Initiation of a conserved trophectoderm program in human, cow and mouse embryos

Abstract

Current understanding of cell specification in early mammalian preimplantation development is mainly based on mouse studies. The first lineage differentiation event occurs at the morula stage with outer cells initiating a trophectoderm (TE) program to become the earliest placental progenitors. At subsequent developmental stages, the inner cell mass (ICM) arises from inner cells and is comprised of precursor cells of the embryo proper and yolk sac 1 . Notably, recent gene expression analyses suggest that the mechanisms regulating early lineage specification in the mouse may differ in other mammals, including human 2-5 and cow 6,7 . Here, we examined evolutionary conservation of cell dynamics and a molecular cascade initiating TE segregation in mouse, cow and human embryos using a comparative embryology approach. We discovered that the expression pattern of key TE lineage-associated factors shows a high degree of conservation among all three species. Specifically, at the morula stage outer cells acquire an apico-basal cell polarity, with expression of aPKC and PARD6B at the surface-free domain, nuclear expression of the Hippo signaling pathway effectors, YAP1 and WWTR1, and restricted expression of the transcription factor GATA3, suggesting initiation of a TE program. Furthermore, we demonstrate that inhibition of aPKC, by small-molecule pharmacological modulation and TRIM-Away protein depletion, impairs TE initiation at the morula stage. Altogether, our comparative embryology analysis provides novel insights into early lineage specification in human preimplantation embryos and suggests a similar mechanism initiating a TE program in mouse, cow and human embryos. Main textOur current understanding of cell specification during mammalian preimplantation development mainly relies on mouse studies. At the 8-cell stage, the mouse embryo undergoes a drastic

Induction of Human Trophoblast Stem Cells from Somatic Cells and Pluripotent Stem Cells

“…Differentially regulated pathways included HIPPO, NOTCH, and ERBB pathways, which are main drivers of the self-renewing state of mouse TSCs (El-Hashash et al, 2010;Home et al, 2012;Nishioka et al, 2009;Rayon et al, 2014;Rivron et al, 2018b) and PPARG that is associated with mouse trophoblast proliferation and differentiation (Parast et al, 2009). These results complete previous studies suggesting conserved mechanisms of trophoblast development across mammals (Gerri et al, 2020;Hunkapiller et al, 2011;Saha et al, 2020;Schaiff et al, 2000), while they also highlight specific features of the human trophoblast lineage such as the steroid hormone biosynthesis pathway that was specifically associated with the ST in humans (Malassiné et al, 2003). Moreover, our analysis pointed to additional pathways including MTOR, estrogen, RAP1, and JAK/STAT signaling pathways that seem to be active in h(i/c)TSCs (Figures S4 and S5).…”

“…Upon additional culture (2 passages), we observed the rapid formation of cobblestone-shaped colonies, morphologically reminiscent of hTSCs ( Figure 1A). These cell lines subsequently lost their transgenes (after 10-15 passages) and expressed the GATA2 and GATA3 genes associated with the trophoblast lineage (Gerri et al, 2020;Home et al, 2017;Krendl et al, 2017;Meistermann et al, 2019). By contrast, they did not express the pluripotency markers NANOG and KLF17 (data not shown).…”

A Comparative Analysis of Hippo Signaling Pathway Components during Murine and Bovine Early Mammalian Embryogenesis

“…These studies will shed more light on the organization hierarchy of Hippo signaling pathway components in the bovine model and will further establish the role of this cell signaling pathway in cell fate specification during the formation of the bovine blastocyst. Understanding the biology of bovine blastocyst formation will also enhance our knowledge about the mechanism of human blastocyst development, as multiple reports suggest that the regulation of human blastocyst formation is more similar to that of bovine as compared with the mouse model [68,69]. The study of Hippo signaling pathway components in various species will help us better understand the biology of mammalian blastocyst formation.…”

A Critical Role for The COP9 Signalosome Subunit 3 as A Gatekeeper of Genome Integrity in 2-Cell Mouse Embryos

“…Together, these two answers predict that a complete depletion by TRIM21-mediated proteasomal degradation may not work, and may not be required to work (depending on one's aim), for every protein. Indeed, it may be noted that out of thirteen studies which applied the TRIM21-mediated proteasomal degradation on oocytic or embryonic proteins in mammals 21,22,27,[65][66][67][68][69][70][71][72][73][74] , four studies reported complete depletion (ITPR1 67 ; SNAP23 27 ; G6PD, PKM, GFPT1 65 ; EG5 also known as KIF11 21 ), four studies reported almost complete depletion (BTG4 68 ; TACC3 69 ; RACGAP1 also known as CYK4 and PLK1 70 ; SMC3 72 ) and five studies reported incomplete depletion (RCC1 66 ; CENPF 71 ; TEAD4 22 ; aPKC also known as PRKC 73 ; HUWE1 74 ). Thus, complete removal of the protein of interest seems to be more the exception than the rule (with current technology).…”