Angiomotin prevents pluripotent lineage differentiation in mouse embryos via Hippo pathway-dependent and -independent mechanisms

Chuen Yan Leung,Magdalena Zernicka-Goetz

doi:10.1038/ncomms3251

Abstract

Cell identity is specified in the early mammalian embryo by the generation of precursors for two cell lineages: the pluripotent inner cell mass and differentiating trophectoderm. Here we identify Angiomotin as a key regulator of this process. We show that the loss of Angiomotin, together with Angiomotin-like 2, leads to differentiation of inner cell mass cells and compromised peri-implantation development. We show that Angiomotin regulates localization of Yap, and Yap-binding motifs are required for full activity of Angiomotin. Importantly, we also show that Angiomotin function can compensate for the absence of Lats1/2 kinases, indicating the ability of Angiomotin to bypass the classical Hippo pathway for Yap regulation. In polarized outside cells, Angiomotin localizes apically, pointing to the importance of cell polarity in regulating Yap to promote differentiation. We propose that both Hippo pathway-dependent and Hippo pathway-independent mechanisms regulate Yap localization to set apart pluripotent and differentiated lineages in the pre-implantation mouse embryo.

Highlights

Cell identity is specified in the early mammalian embryo by the generation of precursors for two cell lineages: the pluripotent inner cell mass and differentiating trophectoderm
When progenitors of the inner cell mass (ICM) and TE lineages become set apart, at the 8- to 16-cell transition, Amot becomes localized throughout the membrane in the inside cells, whereas in outside cells it is restricted to the apical domain (Fig. 1)
We found that co-depletion of Amot and Amotl[2] permitted blastocyst formation (9/10, 90%; control small interfering RNAs (siRNAs): 9/10, 90%) and did not affect the total cell number or number of ICM cells per embryo (Fig. 3b)

Summary

Introduction

Cell identity is specified in the early mammalian embryo by the generation of precursors for two cell lineages: the pluripotent inner cell mass and differentiating trophectoderm. Angiomotin localizes apically, pointing to the importance of cell polarity in regulating Yap to promote differentiation We propose that both Hippo pathwaydependent and Hippo pathway-independent mechanisms regulate Yap localization to set apart pluripotent and differentiated lineages in the pre-implantation mouse embryo. Three cell types have to be set apart by the blastocyst stage: epiblast, which will give rise to the embryo proper, trophectoderm (TE) and primitive endoderm (PE), which will provide the extraembryonic structures such as the placenta and yolk sac Specifying these three cell lineages is mediated through three waves of asymmetric cell divisions that start at the eight-cell stage and generate nonpolar inside and polar outside cells[1,2]. Yap localization and Cdx[2] expression is regulated through a Hippo pathway-dependent mechanism and through a Hippo pathway-independent mechanism

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Conclusion