Talk:Developmental Signals - Hippo
Tension-dependent regulation of mammalian Hippo signaling through LIMD1
J Cell Sci. 2018 Mar 2;131(5). pii: jcs214700. doi: 10.1242/jcs.214700.
Ibar C1, Kirichenko E1, Keepers B1, Enners E1, Fleisch K1, Irvine KD2.
Hippo signaling is regulated by biochemical and biomechanical cues that influence the cytoskeleton, but the mechanisms that mediate this have remained unclear. We show that all three mammalian Ajuba family proteins - AJUBA, LIMD1 and WTIP - exhibit tension-dependent localization to adherens junctions, and that both LATS family proteins, LATS1 and LATS2, exhibit an overlapping tension-dependent junctional localization. This localization of Ajuba and LATS family proteins is also influenced by cell density, and by Rho activation. We establish that junctional localization of LATS kinases requires LIMD1, and that LIMD1 is also specifically required for the regulation of LATS kinases and YAP1 by Rho. Our results identify a biomechanical pathway that contributes to regulation of mammalian Hippo signaling, establish that this occurs through tension-dependent LIMD1-mediated recruitment and inhibition of LATS kinases in junctional complexes, and identify roles for this pathway in both Rho-mediated and density-dependent regulation of Hippo signaling. KEYWORDS: Cytoskeleton; Hippo; Junction; LIMD1; Tension; YAP
PMID: 29440237 DOI: 10.1242/jcs.214700
Role of ROCK Signaling in Formation of the Trophectoderm of the Bovine Preimplantation Embryo
Mol Reprod Dev. 2018 Mar 15. doi: 10.1002/mrd.22976.
Negrón-Pérez VM1, Rodrigues LT2, Mingoti GZ2, Hansen PJ1.
Rho-associated coiled-coil containing protein kinases (ROCK1 and ROCK2) are activated by binding to RHO GTPases and phosphorylate a variety of downstream targets including actinomyosin. In the mouse embryo, ROCK signaling acts to promote formation of trophectoderm (TE) and inhibit formation of the inner cell mass (ICM) by polarizing outer cells of the embryo to inactivate Hippo signaling (Kono et al., 2014; Mihajlović and Bruce, 2016). This article is protected by copyright. All rights reserved. KEYWORDS: trophectoderm, ROCK, bovine, blastocyst
PMID: 29542836 DOI: 10.1002/mrd.22976
Curr Top Dev Biol. 2018;128:59-80. doi: 10.1016/bs.ctdb.2017.10.009. Our First Choice: Cellular and Genetic Underpinnings of Trophectoderm Identity and Differentiation in the Mammalian Embryo. Menchero S1, Sainz de Aja J1, Manzanares M2. Author information Abstract The trophectoderm (TE) is the first cell population to appear in the mammalian preimplantation embryo, as the result of the differentiation of totipotent blastomeres located on the outer surface of the late morula. Trophectodermal cells arrange in a monolayer covering the expanding blastocyst and acquire an epithelial phenotype with distinct apicobasal polarity and a basal lamina placed toward the blastocyst interior. During later development through the periimplantation and gastrulation stages, the TE gives rise to extraembryonic membranes and cell types that will eventually form most of the fetal placenta, the specialized organ through which the embryo obtains maternal nourishment necessary for subsequent exponential growth. The specification of the TE is controlled by the combination of morphological cues arising from cell polarity with differential activity of signaling pathways such as Hippo and Notch, and the restriction to outer cells of lineage specifiers such as CDX2. This is possibly the first symmetry-breaking decision undertaken by the uncommitted cells produced by a handful of mitosis divisions from the newly fertilized zygote. Understanding how this cell lineage is specified will therefore provide unique information about development, differentiation, and how the interplay between cellular morphology and signaling and regulatory factors results in a correctly 3D-patterned embryo. KEYWORDS: Blastocyst; Cdx2; Hippo; Notch; Placenta; Preimplantation development; Stem cells; Trophectoderm PMID: 29477171 DOI: 10.1016/bs.ctdb.2017.10.009
Oocyte-expressed yes-associated protein is a key activator of the early zygotic genome in mouse
Cell Res. 2016 Mar;26(3):275-87. doi: 10.1038/cr.2016.20. Epub 2016 Feb 23.
Yu C1, Ji SY1, Dang YJ2, Sha QQ1, Yuan YF3, Zhou JJ1, Yan LY3, Qiao J3, Tang F2, Fan HY1.
