Requirement for ERK MAP kinase in mouse preimplantation development
Department of Cell and Developmental Biology, Graduate School of Biostudies, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan. Development
(Impact Factor: 6.46).
09/2007; 134(15):2751-9. DOI: 10.1242/dev.003756
Preimplantation development is a crucial step for successful implantation and pregnancy. Although both compaction and blastocyst formation have been extensively studied, mechanisms regulating the early cell division stages before compaction have remained unclear. Here, we show that extracellular signal regulated kinase (ERK) mitogen-activated protein (MAP) kinase function is required for early embryonic cell division before compaction. Our analysis demonstrates that inhibition of ERK activation in late two-cell-stage embryos leads to a reversible arrest in the G2 phase at the four-cell stage. The G2-arrested four-cell-stage embryos showed weakened cell-cell adhesion as compared with control embryos. Remarkably, microarray analyses showed that most of the programmed changes of upregulated and downregulated gene expression during the four- to eight-cell stages proceeded normally in four-cell-stage-arrested embryos that were subsequently released to resume development; however, the expression profiles of a proportion of genes in these embryos closely paralleled the stages of embryonic rather than normal development. These parallel genes included the genes encoding intercellular adhesion molecules, whose expression appeared to be positively regulated by the ERK pathway. We also show that, whereas ERK inactivation in eight-cell-stage embryos did not lead to cell division arrest, it did cause this arrest when cadherin-mediated cell-cell adhesion was disrupted. These results demonstrate an essential role of ERK function in two-cell to eight-cell-stage embryos, and suggest a loose parallelism between the gene expression programs and the developmental stages before compaction.
Available from: molehr.oxfordjournals.org
- "One of the important applications of these tools is to obtain a detailed picture of the early stages of embryonic development based on transcriptional characterization of single cells. 'Bulk' studies of embryogenesis have provided invaluable insight into transcription-factor networks of development and differentiation (Maekawa et al., 2007; Giritharan et al., 2010; Choi et al., 2012). However, when we analyze a pool of cells, as opposed to single cells, we obtain average values of expression and lose information about variability. "
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ABSTRACT: STUDY HYPOTHESIS Does primordial germ cell (PGC) activation start before mouse embryo implantation, and does the possible regulation of the
DNA (cytosine-5-)-methyltransferase 3-like (Dnmt3l) by transcription factor AP-2, gamma (TCFAP2C) have a role in this activation and in the primitive endoderm (PE)–epiblast
(EPI) lineage specification?
- "However, developmental defect is observed at the 16-cell stage and later, due to the aberrant redistribution of the Ezrin-T567A mutant to the basolateral cortex and reduced surface of adherens junctions (Dard et al., 2004). Moreover, some signaling molecules, such as PKC, Mek/Erk and Rho family GTPases, are also involved in blastomere polarization and compaction of the eight-cell embryo (Clayton et al., 1999; Lu et al., 2008; Maekawa et al., 2007; Winkel et al., 1990). Both PKCz and Erk2 show apical distribution in compacted eight-cell embryos (Lu et al., 2008; Pauken and Capco, 2000). "
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ABSTRACT: Phosphorylation of Ezrin T567 plays an important role in eight-cell embryo compaction. Yet, it is not clear how Ezrin phosphorylation is regulated during embryo compaction. Here, we demonstrated that inhibition of Mek/Erk or protein kinase C (PKC) signaling reduced the phosphorylation level of Ezrin T567 in eight-cell compacted embryos. Interestingly, the Rho GTPase inhibitor C3-transferase caused basolateral enrichment of atypical PKC (aPKC), as well as basolateral shift of phosphorylated Ezrin, suggesting aPKC may be a key regulator of Ezrin phosphorylation. Moreover, inhibition of PKC, but not Mek/Erk or Rho GTPases, affected the maintenance of Ezrin phosphorylation in compacted embryos. We further identified that aPKC is indeed required for Ezrin phosphorylation in eight-cell embryos. Taken together, Rho GTPases facilitate the apical distribution of aPKC and Ezrin. Subsequently, aPKC and Mek/Erk work together to promote Ezrin phosphorylation at the apical region, which in turn mediates the apical enrichment of filamentous actin, stabilizing the polarized apical region and allowing embryo compaction. Our data also suggested that aPKC might be the Ezrin kinase during eight-cell embryo compaction.
Available from: Paolo Cinelli
- "Entrance into the G1 phase of the cell cycle is a prerogative for cell differentiation. During the development from the 2-cell to the 8-cell stage embryo, ERK signaling seems to be essential in the G2/M transition . This is in contrast to what is happening in many mammalian cells, where ERK activity is essential for the cell cycle progression from G0/G1 to S phase . "
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ABSTRACT: Developmental biology, regenerative medicine and cancer biology are more and more interested in understanding the molecular mechanisms controlling pluripotency and self-renewal in stem cells. Pluripotency is maintained by a synergistic interplay between extrinsic stimuli and intrinsic circuitries, which allow sustainment of the undifferentiated and self-renewing state. Nevertheless, even though a lot of efforts have been made in the past years, the precise mechanisms regulating these processes remain unclear. One of the key extrinsic factors is leukemia inhibitory factor (LIF) that is largely used for the cultivation and derivation of mouse embryonic and induced pluripotent stem cells. LIF acts through the LIFR/gp130 receptor and activates STAT3, an important regulator of mouse embryonic stem cell self-renewal. STAT3 is known to inhibit differentiation into both mesoderm and endoderm lineages by preventing the activation of lineage-specific differentiation programs. However, LIF activates also parallel circuitries like the PI3K-pathway and the MEK/ERK-pathway, but its mechanisms of action remain to be better elucidated. This review article aims at summarizing the actual knowledge on the importance of LIF in the maintenance of pluripotency and self-renewal in embryonic and induced pluripotent stem cells.
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