,60]. Notably, this requirement for Oct4 cannot be rescued by exogenous FGF, demonstrating that Oct4 acts downstream of FGF signalling and plays a cell-autonomous as well as non-cell-autonomous role in PrE specification [59,60].…”