The formation of proximal and distal definitive endoderm populations in culture requires p38 MAPK activity

Abstract

BSTRACTEndoderm formation in the mammal is a complex process with two lineages forming during the first weeks of development, the primitive (or extraembryonic) endoderm, which is specified in the blastocyst, and the definitive endoderm that forms later, at gastrulation, as one of the germ layers of the embryo proper. Fate mapping evidence suggests that the definitive endoderm arises as two waves, which potentially reflect two distinct cell populations. Early primitive ectoderm-like (EPL) cell differentiation has been used successfully to identify and characterise mechanisms regulating molecular gastrulation and lineage choice during differentiation. The roles of the p38 MAPK family in the formation of definitive endoderm were investigated using EPL cells and chemical inhibitors of p38 MAPK activity. These approaches define a role for p38 MAPK activity in the formation of the primitive streak and a second role in the formation of the definitive endoderm. Characterisation of the definitive endoderm populations formed from EPL cells demonstrates the formation of two distinct populations, defined by gene expression and ontogeny, that were analogous to the proximal and distal definitive endoderm populations of the embryo. Formation of the proximal definitive endoderm was found to require p38 MAPK activity and is correlated with molecular gastrulation, defined by the expression of brachyury (T). Distal definitive endoderm formation also requires p38 MAPK activity but can form when T expression is inhibited. Understanding lineage complexity will be a prerequisite for the generation of endoderm derivatives for commercial and clinical use.

RARβ2-dependent signaling represses neuronal differentiation in mouse ES cells

“…Our antibody microarray analyses indicated that cells treated with a combination of RA plus AC expressed members of the p38/MAPK and PI3K/AKT pathways in a differential manner as compared to cells treated with RA only, which suggests their involvement on the induction of ES to endodermal differentiation by RARβ2. This idea is consistent with reports describing the involvement of the p38 and PI3K cell signaling pathways on the commitment of endodermal lineages either during embryonic carcinoma or ES cell differentiation in culture (Smedberg et al, 2002; Villegas et al, 2013; Yap et al, 2014; also, see Binetruy et al, 2007 for a review). Thus, our findings provide evidence of a role played by the p38 and PI3K cell signaling pathways during the RA-induced differentiation of mouse ES cells along an endodermal lineage.…”

p38 (Mapk14/11) occupies a regulatory node governing entry into primitive endoderm differentiation during preimplantation mouse embryo development

“…Furthermore, previous work conducted using a specific small chemical compound inhibitor of p38α/Mapk14 and p38β/Mapk11 (herein referred to together as p38-Mapk14/11) has demonstrated eight- to 16-cell arrest phenotypes, associated with defects in embryo compaction, filamentous actin formation and glucose uptake, or compromised blastocyst formation typified by failures in appropriate blastocoel formation (for example, associated with tight-junction failure and reduced aquaporin expression), depending upon the exact timing of drug administration relative to the onset of embryo compaction [ 31 – 34 ]. A very recent study has also implicated a role for active p38-Mapk signalling in blastocyst TE formation via mediating autocrine Fgf2/Fgfr2-based signalling [ 19 ], and interesting evidence from experiments investigating the molecular regulators of canonical Wnt3a-signalling, using the mouse F9 teratocarcinoma cell model, suggests a potential role for p38-Mapks in regulating PrE formation [ 35 ]; indeed, the formation of definitive endoderm at gastrulation is known to require p38-Mapk activity [ 36 ].…”

A Modified Murine Embryonic Stem Cell Test for Evaluating the Teratogenic Effects of Drugs on Early Embryogenesis

“…The p38 MAPK signaling pathway is involved in many cellular processes, including inflammation and cell differentiation, survival and death. During embryonic development, the p38 inhibitor SB203580 blocks both mesoderm and endoderm differentiation from the primitive streak [ 15 ][ 18 ]. We have shown that SB203580 treatment inhibits mRNA expression of the primitive streak markers Wnt3 and Brachyury T but induces premature expression of neurogenesis markers, implicating p38 MAPK in the initial stages of primitive streak formation in the EB system.…”