P38-MAPK-mediated translation regulation during early blastocyst development is required for primitive endoderm differentiation in mice

Pablo Bora,Denisa Jansova,Tomáš Mašek,Anna Ajduk,Andrea Hauserova,David Potěšil,Martin Pospíšek,Andrej Susor,Zbyněk Zdráhal,Lenka Gahurova,Alexander W Bruce

doi:10.1038/s42003-021-02290-z

Abstract

Successful specification of the two mouse blastocyst inner cell mass (ICM) lineages (the primitive endoderm (PrE) and epiblast) is a prerequisite for continued development and requires active fibroblast growth factor 4 (FGF4) signaling. Previously, we identified a role for p38 mitogen-activated protein kinases (p38-MAPKs) during PrE differentiation, but the underlying mechanisms have remained unresolved. Here, we report an early blastocyst window of p38-MAPK activity that is required to regulate ribosome-related gene expression, rRNA precursor processing, polysome formation and protein translation. We show that p38-MAPK inhibition-induced PrE phenotypes can be partially rescued by activating the translational regulator mTOR. However, similar PrE phenotypes associated with extracellular signal-regulated kinase (ERK) pathway inhibition targeting active FGF4 signaling are not affected by mTOR activation. These data indicate a specific role for p38-MAPKs in providing a permissive translational environment during mouse blastocyst PrE differentiation that is distinct from classically reported FGF4-based mechanisms.

Highlights

Successful specification of the two mouse blastocyst inner cell mass (ICM) lineages (the primitive endoderm (PrE) and epiblast) is a prerequisite for continued development and requires active fibroblast growth factor 4 (FGF4) signaling
Exposed blastocysts to just three hours (E3.5 + 4 to +7 hours (h)) of p38-MAPKi (20 μM SB22002533,36,37—dimethyl sulfoxide (DMSO) vehicle controls were tested) and found that it was still sufficient to significantly impair PrE differentiation (Fig. 1b), albeit not as robustly as when p38-MAPKi was provided throughout the blastocyst maturation period
We previously observed that such extended p38-MAPKi seemed to cause reduced blastocyst sizes and cavity volumes, in the absence of supplemented AAs37

Summary

Introduction

Successful specification of the two mouse blastocyst inner cell mass (ICM) lineages (the primitive endoderm (PrE) and epiblast) is a prerequisite for continued development and requires active fibroblast growth factor 4 (FGF4) signaling. Due to the general dysregulation of translation-related gene expression in early blastocysts and the confirmed impairment of active protein translation caused by p38-MAPKi, we sought to identify other contributory mechanisms underlying the associated PrE differentiation phenotypes.

Results

Conclusion