In early mammalian embryos, the genome is transcriptionally quiescent until the zygotic genome activation (ZGA) which occurs 2-3 days after fertilization. Despite a long-standing effort, maternal transcription factors regulating this crucial developmental event remain largely elusive. Here, using maternal and paternal mouse models of Yap1 deletion, we show that maternally accumulated yes-associated protein (YAP) in oocyte is essential for ZGA. Maternal Yap1-knockout embryos exhibit a prolonged two-cell stage and develop into the four-cell stage at a much slower pace than the wild-type controls. Transcriptome analyses identify YAP target genes in early blastomeres; two of which, Rpl13 and Rrm2, are required to mediate maternal YAP's effect in conferring developmental competence on preimplantation embryos. Furthermore, the physiological YAP activator, lysophosphatidic acid, can substantially improve early development of wild-type, but not maternal Yap1-knockout embryos in both oviduct and culture. These observations provide insights into the mechanisms of ZGA, and suggest potentials of YAP activators in improving the developmental competence of cultured embryos in assisted human reproduction and animal biotechnology.
Par-aPKC-dependent and -independent mechanisms cooperatively control cell polarity, Hippo signaling, and cell positioning in 16-cell stage mouse embryos
Dev Growth Differ. 2015 Oct;57(8):544-56. doi: 10.1111/dgd.12235. Epub 2015 Oct 9.
Hirate Y1, Hirahara S2, Inoue K3, Kiyonari H3,4, Niwa H5,6, Sasaki H1,7.
In preimplantation mouse embryos, the Hippo signaling pathway plays a central role in regulating the fates of the trophectoderm (TE) and the inner cell mass (ICM). In early blastocysts with more than 32 cells, the Par-aPKC system controls polarization of the outer cells along the apicobasal axis, and cell polarity suppresses Hippo signaling. Inactivation of Hippo signaling promotes nuclear accumulation of a coactivator protein, Yap, leading to induction of TE-specific genes. However, whether similar mechanisms operate at earlier stages is not known. Here, we show that slightly different mechanisms operate in 16-cell stage embryos. Similar to 32-cell stage embryos, disruption of the Par-aPKC system activated Hippo signaling and suppressed nuclear Yap and Cdx2 expression in the outer cells. However, unlike 32-cell stage embryos, 16-cell stage embryos with a disrupted Par-aPKC system maintained apical localization of phosphorylated Ezrin/Radixin/Moesin (p-ERM), and the effects on Yap and Cdx2 were weak. Furthermore, normal 16-cell stage embryos often contained apolar cells in the outer position. In these cells, the Hippo pathway was strongly activated and Yap was excluded from the nuclei, thus resembling inner cells. Dissociated blastomeres of 8-cell stage embryos form polar-apolar couplets, which exhibit different levels of nuclear Yap, and the polar cell engulfed the apolar cell. These results suggest that cell polarization at the 16-cell stage is regulated by both Par-aPKC-dependent and -independent mechanisms. Asymmetric cell division is involved in cell polarity control, and cell polarity regulates cell positioning and most likely controls Hippo signaling. © The Authors Development, Growth & Differentiation published by Wiley Publishing Asia Pty Ltd on behalf of Japanese Society of Developmental Biologists. KEYWORDS: Hippo signaling; Par-aPKC; asymmetric cell division; cell polarity; preimplantation embryo
J Cell Biol. 2015 Sep 28;210(7):1185-97. doi: 10.1083/jcb.201503042.
Bessonnard S1, Mesnard D2, Constam DB1.
The first cell differentiation in mammalian embryos segregates polarized trophectoderm cells from an apolar inner cell mass (ICM). This lineage decision is specified in compacted morulae by cell polarization and adhesion acting on the Yes-associated protein in the Hippo signaling pathway, but the regulatory mechanisms are unclear. We show that morula compaction and ICM formation depend on PC7 and the related proprotein convertases (PCs) Furin and Pace4 and that these proteases jointly regulate cell-cell adhesion mediated by E-cadherin processing. We also mapped the spatiotemporal activity profiles of these proteases by live imaging of a transgenic reporter substrate in wild-type and PC mutant embryos. Differential inhibition by a common inhibitor revealed that all three PCs are active in inner and outer cells, but in partially nonoverlapping compartments. E-cadherin processing by multiple PCs emerges as a novel mechanism to modulate cell-cell adhesion and fate allocation. © 2015 Bessonnard et al.
Position- and polarity-dependent Hippo signaling regulates cell fates in preimplantation mouse embryos
Semin Cell Dev Biol. 2015 May 15. pii: S1084-9521(15)00100-7. doi: 10.1016/j.semcdb.2015.05.003. [Epub ahead of print]
During the preimplantation stage, mouse embryos establish two cell lineages by the time of early blastocyst formation: the trophectoderm (TE) and the inner cell mass (ICM). Historical models have proposed that the establishment of these two lineages depends on the cell position within the embryo (e.g., the positional model) or cell polarization along the apicobasal axis (e.g., the polarity model). Recent findings have revealed that the Hippo signaling pathway plays a central role in the cell fate-specification process: active and inactive Hippo signaling in the inner and outer cells promote ICM and TE fates, respectively. Intercellular adhesion activates, while apicobasal polarization suppresses Hippo signaling, and a combination of these processes determines the spatially regulated activation of the Hippo pathway in 32-cell-stage embryos. Therefore, there is experimental evidence in favor of both positional and polarity models. At the molecular level, phosphorylation of the Hippo-pathway component angiomotin at adherens junctions (AJs) in the inner (apolar) cells activates the Lats protein kinase and triggers Hippo signaling. In the outer cells, however, cell polarization sequesters Amot from basolateral AJs and suppresses activation of the Hippo pathway. Other mechanisms, including asymmetric cell division and Notch signaling, also play important roles in the regulation of embryonic development. In this review, I discuss how these mechanisms cooperate with the Hippo signaling pathway during cell fate-specification processes. Copyright © 2015 Elsevier Ltd. All rights reserved. KEYWORDS: Cell fate specification; Hippo signaling pathway; Preimplantation mouse embryo; Trophectoderm
Angiomotin binding-induced activation of Merlin/NF2 in the Hippo pathway
Cell Res. 2015 Jun 5. doi: 10.1038/cr.2015.69. [Epub ahead of print]
Li Y1, Zhou H2, Li F2, Chan SW3, Lin Z1, Wei Z4, Yang Z1, Guo F3, Lim CJ3, Xing W2, Shen Y2, Hong W3, Long J2, Zhang M5.
The tumor suppressor Merlin/NF2 functions upstream of the core Hippo pathway kinases Lats1/2 and Mst1/2, as well as the nuclear E3 ubiquitin ligase CRL4DCAF1. Numerous mutations of Merlin have been identified in Neurofibromatosis type 2 and other cancer patients. Despite more than two decades of research, the upstream regulator of Merlin in the Hippo pathway remains unknown. Here we show by high-resolution crystal structures that the Lats1/2-binding site on the Merlin FERM domain is physically blocked by Merlin's auto-inhibitory tail. Angiomotin binding releases the auto-inhibition and promotes Merlin's binding to Lats1/2. Phosphorylation of Ser518 outside the Merlin's auto-inhibitory tail does not obviously alter Merlin's conformation, but instead prevents angiomotin from binding and thus inhibits Hippo pathway kinase activation. Cancer-causing mutations clustered in the angiomotin-binding domain impair angiomotin-mediated Merlin activation. Our findings reveal that angiomotin and Merlin respectively interface cortical actin filaments and core kinases in Hippo signaling, and allow construction of a complete Hippo signaling pathway.Cell Research advance online publication 5 June 2015; doi: 10.1038/cr.2015.69.
Development. 2014 Jul;141(14):2813-24. doi: 10.1242/dev.107276. Epub 2014 Jun 19. Initiation of Hippo signaling is linked to polarity rather than to cell position in the pre-implantation mouse embryo. Anani S1, Bhat S2, Honma-Yamanaka N2, Krawchuk D2, Yamanaka Y3. Author information Abstract In the mouse embryo, asymmetric divisions during the 8-16 cell division generate two cell types, polar and apolar cells, that are allocated to outer and inner positions, respectively. This outer/inner configuration is the first sign of the formation of the first two cell lineages: trophectoderm (TE) and inner cell mass (ICM). Outer polar cells become TE and give rise to the placenta, whereas inner apolar cells become ICM and give rise to the embryo proper and yolk sac. Here, we analyze the frequency of asymmetric divisions during the 8-16 cell division and assess the relationships between cell polarity, cell and nuclear position, and Hippo signaling activation, the pathway that initiates lineage-specific gene expression in 16-cell embryos. Although the frequency of asymmetric divisions varied in each embryo, we found that more than six blastomeres divided asymmetrically in most embryos. Interestingly, many apolar cells in 16-cell embryos were located at outer positions, whereas only one or two apolar cells were located at inner positions. Live imaging analysis showed that outer apolar cells were eventually internalized by surrounding polar cells. Using isolated 8-cell blastomeres, we carefully analyzed the internalization process of apolar cells and found indications of higher cortical tension in apolar cells than in polar cells. Last, we found that apolar cells activate Hippo signaling prior to taking inner positions. Our results suggest that polar and apolar cells have intrinsic differences that establish outer/inner configuration and differentially regulate Hippo signaling to activate lineage-specific gene expression programs. KEYWORDS: 16-cell stage; Asymmetric division; Cell sorting; Inner cell mass (ICM); Live imaging; Mouse; Trophectoderm (TE); YAP (Yes-associated protein) PMID: 24948601 DOI: 10.1242/dev.107276